ALBERT

Description: Coeval changes in atmospheric CO2 and 14C contents during the last deglaciation are often attributed to ocean circulation changes that released carbon stored in the deep ocean during the Last Glacial Maximum (LGM). Work is being done to generate records that allow for the identification of the exact mechanisms leading to the accumulation and release of carbon from the oceanic reservoir, but these mechanisms are still the subject of debate. Here we present foraminifera 14C data from five cores in a transect across the Chilean continental margin between ~540 and ~3,100 m depth spanning the last 20,000 years. Our data reveal that during the LGM, waters at ~2,000 m were 50% to 80% more depleted in Δ14C than waters at ~1,500 m when compared to modern values, consistent with the hypothesis of a glacial deep ocean carbon reservoir that was isolated from the atmosphere. During the deglaciation, our intermediate water records reveal homogenization in the Δ14C values between ~800 and ~1,500 m from ~16.5–14.5 ka cal BP to ~14–12 ka cal BP, which we interpret as deeper penetration of Antarctic Intermediate Water. While many questions still remain, this process could aid the ventilation of the deep ocean at the beginning of the deglaciation, contributing to the observed ~40 ppm rise in atmospheric pCO2.

Description: The Arctic Ocean is known to be contaminated by various persistent organic pollutants (POPs). The Fram Strait, the only deepwater passage to the Arctic Ocean (from the Atlantic Ocean), represents an unquantified gateway for POPs fluxes into and out of the Arctic. Polyethylene passive samplers were deployed in vertical profiles in the Fram Strait and in air and surface water in the Canadian Archipelago to determine the concentrations, profiles, and mass fluxes of dissolved polychlorinated biphenyls (PCBs) and organochlorine pesticides. In the Fram Strait, higher concentrations of ΣPCBs (1.3–3.6 pg/L) and dichlorodiphenyltrichloroethanes (ΣDDTs, 5.2–9.1 pg/L) were observed in the deepwater masses (below 1,000 m), similar to nutrient-like vertical profiles. There was net southward transport of hexachlorobenzene and hexachlorocyclohexanes (ΣHCHs) of 0.70 and 14 Mg/year but a net northward transport of ΣPCBs at 0.16 Mg/year through the Fram Strait.

Description: In the future, Earth will be warmer, precipitation events will be more extreme, global mean sea level will rise, and many arid and semi-arid regions will be drier. Human modifications of landscapes will also occur at an accelerated rate as developed areas increase in size and population density. We now have gridded global forecasts, being continually improved, of the climatic and land-use changes (C&LUC) that are likely to occur in the coming decades. Aside from a few exceptions, however, consensus forecasts do not exist for how these C&LUC will likely impact Earth-surface processes and hazards. In some cases we have the tools to forecast the geomorphic responses to likely future C&LUC. Fully exploiting these models and utilizing these tools will require close collaboration among Earth-surface scientists and Earth-system modelers. This paper assesses the state-of-the-art tools and data that are being used or could be used to forecast changes in the state of Earth's surface as a result of likely future C&LUC. We also propose strategies for filling key knowledge gaps, emphasizing where additional basic research and/or collaboration across disciplines is necessary. The main body of the paper addresses cross-cutting issues, including the importance of nonlinear/threshold-dominated interactions among topography, vegetation, and sediment transport, as well as the importance of alternate stable states and extreme, rare events for understanding and forecasting Earth-surface response to C&LUC. Five supplements delve into different scales or process zones (global-scale assessments, and fluvial, aeolian, glacial/periglacial, and coastal process zones) in detail.

Description: Stratigraphy provides insights into the evolution and dynamics of the Earth System over its long history. With recent developments in Earth System science, changes in Earth System dynamics can now be observed directly and projected into the near future. An integration of the two approaches provides powerful insights into the nature and significance of contemporary changes to Earth. From both perspectives, the Earth has been pushed out of the Holocene Epoch by human activities, with the mid-20 th century a strong candidate for the start date of the Anthropocene, the proposed new epoch in Earth history. Here we explore two contrasting scenarios for the future of the Anthropocene, recognizing that the Earth System has already undergone a substantial transition away from the Holocene state. A rapid shift of societies towards the UN Sustainable Development Goals could stabilize the Earth System in a state with more intense interglacial conditions than in the late Quaternary climate regime and with little further biospheric change. In contrast, a continuation of the present Anthropocene trajectory of growing human pressures will likely lead to biotic impoverishment and a much warmer climate with a significant loss of polar ice.

Description: We determine the contribution of glacial isostatic adjustment (GIA) to future relative sea level change for the North American coastline between Newfoundland and Texas. We infer GIA model parameters using recently compiled and quality assessed databases of past sea-level changes, including new databases for the United States Gulf coast and Atlantic Canada. At 13 cities along this coastline, we estimate the GIA contribution to range from a few centimeters (e.g. 3[−1 − 9]cm, Miami) to a few decimeters (e.g. 18[12 − 22]cm, Halifax) for the period 2085-2100 relative to 2006-2015 (1- σ ranges given). We provide estimates of uncertainty in the GIA component using two different methods; the more conservative approach produces total ranges (1- σ confidence) that vary from 3to16cm for the cities considered. Contributions from ocean steric and dynamic changes as well as those from changes in land ice are also estimated to provide context for the GIA projections. When summing the contributions from all three processes at the 13 cities considered along this coastline, using median or best-estimate values, the GIA signal comprises ≈ 5 − 38 % of the total depending on the adopted climate forcing and location. The contributions from ocean dynamic/steric changes and ice mass loss are similar in amplitude but with spatial variation that approximately cancels, resulting in GIA dominating the net spatial variability north of 35 ∘ N).

Description: The literature on the costs of climate change often draws a link between climatic ‘tipping points’ and large economic shocks, frequently called ‘catastrophes’. The phrase ‘tipping points’ in this context can be misleading. In popular and social scientific discourse, ‘tipping points’ involve abrupt state changes. For some climatic ‘tipping points,’ the commitment to a state change may occur abruptly, but the change itself may be rate-limited and take centuries or longer to realize. Additionally, the connection between climatic ‘tipping points’ and economic losses is tenuous, though emerging empirical and process-model-based tools provide pathways for investigating it. We propose terminology to clarify the distinction between ‘tipping points’ in the popular sense, the critical thresholds exhibited by climatic and social ‘tipping elements,’ and ‘economic shocks’. The last may be associated with tipping elements, gradual climate change, or non-climatic triggers. We illustrate our proposed distinctions by surveying the literature on climatic tipping elements, climatically sensitive social tipping elements, and climate-economic shocks, and we propose a research agenda to advance the integrated assessment of all three.

Description: The United States Embassy in Beijing, China, released publicly a record of mass concentrations of particulate matter 2.5 µm and smaller in aerodynamic diameter (PM 2 .5 ) from April 2008 to the present measured with a Beta Attenuation Monitor (BAM). We compare these measurements with observations of particulate matter recorded at the Beijing Institute of Atmospheric Physics and observations of visibility recorded at the Beijing Capital International Airport (BCIA) to assess their value as a record of air quality in the greater Beijing metropolitan area. We find that the PM 2 .5 observations correlate well with the other observations of PM over the period January 1 st to February 1 st 2013 using a Tapered Element Oscillating Microbalance and an Aerosol Mass Spectrometer (AMS), and they exhibit a clear inverse correlation with visibility measured at BCIA. Using inverse visibility as a proxy of radiation extinction, we determine a dry mass extinction efficiency and a dependence of radiation extinction to relative humidity that is consistent with other studies of polluted urban environments. We deduce a strong degree of homogeneity of particulate pollution across the Beijing metropolitan region and conclude that the U.S. Embassy measurements are a reliable sample of this particulate pollution during periods of photochemical smog. The U.S. Embassy observations of PM 2 .5 appear to remain consistent throughout the available record and can serve as a useful dataset for studying future trends in particulate matter as China implements ambitious measures to improve air quality in the region.

Description: Climate change damages agriculture, causing deteriorating food security and increased malnutrition. Many studies have examined the role of distinct physical processes, but impacts have not been previously attributed to individual pollutants. Using a simple model incorporating process-level results from detailed models, here I show that although carbon dioxide (CO 2 ) is the largest driver of climate change, other drivers dominate agricultural yield changes. I calculate that anthropogenic emissions to date have decreased global agricultural yields by 9.5 ± 3.0%, with roughly 93% stemming from non-CO 2 emissions, including methane (-5.2 ± 1.7%) and halocarbons (-1.4 ± 0.4%). The differing impacts stem from atmospheric composition responses: CO 2 fertilizes crops, offsetting much of the loss induced by warming; halocarbons do not fertilize; methane leads to minimal fertilization but increases surface ozone which augments warming-induced losses. By the end of the century, strong CO 2 mitigation improves agricultural yields by ~3 ± 5%. In contrast, strong methane and hydrofluorocarbon mitigation improve yields by ~16 ± 5% and ~5 ± 4%, respectively. These are the first quantitative analyses to include climate, CO 2 and ozone simultaneously, and hence additional studies would be valuable. Nonetheless, as policy makers have leverage over pollutant emissions rather than isolated processes, the perspective presented here may be more useful for decision making than that in the prior work upon which this study builds. The results suggest that policies should target a broad portfolio of pollutant emissions in order to optimize mitigation of societal damages.

Description: Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shoreline erosion, and increased flooding during storm events. Hydrodynamic parameters such as tidal ranges, tidal prisms, tidal asymmetries, increased flooding depths and inundation extents during storm events respond non-additively to SLR. Coastal morphology continually adapts towards equilibrium as sea levels rise, inducing changes in the landscape. Marshes may struggle to keep pace with SLR and rely on sediment accumulation and the availability of suitable uplands for migration. Whether hydrodynamic, morphologic or ecologic, the impacts of SLR are inter-related. To plan for changes under future sea levels, coastal managers need information and data regarding the potential effects of SLR to make informed decisions for managing human and natural communities. This review examines previous studies that have accounted for the dynamic, nonlinear responses of hydrodynamics, coastal morphology and marsh ecology to SLR by implementing more complex approaches rather than the simplistic “bathtub” approach. These studies provide an improved understanding of the dynamic effects of SLR on coastal environments and contribute to an overall paradigm shift in how coastal scientists and engineers approach modeling the effects of SLR, transitioning away from implementing the “bathtub” approach. However, it is recommended that future studies implement a synergetic approach that integrates the dynamic interactions between physical and ecological environments to better predict the impacts of SLR on coastal systems.

Description: ABSTRACT Predictions of coastal evolution driven by episodic and persistent processes associated with storms and relative sea-level rise (SLR) are required to test our understanding, evaluate our predictive capability, and to provide guidance for coastal management decisions. Previous work demonstrated that the spatial variability of long-term shoreline change can be predicted using observed SLR rates, tide range, wave height, coastal slope, and a characterization of the geomorphic setting. The shoreline is not sufficient to indicate which processes are important to causing shoreline change, such as overwash that depends on coastal dune elevations. Predicting dune height is intrinsically important to assessing future storm vulnerability. Here, we enhance shoreline-change predictions by including dune height as a variable in a statistical modeling approach. Dune height can also be used as an input variable, but it does not improve the shoreline-change prediction skill. Dune-height input does help to reduce prediction uncertainty. That is, by including dune height, the prediction is more precise but not more accurate. Comparing hindcast evaluations, better predictive skill was found when predicting dune height (0.8) compared to shoreline change (0.6). The skill depends on the level of detail of the model and we identify an optimized model that has high skill and minimal overfitting. The predictive model can be implemented with a range of forecast scenarios, and we illustrate the impacts of a higher future sea-level. This scenario shows that the shoreline change becomes increasingly erosional and more uncertain. Predicted dune heights are lower and the dune height uncertainty decreases.

Description: The response of runoff and sediment loading in the Apalachicola River under projected climate change scenarios and land use land cover (LULC) change is evaluated. A hydrologic model using the Soil Water Assessment Tool (SWAT) was developed for the Apalachicola region to simulate daily runoff and sediment load under present (circa 2000) and future conditions (2100) to understand how parameters respond over a seasonal time frame to changes in climate, LULC, and coupled climate / LULC. The Long Ashton Research Station-Weather Generator (LARS-WG) was used to downscale temperature and precipitation from three general circulation models (GCM), each under Intergovernmental Panel on Climate Change (IPCC) carbon emission scenarios A2, A1B, and B1. Projected 2100 LULC data provided by the United States Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center was incorporated for each corresponding IPCC scenario. Results indicate climate change may induce seasonal shifts to both runoff and sediment loading. Changes in LULC showed more sediment load was associated with increased agriculture and urban areas and decreased forested regions. A nonlinear response for both runoff and sediment loading was observed by coupling climate and LULC change, suggesting both should be incorporated into hydrologic models when studying future conditions. The outcomes from this research can be used to better guide management practices and mitigation strategies.

Description: This work outlines a dynamic modeling framework to examine the effects of global climate change, and sea level rise (SLR) in particular, on tropical cyclone-driven storm surge inundation. The methodology, applied across the northern Gulf of Mexico, adapts a present day large-domain, high resolution, tide, wind-wave, and hurricane storm surge model to characterize the potential outlook of the coastal landscape under four SLR scenarios for the year 2100. The modifications include shoreline and barrier island morphology, marsh migration, and land use land cover change. Hydrodynamics of ten historic hurricanes were simulated through each of the five model configurations (present day and four SLR scenarios). Under SLR, the total inundated land area increased by 87% and developed and agricultural lands by 138% and 189%, respectively. Peak surge increased by as much as 1 m above the applied SLR in some areas, and other regions were subject to a reduction in peak surge, with respect to the applied SLR, indicating a nonlinear response. Analysis of time-series water surface elevation suggests the interaction between SLR and storm surge is nonlinear in time; SLR increased the time of inundation and caused an earlier arrival of the peak surge, which cannot be addressed using a static (“bathtub”) modeling framework. This work supports the paradigm shift to using a dynamic modeling framework to examine the effects of global climate change on coastal inundation. The outcomes have broad implications and ultimately support a better holistic understanding of the coastal system and aid restoration and long-term coastal sustainability.

Description: This study examines the integrated influence of sea level rise (SLR) and future morphology on tidal hydrodynamics along the Northern Gulf of Mexico (NGOM) coast including seven embayments and three ecologically and economically significant estuaries. A large-domain hydrodynamic model was used to simulate astronomic tides for present and future conditions (circa 2050 and 2100). Future conditions were simulated by imposing four SLR scenarios to alter hydrodynamic boundary conditions and updating shoreline position and dune heights using a probabilistic model that is coupled to SLR. Under the highest SLR scenario, tidal amplitudes within the bays increased as much as 67% (10.0 cm) due to increases in the inlet-cross-sectional area. Changes in harmonic constituent phases indicated tidal propagation was faster in the future scenarios within most of the bays. Maximum tidal velocities increased in all of the bays, especially in Grand Bay where velocities doubled under the highest SLR scenario. In addition, the ratio of the maximum flood to maximum ebb velocity decreased in the future scenarios (i.e., currents became more ebb dominant) by as much as 26% and 39% in Weeks Bay and Apalachicola, respectively. In Grand Bay, the flood-ebb ratio increased (i.e., currents became more flood dominant) by 25% under the lower SLR scenarios, but decreased by 16% under the higher SLR as a result of the offshore barrier islands being overtopped, which altered the tidal prism. Results from this study can inform future storm surge and ecological assessments of SLR, and improve monitoring and management decisions within the NGOM.

Description: Water vapor is the most important greenhouse gas in the atmosphere although changes in carbon dioxide constitute the “control knob” for surface temperatures. While the latter fact is well recognized, resulting in extensive spaceborne and ground based measurement programs for carbon dioxide [et~al.(1996), Chin, and Whorf, et~al.(2009), Suto, Nakajima, and Hamazaki, et~al.(2014), Cai, Yang, Zheng, Duan, and Lu], the need for an accurate characterization of the long-term changes in upper tropospheric and lower stratospheric (UTLS) water vapor has not yet resulted in sufficiently extensive long-term international measurement programs (although first steps have been taken). Here we argue for the implementation of a, long-term balloon-borne measurement program for UTLS water vapor covering the entire globe that likely will have to be sustained for hundreds of years.

Description: This paper analyzes multi-year records of solar flux and climate data from two solar power sites in Vermont. We show the interannual differences of temperature, wind, panel solar flux, electrical power production and cloud cover. Power production has a linear relation to a dimensionless measure of the transmission of sunlight through the cloud field. The difference between panel and air temperatures reaches 24°C with high solar flux and low windspeed. High panel temperatures that occur in summer with low windspeeds and clear skies can reduce power production by as much as 13%. The intercomparison of two sites 63 km apart shows that while temperature is highly correlated on daily (R 2 =0.98) and hourly (R 2 =0.94) timescales, the correlation of panel solar flux drops markedly from daily (R 2 =0.86) to hourly (R 2 =0.63) timescales. Minimum temperatures change little with cloud cover, but the diurnal temperature range shows a nearly linear increase with falling cloud cover to 16°C under nearly clear skies, similar to results from the Canadian Prairies. The availability of these new solar and climate datasets allows local student groups, here a Rutland High School team, to explore the coupled relationships between climate, clouds and renewable power production. As our society makes major changes in our energy infrastructure in response to climate change, it is important that we accelerate the technical education of high school students using real-world data. Citation: Betts, A.K., J. Hamilton, S. Ligon and A.M. Mahar (2015), Integrating solar energy and climate research into science education. Submitted to Earth's Future, 2015EF000315.

Description: Words are integral to thinking and communicating. Words also carry old baggage. The Anthropocene necessitates new thinking and communication at the human-nature interface. Words like progress, natural, and thresholds are pervasive in both scientific and policy discourse, but carry baggage that will likely slow understanding of the Anthropocene and appropriate adaptation. The dynamic systems thinking with emergent properties of ecology needs to replace the efficiency and growth framework of economics. Diversity and resilience are productive and less historically burdened words.

Description: Though climate models exhibit broadly similar agreement on key long-term trends, they have significant temporal and spatial differences due to inter-model variability. Such variability should be considered when using climate models to project the future marine Arctic. Here we present multiple scenarios of 21 st -century Arctic marine access as driven by sea ice output from 10 CMIP5 models known to represent well the historical trend and climatology of Arctic sea ice. Optimal vessel transits from North America and Europe to the Bering Strait are estimated for two periods representing early-century (2011–2035) and mid-century (2036–2060) conditions under two forcing scenarios (RCP 4.5/8.5), assuming Polar Class 6 and open-water vessels with medium and no ice-breaking capability, respectively. Results illustrate that projected shipping viability of the Northern Sea Route (NSR) and Northwest Passage (NWP) depends critically on model choice. The eastern Arctic will remain the most reliably accessible marine space for trans-Arctic shipping by mid-century, while outcomes for the NWP are particularly model-dependent. Omitting three models (GFDL-CM3, MIROC-ESM-CHEM, MPI-ESM-MR), our results would indicate minimal NWP potential even for routes from North America. Furthermore, the relative importance of the NSR will diminish over time as the number of viable central Arctic routes increases gradually toward mid-century. Compared to vessel class, climate forcing plays a minor role. These findings reveal the importance of model choice in devising projections for strategic planning by governments, environmental agencies, and the global maritime industry.

Description: Successful climate change mitigation will involve not only technological innovation, but innovation in how we understand the societal and individual behaviors that shape the demand for energy services. Traditionally, individual energy behaviors have been described as a function of utility optimization and behavioral economics, with price restructuring as the dominant policy lever. Previous research at the macro-level has identified economic activity, power generation and technology, and economic role as significant factors that shape energy use. However, most demand models lack basic contextual information on how dominant social phenomenon, the changing demographics of cities, and the socio-cultural setting within which people operate, affect energy decisions and use patterns. Here we use high-quality Suomi-NPP VIIRS nighttime environmental products to: (1) observe aggregate human behavior through variations in energy service demand patterns during the Christmas and New Year's season and the Holy Month of Ramadan; and (2) demonstrate that patterns in energy behaviors closely track socio-cultural boundaries at the country, city, and district-level. These findings indicate that energy decision-making and demand is a socio-cultural process as well as an economic process, often involving a combination of individual price-based incentives and societal-level factors. While nighttime satellite imagery has been used to map regional energy infrastructure distribution, tracking daily dynamic lighting demand at three major scales of urbanization is novel. This methodology can enrich research on the relative importance of drivers of energy demand and conservation behaviors at fine scales. Our initial results demonstrate the importance of seating energy demand frameworks in a social context.

Description: Despite advances in our understanding of the processes driving contemporary sea level rise, the stability of the Antarctic ice sheets and their contribution to sea level under projected future warming remains uncertain due to the influence of strong ice-climate feedbacks. Disentangling these feedbacks is key to reducing uncertainty. Here we present a series of climate system model simulations that explore the potential effects of increased West Antarctic Ice Sheet (WAIS) meltwater flux on Southern Ocean dynamics. We project future changes driven by sectors of the WAIS, delivering spatially and temporally variable meltwater flux into the Amundsen, Ross and Weddell embayments over future centuries. Focusing on the Amundsen Sea sector of the WAIS over the next 200 years, we demonstrate that the enhanced meltwater flux rapidly stratifies surface waters, resulting in a significant decrease in the rate of Antarctic Bottom Water (AABW) formation. This triggers rapid pervasive ocean warming (〉1°C) at depth due to advection from the original site(s) of meltwater input. The greatest warming predicted along sectors of the ice sheet that are highly sensitized to ocean forcing, creating a feedback loop that could enhance basal ice shelf melting and grounding line retreat. Given that we do not include the effects of rising CO 2 - predicted to further reduce AABW formation - our experiments highlight the urgent need to develop a new generation of fully-coupled ice sheet climate models, that include feedback mechanisms such as this, to reduce uncertainty in climate and sea level projections.

Description: Key Points Demographic limitations involve acute aspects of public policy. Demographic controls cannot be effectively implemented under current Western values. Traditions of social freedom will have to be altered.

Description: Key Points Liberal values in rich democracies are threatened by population growth in poor countries. The most likely repressive policy response will be barriers to immigration. Fertility reduction in high-fertility countries requires increased access to contraception.

Description: Historical extreme storm events are widely used to make Probable Maximum Precipitation (PMP) estimates, which form the cornerstone of large water management infrastructure safety. Past studies suggest that extreme precipitation processes can be sensitive to land surface feedback and the planetary warming trend, that make the future safety of large infrastructures questionable given projected changes in land cover and temperature in the coming decades. In this study, a numerical modeling framework was employed to reconstruct 10 extreme storms over CONUS that occurred during the past 100 years, which are used by the engineering profession for PMP estimation for large infrastructures such as dams. Results show that the correlation in daily rainfall for such reconstruction can range between 0.4 ~ 0.7, while the correlation for -3day accumulation (a standard period used in infrastructure design) is always above 0.5 for post-1948 storms. This suggests that current numerical modeling and reanalysis data allow us to reconstruct big storms after 1948s with acceptable accuracy. For storms prior to 1948, however, reconstruction of storms shows inconsistency with observations. Our study indicates that numerical modeling and data may not have advanced to a sufficient level to understand how such old storms (pre-1948) may behave in future warming and land cover conditions. However, the infrastructure community can certainly rely on the use of model reconstructed extreme storms of the 1948-present period to reassess safety of our large water infrastructures under assumed changes in temperature and land cover.

Description: The project presented here sought to determine whether changes in anthropogenic thermal emission can have a measurable effect on temperature at the national level, taking Japan & Great Britain as type examples. Using energy consumption as a proxy for thermal emission, strong correlations (mean r 2  = 0.90 & 0.89 respectively) are found between national equivalent heat output HO and temperature above background levels ∆ t averaged over 5 to 8 year periods between 1965 and 2013, as opposed to weaker correlations for CMIP5 model temperatures above background levels ∆ mt (mean r 2  = 0.52 & 0.10). It is clear that the fluctuations in ∆ t are better explained by energy consumption than by present climate models, and that energy consumption can contribute to climate change at the national level on these timescales.

Description: Cities generate 70% of anthropogenic greenhouse gas emissions, a fraction that is growing with global urbanization. While cities play an important role in climate change mitigation, there has been little focus on reducing urban methane emissions. Here we develop a conceptual framework for methane mitigation in cities by describing emission processes, the role of measurements, and a need for new institutional partnerships. Urban methane emissions are likely to grow with expanding use of natural gas and organic waste disposal systems in growing population centers; however, we currently lack the ability quantify this increase. We also lack systematic knowledge of the relative contribution of these distinct source sectors on emissions. We present new observations from 4 North American cities to demonstrate that methane emissions vary in magnitude and sector from city to city, and hence require different mitigation strategies. Detections of fugitive emissions from these systems suggest that current mitigation approaches are absent or ineffective. These findings illustrate that tackling urban methane emissions will require research efforts to identify mitigation targets, develop and implement new mitigation strategies, and monitor atmospheric methane levels to ensure the success of mitigation efforts. This research will require a variety of techniques to achieve these objectives, and should be deployed in cities globally. We suggest that metropolitan-scale partnerships may effectively coordinate systematic measurements and actions focused on emission reduction goals.

Description: Recent trends and climate models suggest that the Arctic summer sea ice cover is likely to be lost before climate interventions can stabilize it. There are environmental, socioeconomic and sociocultural arguments for, but also against restoring and sustaining current conditions. Even if global warming can be reversed, some people will experience ice free summers before perennial sea ice begins to return. We ask: How will future generations feel about bringing sea ice back where they have not experienced it before? How will conflicted interests in ice-covered vs ice free conditions be resolved? What role will science play in these debates?

Description: The multi-model ensemble of the Coupled Model Intercomparison Project, Phase 5 (CMIP5) synthesizes the latest research in global climate modeling. The freshwater system on land, particularly runoff, has so far been of relatively low priority in global climate models, despite the societal and ecosystem importance of freshwater changes, and the science and policy needs for such model output on drainage basin scales. Here we investigate the implications of CMIP5 multi-model ensemble output data for the freshwater system across a set of drainage basins in the Northern hemisphere. Results of individual models vary widely, with even ensemble mean results differing greatly from observations and implying unrealistic long-term systematic changes in water storage and level within entire basins. The CMIP5 projections of basin-scale freshwater fluxes differ considerably more from observations and among models for the warm-temperate study basins than for the Arctic and cold-temperate study basins. In general, the results call for concerted research efforts and model developments for improving the understanding and modeling of the freshwater system and its change drivers. Specifically, more attention to basin-scale water flux analyses should be a priority for climate model development, and an important focus for relevant model-based advice for adaptation to climate change.

Description: We explore potential changes in Greenland ice sheet form and flow associated with increasing ice temperatures and relaxing effective ice viscosities. We define "thermal-viscous collapse" as a transition from the polythermal ice sheet temperature distribution characteristic of the Holocene to temperate ice at the pressure-melting-point and associated lower viscosities. The conceptual model of thermal-viscous collapse we present is dependent on: (i) sufficient energy available in future meltwater runoff, (ii) routing of meltwater to the bed of the ice sheet interior, and (iii) efficient energy transfer from meltwater to the ice. While we do not attempt to constrain the probability of thermal-viscous collapse, it appears thermodynamically plausible to warm the deepest 15 % of the ice sheet, where the majority of deformational shear occurs, to the pressure-melting-point within five centuries. First-order numerical modelling of an end-member scenario, in which prescribed ice temperatures are warmed at an imposed rate of 0.05 K/a, infers a decrease in ice sheet volume of 5 ± 2 % within five centuries of initiating collapse. This is equivalent to a cumulative sea level rise contribution of 33 ± 18 cm. The vast majority of the sea level rise contribution associated with thermal-viscous collapse, however, would likely be realized over subsequent millennia.

Description: We report on a detailed time series analysis of long total column ozone (TO) records based on multi-satellite observations of daily resolution. We concentrate on three geographic latitudes over and around the Antarctic area, specifically on three circles at 58.5° S, 59.5°S, and 79.5°S. Almost continuous observations are available at the two former latitudes, however data are lacking during the polar winter periods at 79.5°S, because the measurement technique requires sunlight. The methodology is motivated by level-crossing statistics, where subsets of the records above or below particular threshold levels are evaluated. Long term trend reversal at around the turn of the century is already detectable for low TO levels in the raw time series in the “ozone hole” region (79.5°S). In order to overcome the apparent non-stationarities of the time series, we determined daily TO differences (ΔTO) belonging to the same geographic longitudes between the different latitudinal circles. The result is a stable, stationary behavior for small (absolute) ΔTO values in the period January-February-March without any significant detectable trends. The high absolute value ΔTO subsets (September-October-November) indicate a robust trend reversal in the middle of the 1990s. The observed trend reversal in the total column ozone time series is consistent with the temporal development of the stratospheric halogen loading. However, a close correspondence of ozone and halogen turnaround years is not expected because of the statistical uncertainties in the determination of the ozone turnaround, and the many factors contributing to ozone depletion processes.

Description: Historical examples of demographic change, in China, Italy, Nigeria, Utah, Easter Island, and elsewhere, together with simple mathematics and biological principles, show that stabilizing world population before it is limited by food supply will be more difficult than is generally appreciated. United Nations population projections are wrong because they assume, in spite of the absence of necessary feedbacks, that all nations will converge rapidly to replacement-level fertility and thereafter remain at that level. Education of women and provision of contraceptives have caused dramatic reductions in fertility, but many groups, including some that are well-educated, maintain high fertility. Small groups with persistent high fertility can grow to supplant low-fertility groups, resulting in continued growth of the total population. The global average fertility rate could rise even if each country's fertility rate is falling. In some low-fertility European countries where deaths exceed births, the population continues to grow because of immigration. Producing more than two offspring is normal for all animal species with stable populations, because their populations are limited by resources or predation rather than birth control. It may therefore be appropriate to view the growth of human population as the result not of excess fertility but rather of excess food.

Description: Tides exert a major control on the coastal zone by influencing high sea levels and coastal flooding, navigation, sediment dynamics and ecology. Therefore, any changes to tides have wide ranging and important implications. In this paper, we uniquely assess secular changes in 15 regularly used tidal levels (five high water, five low water and five tidal ranges), which have direct practical applications. Using sea level data from 220 tide gauge sites, we found changes have occured in all analysed tidal levels in many parts of the world. For the tidal levels assessed, between 36% and 63% of sites had trends significantly different (at 95% confidence level) from zero. At certain locations, the magnitude of the trends in tidal levels were similar to trends in mean sea level over the last century, with observed changes in tidal range and high water levels of over 5mm/yr and 2mm/yr respectively. More positive than negative trends were observed in tidal ranges and high water levels, and vice versa for low water levels. However we found no significant correlation between trends in mean sea level and any tidal levels. Spatially coherent trends were observed in some regions, including the north-east Pacific, German Bight and Australasia, and we also found that differences in trends occur between different tidal levels. This implies that analysing different tidal levels is important. Because changes in the tide are widespread and of similar magnitude to mean sea level rise at a number sites, changes in tides should be considered in coastal risk assessments.

Description: How climate controls hurricane variability has critical implications for society but is not well understood. In part, our understanding is hampered by the short and incomplete observational hurricane record. Here we present a synthesis of intense-hurricane activity from the western North Atlantic over the past two millennia, which is supported by a new, exceptionally well-resolved record from Salt Pond, Massachusetts (USA). At Salt Pond, three coarse grained event beds deposited in the historical interval are consistent with severe hurricanes in 1991 (Bob), 1675, and 1635 CE, and provide modern analogs for thirty-two other prehistoric event beds. Two intervals of heightened frequency of event bed deposition between 1400 and 1675 CE (10 events) and 150 and 1150 CE (23 events), represent the local expression of coherent regional patterns in intense-hurricane-induced event beds. Our synthesis indicates that much of the western North Atlantic appears to have been active between 250 and 1150 CE, with high levels of activity persisting in the Caribbean and Gulf of Mexico until 1400 CE. This interval was one with relatively warm sea surface temperatures in the main development region. A shift in activity to the North American east coast occurred ca. 1400 CE, with more frequent severe hurricane strikes recorded from The Bahamas to New England between 1400 and 1675 CE. A warm sea surface temperature anomaly along the western North Atlantic, rather than within the main development region, likely contributed to the later active interval being restricted to the east coast.

Description: This study performs high-spatial-resolution (12 km) Weather Research and Forecasting (WRF) simulations over a very large domain (7200 km × 6180 km, covering much of North America) to explore changes in mean and extreme precipitation in the mid and late 21st century under Representative Concentration Pathways 4.5 (RCP 4.5) and 8.5 (RCP 8.5). We evaluate WRF model performance for a historical simulation and future projections, applying the Community Climate System Model version 4 (CCSM4) as initial and boundary conditions with and without a bias correction. WRF simulations using boundary and initial conditions from both versions of CCSM4 show smaller biases versus evaluation data sets than does CCSM4 over western North America. WRF simulations also improve spatial details of precipitation over much of North America. However, driving the WRF with the bias-corrected CCSM4 does not always reduce the bias. WRF-projected changes in precipitation include decreasing intensity over the U.S. Southwest, increasing intensity over the eastern United Sates and most of Canada, and an increase in the number of days with heavy precipitation over much of North America. Projected precipitation changes are more evident in the late 21st century than the mid 21st century, and they are more evident under RCP 8.5 than RCP 4.5 in the late 21st century. Uncertainties in the projected changes in precipitation due to different warming scenarios are non-negligible. Differences in summer precipitation changes between WRF and CCSM4 are significant over most of the United States.

Description: In the context of climate change, both climate researchers and decision-makers deal with uncertainties, but these uncertainties differ in fundamental ways. They stem from different sources, cover different temporal and spatial scales, might or might not be reducible or quantifiable, and are generally difficult to characterize and communicate. Hence, for adaptation strategies and planning to progress, mutual understanding between current and future climate researchers and decision-makers needs to evolve. Iterative two-way dialogue can help to improve the decision-making process and bridge current top-down and bottom-up approaches. One way to cultivate such interactions is by providing venues for these actors to interact and exchange about the uncertainties they face. We use a workshop-seminar series including academic researchers, students, and decision-makers as an opportunity to put this idea into practice and evaluate it. Seminars, case studies and a round table allowed participants to reflect upon and experiment with uncertainties. An opinion survey conducted before and after the workshop-seminar series allowed us to qualitatively evaluate its influence on the participants. We find that the event stimulated new perspectives on communication processes and research priorities, and suggest that similar events may ultimately contribute to the mid-term goal of improving support for decision-making in a changing climate. Therefore, we recommend integrating interdisciplinary bridging events into university curriculum with the goal of exposing researchers, decision-makers and students to these concepts.

Description: Key Points There are historical antecedents for the Anthropocene idea. The Anthropocene idea has roots in social theory. Rousseau's social theory anticipates the Anthropocene idea.

Description: Biospheric relationships between production and consumption of biomass have been resilient to changes in the Earth system over billions of years. This relationship has increased in its complexity, from localised ecosystems predicated on anaerobic microbial production and consumption, to a global biosphere founded on primary production from oxygenic photoautotrophs, through the evolution of Eukarya, metazoans, and the complexly networked ecosystems of microbes, animals, fungi and plants that characterise the Phanerozoic Eon (the last ~541 million years of Earth history). At present, one species, Homo sapiens , is refashioning this relationship between consumption and production in the biosphere with unknown consequences. This has left a distinctive stratigraphy of the production and consumption of biomass, of natural resources, and of produced goods. This can be traced through stone tool technologies and geochemical signals, later unfolding into a diachronous signal of technofossils and human bioturbation across the planet, leading to stratigraphically almost isochronous signals developing by the mid-20 th century. These latter signals may provide an invaluable resource for informing and constraining a formal Anthropocene chronostratigraphy, but are perhaps yet more important as tracers of a biosphere state that is characterised by a geologically unprecedented pattern of global energy flow that is now pervasively influenced and mediated by humans, and which is necessary for maintaining the complexity of modern human societies.

Description: The impacts of climate change on Small Island Developing States (SIDS) are leading to discussions regarding decision-making about the potential need to migrate. Despite the situation being well-documented, with many SIDS aiming to raise the topic to prominence and to take action for themselves, limited support and interest has been forthcoming from external sources. This paper presents, analyzes and critiques a decision-making flowchart to support actions for SIDS dealing with climate change linked migration. The flowchart contributes to identifying the pertinent topics to consider and the potential support needed to implement decision-making. The flowchart has significant limitations and there are topics which it cannot resolve. On-the-ground considerations include who decides, finances, implements, monitors and enforces each decision. Additionally, views within communities differ, hence mechanisms are needed for dealing with differences, while issues to address include moral and legal blame for any climate change linked migration, the ultimate goal of the decision-making process, the wider role of migration in SIDS communities and the right to judge decision-making and decisions. The conclusions summarize the paper, emphasizing the importance of considering contexts beyond climate change and multiple SIDS voices.

Description: The Antarctic ozone hole will continue to be observed in the next 35–50 years, although the emissions of chlorofluorocarbons have gradually been phased out during the last two decades. In this paper, we suggest a geo-engineering approach that will remove substantial amounts of hydrogen chloride (HCl) from the lower stratosphere in fall and hence limit the formation of the Antarctic ozone hole in late winter and early spring. HCl will be removed by ice from the atmosphere at temperatures higher than the threshold under which polar stratospheric clouds (PSCs) are formed if sufficiently large amounts of ice are supplied to produce water saturation. A detailed chemical-climate numerical model is used to assess the expected efficiency of the proposed geo-engineering method, and specifically to calculate the removal of HCl by ice particles. The size of ice particles appears to be a key parameter: larger particles (with a radius between 10 and 100 µm) appear to be most efficient for removing HCl. Sensitivity studies lead to the conclusions that the ozone recovery is effective when ice particles are supplied during May and June in the latitude band ranging from 70 to 90°S and in the altitude layer ranging from the 10 to 26 km. It appears therefore that supplying ice particles to the Antarctic lower stratosphere could be effective in reducing the depth of the ozone hole. In addition, photodegradation of chlorofluorocarbons (CFCs) might be accelerated when ice is supplied due to enhanced vertical transport of this efficient greenhouse gas.

Description: A regional nuclear war between India and Pakistan could decrease global surface temperature by 1 to 2°C for 5 to 10 years, and have major impacts on precipitation and solar radiation reaching Earth's surface. Using a crop simulation model forced by three global climate model simulations, we investigate the impacts on agricultural production in China, the largest grain producer in the world. In the first year after the regional nuclear war, a cooler, drier, and darker environment would reduce annual rice production by 30 Mt (29%), maize production by 36 Mt (20%), and wheat production by 23 Mt (53%). With different agriculture managements – no irrigation, auto irrigation, 200 kg/ha nitrogen fertilizer and 10 days delayed planting date, simulated national crop productions reduce 16-26% for rice, 9-20% for maize and 32-43% for wheat during five years after the nuclear war event. This reduction of food availability would continue, with gradually decreasing amplitude, for more than a decade. Assuming these impacts are indicative of those in other major grain producers, a nuclear war using much less than 1% of the current global arsenal could produce a global food crisis and put a billion people at risk of famine.

Description: Decision makers and consultants are particularly interested in “detailed” information on future climate to prepare adaptation strategies and adjust design criteria. Projections of future climate at local spatial scales and fine temporal resolutions are subject to the same uncertainties as those at the global scale but the partition among uncertainty sources (emission scenarios, climate models, and internal climate variability) remains largely unquantified. At the local scale the uncertainty of the mean and extremes of precipitation is shown to be irreducible for mid and end-of-century projections because it is almost entirely due to internal climate variability (stochasticity). Conversely, projected changes in mean air temperature and other meteorological variables can be largely constrained, even at local scales, if more accurate emission scenarios can be developed. The results were obtained by applying a comprehensive stochastic downscaling technique to climate model outputs for three exemplary locations. In contrast with earlier studies, the three sources of uncertainty are considered as dependent and, therefore, non-additive. The evidence of the predominant role of internal climate variability leaves little room for uncertainty reduction in precipitation projections; however, the inference is not necessarily negative, since the uncertainty of historic observations is almost as large as that for future projections with direct implications for climate change adaptation measures.

Description: The Arctic temperature response to emissions of aerosols – specifically black carbon (BC), organic carbon (OC), and sulfate – depends on both the sector and the region where these emissions originate. Thus, the net Arctic temperature response to global aerosol emissions reductions will depend strongly on the blend of emissions sources being targeted. We use recently published equilibrium Arctic temperature response factors for BC, OC, and sulfate to estimate the range of present-day and future Arctic temperature changes from seven different aerosol emissions scenarios. Globally, Arctic temperature changes calculated from all of these emissions scenarios indicate that present-day emissions from the domestic and transportation sectors generate the majority of present-day Arctic warming from BC. However, in all of these scenarios, this warming is more than offset by cooling resulting from SO 2 emissions from the energy sector. Thus, long-term climate mitigation strategies that are focused on reducing carbon dioxide (CO 2 ) emissions from the energy sector could generate short-term, aerosol-induced Arctic warming. A properly phased approach that targets BC-rich emissions from the transportation sector as well as the domestic sectors in key regions – while simultaneously working toward longer-term goals of CO 2 mitigation – could potentially avoid some amount of short-term Arctic warming.

