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  • 1
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    Aerosol analysis and forecast in the European Centre for Medium-Range Weather Forecasts Integrated Forecast System: 3. Evaluation by means of case studies (2011)
    Wiley
    Details
    Publication Date: 2011-02-08
    Description: A near real-time system for assimilation and forecasts of aerosols, greenhouse and trace gases, extending the ECMWF Integrated Forecasting System (IFS), has been developed in the framework of the Global and regional Earth-system Monitoring using Satellite and in-situ data (GEMS) project. The GEMS aerosol modeling system is novel as it is the first aerosol model fully coupled to a numerical weather prediction model with data assimilation. A reanalysis of the period 2003–2009 has been carried out with the same system. During its development phase, the aerosol system was first run for the time period January 2003 to December 2004 and included sea salt, desert dust, organic matter, black carbon, and sulfate aerosols. In the analysis, Moderate Resolution Imaging Spectroradiometer (MODIS) total aerosol optical depth (AOD) at 550 nm over ocean and land (except over bright surfaces) was assimilated. This work evaluates the performance of the aerosol system by means of case studies. The case studies include (1) the summer heat wave in Europe in August 2003, characterized by forest fire aerosol and conditions of high temperatures and stagnation, favoring photochemistry and secondary aerosol formation, (2) a large Saharan dust event in March 2004, and (3) periods of high and low sea salt aerosol production. During the heat wave period in 2003, the linear correlation coefficients between modeled and observed AOD (550 nm) and between modeled and observed PM2.5 mass concentrations are 0.82 and 0.71, respectively, for all investigated sites together. The AOD is slightly and the PM2.5 mass concentration is clearly overestimated by the aerosol model during this period. The simulated sulfate mass concentration is significantly correlated with observations but is distinctly overestimated. The horizontal and vertical locations of the main features of the aerosol distribution during the Saharan dust outbreak are generally well captured, as well as the timing of the AOD peaks. The aerosol model simulates winter sea salt AOD reasonably well, however, showing a general overestimation. Summer sea salt events show a better agreement. Overall, the assimilation of MODIS AOD data improves the subsequent aerosol predictions when compared with observations, in particular concerning the correlation and AOD peak values. The assimilation is less effective in correcting a positive (PM2.5, sulfate mass concentration, Angström exponent) or negative (desert dust plume AOD) model bias.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Detection of solar dimming and brightening effects on Northern Hemisphere river flow (2014)
    Springer Nature
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    Publication Date: 2014-10-31
    Description: Nature Geoscience 7, 796 (2014). doi:10.1038/ngeo2263 Authors: N. Gedney, C. Huntingford, G. P. Weedon, N. Bellouin, O. Boucher & P. M. Cox Anthropogenic aerosols in the atmosphere have the potential to affect regional-scale land hydrology through solar dimming. Increased aerosol loading may have reduced historical surface evaporation over some locations, but the magnitude and extent of this effect is uncertain. Any reduction in evaporation due to historical solar dimming may have resulted in an increase in river flow. Here we formally detect and quantify the historical effect of changing aerosol concentrations, via solar radiation, on observed river flow over the heavily industrialized, northern extra-tropics. We use a state-of-the-art estimate of twentieth century surface meteorology as input data for a detailed land surface model, and show that the simulations capture the observed strong inter-annual variability in runoff in response to climatic fluctuations. Using statistical techniques, we identify a detectable aerosol signal in the observed river flow both over the combined region, and over individual river basins in Europe and North America. We estimate that solar dimming due to rising aerosol concentrations in the atmosphere around 1980 led to an increase in river runoff by up to 25% in the most heavily polluted regions in Europe. We propose that, conversely, these regions may experience reduced freshwater availability in the future, as air quality improvements are set to lower aerosol loading and solar dimming.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 3
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    Impact of changes in diffuse radiation on the global land carbon sink (2009)
    Nature Publishing Group (NPG)
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    Publication Date: 2009-04-28
    Description: Plant photosynthesis tends to increase with irradiance. However, recent theoretical and observational studies have demonstrated that photosynthesis is also more efficient under diffuse light conditions. Changes in cloud cover or atmospheric aerosol loadings, arising from either volcanic or anthropogenic emissions, alter both the total photosynthetically active radiation reaching the surface and the fraction of this radiation that is diffuse, with uncertain overall effects on global plant productivity and the land carbon sink. Here we estimate the impact of variations in diffuse fraction on the land carbon sink using a global model modified to account for the effects of variations in both direct and diffuse radiation on canopy photosynthesis. We estimate that variations in diffuse fraction, associated largely with the 'global dimming' period, enhanced the land carbon sink by approximately one-quarter between 1960 and 1999. However, under a climate mitigation scenario for the twenty-first century in which sulphate aerosols decline before atmospheric CO(2) is stabilized, this 'diffuse-radiation' fertilization effect declines rapidly to near zero by the end of the twenty-first century.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mercado, Lina M -- Bellouin, Nicolas -- