ALBERT

Description: We review developments in radiocarbon measuring techniques from the Libby counter through proportional gas counters and liquid scintillation spectrometers to the more recent developments of accelerator mass spectrometry (AMS), followed by a coupling of gas chromatography with AMS for compound-specific 14C analyses. While during the first 60 yr of 14C measurements beta counting, specifically gas counting, was the dominant technique, in the future of 14C science AMS will be the dominant technology.

Description: How do multilateral institutions influence the strategic choices and actions of international managers? This paper addresses the question by exploring the impact of the World Trade Organization's (WTO) decision-making process on multinational enterprises (MNEs). We discuss the three phases of the WTO decision-making lifecycle - the formulation of trade rules, the implementation of those rules, and the enforcement of the rules – and propose a strategic adjustment framework for understanding how companies alter their strategies and structures in response to the WTO's rules and operations. We argue that the increased relevance of multilateral rules and enforcement mechanisms – embodied in the WTO - is an important influence on MNE strategies and structures because of the increasing embeddedness of the WTO in national levels of regulation. We illustrate this through examples taken from the pharmaceutical, textiles and sugar industries sectors that have witnessed substantial multilateral regulation.

Description: Although the global economy has flourished in the current global economic governance regime, the foundations of this order are starting to crumble. Both in trade and in finance, the existing institutions are under severe stress. In trade, more and more countries undermine the WTO by implementing preferential trade agreements. In finance, the IMF has been weak for most of this decade, although it experienced a revival in the current crisis. First and foremost, this weakness of the institutions of global economic governance is the result of policies implemented by the transatlantic powers. Both the European Union and the United States are actively pursuing policies that weaken the existing institutions. In trade, there is a large gap between the official rhetoric, which highlights the importance of the multilateral regime, and the trade policy practice, which is weakening the WTO. In finance, the transatlantic powers have until very recently blocked any progress in the IMF with regard to lending policies. In addition, the EU continues to defend its unjustified overrepresentation in the IMF's governance structures. The article suggests that one of the key explanations for this development is the weak support for globalization in most OECD-countries. Confronted with no enthusiasm for globalization in their domestic constituencies, policy makers in Europe and the United States are increasingly opting for policies that will, over time, erode the existing regimes of global economic governance.

Description: This essay explores the relationship between commerce and culture in the context of the recent debate over the social effect of Wal-Mart. In spite of much public debate, little is known about how Wal-Mart affects values. Using data collected from multiple sources, we show there is little evidence that Wal-Mart makes communities more conservative or more progressive.

Description: Seeking to build on related successes in other information technology sectors, the government of India has signaled its intent to transform the country's performance in microelectronics. Facing a young and expanding population, India needs to create manufacturing jobs in promising industries, and it needs to build out from its limited high-technology base. Semiconductors are foundational in this regard. Today, there is much discussion within India about the link between semiconductors and innovation in bio-electronics, alternative energy production and storage, and various micro- and nano-devices. The government's contemporary attempt to promote the building of infrastructure for manufacturing and applied research in semiconductors highlights reasons for hope. So too does the remarkable talent now available in the Indian diaspora. But significant impediments, especially in postsecondary and graduate-level education, must still be overcome if the necessary human capital is to be developed, equipped, and deployed effectively.

Description: The U.S. is no longer providing leadership in trade policy. In recent years, we have seen a sharp turn toward a rapid proliferation of bilateral preferential trade agreements, accords that are likely to undermine the World Trade Organization (WTO). By pursuing a strategy of ‘competitive liberalization’ both on a sectoral basis under the Bill Clinton administration, and then a policy of seeking bilateral arrangements under the George W. Bush administration, this article argues that American administrations have undermined the coalition for free trade in the United States. Consequently, protectionist industries including textiles, steel, and agriculture have made further liberalization more difficult and thus the prospects for promoting continued trade liberalization have grown dimmer.

Description: How and to what effect do firms coordinate their actions to deal with the negative external effects of productive activity? Under which conditions do associations engage in self-regulation and how do they tackle the specific regulatory challenges at stake? When developing hypotheses, we first vary attributes of the information environment in which private actors interact; and, secondly, actors' preferences as a function of the problem type at hand. With respect to the environmental conditions, our findings show that a regulatory threat matters when developing associative action, whilst the evidence is less clear as regards NGO campaigns. In terms of the problem type, we find that redistributive issues and prisoner's dilemma situations are much more conflict prone than coordination/win-win type of problems. Industry actors recur to various governance devices such as flexible contract design and compensation mechanisms to solve redistributive problems. Prisoner's dilemma (PD) problems may only partially be addressed by governance devices to the extent that free-riding is controlled and sanctioned within an association. We conclude that private actors engaging in self-regulation will not successfully manage all types of conflicts. They lack powerful sanctioning tools to deal with PD situations, but prove to be able to flexibly handle redistributive problems.

Description: For many, transnational capital is one of the most important driving forces of economic globalization; yet, we know little about what determines cross-border portfolio investments. In addition to recent economic literature's focus on information asymmetries as one key determinant of cross-border investment, this study brings in a political aspect to the field of international trade in assets. The –race to the bottom’ thesis connects domestic economic policies to investment decisions and argues that capital is more likely to move towards economies characterized by economic liberalism; political institutions are also relevant for portfolio investments, because democratic institutions often provide more credible protection against predatory practices. In this study, I model bilateral portfolio investments as a function of economic policies, political institutions, and levels of transparency of sending and receiving countries as well as important international connections. Empirical findings indicate the importance of transparency to attract portfolio investments. Moreover, transnational portfolio investments are only sensitive to some fiscal policy indictors and only within the OECD countries. Therefore, for non-OECD countries, there is still ‘room to move’ in maneuvering different aspects of fiscal policies. Finally, I find that investors care about the nature of political institutions as democratic institutions tend to be associated with higher levels of portfolio investment inflows. This is good news for developing countries that have undergone or are in the process of democratization. In addition to democratizing for peace, increased foreign capital further incentivizes a progression towards democratization.

Description: Is it possible to generate more efficient outcomes with respect to public procurement in general and defense acquisition in particular? Or are cost overruns inevitable when it comes to major engineering projects, like the development of modern weaponry? In this article, we draw on a unique data set of nearly 50 French armaments contracts in order to examine how one government has reformed its defense acquisition process over the past twenty years. Beginning in the early 1990s, France embarked on a series of policy reforms that enabled the state to contain skyrocketing weapons costs. We emphasize three, inter-related aspects of the defense acquisition environment in France that favored cost containment: first, hard budget constraints; second, the great technical capacity that the French government brought to bear on the weapons acquisition process, coupled with its iterative relationship with a small number of suppliers; and third, the use of contracting techniques that empowered project managers.

Description: Drawing upon a comprehensive database of contemporary protectionism, this paper offers an initial assessment of the extent to which our understanding of protectionism may have to evolve. While some long-standing features of protectionism appear to have endured (such as the distribution of discriminatory measures across economic sectors), specific corporate needs arising from the global financial crisis and particular national attributes are more likely to have influenced the choice of beggar-thy-neighbor policy instruments than binding trade rules and other international accords.

Description: American political campaigns have become a multi-billion dollar industry. Rather than assume that only political factors affect the campaigns that voters see, scholars must assess the importance of the business incentives associated with political consulting. Economic competition does not match political competition; firms compete for clients within the two major parties, against their political allies. I argue that the supply of firms in each party, the revenue models in the industry, the diversification of client types, and the cooperative structure in each party all may affect political campaigns. The way the industry operates and the different patterns of behavior within each party create incentives and practices that may alter campaigns in response to economic factors having little to do with optimal political strategy. Using two original surveys and a network analysis, I analyze how the industry is changing and how consultants in each party cooperate and compete.

Description: Why do many States in transitional economies lack the regulative capacities to evenly distribute property rights among emerging private firms resulting in having public good devoured by particularistic interests? I argue that uneven distribution of property rights is deeply embedded within broader power relations permeating political regimes. This study attempts to develop the concept of politically-embedded cronyism where State incumbents generate and protract uneven distribution of property rights in favor of a few private actors as tactics of regime survival that go beyond the mere interest of self-enrichment as the capture thesis would argue. Politically-embedded cronyism is likely to emerge the more State incumbents retain their relative autonomy from their cronies through higher concentration of power in the executive, less role of societal groups in general and business in particular in the reproduction of the power of top incumbents and higher public asset retention in the post-liberalization period in addition to possessing channels of political incorporation to fledging business.

Description: When comparing dendrodates and radiocarbon dates, I advocate using the mean value for archaeologically defined data series, as in the usual case, the correct dating is always more precise than the calibrated areas. However, in the extreme gradient of the calibration curve, we must consider the errors. Based on the Corded Ware from the Tauber basin, I put forward a first example in which a contradiction between the archaeological and 14C dating occurs. If one cleanly separates the older measurements from Köln and the younger ones from Heidelberg, the contradiction towards the archaeological dating is canceled out when only the younger Heidelberg dates are taken into account. Regarding the Early Bronze Age, I shall first deal with the cemetery at Singen and will show, using the typology and the horizontal distribution of the graves, how outliers can be identified, thus narrowing the range for dating of the cemetery. The comparison of 2 archaeologically contemporaneous cemeteries in the Neckar basin (Rottenburg and Gäufelden) again results in contradictions between the archaeological and 14C dating. In this case, the contradictions cannot be solved without any new dating measurements. It is recommended that these should be carried out by at least 2 laboratories. Finally, some recommendations are given to archaeologists. In my opinion, 14C dates that are archaeologically unsuitable should be used to check the findings and the archaeological-typological classification. The contradictions should be reported immediately to the 14C laboratory, so that any possible experimental errors can be identified.

Description: In September 2005, an accelerator mass spectrometry (AMS) system based on a 1MV Tandetron accelerator arrived at the Centro Nacional de Aceleradores (CNA). One of the main research programs for this AMS facility is based on radiocarbon. At the same time as the AMS facility was installed and tested, the 14C sample preparation laboratory was designed and set up. A graphitization line that allows the preparation of 5 samples in parallel was designed and built in October 2006. The first months were mainly dedicated to check and optimize all the sample processing. For such a task, several reference samples have been prepared and measured. Since the beginning of 2007, the laboratory has been fully operational and is currently performing as a service for the scientific community. During 2007, nearly 100 unknown samples were prepared and measured in our AMS system. Most of them were for dating purposes, but also other applications were investigated. The performance of the 14C laboratory and dating service will be shown, with some examples as illustration.

Description: The iron dating project Aikarauta has been launched in Finland. This paper presents the results of the preliminary investigations. The ability for radiocarbon measurement by accelerator mass spectrometry (AMS) of iron in Finland has been demonstrated by using coal-produced iron as reference material. An elemental analyzer has been harnessed to measure the carbon content of small iron samples. In addition, we have hypothesized that a fingerprint of the limestone usage in the smelting process is the high Ca content of iron and slag. This has been examined by performing an iron smelting experiment with limestone as flux, by making elemental analyses of ingredients and the resulting slag and iron, and by a 14C analysis of the produced iron. It is possible that limestone dilutes the 14C contents of the produced iron, making its age determination challenging.

Description: Archaeological excavations performed for many years in Łekno, central Poland, have exposed relicts of wooden fortified settlements, and in its enclosure also basements of stone buildings, consisting of Romanesque rotunda and a Cistercian monastery, including an oratory, church, and abbot's house. Earlier archaeological, structural, and stratigraphical studies have shown that these buildings were constructed in a sequence and represented several phases of development.In this paper, we present results of radiocarbon dating of stone buildings of the rotunda and the monastery. For 14C dating, we used tiny pieces of charcoal retrieved from calcareous and gypsum mortar binding stone elements from the buildings. These pieces were incorporated in mortar during the firing process, where the fuel used for firing was wood. Most of the obtained 14C dates formed clear groups, confirming that individual buildings were constructed in separate periods. Calibrated 14C dates of these phases agree well with the constraints provided by historical sources, and enable us to set their ages with accuracy better than previously available. In particular, we have learned that the oldest rotunda was built at the boundary of the 10/11th centuries, and the church and the abbot's house, before AD 1250. However, some samples gave much too old 14C ages, clearly reflecting the use of old wood for firing. These problems were revealed only for samples from the rotunda and for the gypsum stone ornamental details.

Description: Understanding of processes that determined the expansion of farming and animal husbandry in south-western Europe is hampered by poor chronologies of the early Neolithic in this region. This paper presents new radiocarbon dates, which are used to construct such a chronological frame for a regional group of the most important culture of the early Neolithic in the western Mediterranean: the Cardial culture.

Description: The field of dendrochronology had a developmental “head start” of at least several decades relative to the inception of radiocarbon dating in the late 1940s, but that evolution was sufficiently advanced so that unique capabilities of tree-ring science could assure success of the 14C enterprise. The Laboratory of Tree-Ring Research (LTRR) at the University of Arizona played a central role in the cross-pollination of these disciplines by providing the first wood samples of exactly known age for the early testing and establishment of the “Curve of Knowns” by Willard Libby. From the 1950s into the early 1980s, LTRR continued to contribute dated wood samples (bristlecone pine and other wood species) to 14C research and development, including the discovery and characterization of de Vries/Suess “wiggles,” calibration of the 14C timescale, and a variety of tests to understand the natural variability of 14C and to refine sample treatment for maximum accuracy. The long and varied relationship of LTRR with 14C initiatives has continued with LTRR contributions to high-resolution studies through the 1990s and systematic efforts now underway that may eventually extend the bristlecone pine chronology back beyond its beginning 8836 yr ago as of 2009. This relationship has been mutualistic such that a half-century ago the visibility and stature of LTRR and dendrochronology were also elevated through their association with 14C-allied “hard sciences.”

Description: Newly available radiocarbon dates show the early signs of pottery-making in the North Caspian area, the Middle-Lower Volga, and the Lower Don at 8–7 kyr cal BC. Stable settlements, as indicated by “coeval subsamples,” are recognized in the Middle-Lower Volga (Yelshanian) at 6.8 kyr cal BC and the Caspian Lowland at about 6 kyr cal BC. The ages of the Strumel-Gostyatin, Surskian, and Bug-Dniesterian sites are in the range of 6.6–4.5 kyr BC, overlapping with early farming entities (Starčevo-Körös-Criş and Linear Pottery), whose influence is perceptible in archaeological materials. Likewise, the 14C-dated pollen data show that the spread of early pottery-making coincided with increased precipitation throughout the forest-steppe area.

Description: The direct measurement of organic matter included in archaeological pottery may yield a reliable assessment of age. The main problem consists in the identification of possible origins and assessment of distortion for the age of organic inclusions. Our experiments show that shells included in pottery fabrics are strongly influenced by the reservoir effect, which may reach 500 yr or more. Other organic inclusions, such as lake ooze, do not visibly distort the age. The obtained series of radiocarbon dates have been used for the assessing the age of the early stages of pottery manufacture in southern Russia.

Description: The subject of this article is the radiocarbon dating on bones in the western European Neolithic. By gathering 14C dates for 2 examples, one chosen in the middle Neolithic of the Rhine region and the other in the end of the early Neolithic in the same region and in the Paris Basin, a significant gap appears between the sum probabilities of dates on charcoals and the ones obtained with bones. A comparison between these results with the few available dendrochronological dates shows that dates on bones seem too young, while the sequence based on charcoals fits. The existence of too-young 14C dates of bones is not new: this phenomenon was already indicated in previous studies. Most explanations agree that there was a source of contamination, during the sample's burial or its treatment in laboratory. These examples illustrate that consequences can be heavy on a chronology built, partly or entirely, on 14C dates of bones.

Description: In the Monastery of Our Saviour and St. Andronicus in Moscow, skeletal remains of clerics and of (possibly) famous icon painters were discovered. The bones were radiocarbon dated, and concentrations of trace elements in bone tissues were measured. From tombs 1–4, the 14C dates obtained from human bones (likely monks) and from associated wood date to the 14th–15th centuries AD, as expected. Trace element concentrations indicate signs of fasting. Tomb 5 contained 2 burials; these could belong to the famous icon painters Rublev and Chernyi. Indeed, the bones show high concentrations of lead, zinc, and copper, which is typical for remains of artists and metallurgists. The 14C dates of the 2 skeletons, however, differ by 200 yr, and seem to be too old for Rublev and Chernyi. At this stage, it is not clear if the burials can be assigned to these painters.

Description: An attempt was made to trace the antiquity of custard apple in India on the basis of accelerator mass spectrometry (AMS) and liquid scintillation counting (LSC) radiocarbon dates. Recently, seed remains of custard apple (Annona squamosa L.) in association with wood charcoals were encountered from the Neolithic archaeological site of Tokwa at the confluence of the Belan and Adwa rivers, Mirzapur District, in the Vidhyan Plateau region of north-central India. The wood charcoal sample was dated at the 14C laboratory of the Birbal Sahni Institute of Palaeobotany (BSIP), Lucknow, by conventional LSC 14C dating. The sample dated to 1740 cal BC (BS-2054). A seed sample of custard apple was dated by AMS at the Institute of Physics 14C laboratory, Bhubaneswar, India (3MV tandem Pelletron accelerator). Interestingly, the AMS date was given as 1520 cal BC (IOPAMS-10), showing a reasonable agreement with the LSC date carried out at BSIP. On botanical grounds, the custard apple is native to South America and the West Indies and was supposed to have been introduced in India by the Portuguese in the 16th century. The present 14C dates of the samples pushes back the antiquity of custard apple on Indian soil to the 2nd millennium BC, favoring a group of specialists proposing diverse arguments for Asian-American transoceanic contacts before the discovery of America by Columbus in AD 1492.

Description: Exploratory work was performed to investigate the feasibility of using a simplified radiometric analytical approach for determining the bioethanol content of US automotive fuels. The method involves mixing fuel samples directly with a suitable fluor. Sample preparation is extremely rapid since all conventional sample preparation steps are essentially eliminated. Results are based on the background-corrected DPM values obtained when using 10 mL of sample mixed with 10 mL of Permafluor E+. Results are also reported in terms of conventional pMC for some of the samples. Bioethanol from a dry-mill ethanol plant served as the analytical reference sample that represented a 100% bioethanol content. Using current-day bioethanol as a reference sample eliminates the need to correct for “bomb carbon.” For 1:1 mixtures of sample and fluor, the background-corrected DPM showed a linear relationship with the bioethanol concentration, indicating that the quench correction approach was effective for the variable-quench samples. Based on the analysis of E0 (pure gasoline), E10, and “E85” from local gas stations, it appears that the method has good potential for determining the bioethanol content in commercial ethanol/gasoline blends. However, a variety of potential sources of error still require investigation in order to refine the method.

Description: Santa Lucía is a pottery production site dating to the Formative period (about 1600 BC to AD 200). It is located in the Cochabamba valleys of the eastern Bolivian Andes. The settlement consists of a residential area and a separate workshop area. A peripheral sector of ash mounds was used as refuse sites and burial grounds. The excavations yielded a total of 16 radiocarbon samples from all 3 sectors, which were dated at the Gliwice Radiocarbon Laboratory (Gliwice, Poland). The results from the deepest trench in the workshop sector (Trench 5) provide information for the stratigraphic sequence and help to define spatial and socioeconomic changes at around 600–500 BC with the beginning of the Late Formative or Santa Lucía III phase. The 14C dates from Santa Lucía, therefore, contribute to a better definition of the existing regional Formative period phases and finally to a better understanding of the processes during the Formative period in the south-central Andes.

Description: Complex interdisciplinary studies carried out in the territory of the Vilnius Lower Castle, E Lithuania, were used to construct a chronological framework based on radiocarbon data and archaeological information. Bulk samples (wood and sediment) were collected from an approximately 3-m core that crossed cultural layers and underlying strata. 14C dates indicate that the underlying bed possibly formed during the 6th century AD, although no archaeological finds were discovered there. Paleobotanical (pollen and plant macrofossil) investigations reveal evidence of agriculture that points to the existence of a permanent settlement in the area at that time. The chronological data indicates a sedimentation hiatus before the onset of the deposition of the cultural layer in the studied area. The 14C dates showed that the formation of the cultural bed began during the late 13th–early 14th centuries AD, that is, earlier than expected according to the archaeological record. The ongoing deposition of the cultural beds continued throughout the middle to latter half of the 14th century AD as revealed by the archaeological records and confirmed by well-correlated 14C results. After some decline in human activity in the middle of the 14th century AD, a subsequent ongoing development of the open landscape, along with intensive agriculture, points to an increase in human activity during the second half of the 14th century AD. The first half of the 15th century AD was marked by intensive exploitation of the territory, indicating a period of economic and cultural prosperity. The chronological framework indicates that the investigated cultural beds continued forming until the first half of the 16th century AD.

Description: The archaeological site of Populonia-Baratti, in the southern part of Tuscany (Italy), was one of the most important centers in ancient Etruria, as seen in the evidence of metallurgical activities carried out at that time. During recent archaeological excavations (2005) in the ancient industrial area of Populonia, along the Baratti beach, 2 interesting tombs were found. The 2 graves were unusually located in an area dedicated to metallurgical activity and showed a particular structure of the burial chambers and an extreme richness in the grave goods. The unique character of the 2 tombs prompted many questions: who were these 2 individuals (a woman wearing many jewels and a tall, vigorous man) and when did they die? In order to obtain useful information about the chronology of the 2 tombs, accelerator mass spectrometry (AMS) radiocarbon analyses were performed on samples taken from the ribs of the 2 skeletons. Measured 14C ages were converted to calibrated ages using additional information derived from stable isotope ratios measured in the extracted collagen. Actually, the 13C data provided useful hints about the diet of the 2 individuals, thus allowing us to estimate the percentage of marine food consumed (about 30%) and exploit a combined marine-terrestrial calibration curve. As a result, the age of the 2 individuals can be dated to the 2nd century AD, during Roman times, which is in good agreement with the information obtained from archaeological, anthropological, and stylistic studies of the 2 tombs.

Description: The results of a tentative oak tree-ring chronology built from charcoal samples found in Late Bronze to early Iron Age contexts (late 2nd millennium to early 1st millennium BCE) at the site of Tille Höyük in southeast Turkey, and its placement in time, was published in 1993 (Summers 1993). This represented one of the few publications about archaeological dendrochronology for this period and region. However, the dendrochronological sequence and its crossdating have been questioned, including in this journal (Keenan 2002). Here, we critically reassess and revise the dendrochronological positioning of the site's building phases and their place in time by absolutely dating 7 decadal tree-ring sequences via radiocarbon wiggle-matching.

Description: The inception of the radiocarbon dating method in 1949 was immediately supported by many archaeologists. In the following 2 decades, many important archaeological sites in the Old World were dated, marking the beginning of building a reliable chronological framework for prehistoric and early historic cultural complexes worldwide. The author presents an observation of some of the most important results in establishing a chronology for Old World archaeology, based on 14C dating performed in the last 50 yr. An extensive bibliography should help scholars to get acquainted with early summaries on archaeological chronologies based on 14C data and their evaluation, as well as with some recent examples of the application of 14C dating in Old World archaeology.

Description: Mortar as a mixture of binder and aggregate can be reliably dated with radiocarbon if the applied preparation method allows one to eliminate unburnt carbonate fragments, bearing 14C-depleted carbon and causing overestimation of 14C age. To avoid these problems, separation of specific grain-size fractions of mortar and 14C analysis of the CO2 portions collected in different time intervals of the acid-leaching reaction is usually helpful. In the present paper, we demonstrate that the rate of the leaching reaction of mortars with dense carbonate aggregate differs from that of mortars with crumbled limestone and scattered shells (e.g. of foraminifera). Verification of the obtained 14C dates against historical sources shows that for mortars rich in foraminiferous limestone, a reaction rate-based chemical elimination of “dead carbon” may appear impossible.

Description: Preparation of bone material for radiocarbon dating is still a subject of investigation. In the past, the most problematic ages appeared to be the very old bones, i.e. those with ages close to the limit of the dating method. Development of preparative methods requires sufficient amounts of bone material as well as the possibility of verification of the ages. In the peat section at Niederweningen, ZH Switzerland, numerous bones of mammoth and other animals were found in the late 19th century. The first accelerator mass spectrometry (AMS) radiocarbon ages of those bones from 1890/1891 excavations placed the age between 33,000 and 35,000 BP. The excavations in 2003/2004 provided additional material for 14C dating. An age of 45,870 ± 1080 BP was obtained on base (NaOH step) cleaned gelatin from mammoth bone, which was very close to the age of 45,430 ± 1020 BP obtained for the peat layer that buried the mammoths. The 14C age of gelatin cleaned using the ultrafiltration method obtained in this study, 45,720 ± 710 BP, is in a very good agreement with the previously obtained results. Moreover, the study shows that 3 pretreatment methods (base+Longin, Longin+ultrafiltration, and base+Longin+ultrafiltration) give ages consistent with each other and with the age of the peat section.

Description: Radiocarbon measurements of hermatypic corals from 4 sites in the Gulf of Mexico (GOM) and Caribbean Sea were made to estimate the marine 14C reservoir age (R) and the marine regional correction (ΔR) for this region. Coral skeletal material from the Flower Garden Banks (northern GOM continental shelf), Veracruz, Mexico, and 2 reefs from the Cariaco Basin, Venezuela, were analyzed. Annual and subannual samples from 1945–1955 were milled and 14C composition was determined. In the Gulf of Mexico, average coral Δ14C is −52.6 ± 0.7‰ and average Δ14C for the Cariaco Basin corals is −53.4 ± 0.8‰. Average values for the marine reservoir age and ΔR are computed with this data and compared with results derived from previous measurements made in the same regions. These values are important in calibrating the 14C ages of carbonate samples from the area.

Description: This article reports on 10 new accelerator mass spectrometry (AMS) radiocarbon dates from early phases of the Early Bronze Age at the long-lived settlement of Pella (modern Tabaqat Fahl) in the north Jordan Valley. The new AMS dates fall between 3400 and 2800 cal BC, and support a recent suggestion that all Chalcolithic period occupation had ceased by 3800/3700 cal BC at the latest (Bourke et al. 2004b). Other recently published Early Bronze Age14C data strongly supports this revisionist scenario, suggesting that the earliest phase of the Early Bronze Age (EBA I) occupied much of the 4th millennium cal BC (3800/3700 to 3100/3000 cal BC). As this EB I period in the Jordan Valley is generally viewed as the key precursor phase in the development of urbanism (Joffe 1993), this revisionist chronology has potentially radical significance for understanding both the nature and speed of the move from village settlement towards a complex urban lifeway.

Description: With the introduction of the radiocarbon method in 1949 and the calibration curve constantly improving since 1965, but especially due to the development of the more accurate accelerator mass spectrometry (AMS) dating some 30 yr ago, the application of the 14C method in prehistory revolutionized traditional chronological frameworks. Theories and models are adjusted to new 14C sequences, and such sequences even lead to the creation of new theories and models. In our contribution, we refer to 2 major issues that are still heavily debated, although their first absolute dating occurred some decades ago: 1) the transition from the Mesolithic to the Early Neolithic in the eastern and western Aegean. Very high 14C data for the beginning of the Neolithic in Greece around 7000 BC fueled debates around the Preceramic period in Thessaly (Argissa-Magoula, Sesklo) and the Early Neolithic in Macedonia (Nea Nikomedeia). A reinterpretation of these data shows that the Neolithic in Greece did not start prior to 6400/6300 BC; 2) the beginning and the end of the Chalcolithic period in SE Europe. Shifting from relative chronologies dating the Chalcolithic to the 3rd millennium BC to an absolute chronology assigning the Kodžadermen-Gumelniţa-Karanovo VI cultural complex to the 5th millennium BC, the exact beginning and the end of the period are still under research. New data from Varna (Bulgaria) and Pietrele (Romania) suggest that start and end of the SE European Chalcolithic have to be dated deeper into the 5th millennium BC.

Description: The present research is focused on the dating of the Oglakhty burial ground, the key site of stage I of the Tashtyk culture. Despite the numerous well-preserved burials of that type investigated at the Oglakhty complexes, their chronological position has remained unclear. From the early 20th century until the present, 2 different time periods had been identified for the Tashtyk burials: (1) from the 1st century BC until the 1st century AD and (2) from the 1st until the 2nd century AD. New data obtained in the 1990s suggested a different age for Tashtyk burials, namely the 3rd–4th centuries AD. This considerable shift in chronology needed to be checked with independent data. The chronological position of one of the Oglakhty burials, tomb 4, has been investigated with the use of wiggle-matching, applied to wooden logs used in the construction of tomb 4. The resulting dates for this burial strongly suggest its age as being limited to the 3rd–4th centuries AD, which is corroborated by the archaeological dates of the imported artifacts found in the grave and which is in agreement with the chronological position of the Oglakhty site, as proposed by previous investigations.

Description: Over the last 30 yr, there has been an ongoing debate on the dates and modes of the earliest colonization of East Polynesia, namely the Cook Islands, the 5 archipelagos of French Polynesia, the Hawai'i Islands, Easter Island, and New Zealand. At least 3 alternative models were proposed by Sinoto, Anderson, Kirch, and Conte, but interestingly all these models basically relied on the same set of roughly 200 radiocarbon dates on various organic materials from archaeological excavations as far back as the 1950s. Some of the models differed by 500–1000 yr—for a proposed initial colonization around the turn of the BC/AD eras, if not considerably later. By comparing the different approaches to this chronological issue, it becomes evident that almost all known problems in dealing with 14C dates from archaeological excavations are involved: stratigraphy and exact location of samples, sample material and quality, inbuilt ages and reservoir effects, lab errors in ancient dates, etc. More recently, research into landscape and vegetation history has produced alternative 14C dating for early human impact, adding to the confusion about the initial stages of island colonization, while archaeological 14C dates, becoming increasingly “young” as compared to former investigations, now advocate a rapid and late (post-AD 900) colonization of the archipelagos. As it appears, the Polynesian case is more than just another case study, it's a lesson on 14C-based archaeological chronology. The present paper does not pretend to solve the problems of early Polynesian colonization, but intends to contribute to the debate on how 14C specialists and archaeologists might cooperate in the future.

Description: Recent investigations devoted to the Eurasian loess formations have provided an integrated high-resolution climatic sequence well radiocarbon dated between 13.4 and 42.5 kyr BP on charcoal and wood remains. Here, we show that the reproducible climatic signature of this loess sequence can be compared by proxy-correlation with the Greenland ice climatic signals, taking into account the distribution of the aeolian components in both records. This correlation allows situating with precision the series of 14C dates obtained from loess with regard to the Greenland climatic sequence. In this way, comparing the atmospheric loess-derived 14C chronology with the chronologies of the marine sequences becomes possible.

Description: There are 2 fundamental assumptions in radiocarbon dating, which were known early in the method development to be approximations, and which lead directly to the need to calibrate 14C dates: 1.The rate of formation of 14C in the upper atmosphere has been constant over the entire applied 14C dating timescale (approximately the last 65,000 yr).2.The 14C activity of the atmosphere has been in equilibrium with the biosphere and ocean over the applied timescale.

Description: Human bones from 3 Mesolithic sites in the Upper Volga basin were analyzed for trace elements, and dated by accelerator mass spectrometry (AMS). The radiocarbon dates of the bones correspond to the Mesolithic era. However, some dates differ from those obtained for the enclosing deposits and for the worked wood fragments in the cultural layer. The elemental composition of the bones is interpreted in terms of increased concentrations of some elements and their impact on human health and behavior.

Description: Glacier fluctuations and paleoclimatic oscillations during the Late Quaternary in Val di Rabbi (Trentino, northern Italy) were reconstructed using a combination of absolute dating techniques (14C and 10Be) and soil chemical characterization. Extraction and dating of the stable fraction of soil organic matter (SOM) gave valuable information about the minimum age of soil formation and contributed to the deciphering of geomorphic surface dynamics. The comparison of 10Be surface exposure dating (SED) of rock surfaces with the 14C ages of resilient (resistant to H2O2 oxidation) soil organic matter gave a fairly good agreement, but with some questionable aspects. It is concluded that, applied with adequate carefulness, dating of SOM with 14C might be a useful tool in reconstructing landscape history in high Alpine areas with siliceous parent material. The combination of 14C dating of SOM with SED with cosmogenic 10Be (on moraines and erratic boulders) indicated that deglaciation processes in Val di Rabbi were already ongoing by around 14,000 cal BP at an altitude of 2300 m asl and that glacier oscillations might have affected the higher part of the region until about 9000 cal BP. 10Be and 14C ages correlate well with the altitude of the sampling sites and with the established Lateglacial chronology.

Description: Ultrafiltration of bone collagen, dissolved as gelatin (M ~100,000 D), has received considerable attention as a means to remove small contaminants and thus produce more reliable dates (Brown et al. 1988; Bronk Ramsey et al. 2004; Higham et al. 2006; Mellars 2006). However, comparative dating studies have raised the question whether this cleaning step itself may introduce contamination with carbon from the filters used (Bronk Ramsey et al. 2004; Brock et al. 2007; Hüls et al. 2007).Here, we present results of further ultrafiltration experiments with modern and fossil collagen samples using Vivaspin 20™ and Vivaspin 15R™ ultrafilters. Evidently, the Vivaspin 20 (VS 20) ultrafilter with a polyethersulfone (PES) membrane retains more material in the 〉30 kD fraction than the Vivaspin 15R (VS 15R) filter with a regenerated cellulose membrane (Hydrosat), which may be related to increased retention of proteins due to suboptimal electrostatic conditions during ultrafiltration with the PES membrane. In addition, this filter type shows clear evidence for contamination with fossil carbon, presumably from membrane fibers, in the

Description: A celebration is in order: the journal Radiocarbon is now a mature 50 years without drastic changes in its identity. There have been, of course, additions in terms of specific isotopes (it is now an international journal of cosmogenic isotope research), but the 14C content is still very extensive. The triannual offshoots, conference proceedings (started in 1980), and calibration issues (the first in 1986) testify to the strength of the 14C component.

Description: While kept at the Rockefeller Museum in East Jerusalem, many Dead Sea Scroll fragments were exposed to castor oil by the original team of editors in the course of cleaning the parchments. Castor oil must be regarded as a serious contaminant in relation to radiocarbon dating. If modern castor oil is present and is not removed prior to dating, the 14C dates will be skewed artificially towards modern values. In Rasmussen et al. (2001), it was shown that the standard AAA pretreatment procedure used in the 2 previous studies dating Dead Sea Scroll samples (Bonani et al. 1992; Jull et al. 1995) is not capable of removing castor oil from parchment samples. In the present work, we show that it is unlikely that castor oil reacts with the amino acids of the parchment proteins, a finding which leaves open the possibility of devising a cleaning method that can effectively remove castor oil. We then present 3 different pretreatment protocols designed to effectively remove castor oil from parchment samples. These involve 3 different cleaning techniques: extraction with supercritical CO2, ultrasound cleaning, and Soxhlet extraction—each with their own advantages and disadvantages. Our data show that the protocol involving Soxhlet extraction is the best suited for the purpose of decontaminating the Dead Sea Scrolls, and we recommend that this protocol be used in further attempts to 14C date the Dead Sea Scrolls. If such an attempt is decided on by the proper authorities, we propose a list of Scroll texts, which we suggest be redated in order to validate the 14C dates done earlier by Bonani et al. (1992) and Jull et al. (1995).

Description: The 5th International Radiocarbon and Archaeology Symposium was held at the ETH Zurich between March 26th and 28th, 2008. A total of 164 participants (including 47 students) from 28 countries attended the symposium. We had presentations of 13 invited speakers who opened 6 thematic/topic sessions that included 31 oral presentations and 49 posters.

Description: The most extensive chronometric study ever undertaken on Egyptian Dynastic sites was published in Radiocarbon by Bonani et al. (2001). It comprised 269 radiocarbon measurements on monuments ranging from the 1st–12th dynasties. However, many of the calibrated dates obtained were significantly offset from historical estimates. The greatest discrepancies occurred in the 4th Dynasty where, paradoxically, the dating program had been most rigorous. For this period, 158 measurements were made at 12 sites, with the majority of the dates being 200–300 yr older than expected. The 4th Dynasty results were especially significant as they included some of the most important monuments in Egypt. In this paper, the raw data from that study have been reanalyzed using the OxCal calibration program, making particular use of its new outlier detection functionality. This Bayesian approach has resulted in a new series of calibrations that show much closer agreement with conventional chronological records.

Description: Since the publication of the first article (Lanting and van der Plicht 2001/2002) about the possibilities of dating cremated bones, the number of dated cremation remains has grown exponentially. The success of this dating technique lies in the fact that an absolute date now can be attributed to archaeological phenomena that previously were only datable indirectly. When archaeological artifacts where present, the cremation burials were dated based on the typology of ceramics and metals. An absolute date could be attributed if charcoal from the pyre were present. Unfortunately, these items were not omnipresent at the burial sites. Consequently, a complete site was dated by means of the few datable burials present. This implies that the internal chronology of the site could not be studied. Furthermore, the typochronology of the ceramics and the metals remains questionable. A series of dating projects on urnfield cemeteries in the Low Countries (northern France, Belgium, and the Netherlands) have shown that the classical chronology of these sites must be revised.

Description: Until the 1990's, Switzerland could be classified as either a corporatist, cooperative or coordinated market economy where non-market mechanisms of coordination among economic and political actors were very important. In this respect, Business Interest Associations (BIAs) played a key role. The aim of this paper is to look at the historical evolution of the five main peak Swiss BIAs through network analysis for five assorted dates during the 20th century (1910, 1937, 1957, 1980 and 2000) while relying on a database that includes more than 12,000 people. First, we examine the logic of membership in these associations, which allows us to analyze their position and function within the network of the Swiss economic elite. Until the 1980's, BIAs took part in the emergence and consolidation of a closely meshed national network, which declined during the two last decades of the 20th century. Second, we investigate the logic of influence of these associations by looking at the links they maintained with the political and administrative worlds through their links to the political parties and Parliament, and to the administration via the extra-parliamentary commissions (corporatist bodies). In both cases, the recent dynamic of globalization called into question the traditional role of BIAs.

Description: With increasing fragmentation of worldwide production chains and the corresponding contracting relations between companies, the “firm as an inspector” has become a frequent phenomenon. Buyer firms deploy supervising activities over their suppliers' products and production processes in order to ensure their compliance with regulatory standards, thereby taking on tasks commonly performed by public authorities. Why would a firm engage in such activities? In this article we will analyze the conditions under which firms play the role of an inspector vis-à-vis their sub-contractor firms to guarantee compliance with quality and environmental regulations. We develop a theoretical argument based on transaction cost economics and institutionalism to offer hypothetical answers to this question and provide an empirical assessment of our hypotheses.

Description: This paper broadens the scope and depth of business alliance research by way of interdisciplinary enrichment. The paper draws on the political science literature on nation-state alliances to generate insights into the establishment, operations and performance of inter-firm alliances. Shared theory bases of game theory and transaction cost economics, as well as theories, variables and research findings indigenous to political science are posited as a platform from which propositions regarding inter-firm alliances are derived.

Description: This paper discusses the pros and cons of a Transatlantic Free Trade Area (TAFTA) in comparison with an informal trade-facilitating marketplace between Europe and the US. It finds considerably more cons, especially since TAFTA would be expected to produce larger, more detrimental discriminatory effects on dynamic non-member economies, mainly in Asia but also in food-exporting regions as well. Efficiency-enhancing effects are argued to be achievable under a marketplace concept which does not separate insiders from outsiders. It is also shown that in foreign direct investment (FDI) and FDI-related service trade, TAFTA seems redundant as in recent years bilateral capital and trade flows have proven to be buoyant without preferential treatment.

Description: Over the last 60 years, the multilateral management of trade through the GATT and subsequently through the WTO has been led by the United States and Europe. Since the turn of the new millennium, however, developing countries have increasingly used their leverage to insist that talks on agriculture receive priority attention, deny the inclusion of investment and competition policy on the negotiating agenda, and block agreement on negotiating modalities for agriculture and non-agricultural market access (NAMA). Cooperation between the United States and the European Union is still essential, but no longer sufficient, for successful multilateral negotiations. Specifically, the “BRICKs” (Brazil, Russia, India, China, and Korea) are likely to be pivotal in directing the course and contributing to the success or failure of the WTO.

Description: Most of the existing studies of the welfare state have dealt with OECD countries. Moreover, these studies have focused on government partisanship (left versus right), or institutional features under democracy, as primary causal variables. By providing four primary causal mechanisms (the power of popularly based parties, labor strength, democracy, and political instability) that are different from those of OECD countries, I answer the question of whether and why the efficiency or compensation hypothesis holds for developing countries. I show that either the efficiency or compensation thesis can hold for developing countries depending on the type of globalization with which popularly based governments interact.

Description: In this study we advance the current research on corporate political strategy by examining how firms decide on their level of engagement in political action. This study proposes a contingency approach that identifies conditions in which firms prefer individual action to collective action in their pursuit of political strategy and introduces a framework that addresses this preference. Our results show that even in concentrated industries, a firm's preference of individual action over collective action varies when government contracts or research and development intensity are important considerations.

Description: Reform of the multilateral trade regime is not simply a second order problem within a wider economic crisis. The completion of the Doha Round may be a second order question but the global trade regime faces a series of broader systemic challenges beyond the completion of the current negotiations. This paper identifies five challenges: (i) a marked reduction in popular support for open markets in major OECD countries; (ii) the stalling of a transition from one global economic equilibrium to another; (iii) a lack of clarity and agreement on the agenda and objectives for the WTO as we move deeper into the 21st century; (iv) the demand for fairness and justice in the governance of the WTO'the ‘legitimacy’ question and (v) the rise of regional preferentialism as a challenge to multilateralism. Failure to address these challenges will represent not only a fundamental question for the future of the WTO as the guarantor of the norms and rules of the global trade regime specifically, but also the ability to establish greater coherence in global economic governance overall when its need is arguably greater than at any time since the depression years of the 20th century inter-war period.

Description: A global atmospheric model with roughly 50-km horizontal grid spacing is used to simulate the interannual variability of tropical cyclones using observed sea surface temperatures (SSTs) as the lower boundary condition. The model’s convective parameterization is based on a closure for shallow convection, with much of the deep convection allowed to occur on resolved scales. Four realizations of the period 1981–2005 are generated. The correlation of yearly Atlantic hurricane counts with observations is greater than 0.8 when the model is averaged over the four realizations, supporting the view that the random part of this annual Atlantic hurricane frequency (the part not predictable given the SSTs) is relatively small (

Description: Winter sea ice dramatically cools the Arctic climate during the coldest months of the year and may have remote effects on global climate as well. Accurate forecasting of winter sea ice has significant social and economic benefits. Such forecasting requires the identification and understanding of all of the feedbacks that can affect sea ice. A convective cloud feedback has recently been proposed in the context of explaining equable climates, for example, the climate of the Eocene, which might be important for determining future winter sea ice. In this feedback, CO2-initiated warming leads to sea ice reduction, which allows increased heat and moisture fluxes from the ocean surface, which in turn destabilizes the atmosphere and leads to atmospheric convection. This atmospheric convection produces optically thick convective clouds and increases high-altitude moisture levels, both of which trap outgoing longwave radiation and therefore result in further warming and sea ice loss. Here it is shown that this convective cloud feedback is active at high CO2 during polar night in the coupled ocean–sea ice–land–atmosphere global climate models used for the 1% yr−1 CO2 increase to the quadrupling (1120 ppm) scenario of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. At quadrupled CO2, model forecasts of maximum seasonal (March) sea ice volume are found to be correlated with polar winter cloud radiative forcing, which the convective cloud feedback increases. In contrast, sea ice volume is entirely uncorrelated with model global climate sensitivity. It is then shown that the convective cloud feedback plays an essential role in the elimination of March sea ice at quadrupled CO2 in NCAR’s Community Climate System Model (CCSM), one of the IPCC models that loses sea ice year-round at this CO2 concentration. A new method is developed to disable the convective cloud feedback in the Community Atmosphere Model (CAM), the atmospheric component of CCSM, and to show that March sea ice cannot be eliminated in CCSM at CO2 = 1120 ppm without the aide of the convective cloud feedback.

Description: Tide gauge data are used to estimate trends in global sea level for the period from 1955 to 2007. Linear trends over 15-yr segments are computed for each tide gauge record, averaged over latitude bands, and combined to form an area-weighted global mean trend. The uncertainty of the global trend is specified as a sampling error plus a random vertical land motion component, but land motion corrections do not change the results. The average global sea level trend for the time segments centered on 1962–90 is 1.5 ± 0.5 mm yr−1 (standard error), in agreement with previous estimates of late twentieth-century sea level rise. After 1990, the global trend increases to the most recent rate of 3.2 ± 0.4 mm yr−1, matching estimates obtained from satellite altimetry. The acceleration is distinct from decadal variations in global sea level that have been reported in previous studies. Increased rates in the tropical and southern oceans primarily account for the acceleration. The timing of the global acceleration corresponds to similar sea level trend changes associated with upper ocean heat content and ice melt.

Description: Extremes of precipitation are examined in a wide range of climates simulated with an idealized aquaplanet GCM. The high percentiles of daily precipitation increase as the climate warms. Their fractional rate of increase with global-mean surface temperature is generally similar to or greater than that of mean precipitation, but it is less than that of atmospheric (column) water vapor content. A simple scaling is introduced for precipitation extremes that accounts for their behavior by including the effects of changes in the moist-adiabatic lapse rate, the circulation strength, and the temperature when the extreme events occur. The effects of changes in the moist-adiabatic lapse rate and circulation strength on precipitation extremes are important globally, whereas the difference in the mean temperature and the temperature at which precipitation extremes occur is important only at middle to high latitudes.

Description: The too diverse representation of ENSO in a coupled GCM limits one’s ability to describe future change of its properties. Several studies pointed to the key role of atmosphere feedbacks in contributing to this diversity. These feedbacks are analyzed here in two simulations of a coupled GCM that differ only by the parameterization of deep atmospheric convection and the associated clouds. Using the Kerry–Emanuel (KE) scheme in the L’Institut Pierre-Simon Laplace Coupled Model, version 4 (IPSL CM4; KE simulation), ENSO has about the right amplitude, whereas it is almost suppressed when using the Tiedke (TI) scheme. Quantifying both the dynamical Bjerknes feedback and the heat flux feedback in KE, TI, and the corresponding Atmospheric Model Intercomparison Project (AMIP) atmosphere-only simulations, it is shown that the suppression of ENSO in TI is due to a doubling of the damping via heat flux feedback. Because the Bjerknes positive feedback is weak in both simulations, the KE simulation exhibits the right ENSO amplitude owing to an error compensation between a too weak heat flux feedback and a too weak Bjerknes feedback. In TI, the heat flux feedback strength is closer to estimates from observations and reanalysis, leading to ENSO suppression. The shortwave heat flux and, to a lesser extent, the latent heat flux feedbacks are the dominant contributors to the change between TI and KE. The shortwave heat flux feedback differences are traced back to a modified distribution of the large-scale regimes of deep convection (negative feedback) and subsidence (positive feedback) in the east Pacific. These are further associated with the model systematic errors. It is argued that a systematic and detailed evaluation of atmosphere feedbacks during ENSO is a necessary step to fully understand its simulation in coupled GCMs.

Description: The simulation of atmospheric–land–ocean CO2 exchange for the 1850–2000 period offers the possibility of testing and calibrating the carbon budget in earth system models by comparing the simulated changes in atmospheric CO2 concentration and in land and ocean uptake with observation-based information. In particular, some of the uncertainties associated with the treatment of land use change (LUC) and the role of down regulation in affecting the strength of CO2 fertilization for terrestrial photosynthesis are assessed using the Canadian Centre for Climate Modelling and Analysis Earth System Model (CanESM1). LUC emissions may be specified as an external source of CO2 or calculated interactively based on estimated changes in crop area. The evidence for photosynthetic down regulation is reviewed and an empirically based representation is implemented and tested in the model. Four fully coupled simulations are performed: with and without terrestrial photosynthesis down regulation and with interactively determined or specified LUC emissions. Simulations without terrestrial photosynthesis down regulation yield 15–20 ppm lower atmospheric CO2 by the end of the twentieth century, compared to observations, regardless of the LUC approach used because of higher carbon uptake by land. Implementation of down regulation brings simulated values of atmospheric CO2 and land and ocean carbon uptake closer to observation-based values. The use of specified LUC emissions yields a large source in the tropics during the 1981–2000 period, which is inconsistent with studies suggesting the tropics to be near-neutral or small carbon sinks. The annual cycle of simulated global averaged CO2, dominated by the Northern Hemisphere terrestrial photosynthesis and respiration cycles, is reasonably well reproduced, as is the latitudinal distribution of CO2 and the dependence of interhemispheric CO2 gradient on fossil fuel emissions. The empirical approach used here offers a reasonable method of implementing down regulation in coupled carbon–climate models in the absence of a more explicit biogeochemical representation.

Description: Composites based on observations and model outputs from the Climate Variability and Predictability (CLIVAR) drought experiments were used to examine the impact of El Niño–Southern Oscillation (ENSO) and the Atlantic multidecadal oscillation (AMO) on drought over the United States. Because drought implies persistent dryness, the 6-month standardized precipitation index, standardized runoff index, and soil moisture anomalies are used to represent drought. The experiments were performed by forcing an AGCM with prescribed sea surface temperature anomalies (SSTAs) superimposed on the monthly mean SST climatology. Four model outputs from the NCEP Global Forecast System (GFS), NASA’s Seasonal-to-Interannual Prediction Project, version 1 (NSIPP1), GFDL’s global atmospheric model, version 2.1 (AM2.1), and the Lamont-Doherty Earth Observatory (LDEO)/NCAR Community Climate System Model, version 3 (CCM3) were analyzed in this study. Each run lasts from 36 to 51 yr. The impact of ENSO on drought over the United States is concentrated over the Southwest, the Great Plains, and the lower Colorado River basin, with cold (warm) ENSO events favoring drought (wet spells). Over the East Coast and the Southeast, the impact of ENSO is small because the precipitation responses to ENSO are opposite in sign for winter and summer. For these areas, a prolonged ENSO does not always favor either drought or wet spells. The direct influence of the AMO on drought is small. The major influence of the AMO is to modulate the impact of ENSO on drought. The influence is large when the SSTAs in the tropical Pacific and in the North Atlantic are opposite in phase. A cold (warm) event in a positive (negative) AMO phase amplifies the impact of the cold (warm) ENSO on drought. The ENSO influence on drought is much weaker when the SSTAs in the tropical Pacific and in the North Atlantic are in phase.

Description: Global-mean surface temperature is affected by both natural variability and anthropogenic forcing. This study is concerned with identifying and removing from global-mean temperatures the signatures of natural climate variability over the period January 1900–March 2009. A series of simple, physically based methodologies are developed and applied to isolate the climate impacts of three known sources of natural variability: the El Niño–Southern Oscillation (ENSO), variations in the advection of marine air masses over the high-latitude continents during winter, and aerosols injected into the stratosphere by explosive volcanic eruptions. After the effects of ENSO and high-latitude temperature advection are removed from the global-mean temperature record, the signatures of volcanic eruptions and changes in instrumentation become more clearly apparent. After the volcanic eruptions are subsequently filtered from the record, the residual time series reveals a nearly monotonic global warming pattern since ∼1950. The results also reveal coupling between the land and ocean areas on the interannual time scale that transcends the effects of ENSO and volcanic eruptions. Globally averaged land and ocean temperatures are most strongly correlated when ocean leads land by ∼2–3 months. These coupled fluctuations exhibit a complicated spatial signature with largest-amplitude sea surface temperature perturbations over the Atlantic Ocean.

Description: Water vapor in the midtroposphere is an important element for the earth radiation budget. Despite its importance, the relative humidity in the free troposphere is not very well documented, mainly because of the difficulties associated with its measurements. A new long-term archive of free tropospheric humidity (FTH) derived from the water vapor channel of the Meteosat satellite from 1983 to 2005 is introduced. Special attention is dedicated to the long-term homogeneity and the definition of the retrieval layer. It is shown to complement the existing databases and is used to establish the climatology of FTH. Interannual variability is then evaluated for each season by using a normalized interannual standard deviation. This normalization approach reveals the importance of the relative variability of the dry areas to the moist regions. In consequence, emphasis is on the driest area of the region. Focusing on composites of the moist and dry seasons of the time series, the authors demonstrate that the 500-hPa relative humidity field, reconstructed using an idealized Lagrangian model, is a good proxy for the FTH variability there. The analysis of the origin of the air mass, using the back trajectory model, points out that lateral mixing between the deep tropics and extratropical latitudes takes place over this area, as advocated in previous theoretical studies. Systematic estimation of this large-scale mixing shows that, indeed, a significant part of the interannual variability of the free tropospheric humidity in this subtropical region stems from the amount of mixing of air originating from the deep tropics versus extratropical latitudes. The importance of this mechanism in the general understanding of the FTH distribution and variability is then discussed.

Description: The variability of the north Australian wet season is examined by performing cluster analysis on the wind and thermodynamic information contained in the 2300 UTC radiosonde data at Darwin for 49 wet seasons (September–April) from 1957/58 to 2005/06. Five objectively derived regimes of the wet season are obtained and are found to differ significantly in their synoptic environment, cloud patterns, and rainfall distributions. One regime is primarily associated with the trade wind regime. Two regimes are associated with the lead up to and break periods of the monsoon at Darwin. A fourth regime is clearly identified with the active monsoon at Darwin and is offered as a definition of monsoon onset. This regime captures the active monsoon environment associated with significant widespread rainfall. The fifth regime is a mixed regime, with some days associated with the inactive monsoon, a period of westerly zonal winds at Darwin associated with relatively suppressed convection compared with the active monsoon. Other days for this regime are break period conditions with a low-level westerly flow below 900 hPa.

Description: Sea fog is frequently observed over the Yellow Sea, with an average of 50 fog days on the Chinese coast during April–July. The Yellow Sea fog season is characterized by an abrupt onset in April in the southern coast of Shandong Peninsula and an abrupt, basin-wide termination in August. This study investigates the mechanisms for such steplike evolution that is inexplicable from the gradual change in solar radiation. From March to April over the northwestern Yellow Sea, a temperature inversion forms in a layer 100–350 m above the sea surface, and the prevailing surface winds switch from northwesterly to southerly, both changes that are favorable for advection fog. The land–sea contrast is the key to these changes. In April, the land warms up much faster than the ocean. The prevailing west-southwesterlies at 925 hPa advect warm continental air to form an inversion over the western Yellow Sea. The land–sea differential warming also leads to the formation of a shallow anticyclone over the cool Yellow and northern East China Seas in April. The southerlies on the west flank of this anticyclone advect warm and humid air from the south, causing the abrupt fog onset on the Chinese coast. The lack of such warm/moist advection on the east flank of the anticyclone leads to a gradual increase in fog occurrence on the Korean coast. The retreat of Yellow Sea fog is associated with a shift in the prevailing winds from southerly to easterly from July to August. The August wind shift over the Yellow Sea is part of a large-scale change in the East Asian–western Pacific monsoons, characterized by enhanced convection over the subtropical northwest Pacific and the resultant teleconnection into the midlatitudes, the latter known as the western Pacific–Japan pattern. Back trajectories for foggy and fog-free air masses support the results from the climatological analysis.

Description: The impact of explosive volcanic eruptions on the atmospheric circulation at high northern latitudes is assessed in two versions of the Met Office Hadley Centre’s atmospheric climate model. The standard version of the model extends to an altitude of around 40 km, while the extended version has enhanced stratospheric resolution and reaches 85-km altitude. Seasonal hindcasts initialized on 1 December produce a strengthening of the winter polar vortex and anomalous warming over northern Europe characteristic of the positive phase of the Arctic Oscillation (AO) when forced with volcanic aerosol following the 1963 Mount Agung, 1982 El Chichón, and 1991 Mount Pinatubo eruptions, as is observed. The AO signal in the extended model is of comparable strength to that in the standard model, showing that there is little impact from both increasing the vertical resolution in the stratosphere and extending the model domain to near the mesopause. The presence of this signal in the models, however, is likely due to the persistence of the observed signal from the initial conditions, because a similar set of experiments initiated with the same conditions, but with no volcanic aerosol forcing, exhibits a similar response as the forced runs. This suggests that the model has limited fidelity in capturing the response to volcanic aerosols on its own, consistent with previous studies on the impact of volcanic forcing in long climate simulations, but does support the premise that seasonal winter forecasts are substantially improved with the inclusion of stratospheric information.

Description: In this study, the role of the Saharan air layer (SAL) is investigated in the development and intensification of tropical cyclones (TCs) via modifying environmental stability and moisture, using multisensor satellite data, long-term TC track and intensity records, dust data, and numerical simulations with a state-of-the-art Weather Research and Forecasting model (WRF). The long-term relationship between dust and Atlantic TC activity shows that dust aerosols are negatively associated with hurricane activity in the Atlantic basin, especially with the major hurricanes in the western Atlantic region. Numerical simulations with the WRF for specific cases during the NASA African Monsoon Multidisciplinary Analyses (NAMMA) experiment show that, when vertical temperature and humidity profiles from the Atmospheric Infrared Sounder (AIRS) were assimilated into the model, detailed features of the warm and dry SAL, including the entrainment of dry air wrapping around the developing vortex, are well simulated. Active tropical disturbances are found along the southern edge of the SAL. The simulations show an example where the dry and warm air of the SAL intruded into the core of a developing cyclone, suppressing convection and causing a spin down of the vortical circulation. The cyclone eventually weakened. To separate the contributions from the warm temperature and dry air associated with the SAL, two additional simulations were performed, one assimilating only AIRS temperature information (AIRST) and one assimilating only AIRS humidity information (AIRSH) while keeping all other conditions the same. The AIRST experiments show almost the same simulations as the full AIRS assimilation experiments, whereas the AIRSH is close to the non-AIRS simulation. This is likely due to the thermal structure of the SAL leading to low-level temperature inversion and increased stability and vertical wind shear. These analyses suggest that dry air entrainment and the enhanced vertical wind shear may play the direct roles in leading to the TC suppression. On the other hand, the warm SAL temperature may play the indirect effects by enhancing vertical wind shear; increasing evaporative cooling; and initiating mesoscale downdrafts, which bring dry air from the upper troposphere to the lower levels.

Description: This study demonstrates that during the passage of the MJO through the Maritime Continent in the boreal winter, the corresponding deep convection and near-surface wind anomalies tend to skirt around mountainous islands. Flow bifurcation around elongated mountainous islands, such as New Guinea, is clearly seen. Topographic blocking generates distinctive vorticity and convergence distributions in this specific domain. Mountain-wave-like structures are also observed throughout the Maritime Continent, with a clear spatial relationship with the high terrains in Sumatra, Sulawesi, and New Guinea. The existence of topography seems to create extra lifting and sinking within the large-scale circulation and thus the convective system exhibits quasi-stationary features near the major topography during the MJO passage through the Maritime Continent. It is suggested that resolving the detailed topographic effects may play a key role in simulating realistic characteristics of the MJO in the Maritime Continent.

Description: A global climatology of height-resolved variance scaling within the troposphere is presented using derived temperature (T) and water vapor (q) profiles from the Atmospheric Infrared Sounder (AIRS). The power-law exponent of T variance scaling approaches 1.0 outside of the tropics at scales 〉500–800 km, but it is closer to 0.3 at scales

Description: The dynamics of Northern Hemisphere major midwinter stratospheric sudden warmings (SSWs) are examined using transient climate change simulations from the Canadian Middle Atmosphere Model (CMAM). The simulated SSWs show good overall agreement with reanalysis data in terms of composite structure, statistics, and frequency. Using observed or model sea surface temperatures (SSTs) is found to make no significant difference to the SSWs, indicating that the use of model SSTs in the simulations extending into the future is not an issue. When SSWs are defined by the standard (wind based) definition, an absolute criterion, their frequency is found to increase by ∼60% by the end of this century, in conjunction with a ∼25% decrease in their temperature amplitude. However, when a relative criterion based on the northern annular mode index is used to define the SSWs, no future increase in frequency is found. The latter is consistent with the fact that the variance of 100-hPa daily heat flux anomalies is unaffected by climate change. The future increase in frequency of SSWs using the standard method is a result of the weakened climatological mean winds resulting from climate change, which make it easier for the SSW criterion to be met. A comparison of winters with and without SSWs reveals that the weakening of the climatological westerlies is not a result of SSWs. The Brewer–Dobson circulation is found to be stronger by ∼10% during winters with SSWs, which is a value that does not change significantly in the future.

Description: Perturbations to the carbon cycle could constitute large feedbacks on future changes in atmospheric CO2 concentration and climate. This paper demonstrates how carbon cycle feedback can be expressed in formally similar ways to climate feedback, and thus compares their magnitudes. The carbon cycle gives rise to two climate feedback terms: the concentration–carbon feedback, resulting from the uptake of carbon by land and ocean as a biogeochemical response to the atmospheric CO2 concentration, and the climate–carbon feedback, resulting from the effect of climate change on carbon fluxes. In the earth system models of the Coupled Climate–Carbon Cycle Model Intercomparison Project (C4MIP), climate–carbon feedback on warming is positive and of a similar size to the cloud feedback. The concentration–carbon feedback is negative; it has generally received less attention in the literature, but in magnitude it is 4 times larger than the climate–carbon feedback and more uncertain. The concentration–carbon feedback is the dominant uncertainty in the allowable CO2 emissions that are consistent with a given CO2 concentration scenario. In modeling the climate response to a scenario of CO2 emissions, the net carbon cycle feedback is of comparable size and uncertainty to the noncarbon–climate response. To quantify simulated carbon cycle feedbacks satisfactorily, a radiatively coupled experiment is needed, in addition to the fully coupled and biogeochemically coupled experiments, which are referred to as coupled and uncoupled in C4MIP. The concentration–carbon and climate–carbon feedbacks do not combine linearly, and the concentration–carbon feedback is dependent on scenario and time.

Description: A large ensemble of general circulation model (GCM) integrations coupled to a fully interactive sulfur cycle scheme were run on the climateprediction.net platform to investigate the uncertainty in the climate response to sulfate aerosol and carbon dioxide (CO2) forcing. The sulfate burden within the model (and the atmosphere) depends on the balance between formation processes and deposition (wet and dry). The wet removal processes for sulfate aerosol are much faster than dry removal and so any changes in atmospheric circulation, cloud cover, and precipitation will feed back on the sulfate burden. When CO2 is doubled in the Hadley Centre Slab Ocean Model (HadSM3), global mean precipitation increased by 5%; however, the global mean sulfate burden increased by 10%. Despite the global mean increase in precipitation, there were large areas of the model showing decreases in precipitation (and cloud cover) in the Northern Hemisphere during June–August, which reduced wet deposition and allowed the sulfate burden to increase. Further experiments were also undertaken with and without doubling CO2 while including a future anthropogenic sulfur emissions scenario. Doubling CO2 further enhanced the increases in sulfate burden associated with increased anthropogenic sulfur emissions as observed in the doubled CO2-only experiment. The implications are that the climate response to doubling CO2 can influence the amount of sulfate within the atmosphere and, despite increases in global mean precipitation, may act to increase it.

Description: A principal component analysis is performed to characterize intraseasonal variability in the boreal stratospheric polar vortex. In contrast to previous studies, the current analysis examines daily zonal-mean variability within a limited spatial domain encompassing the stratospheric polar vortex. The leading EOFs are vertically coherent north–south dipoles in the zonal-mean zonal wind extending through the lower stratosphere. The first mode represents variability in polar vortex strength and is highly correlated with the stratospheric northern annular mode (SNAM). The second mode, the polar annular mode (PAM), represents variability in the latitudinal position of the polar vortex and possesses a poleward-retracted dipole anomaly structure. Composite analyses indicate that large-amplitude PAM events are relatively short lived (1–2 weeks) compared to SNAM events (1 month or longer). Trend analyses further reveal that recent decadal trends in the boreal polar vortex project more strongly onto PAM than SNAM. Composite analyses illustrate that the time evolution of sudden stratospheric warming events is dominated by SNAM, whereas SNAM and PAM play approximately equal roles in final warming events. Linear regression analyses reveal that SNAM and PAM result in circumpolar circulation and temperature anomalies of similar magnitudes within the high-latitude troposphere. It is concluded that PAM represents a previously unrecognized annular mode that strongly couples the stratosphere and troposphere on submonthly time scales at mid- to high latitudes. It is further suggested that the SNAM/PAM framework provides a means for isolating the proximate tropospheric response to respective variations in the strength and position of the stratospheric polar vortex.

Description: Seasonal reconstructions of the Southern Hemisphere annular mode (SAM) index are derived to extend the record before the reanalysis period, using station sea level pressure (SLP) data as predictors. Two reconstructions using different predictands are obtained: one [Jones and Widmann (JW)] based on the first principal component (PC) of extratropical SLP and the other (Fogt) on the index of Marshall. A regional-based SAM index (Visbeck) is also considered. These predictands agree well post-1979; correlations decline in all seasons except austral summer for the full series starting in 1958. Predictand agreement is strongest in spring and summer; hence agreement between the reconstructions is highest in these seasons. The less zonally symmetric SAM structure in winter and spring influences the strength of the SAM signal over land areas, hence the number of stations included in the reconstructions. Reconstructions from 1865 were, therefore, derived in summer and autumn and from 1905 in winter and spring. This paper examines the skill of each reconstruction by comparison with observations and reanalysis data. Some of the individual peaks in the reconstructions, such as the most recent in austral summer, represent a full hemispheric SAM pattern, while others are caused by regional SLP anomalies over the locations of the predictors. The JW and Fogt reconstructions are of similar quality in summer and autumn, while in winter and spring the Marshall index is better reconstructed by Fogt than the PC index is by JW. In spring and autumn the SAM shows considerable variability prior to recent decades.

Description: The role of Saharan dust and dry anomaly in maintaining the temperature inversion in the Saharan air layer (SAL) is investigated. The dust aerosol optical thickness (AOT) in the SAL is inferred from the measurements taken by Aqua Moderate Resolution Imaging Spectroradiometer (MODIS), and the corresponding temperature and specific humidity anomalies are identified using the National Centers for Environmental Prediction (NCEP) data in August–September over the North Atlantic tropical cyclone (TC) main development region (MDR; 10°–20°N, 40°–60°W). The authors also study the SAL simulated in the National Center of Atmospheric Research (NCAR) Community Atmosphere Model, version 3 (CAM3), coupled with dust radiative effect. It is found that higher AOT is associated with warmer and dryer anomalies below 700 hPa, which increases the atmospheric stability. The calculated instantaneous radiative heating anomalies from a radiative transfer model indicate that both the dust and low humidity are essential to maintaining the temperature structure in the SAL against thermal relaxation. At 850 hPa, heating anomalies caused by both the dust and dry anomalies (for AOT 〉 0.8) are 0.2–0.4 K day−1. The dust heats the atmosphere below 600 hPa, while the dry anomaly cools the atmosphere below 925 hPa, resulting in a peak of heating rate anomaly located at 700–850 hPa. In the eastern Atlantic, dust contributes about 50% of the heating rate anomaly. Westward of 40°W, when the dust content becomes small (AOT 〈 0.6), the heating rates are more sensitive to the water vapor profile used in the radiative transfer calculation. Retrieving or simulating correct water vapor profiles is essential to the assessment of the SAL heating budgets in regions where the dust content in the SAL is small.