Description: The Great Lakes basin hosts the world's most abundant surface fresh water reserve. Historically an industrial and natural resource powerhouse, the region has suffered economic stagnation in recent decades. Meanwhile, growing water resource scarcity around the world is creating pressure on water-intensive human activities. This situation creates the potential for the Great Lakes region to sustainably utilize its relative water wealth for economic benefit. We combine economic production and trade datasets with water consumption data and models of surface water depletion in the region. We find that, on average, the current economy does not create significant impacts on surface waters, but there is some risk that unregulated large water uses can create environmental flow impacts if they are developed in the wrong locations. Water uses drawing on deep groundwater or the Great Lakes themselves are unlikely to create a significant depletion, and discharge of groundwater withdrawals to surface waters offsets most surface water depletion. This relative abundance of surface water means that science-based management of large water uses to avoid accidentally creating “hotspots” is likely to be successful in avoiding future impacts, even if water use is significantly increased. Commercial water uses are the most productive, with thermoelectric, mining, and agricultural water uses in the lowest tier of water productivity. Surprisingly for such a water-abundant economy, the region is a net importer of water-derived goods and services. This, combined with the abundance of surface water, suggests that the region's water-based economy has room to grow in the 21 st century.

Description: A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes the bulk volume of sediment equates to the sum of self-packing volumes of organic and mineral components or BD = 1/[LOI/ k 1 + (1-LOI)/ k 2 ], where k 1 and k 2 are the self-packing densities of the pure organic and inorganic components, respectively. The model explained 78% of the variability in total BD when fitted to 5075 measurements drawn from 33 wetlands distributed around the conterminous United States. The values of k 1 and k 2 were estimated to be 0.085 -±0.0007 g cm −3 and 1.99 ± 0.028 g cm −3 , respectively. Based on the fitted organic density ( k 1 ) and constrained by primary production, the model suggests that the maximum steady state accretion arising from the sequestration of refractory organic matter is ≤ 0.3 cm yr −1 . Thus, tidal peatlands are unlikely to survive indefinitely a higher rate of sea-level rise in the absence of a significant source of mineral sediment. Application of k 2 to a mineral sediment load typical of East and eastern Gulf Coast estuaries gives a vertical accretion rate from inorganic sediment of 0.2 cm yr −1 . Total steady state accretion is the sum of the parts and therefore should not be greater than 0.5 cm yr −1 under the assumptions of the model. Accretion rates could deviate from this value depending on variation in plant productivity, root:shoot ratio, suspended sediment concentration, sediment-capture efficiency, and episodic events.

Description: Key Points Thank you to the reviewers of Earth's Future in 2015

Description: This paper addresses the question of what effect can local regulations have on pollutants with different lifetimes and how surface observations and remotely sensed data can be used to determine the impacts. We investigated the decadal trends of tropospheric sulfur dioxide (SO 2 ) and aerosol pollution over Maryland and its surrounding states, using surface, aircraft, and satellite measurements. Aircraft measurements indicated fewer isolated SO 2 plumes observed in summers, a ~40% decrease of column SO 2 , and a ~20% decrease of atmospheric optical depth (AOD) over Maryland after the implementation of local regulations on sulfur emissions from power plants (~90% reduction from 2010). Surface observations of SO 2 and particulate matter (PM) concentrations in Maryland show similar trends. OMI SO 2 and MODIS AOD observations were used to investigate the column contents of air pollutants over the eastern U.S.; these indicate decreasing trends in column SO 2 (~60% decrease) and AOD (~20% decrease). The decrease of upwind SO 2 emissions also reduced aerosol loadings over the downwind Atlantic Ocean near the coast by ~20%, while indiscernible changes of SO 2 column were observed. A step change of SO 2 emissions in Maryland starting in 2009-2010 had an immediate and profound benefit in terms of local surface SO 2 concentrations, but a modest impact on aerosol pollution, indicating that short-lived pollutants are effectively controlled locally while long-lived pollutants require regional measures.

Description: The 2030 Agenda for Sustainable Development includes a set of 17 Sustainable Development Goals (SDG) with 169 specific targets. As such, it could be a step forward in achieving efficient governance and policies for global sustainable development. However, the current indicator framework with its broad set of individual indicators prevents straightforward assessment of synergies and trade-offs between the various indicators, targets, and goals thus heightening the significance of policy guidance in achieving sustainable development. With our detailed analysis of SDG 14 (Ocean) for European Union coastal states, we demonstrate how the (complementary) inclusion of composite indicators that aggregate the individual indicators by applying a generalized mean can provide important additional information and facilitate the assessment of sustainable development in general and in the SDG context in particular. Embedded in the context of social choice theory, the generalized mean varies the specification of substitution elasticity and thus allows a) for a straightforward distinction between a concept of weak and strong sustainability and b) for straightforward sensitivity analysis. We show that while in general the EU coastal states have a fairly balanced record at the SDG 14 level, certain countries like Slovenia and Portugal with a fairly balanced and a fairly unbalanced showing, respectively, rank very differently in terms of the two concepts of strong sustainability.

Description: We are interested in the spatial distribution of fossil-fuel-related emissions of CO 2 for both geochemical and geopolitical reasons, but it is important to understand the uncertainty that exists in spatially explicit emissions estimates. Working from one of the widely-used gridded data sets of CO 2 emissions, we examine the elements of uncertainty, focusing on gridded data for the U.S. at the scale of 1 degree latitude by 1 degree longitude. Uncertainty is introduced in the magnitude of total U.S. emissions, the magnitude and location of large point sources, the magnitude and distribution of non-point sources, and from the use of proxy data to characterize emissions. For the U.S. we develop estimates of the contribution of each component of uncertainty. At 1 degree resolution, in most grid cells, the largest contribution to uncertainty comes from how well the distribution of the proxy (in this case population density) represents the distribution of emissions. In other grid cells the magnitude and location of large point sources make the major contribution to uncertainty. Uncertainty in population density can be important where a large gradient in population density occurs near a grid cell boundary. Uncertainty is strongly scale-dependent with uncertainty increasing as grid size decreases. Uncertainty for our data set with one degree grid cells for the U.S. is typically on the order of +/− 150%, but this is perhaps not excessive in a data set where emissions per grid cell vary over 8 orders of magnitude.

Description: There is increasing emphasis from funding agencies on transdisciplinary approaches to integrate science and end-users. However, transdisciplinary research can be laborious and costly and knowledge of effective collaborative processes in these endeavors is incomplete. More guidance grounded in actual project experiences is needed. Thus, this paper describes and examines the collaborative process of the Ecological Effects of Sea Level Rise in the Northern Gulf of Mexico (EESLR-NGOM) transdisciplinary research project, including its development, implementation, and evaluation. Reflections, considerations, and lessons learned from firsthand experience are shared, supported with examples, and connected to relevant scholarly literature.

Description: Precipitation extremes are expected to become more frequent in the changing global climate, which may considerably affect the terrestrial hydrological cycle. In this study, Coupled Model Intercomparison Project Phase 5 (CMIP5) archives have been examined to explore the changes in normalized terrestrial water fluxes (TWFn) (precipitation minus evapotranspiration minus total runoff, divided by the precipitation climatology) in three tropical rainforest areas: Maritime Continent, Congo, and Amazon. Results reveal that a higher frequency of intense precipitation events is predicted for the Maritime Continent in the future climate than in the present climate, but not for the Amazon or Congo rainforests. Nonlinear responses to extreme precipitation lead to a reduced groundwater recharge and a proportionately greater amount of direct runoff, particularly for the Maritime Continent, where both the amount and intensity of precipitation increase under global warming. We suggest that the nonlinear response is related to the existence of a higher near-surface soil moisture over the Maritime Continent than that over the Amazon and Congo rainforests. The wetter soil over the Maritime Continent also leads to an increased subsurface runoff. Thus, increased precipitation extremes and concomitantly reduced terrestrial water fluxes (TWF) lead to an intensified hydrological cycle for the Maritime Continent. This has the potential to result in a strong temporal heterogeneity in soil water distribution affecting the ecosystem of the rainforest region and increasing the risk of flooding and/or landslides.

Description: There is a pressing need to improve food security and reduce environmental impacts of agricultural production globally. Two of the proposed measures are diet change from animal-based to plant-based foodstuffs and reduction of food losses and waste. These two measures are linked, as diet change affects production and consumption of foodstuffs and consequently loss processes through their different water footprints and loss percentages. This paper takes this link into account for the first time and provides an assessment of the combined potential contribution of diet change and food loss reduction for reducing water footprints and water scarcity. We apply scenarios in which we change diets to follow basic dietary recommendations, limit animal-based protein intake to 25% of total protein intake, and halve food losses to study single and combined effects of diet change and loss reduction. Dietary recommendations alone would achieve 6% and 7% reductions of blue and green water consumption, respectively, while changing diets to contain less animal-products would result in savings of 11% and 18%. Halving food loss would alone achieve 12% reductions for both blue and green water. Combining the measures would reduce water consumption by 23% and 28%, respectively, lowering water scarcity in areas with a population of over 600 million. At a global scale, effects of diet change and loss reduction were synergistic with loss reductions being more effective under changed diet. This demonstrates the importance of considering the link between diet change and loss reduction in assessments of food security and resource use.

Description: This perspective paper reviews progress made in the last decades to enhance the communication and use of climate information relevant to the political and economic decision process. It focuses, specifically, on the creation and development of climate services, and highlights a number of difficulties that have limited the success of these services. Among them are the insufficient awareness by societal actors of their vulnerability to climate change, the lack of relevant products and services offered by the scientific community, the inappropriate format in which the information is provided, and the inadequate business model adopted by climate services. The authors suggest that, to be effective, centers should host within the same center a diversity of staff including experts in climate science, specialists in impact, adaptation and vulnerability, representatives of the corporate world, agents of the public service as well as social managers and communication specialists. The role and importance of environmental engineering is emphasized.

Description: The historical developments are reviewed that have led from a bottom-up responsibility initiative of concerned scientists to the emergence of a nationwide interdisciplinary Priority Program on the assessment of Climate Engineering (CE), funded by the German Research Foundation (DFG). Given the perceived lack of comprehensive and comparative appraisals of different CE methods, the Priority Program was designed to encompass both solar radiation management (SRM) and carbon dioxide removal (CDR) ideas, and to cover the atmospheric, terrestrial and oceanic realm. First key findings obtained by the ongoing Priority Program are summarized and reveal that compared to earlier assessments, such as the 2009 Royal Society report, more detailed investigations tend to indicate less efficiency, lower effectiveness and often lower safety. Emerging research trends are discussed in the context of the recent Paris agreement to limit global warming to less than two degrees and the associated increasing reliance on negative emission technologies. Our results show then when deployed at scales large enough to have a significant impact on atmospheric CO 2 , even CDR methods such as afforestation – often perceived as ‘benign’ – can have substantial side effects and may raise severe ethical, legal and governance issues. We suppose that before being deployed at climatically relevant scales, any negative-emission or climate engineering method will require careful analysis of efficiency, effectiveness and undesired side effects.

Description: Since 1960's, India experiences a series of extreme drought and flood events during the summer months. The Humid Subtropical Climatic Zone (HSTC), which comprises the Indo-Gangetic Plain (IGP) region of India, is highly vulnerable to the climatic extremities. This region is the home for ~40% of total population and yields ~50% of total agricultural production of India. We investigate the historical variation in dry/wet conditions and project the future changes in extreme events under two different scenarios of the CMIP5 models. Firstly, the model parameters i.e. precipitation ( P ) and temperature ( T ) are bias corrected with respect to observation data and finally 6 models are selected, which are in right phase with the observation for composite analysis. Next, we calculate the potential evapo-transpiration ( PET ) and the Standardized Potential Evapo-transpiration Index ( SPEI ) to characterize the extreme events. Both P and PET are projected to increase in the HSTC zone; however, both the wet and dry conditions demonstrate a persistent increase in future. In relative terms, P increases faster than PET along the Gangetic Plain region (wet condition) and decreases in the southern and eastern part of the region (dry condition). The mitigating effect (RCP4.5 scenario) of precipitation increase will be overridden by strengthened PET and extreme dry condition project markedly under RCP8.5 scenario. The features are consistent with the increase/ decrease in multi-model mean SPEI, consistent with the spatial pattern of P−PET . The area affected due to wet and dry events will be relatively higher under the RCP4.5 and RCP8.5 scenario, respectively.

Description: In the 2000s, the rapid growth of CO 2 emitted in the production of exports from developing to developed countries, in which China accounted for the dominant share, led to concerns that climate polices had been undermined by international trade. Arguments on ‘carbon leakage’ and ‘competitiveness’ – which led to the refusal of the United States to ratify the Kyoto Protocol – put pressure on developing countries, especially China, to limit their emissions with Border Carbon Adjustments used as one threat. After strong growth in the early 2000s, emissions exported from developing to developed countries plateaued and could have even decreased since 2007. These changes were mainly due to China: In 2002–2007, China’s exported emissions grew by 827 MtCO 2 , amounting to almost all the 892 MtCO 2 total increase in emissions exported from developing to developed countries, while in 2007–2012, emissions exported from China decreased by 229 MtCO 2 , contributing to the total decrease of 172 MtCO 2 exported from developing to developed countries. We apply Structural Decomposition Analysis to find that, in addition to the diminishing effects of the global financial crisis, the slowdown and eventual plateau was largely explained by several potentially permanent changes in China: Decline in export volume growth, improvements in CO 2 intensity, and changes in production structure and the mix of exported products. We argue that growth in China’s exported emissions will not return to the high levels during the 2000s, therefore the arguments for climate polices focused on embodied emissions such as Border Carbon Adjustments are now weakened.

Description: We present new detail on how future SLR will modify nonlinear wave transformation processes, shoreline wave energy and wave driven flooding on atoll islands. Frequent and destructive wave inundation is a primary climate-change hazard that may render atoll islands uninhabitable in the near future. However, limited research has examined the physical vulnerability of atoll islands to future SLR and sparse information is available to implement process based coastal management on coral reef environments. We utilize a field-verified numerical model capable of resolving all nonlinear wave transformation processes to simulate how future SLR will modify wave dissipation and overtopping on Funafuti Atoll, Tuvalu, accounting for static and accretionary reef adjustment morphologies. Results show that future SLR coupled with a static reef morphology will not only increase shoreline wave energy and overtopping but will fundamental alter the spectral composition of shoreline energy by decreasing the contemporary influence of low frequency infragravity waves. ‘ Business-as-usual ' emissions (RCP 8.5) will result in annual wave overtopping on Funafuti Atoll by 2030, with overtopping at high tide under mean wave conditions occurring from 2090. Comparatively, vertical reef accretion in response to SLR will prevent any significant increase in shoreline wave energy and mitigate wave driven flooding volume by 72%. Our results provide the first quantitative assessment of how effective future reef accretion can be at mitigating SLR associated flooding on atoll islands and endorse active reef conservation and restoration for future coastal protection.

Description: ABSTRACT Risk perception research has played an influential role in supporting risk management and risk communication policy. Risk perception studies are popular across a range of disciplines in the social and natural sciences for a wide range of hazard types. Their results have helped to articulate the complex individual, relational, structural, and environmental factors influencing people's behavior. Connections between individual and collective behaviors and norms impacting global climate change, and consequently, local disaster risk, however, are infrequently included in disaster risk management. This paper presents results from two diverse and complementary European risk perception studies examining both natural and anthropogenic hazards. Research gaps and recommendations for developing more comprehensive risk management strategies are presented.

Description: Multi-sectoral partnerships (MSPs) form an increasingly popular and important part of the global climate and disaster risk governance landscape, but literature offers little critical investigation of this phenomenon. In particular it remains unclear how MSPs can support the transition from agenda-setting to implementation in response to multiple current and future pressures threatening the resilience of cities. Through the lens of the London Climate Change Partnership (LCCP) and drawing from other MSP examples, this paper investigates the scope for MSPs to enhance climate adaptation in an urban context. Our paper has two main aims: to expand understanding of the role of MSPs in the adaptation decision process in the context of the wider governance literature, and to shed some light on the complexities of transitioning through that process. To clarify the role of a MSP we propose a distinction between ‘first generation’ and ‘second generation’ MSPs, illustrating the progression from agenda-setting to implementation: ‘first generation’ MSPs are focused on agenda-setting and knowledge sharing in order to support decision-makers, while ‘second generation’ partnerships are aimed at implementing solutions. We consider this distinction from the perspective of the individual members and their perceptions, motivations and expectations. We find that the dynamic nature of urban adaptation with a shifting focus from initial agenda setting towards the implementation of actions presents challenges for existing MSPs, particularly such long-established ones like the LCCP. Our investigation shows that ‘first generation’ MSPs can play important roles in agenda-setting, but finds little evidence of ‘second generation’ MSPs achieving implementation.

Description: Improving society's ability to prepare for, respond to and recover from flooding requires integrated, anticipatory flood risk management (FRM) . However, most countries still focus their efforts on responding to flooding events if and when they occur rather than addressing their current and future vulnerability to flooding. Flood insurance is one mechanism that could a more ex-ante approach to risk by supporting risk reduction activities. This paper uses an adapted version of Easton's System Theory to investigate the role of insurance for FRM in Germany and England. We introduce an anticipatory FRM framework, which allows to consider flood insurance as part of a broader policy field. We analyse if and how flood insurance can catalyse a change towards a more anticipatory approach to FRM. In particular we consider insurance's role in influencing five key components of an anticipatory FRM: risk knowledge, prevention through better planning, property-level protection measures, structural protection and preparedness (for response). We find that in both countries FRM is still a reactive, event-driven process, while anticipatory FRM remains underdeveloped. However, collaboration between insurers and FRM decision-makers has already been successful, for example in improving risk knowledge and awareness, while in other areas insurance acts as a disincentive for more risk reduction action. In both countries there is evidence that insurance can play a significant role in encouraging anticipatory FRM, but this remains underutilized. Effective collaboration between insurers and government, should not be seen as a cost, but as an investment to secure future insurability through flood resilience.

Description: Just as carbon fueled the Industrial Revolution, nitrogen has fueled an Agricultural Revolution. The use of synthetic nitrogen fertilizers and the cultivation of nitrogen-fixing crops both expanded exponentially during the last century, with most of the increase occurring after 1960. As a result, the current flux of reactive, or fixed, nitrogen compounds to the biosphere due to human activities is roughly equivalent to the total flux of fixed nitrogen from all natural sources, both on land masses and in the world's oceans. Natural fluxes of fixed nitrogen are subject to very large uncertainties, but anthropogenic production of reactive nitrogen has increased almost five-fold in the last half-century, and this rapid increase in anthropogenic fixed nitrogen has removed any uncertainty on the relative importance of anthropogenic fluxes to the natural budget. The increased use of nitrogen has been critical for increased crop yields and protein production needed to keep pace with the growing world population. However, similar to carbon, the release of fixed nitrogen into the natural environment is linked to adverse consequences at local, regional, and global scales. Anthropogenic contributions of fixed nitrogen continue to grow relative to the natural budget, with uncertain consequences.

Description: Land surface albedo is a key parameter controlling the local energy budget, and altering the albedo of built surfaces has been proposed as a tool to mitigate high near-surface temperatures in the Urban Heat Island. However, most research on albedo in urban landscapes has used coarse-resolution data, and few studies have attempted to relate albedo to other urban land cover characteristics. This study provides an empirical description of urban summertime albedo using 30 m remote sensing measurements in the metropolitan area around Boston, Massachusetts, relating albedo to metrics of impervious cover fraction, tree canopy coverage, population density, and land surface temperature (LST). At 30 m spatial resolution, median albedo over the study area (excluding open water) was 0.152 (0.112–0.187). Trends of lower albedo with increasing urbanization metrics and temperature emerged only after aggregating data to 500 m or the boundaries of individual towns, at which scale a −0.01 change in albedo was associated with a 29 (25–35)% decrease in canopy cover, a 27 (24–30)% increase in impervious cover, and an increase in population from 11–386 km −2 . The most intensively urbanized towns in the region showed albedo up to 0.035 lower than the least urbanized towns, and mean mid-morning LST 12.6 °C higher. Trends in albedo derived from 500 m MODIS measurements were comparable, but indicated a strong contribution of open water at this coarser resolution. These results reveal linkages between albedo and urban land cover character, and offer empirical context for climate resilient planning and future landscape functional changes with urbanization.