Description: A 5-yr climatology of the meteorology, including boundary layer cloudiness, for the southeast Pacific region is presented using observations from a buoy located at 20°S, 85°W. The sea surface temperature and surface air temperature exhibit a sinusoidal seasonal cycle that is negatively correlated with surface pressure. The relative humidity, wind speed, and wind direction show little seasonal variability. But the advection of cold and dry air from the southeast varies seasonally and is highly correlated with the latent heat flux variations. A simple model was used to estimate the monthly cloud fraction using the observed surface downwelling longwave radiative flux and surface meteorological parameters. The annual cycle of cloud fraction is highly correlated to that of S. A. Klein: lower-tropospheric stability parameter (0.87), latent heat flux (−0.59), and temperature and moisture advection (0.60). The derived cloud fraction compares poorly with the International Satellite Cloud Climatology Project (ISCCP)-derived low-cloud cover but compares well (0.86 correlation) with ISCCP low- plus middle-cloud cover. The monthly averaged diurnal variations in cloud fraction show marked seasonal variability in the amplitude and temporal structure. The mean annual cloud fraction is lower than the mean annual nighttime cloud fraction by about 9%. Annual and diurnal cycles of surface longwave and shortwave cloud radiative forcing were also estimated. The longwave cloud radiative forcing is about 45 W m−2 year-round, but, because of highly negative shortwave cloud radiative forcing, the net cloud radiative forcing is always negative with an annual mean of −50 W m−2.

Description: Multiyear satellite observations are used to document a relationship between the large-scale variability in precipitation over the tropical Atlantic and aerosol traced to African sources. During boreal winter and spring there is a significant reduction in precipitation south of the Atlantic marine intertropical convergence zone (ITCZ) during months when aerosol concentrations are anomalously high over a large domain of the tropical Atlantic Ocean. This reduction cannot be linearly attributed to known climate factors such as El Niño–Southern Oscillation, the North Atlantic Oscillation, and zonal and meridional modes of tropical Atlantic sea surface temperature or to meteorological factors such as water vapor. The fractional variance in precipitation related to aerosol is about 12% of the total interannual variance, which is of the same order of magnitude as that related to each of the known climate and weather factors. A backward trajectory analysis confirms the African origin of aerosols that directly affect the changes in precipitation. The reduction in mean precipitation mainly comes from decreases in moderate rain rates (10–20 mm day−1), while light rain (

Description: The authors investigate the effects of tropical cyclones (TCs) on seasonal and interannual rainfall variability over the western North Pacific (WNP) by using rainfall data at 22 stations. The TC-induced rainfall at each station is estimated by using station data when a TC is located within the influential radius (1000 km) from the station. The spatial–temporal variability of the proportion of TC rainfall is examined primarily along the east–west island chain near 10°N (between 7° and 13°N) and the north–south island chain near 125°E (between 120° and 130°E). Along 10°N the seasonality of total rainfall is mainly determined by non-TC rainfall that is influenced by the WNP monsoon trough. The proportion of the TC rain is relatively low. During the high TC season from July to December, TC rainfall accounts for 30% of the total rainfall in Guam, 15%–23% in Koror and Yap, and less than 10% at other stations. In contrast, along 125°E where the WNP subtropical high is located, the TC rainfall accounts for 50%–60% of the total rainfall between 18° and 26°N during the peak TC season from July to October. In Hualien of Taiwan, TC rainfall exceeds 60% of the total rainfall. The interannual variability of the TC rainfall and total rainfall is primarily modulated by El Niño–Southern Oscillation (ENSO). Along 10°N, the ratio of TC rainfall versus total rainfall is higher than the climatology during developing and mature phases of El Niño (from March to the following January), whereas the ratio is below the climatology during the decaying phase of El Niño. The opposite is true for La Niña, except that the impact of La Niña is shorter in duration. Furthermore, in summer of El Niño developing years, the total seasonal rainfall increases primarily because of the increase of TC rainfall. In the ensuing autumn, an anticyclonic anomaly develops over the Philippine Sea and TC rainfall shifts eastward; as a result, the total rainfall over the Philippines and Taiwan decreases. The total rainfall to the east of 140°E, however, changes little, because the westward passage of TCs enhances TC rainfall, which offsets the decrease of non-TC rainfall. Along the meridional island chain between 120° and 130°E, the total rainfall anomaly is affected by ENSO starting from the autumn to the following spring, and the variation in TC rainfall dominates the total rainfall variation only in autumn (August–November) of ENSO years. The results from this study suggest that in the tropical WNP and subtropical East Asian monsoon regions (east of 120°E), the seasonal and interannual variations of rainfall are controlled by changes in nonlocal circulations. These changes outside the monsoon domain may substantially affect summer monsoon rainfall by changing TC genesis and tracks.

Description: The Massachusetts Institute of Technology (MIT) Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model’s first projections were published in 2003, substantial improvements have been made to the model, and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections; for example, the median surface warming in 2091–2100 is 5.1°C compared to 2.4°C in the earlier study. Many changes contribute to the stronger warming; among the more important ones are taking into account the cooling in the second half of the twentieth century due to volcanic eruptions for input parameter estimation and a more sophisticated method for projecting gross domestic product (GDP) growth, which eliminated many low-emission scenarios. However, if recently published data, suggesting stronger twentieth-century ocean warming, are used to determine the input climate parameters, the median projected warming at the end of the twenty-first century is only 4.1°C. Nevertheless, all ensembles of the simulations discussed here produce a much smaller probability of warming less than 2.4°C than implied by the lower bound of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) projected likely range for the A1FI scenario, which has forcing very similar to the median projection in this study. The probability distribution for the surface warming produced by this analysis is more symmetric than the distribution assumed by the IPCC because of a different feedback between the climate and the carbon cycle, resulting from the inclusion in this model of the carbon–nitrogen interaction in the terrestrial ecosystem.

Description: Dominant modes of individual and joint variability in global sea surface temperatures (SST) and global Palmer drought severity index (PDSI) values for the twentieth century are identified through a multivariate frequency domain singular value decomposition. This analysis indicates that a secular trend and variability related to the El Niño–Southern Oscillation (ENSO) are the dominant modes of variance shared among the global datasets. For the SST data the secular trend corresponds to a positive trend in Indian Ocean and South Atlantic SSTs, and a negative trend in North Pacific and North Atlantic SSTs. The ENSO reconstruction shows a strong signal in the tropical Pacific, North Pacific, and Indian Ocean regions. For the PDSI data, the secular trend reconstruction shows high amplitudes over central Africa including the Sahel, whereas the regions with strong ENSO amplitudes in PDSI are the southwestern and northwestern United States, South Africa, northeastern Brazil, central Africa, the Indian subcontinent, and Australia. An additional significant frequency, multidecadal variability, is identified for the Northern Hemisphere. This multidecadal frequency appears to be related to the Atlantic multidecadal oscillation (AMO). The multidecadal frequency is statistically significant in the Northern Hemisphere SST data, but is statistically nonsignificant in the PDSI data.

Description: A representative temperature record for New Zealand based on station data from 1853 onward is used in conjunction with four coupled climate models to investigate the causes of recent warming over this small midlatitude country. The observed variability over interannual and decadal time scales is simulated well by the models. The variability of simulated 50-yr trends is consistent with the very short observational record. For a simple detection analysis it is not possible to separate the observed 30- and 50-yr temperature trends from the distribution created by internal variability in the model control simulations. A pressure index that is representative of meridional flow (M1) is used to show that the models fail to simulate an observed trend to more southerly flows in the region. The strong relationship between interannual temperature variability and the M1 index in both the observations and the models is used to remove the influence of this circulation variability from the temperature records. Recent 50-yr trends in the residual temperature record cannot be explained by natural climate variations, but they are consistent with the combined climate response to anthropogenic greenhouse gas emissions, ozone depletion, and sulfate aerosols, demonstrating a significant human influence on New Zealand warming. This result highlights the effect of circulation variability on regional detection and attribution analyses. Such variability can either mask or accelerate human-induced warming in observed trends, underscoring the importance of determining the underlying forced trend, and the need to adequately capture regional circulation effects in climate models.

Description: Projections for twenty-first-century changes in summertime Sahel precipitation differ greatly across models in the third Coupled Model Intercomparison Project (CMIP3) dataset and cannot be explained solely in terms of discrepancies in the projected anomalies in global SST. This study shows that an index describing the low-level circulation in the North Atlantic–African region, namely, the strength of the low-level Saharan low, correlates with Sahel rainfall in all models and at the time scales of both interannual and interdecadal natural variability and of the forced centennial trend. An analysis of Sahel interannual variability provides evidence that variations in the Sahara low can be a cause, not just a consequence, of variations in Sahel rainfall and suggests that a better understanding of the sources of model discrepancy in Sahel rainfall predictions might be gained from an analysis of the mechanisms influencing changes in the Sahara low.

Description: Simple Ocean Data Assimilation (SODA) reanalysis data are used to produce a 50-yr record of flow through the Makassar Strait, the primary conduit for the Indonesian Throughflow (ITF). Two time series are constructed for comparison to the flow through the Makassar Strait as observed during 1997–98 and 2004–06: SODA along-channel speed within the Makassar Strait and Pacific to Indian Ocean interocean pressure difference calculated on isopycnal layers from SODA hydrology. These derived time series are compared to the total ITF as well as to the vertical distribution and frequency bands of ITF variability. The pressure difference method displays higher skill in replicating the observed Makassar ITF time series at periods longer than 9 months, particularly within the thermocline layer (50–200 m), the location of maximum flow. This is attributed to the connection between the thermocline layer and large-scale wind forcing, which affects the hydrology of the ITF inflow and outflow regions. In contrast, the surface layer (0–50 m) is more strongly correlated with local wind flow, and it is better predicted by SODA along-channel velocity. The pressure difference time series is extended over the 50-yr period of SODA and displays a strong correlation with ENSO as well as a correlation at the decadal scale with the island rule.

Description: A new analysis of historical radiosonde humidity observations is described. An assessment of both known and unknown instrument and observing practice changes has been conducted to assess their impact on bias and uncertainty in long-term trends. The processing of the data includes interpolation of data to address known sampling bias from missing dry day and cold temperature events, a first-guess adjustment for known radiosonde model changes, and a more sophisticated ensemble of estimates based on 100 neighbor-based homogenizations. At each stage the impact and uncertainty of the process has been quantified. The adjustments remove an apparent drying over Europe and parts of Asia and introduce greater consistency between temperature and specific humidity trends from day and night observations. Interannual variability and trends at the surface are shown to be in good agreement with independent in situ datasets, although some steplike discrepancies are apparent between the time series of relative humidity at the surface. Adjusted trends, accounting for documented and undocumented break points and their uncertainty, across the extratropical Northern Hemisphere lower and midtroposphere show warming of 0.1–0.4 K decade−1 and moistening on the order of 1%–5% decade−1 since 1970. There is little or no change in the observed relative humidity in the same period, consistent with climate model expectation of a positive water vapor feedback in the extratropics with near-constant relative humidity.