Description: Despite a growing literature on the climate response to solar geoengineering – proposals to cool the planet by increasing the planetary albedo – there has been little published on the impacts of solar geoengineering on natural and human systems such as agriculture, health, water resources, and ecosystems. An understanding of the impacts of different scenarios of solar geoengineering deployment will be crucial for informing decisions on whether and how to deploy it. Here we review the current state of knowledge about impacts of a solar geoengineered climate and identify major research gaps. We suggest that a thorough assessment of the climate impacts of a range of scenarios of solar geoengineering deployment is needed and can build upon existing frameworks. However, solar geoengineering poses a novel challenge for climate impacts research as the manner of deployment could be tailored to pursue different objectives making possible a wide range of climate outcomes. We present a number of ideas for approaches to extend the survey of climate impacts beyond standard scenarios of solar geoengineering deployment to address this challenge. Reducing the impacts of climate change is the fundamental motivator for emissions reductions and for considering whether and how to deploy solar geoengineering. This means that the active engagement of the climate impacts research community will be important for improving the overall understanding of the opportunities, challenges and risks presented by solar geoengineering.

Description: ABSTRACT In the last decade, solar geoengineering (solar radiation management, or SRM) has received increasing consideration as a potential means to reduce risks of anthropogenic climate change. Some ideas regarding SRM that have been proposed have receded after being appropriately scrutinized, while others have strengthened through testing and critique. This process has improved understanding of SRM’s potential and limitations. However, a number of claims are frequently made in the academic and popular SRM discourses and, despite evidence to the contrary, pose the risk of hardening into accepted facts. Here, in order to foster a more productive and honest debate, we identify, describe, and refute five of the most problematic claims that are unsupported by existing evidence, unlikely to occur, or greatly exaggerated. These are (1) once started, SRM cannot be stopped; (2) SRM is a right-wing project; (3) SRM would cost only a few billion dollars per year; (4) Modelling studies indicate that SRM would disrupt monsoon precipitation; and (5) there is an international prohibition on outdoors research. SRM is a controversial proposed set of technologies that could prove to be very helpful or very harmful, and it warrants vigorous and informed public debate. By highlighting and debunking some persistent but unsupported claims, this paper hopes to bring rigor to such discussions.

Description: We offer a hypothesis that if SG were deployed to offset half of the increase in global-mean temperature from the date of deployment using a technology and deployment method chosen to approximate a reduction in the solar constant then, over the 21st Century, it would (a) substantially reduce the global aggregate risks of climate change, (b) without making any country worse off, and (c) with the aggregate risks from side-effects being small in comparison to the reduction in climate risks. We do not set out to demonstrate this hypothesis; rather we propose it with the goal of stimulating a strategic engagement of the SG research community with policy-relevant questions. We elaborate 7 sub-hypotheses on the effects of our scenario for key risks of climate change that could be assessed in future modelling work. As an example, we provide a defence of one of our sub-hypotheses, that our scenario of SG would reduce the risk of drought in dry regions, but also identify issues that may undermine this sub-hypothesis and how future work could resolve this question. Solar geoengineering cannot substitute for emissions mitigation but it may be a useful supplement. It is our hope that scientific and technical research over the next decade focuses more closely on well-articulated variants of the key policy-relevant question: could solar geoengineering be designed and deployed in such a way that it could substantially and equitably reduce climate risks?

Description: Earth's Future invited “leading experts in the field of geoengineering research to contribute brief reflections (2 - 5 pages) on the development of the discussion over the past decade and to consider where it may be going in the next 10 years”. Responding to this request, we offer the following text in the spirit of reflections that emphasize our personal roles and viewpoints. The primary focus of many of our comments is solar geoengineering and not carbon dioxide removal. Thus, this text is not intended to comprise a comprehensive review or set of carefully documented analyses. Our primary conclusion is that sustained progress in ‘geoengineering’ research will depend on social and material support for experimental work that can provide the observational basis for improved modeling and analysis, and, potentially, development and deployment of systems that may help protect the environment and improve human well-being. Relevant issues, and potential future trajectories, for carbon dioxide removal technologies may differ dramatically from those for solar geoengineering technologies.

Description: A decade has passed since Paul Crutzen published his editorial essay on the potential for stratospheric geoengineering to cool the climate in the Anthropocene. He synthesised the effects of the 1991 Pinatubo eruption on the planet's radiative budget and used this large scale event to broaden and deepen the debate on the challenges and opportunities of large scale geoengineering. Pinatubo had pronounced effects, both short and longer term (months to years) on the ocean, land and the atmosphere. This rich set of data on how a large scale natural event influences many regional and global facets of the Earth System provides a comprehensive viewpoint to assess the wider ramifications of geoengineering. Here, I use the Pinatubo archives to develop a range of geopolitically-relevant ranking criteria for a suite of different geoengineering approaches. The criteria focus on the spatial scales needed for geoengineering, and whether large-scale dispersal is a necessary requirement for a technique to deliver significant cooling or carbon dioxide reductions. These categories in turn inform whether geoengineering approaches are amenable to participation (the ‘democracy of geoengineering’), and whether they will lead to transboundary issues which could precipitate geopolitical conflicts. The criteria provide the requisite detail to demarcate different geoengineering approaches in the context of geopolitics. Hence they offer another tool that can be used in the development of a more holistic approach to the debate on geoengineering.

Description: The concept of Earth's Equilibrium Climate Sensitivity (ECS) is reviewed. A particular problem in quantifying plausible bounds for ECS has been how to account for all of the diverse lines of relevant scientific evidence. It is argued that developing and refuting physical storylines (hypotheses) for values outside any proposed range has the potential to better constrain these bounds and to help articulate the science needed to narrow the range further. A careful reassessment of all important lines of evidence supporting these storylines, their limitations, and the assumptions required to combine them is therefore urgently required.

Description: In this study, we demonstrate skillful spring forecasts of detrended September Arctic sea ice extent using passive microwave observations of sea ice concentration (SIC) and melt onset (MO). We compare these to forecasts produced using data from a sophisticated melt pond model, and find similar to higher skill values, where the forecast skill is calculated relative to linear trend persistence. The MO forecasts shows the highest skill in March–May, while the SIC forecasts produce the highest skill in June–August, especially when the forecasts are evaluated over recent years (since 2008). The high MO forecast skill in early spring appears to be driven primarily by the presence and timing of open water anomalies, while the high SIC forecast skill appears to be driven by both open water and surface melt processes. Spatial maps of detrended anomalies highlight the drivers of the different forecasts, and enable us to understand regions of predictive importance. Correctly capturing sea ice state anomalies, along with changes in open water coverage appear to be key processes in skillfully forecasting summer Arctic sea ice.

Description: Society has set ambitious targets for stabilizing mean global temperature. To attain these targets, it will have to reduce CO 2 emissions to near zero by mid-century and subsequently remove CO 2 from the atmosphere during the latter half of the century. There is a recognized need to develop technologies for CO 2 removal; however, attempts to develop direct air capture systems have faced both energetic and financial constraints. Recently, BioEnergy with Carbon Capture and Storage (BECCS) has emerged as a leading candidate for removing CO 2 from the atmosphere. However, BECCS can have negative consequences on land, nutrient, and water use as well as biodiversity and food production. Here, we describe an alternative approach based on the large-scale industrial production of marine microalgae. When cultivated with proper attention to power, carbon, and nutrient sources, microalgae can be processed to produce a variety of biopetroleum products, including carbon neutral biofuels for the transportation sector and long-lived, potentially carbon-negative construction materials for the built environment. In addition to these direct roles in mitigating and potentially reversing the effects of fossil CO 2 emissions, microalgae can also play an important indirect role. Because microalgae exhibit much higher primary production rates than terrestrial plants, they require much less land area to produce an equivalent amount of bioenergy and/or food. On a global scale, the avoided emissions resulting from displacement of conventional agriculture may exceed the benefits of microalgae biofuels in achieving climate stabilization goals.

Description: Biome-specific soil respiration (Rs) has important yet different roles in both the carbon cycle and climate change from regional to global scales. To date, no comparable studies related to global biome-specific Rs have been conducted applying comprehensive global Rs databases. The goal of this study was to develop artificial neural network (ANN) models capable of spatially estimating global Rs and to evaluate the effects of interannual climate variations on 10 major biomes. We used 1,976 annual Rs field records extracted from global Rs literature to train and test the ANN models. We determined that the best ANN model for predicting biome-specific global annual Rs was the one that applied mean annual temperature (MAT), mean annual precipitation (MAP) and biome type as inputs ( r 2  = 0.60). The ANN models reported an average global Rs of 93.3 ± 6.1 Pg C year −1 from 1960 to 2012 and an increasing trend in average global annual Rs of 0.04 Pg C year −1 . Estimated annual Rs increased with increases in MAT and MAP in cropland, boreal forest, grassland, shrubland and wetland biomes. Additionally, estimated annual Rs decreased with increases in MAT and increased with increases in MAP in desert and tundra biomes, and only significantly decreased with increases in MAT ( r 2  = 0.87) in the savannah biome. The developed biome-specific global Rs database for global land and soil carbon models will aid in understanding the mechanisms underlying variations in soil carbon dynamics and in quantifying uncertainty in the global soil carbon cycle.

Description: ABSTRACT Monitoring is science keeping our thumb on the pulse of the environment to detect any changes of concern for societies. Basic science is the question-driven search for fundamental processes and mechanisms. Given the firm root of monitoring in human interests and needs, basic sciences have often been regarded as scientifically “purer” – particularly within university-based research communities. We argue that the dichotomy between “research” and “monitoring” is an artificial one, and that this artificial split clouds the definition of scientific goals and leads to suboptimal use of resources. We claim that the synergy between the two scientific approaches is well distilled by science conducted under extreme logistic constraints, when scientists are forced to take full advantage of both the data and the infrastructure available. In evidence of this view, we present our experiences from two decades of uniting research and monitoring at the remote research facility Zackenberg in High Arctic Greenland. For this site, we show how the combination of insights from monitoring with the mechanistic understanding obtained from basic research has yielded the most complete understanding of the system – to the benefit of all, and as an example to follow. We therefore urge scientists from across the continuum from monitoring to research to come together, to disregard old division lines, and to work together to expose a comprehensive picture of ecosystem change and its consequences.

Description: Although recent decades have been the warmest since 1850, and global mean temperatures during 2015 and 2016 beat all instrumental records, the rate of increase in global surface air temperature (GSAT) significantly decreased at the beginning of the 21st Century. In this context, we examine the roles of ice melting and associated increase in sea-water mass, both of which significantly increased at the same time as GSAT decreased. Specifically, we show that (1) the slowdown of the rate of increase in GSAT between the specific periods 1992–2001 and 2002–2011 exists in all three climate records analyzed and is statistically significant at the 5% level amounting between 0.029 and 0. 036 °C/yr and leaving an energy of 14.8 to 18.4 10 19  J/yr available; (2) the increase of the atmosphere-related ice melt between these two periods amounts to 316 Gt/yr which requires 10.5 10 19  J/yr, i.e. between 57% and 71 % of the energy left by the slowdown; and (3) the energy budget shows therefore that the heat required to melt this additional 316 Gt/yr of ice is of the same order as the energy needed to warm the atmosphere during the decade 2002–2011 as much as during the previous one, suggesting a redistribution of heat within the atmosphere-cryosphere system.

Description: Climate change is a major driver of vegetation activity but its complex ecological relationships impede research efforts. In this study, the spatial distribution and dynamic characteristics of climate change effects on vegetation activity in China from the 1980s to the 2010s and from 2021 to 2050 were investigated using a geographically weighted regression (GWR) model. The GWR model was based on combined datasets of satellite vegetation index, climate observation and projection, and future vegetation productivity simulation. Our results revealed that the significantly positive precipitation-vegetation relationship was and will be mostly distributed in North China. However, the regions with temperature-dominated distribution of vegetation activity were and will be mainly located in South China. Due to the varying climate features and vegetation cover, the spatial correlation between vegetation activity and climate change may be altered. There will be different dominant climatic factors for vegetation activity distribution in some regions such as Northwest China, and even opposite correlations in Northeast China. Additionally, the response of vegetation activity to precipitation will move southward in the next three decades. In contrast, although the high warming rate will restrain the vegetation activity, precipitation variability could modify hydrothermal conditions for vegetation activity. This observation is exemplified in the projected future enhancement of vegetation activity in the Tibetan Plateau and weakened vegetation activity in East and Middle China. Furthermore, the vegetation in most parts of North China may adapt to an arid environment, whereas in many southern areas, vegetation will be repressed by water shortage in the future.

Description: We examine some unexpected epistemological conflicts that arise at the interfaces between ecological science, the ecosystem services framework, policy and industry. We use an example from our own research to motivate and illustrate our main arguments, while also reviewing standard approaches to ecological science using the ecosystem services framework. While we agree that the ecosystem services framework has benefits in its industrial applications because it may force economic decision makers to consider a broader range of costs and benefits than they would do otherwise, we find that many alignments of ecology with the ecosystem services framework are asking questions that are irrelevant to real-world applications, and generating data that does not serve real-world applications. We attempt to clarify why these problems arise and how to avoid them. We urge fellow ecologists to reflect on the kind of research that can lead to both scientific advances and applied relevance to society. In our view, traditional empirical approaches at landscape scales or with place-based emphases are necessary to provide applied knowledge for problem solving, which is needed once decision makers identify risks to ecosystem services. We conclude that the ecosystem services framework is a good policy tool when applied to decision-making contexts, but not a good theory either of social valuation or ecological interactions, and should not be treated as one.

Description: Because of its low level of energy consumption and the small scale of its industrial development, the Tibet Autonomous Region has historically been excluded from China's reported energy statistics, including those regarding CO 2 emissions. In this paper, we estimate Tibet's energy consumption using limited online documents, and we calculate the 2014 energy-related and process-related CO 2 emissions of Tibet and its seven prefecture-level administrative divisions for the first time. Our results show that 5.52 million tons of CO 2 were emitted in Tibet in 2014; 33% of these emissions are associated with cement production. Tibet's emissions per capita amounted to 1.74 tons in 2014, which is substantially lower than the national average, although Tibet's emission intensity is relatively high at 0.60 tons per thousand yuan in 2014. Among Tibet's seven prefecture-level administrative divisions, Lhasa City and Shannan Region are the two largest CO 2 contributors and have the highest per capita emissions and emission intensities. The Nagqu and Nyingchi regions emit little CO 2 due to their farming/pasturing-dominated economies. This quantitative measure of Tibet's regional CO 2 emissions provides solid data support for Tibet's actions on climate change and emission reductions.

Description: Evapotranspiration is a key variable in hydrology, playing an important role in water and energy balance of the land surface. There has been speculation on the direction of trend in potential and actual evapotranspiration (PET and AET) resulting from rising global temperatures, in both observational and derived records representing the historical climate. In this study, PET and AET trends of 8 different global model datasets where analyzed over two time periods: from 2003 to 2012 (short term) and from 1980 to 2012 (multi-decadal), to identify regions where the trends coincide or differ and to study the reasons behind these changes. The short-term analysis showed considerable uncertainty exists on the detection and direction of significant trends on both PET and AET. There was little agreement amongst the datasets about the direction of the global trends. The multi-decadal study showed much more consistent trends throughout the datasets, particularly in relation to positive significant PET trends. During this period, the global PET mean increased 0.091mm/month/year, while the global AET rose at 0.045 mm/month/year. Much of the opposite PET/AET trends can be attributed to changes in the precipitation. Most of the regions which present these trends are water-limited and present strong correlations between AET and precipitation trends. Some energy-limited regions showed an increasing gap between PET and AET, suggesting the influence of additional variables controlling AET.

Description: As flood impacts are increasing in large parts of the world, understanding the primary drivers of changes in risk is essential for effective adaptation. To gain more knowledge on the basis of empirical case studies, we analyze eight paired floods, i.e. consecutive flood events that occurred in the same region, with the second flood causing significantly lower damage. These success stories of risk reduction were selected across different socio-economic and hydro-climatic contexts. The potential of societies to adapt is uncovered by describing triggered societal changes, as well as formal measures and spontaneous processes that reduced flood risk. This novel approach has the potential to build the basis for an international data collection and analysis effort to better understand and attribute changes in risk due to hydrological extremes in the framework of the IAHSs Panta Rhei initiative. Across all case studies, we find that lower damage caused by the second event was mainly due to significant reductions in vulnerability, e.g. via raised risk awareness, preparedness and improvements of organizational emergency management. Thus, vulnerability reduction plays an essential role for successful adaptation. Our work shows that there is a high potential to adapt, but there remains the challenge to stimulate measures that reduce vulnerability and risk in periods in which extreme events do not occur. Index Terms 1821 Floods (4303); 4327 Resilience; 4328 Risk; 4330 Vulnerability; 4339 Disaster mitigation

Description: Global multi-model wave climate projections are obtained at 1.0°x1.0° scale from 30 CMIP5 Global Climate Model (GCM) realizations. A semi-supervised weather-typing approach based on a characterization of the ocean wave generation areas and the historical wave information from the recent GOW2 database are used to train the statistical model. This framework is also applied to obtain high resolution projections of coastal wave climate and coastal impacts as port operability and coastal flooding. Regional projections are estimated using the collection of weather types at spacing of 1.0°. This assumption is feasible because the predictor is defined based on the wave generation area and the classification is guided by the local wave climate. The assessment of future changes in coastal impacts is based on direct downscaling of indicators defined by empirical formulations (total water level for coastal flooding and number of hours per year with overtopping for port operability). Global multi-model projections of the significant wave height and peak period are consistent with changes obtained in previous studies. Statistical confidence of expected changes is obtained due to the large number of GCMs to construct the ensemble. The proposed methodology is proved to be flexible to project wave climate at different spatial scales. Regional changes of additional variables as wave direction or other statistics can be estimated from the future empirical distribution with extreme values restricted to high percentiles (i.e., 95th, 99th percentiles). The statistical framework can also be applied to evaluate regional coastal impacts integrating changes in storminess and sea level rise.

Description: Large parts of tropical coastlines are influenced by the presence of reefs that shape its coastline. Wave attenuation crossing reefs as they approach the coast results in accretionary coastal features developed in its shadow zones. With the aim of assessing the level of wave exposure of the coastline under different sea-level rise scenarios, numerical modeling experiments have been designed considering a coastline segment of approximately 450 km in northeast Brazil. Results show the distribution of wave power along the area of interest, with higher values being found in areas without reefs. However, when considering sea-level rise scenarios, it is behind the reefs where the maximum differences in wave power are observed. The increase in the free surface over the reef structures as a result of rising sea level reduces the wave attenuation effects caused by these structures. Thus, the waves hit the shore with greater force in the shadow zone protected by the reef. Here we demonstrate that regions within the reef shadow zones are most strongly affected by sea-level rise with up to a 90% increase in the wave power, which will lead to increase in sediment transport and erosion processes. Such processes indicate a trend toward coastline flattening and alignment in response to less effective shadow zones.

Description: Changes in land use and land cover (LULC) have important and fundamental interactions with the global climate system. Top-down global scale projections of land use change have been an important component of climate change research, however, their utility at local to regional scales is often limited. The goal of this study was to develop an approach for projecting changes in LULC based on land use histories and demographic trends. We developed a set of stochastic, empirically-based projections of LULC change for the state of California, USA, for the period 2001–2100. Land-use histories and demographic trends were used to project a “business-as-usual” (BAU) scenario and three population growth scenarios. For the BAU scenario, we projected developed lands would more than double by 2100. When combined with cultivated areas, we projected a 28% increase in anthropogenic land use by 2100. As a result, natural lands were projected to decline at a rate of 139 km 2  yr −1 ; grasslands experienced the largest net decline, followed by shrublands and forests. The amount of cultivated land was projected to decline by approximately 10%, however the relatively modest change masked large shifts between annual and perennial crop types. Under the three population scenarios, developed lands were projected to increase 40-90% by 2100. Our results suggest that when compared to the BAU projection, scenarios based on demographic trends may underestimate future changes in LULC. Furthermore, regardless of scenario, the spatial pattern of LULC change was likely to have the greatest negative impacts on rangeland ecosystems.