Description: The strength of the water vapor feedback has been estimated by analyzing the changes in tropospheric specific humidity during El Niño–Southern Oscillation (ENSO) cycles. This analysis is done in climate models driven by observed sea surface temperatures [Atmospheric Model Intercomparison Project (AMIP) runs], preindustrial runs of fully coupled climate models, and in two reanalysis products, the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) and the NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA). The water vapor feedback during ENSO-driven climate variations in the AMIP models ranges from 1.9 to 3.7 W m−2 K−1, in the control runs it ranges from 1.4 to 3.9 W m−2 K−1, and in the ERA-40 and MERRA it is 3.7 and 4.7 W m−2 K−1, respectively. Taken as a group, these values are higher than previous estimates of the water vapor feedback in response to century-long global warming. Also examined is the reason for the large spread in the ENSO-driven water vapor feedback among the models and between the models and the reanalyses. The models and the reanalyses show a consistent relationship between the variations in the tropical surface temperature over an ENSO cycle and the radiative response to the associated changes in specific humidity. However, the feedback is defined as the ratio of the radiative response to the change in the global average temperature. Differences in extratropical temperatures will, therefore, lead to different inferred feedbacks, and this is the root cause of spread in feedbacks observed here. This is also the likely reason that the feedback inferred from ENSO is larger than for long-term global warming.

Description: Feedback between the North Atlantic Oscillation (NAO) and winter sea ice variability is detected and quantified using approximately 30 years of observations, a vector autoregressive model (VAR), and testable definitions of Granger causality and feedback. Sea ice variability is quantified based on the leading empirical orthogonal function of sea ice concentration over the North Atlantic [the Greenland Sea ice dipole (GSD)], which, in its positive polarity, has anomalously high sea ice concentrations in the Labrador Sea region to the southwest of Greenland and low sea ice concentrations in the Barents Sea region to the northeast of Greenland. In weekly data for December through April, the VAR indicates that NAO index (N) anomalies cause like-signed anomalies of the standardized GSD index (G), and that G anomalies in turn cause oppositely signed anomalies of N. This negative feedback process operates explicitly on lags of up to four weeks in the VAR but can generate more persistent effects because of the autocorrelation of G. Synthetic data are generated with the VAR to quantify the effects of feedback following realistic local maxima of N and G, and also for sustained high values of G. Feedback can change the expected value of evolving system variables by as much as a half a standard deviation, and the relevance of these results to intraseasonal and interannual NAO and sea ice variability is discussed.

Description: The temporal stability of the southern annular mode (SAM) impacts on Southern Hemisphere climate during austral spring is analyzed. Results show changes in the typical hemispheric circulation pattern associated with SAM, particularly over South America and Australia, between the 1960s–70s and 1980s–90s. In the first decades, the SAM positive phase is associated with an anomalous anticyclonic circulation developed in the southwestern subtropical Atlantic that enhances moisture advection and promotes precipitation increase over southeastern South America (SESA). On the other hand, during the last decades the anticyclonic anomaly induced by the SAM’s positive phase covers most of southern South America and the adjacent Atlantic, producing weakened moisture convergence and decreased precipitation over SESA as well as positive temperature anomaly advection over southern South America. Some stations in the Australia–New Zealand sector and Africa exhibit significant correlations between the SAM and precipitation anomalies in both or one of the subperiods, but they do not characterize a consistent area in which the SAM signal can be certainly determined. Significant changes of SAM influence on temperature anomalies on multidecadal time scales are observed elsewhere. Particularly over the Australia–New Zealand sector, significant positive correlations during the first decades become insignificant or even negative in the later period, whereas changes of opposite sign occur in the Antarctic Peninsula between both subperiods.

Description: This study explores the impact of meridional sea surface temperature (SST) gradients across the eastern Indian Ocean on interannual variations in Australian precipitation. Atmospheric general circulation model (AGCM) experiments are conducted in which the sign and magnitude of eastern Indian Ocean SST gradients are perturbed. This results in significant rainfall changes for western and southeastern Australia. A reduction (increase) in the meridional SST gradient drives a corresponding response in the atmospheric thickness gradients and results in anomalous dry (wet) conditions over Australia. During simulated wet years, this seems to be due to westerly anomalies in the thermal wind over Australia and anomalous onshore moisture advection, with a suggestion that the opposite occurs during dry conditions. Thus, an asymmetry is seen in the magnitude of the forced circulation and precipitation response between the dry and wet simulations. To assess the relative contribution of the SST anomalies making up the meridional gradient, the SST pattern is decomposed into its constituent “poles,” that is, the eastern tropical pole off the northwest shelf of Australia versus the southern pole in the central subtropical Indian Ocean. Overall, the simulated Australian rainfall response is linear with regard to the sign and magnitude of the eastern Indian Ocean SST gradient. The tropical eastern pole has a larger impact on the atmospheric circulation and Australian precipitation changes relative to the southern subtropical pole. However, there is clear evidence of the importance of the southern pole in enhancing the Australian rainfall response, when occurring in conjunction with but of opposite sign to the eastern tropical pole. The observed relationship between the meridional SST gradient in the eastern Indian Ocean and rainfall over western and southeastern Australia is also analyzed for the period 1970–2005. The observed relationship is found to be consistent with the AGCM results.

Description: This study examines the observed interannual variability of the cyclonic activity along the U.S. Pacific coast and quantifies its impact on the characteristics of both the winter total and extreme precipitation in the western United States. A cyclonic activity function (CAF) was derived from a dataset of objectively identified cyclone tracks in 27 winters (1979/80–2005/06). The leading empirical orthogonal function (EOF1) of the CAF was found to be responsible for the EOF1 of the winter precipitation in the western United States, which is a monopole mode centered over the Pacific Northwest and northern California. On the other hand, the EOF2 of the CAF contributes to the EOF2 of the winter precipitation, which indicates that above-normal precipitation in the Pacific Northwest and its immediate inland regions tends to be accompanied by below-normal precipitation in California and the southwestern United States and vice versa. The first two EOFs of CAF (precipitation) account for about 70% (78%) of the total interannual variance of CAF (precipitation). The second EOF modes of both the CAF and precipitation are significantly linked to the ENSO signal on interannual time scales. A composite analysis further reveals that the leading CAF modes increase (decrease) the winter total precipitation by increasing (decreasing) both the number of rainy days per winter and the extremeness of precipitation. The latter was quantified in terms of the 95th percentile of the daily rain rate and the probability of precipitation being heavy given a rainy day. The implications of the leading CAF modes for the water resources and the occurrence of extreme hydrologic events in the western United States, as well as their dynamical linkages to the Pacific storm track and various atmospheric low-frequency modes (i.e., teleconnection patterns), are also discussed.

Description: The spread among the predictions by climate models for the strengthening of the global hydrological cycle [i.e., the global mean surface latent heat flux (LH), or, equivalently, precipitation] at a given level of CO2-induced global warming is of the same magnitude as the intermodel mean. By comparing several climate models from the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3) database under idealized CO2 forcings, it is shown that differences in the increase in global atmospheric shortwave heating (SWabs) induced by clear-sky absorption, presumably by water vapor, partly explains this spread. The increases in SWabs and LH present similar spreads across models but are anticorrelated, so the sum SWabs + LH increases more robustly than either alone. This is consistent with a recently proposed theory (Takahashi) that predicts that this sum (or, equivalently, the net longwave divergence minus the surface sensible heat flux) is constrained by energy conservation and robust longwave physics. The intermodel scatter in SWabs changes is explained neither by differences in the radiative transfer models nor in intermodel differences in global water vapor content change, but perhaps by more subtle aspects of the changes in the water vapor distribution. Nevertheless, the fact that the radiative transfer models generally underestimate the increase in SWabs relative to the corresponding line-by-line calculation for a given change in water vapor content suggests that the climate models might be overestimating the rate of increase in the global hydrological cycle with global warming.

Description: During the past two decades, particular scientific attention has been drawn to the potential cosmic ray–atmospheric coupling. Galactic cosmic rays reaching the upper troposphere are suggested as the key modulators of the global electric circuit, with further implications on cloud microphysical processes. Unfortunately, the scarcity of the associated observations renders the evaluation of the theoretical mechanisms rather difficult. This contribution proposes a different approach by introducing observations provided by the National Lightning Detection Network for the period 1990–2005. The study area encompasses the greater part of continental United States and the surrounding waters. The results highlight a statistically significant positive trend between monthly lightning activity and galactic cosmic ray fluxes during the winter season. During the summer season, the trend becomes statistically nonsignificant. In addition, the featured analysis introduces a technique to assess the potential impact of Forbush events on daily lightning activity. Results illustrate that lightning activity may be responsive (minimized) 4–5 days after a Forbush event.

Description: To date, neither observational studies nor direct climate model simulations have been able to document trends in the frequency or severity of deep moist convection associated with global climate change. The lack of such evidence is not unexpected as the observational record is insufficiently long and computational limitations prevent modeling at the scales necessary to simulate explicitly such phenomena. Nonetheless, severe deep moist convection represents an important aspect of regional climate, particularly in the central United States, where damage, injuries, and fatalities are a frequent result of such phenomena. Accordingly, any comprehensive assessment of the regional effects of climate change must account for these effects. In this work, the authors present a “perfect prog” approach to estimating the potential for surface-based convective initiation and severity based upon the large-scale variables well resolved by climate model simulations. This approach allows for the development of a stable estimation scheme that can be applied to any climate model simulation, presently and into the future. The scheme is applied for the contiguous United States using the output from the Parallel Climate Model, with the Intergovernmental Panel on Climate Change third assessment A2 (business as usual) as input. For this run, relative to interannual variability, the potential frequency of deep moist convection does not change, but the potential for severe convection is found to increase east of the Rocky Mountains and most notably in the “tornado alley” region of the U.S. Midwest. This increase in severe potential is mostly tied to increases in thermodynamic instability as a result of ongoing warm season surface warming and moistening. Finally, approaches toward improving such estimation methods are briefly discussed.

Description: In this work, 45 years (1961–2005) of hourly meteorological data in Taiwan, including temperature, humidity, and precipitation, have been analyzed with emphasis on their diurnal asymmetries. A long-term decreasing trend for relative humidity (RH) is found, and the trend is significantly greater in the nighttime than in the daytime, apparently resulting from a greater warming at night. The warming at night in three large urban centers is large enough to impact the average temperature trend in Taiwan significantly between 1910 and 2005. There is a decrease in the diurnal temperature range (DTR) that is largest in major urban areas, and it becomes smaller but does not disappear in smaller cities and offshore islands. The nighttime reduction in RH is likely the main cause of a significant reduction of fog events over Taiwan. The smaller but consistent reductions in DTR and RH in the three off-coast islands suggests that, in addition to local land use changes, a regional-scale process such as the indirect effect of anthropogenic aerosols may also contribute to these trends. A reduction in light precipitation (10 mm h−1) are found over Taiwan and the offshore islands. The changes in precipitation are similar to the changes of other areas in Asia, but they are different from those of the United States, Europe, and the tropical oceans. The latter do not show any reduction in light precipitation.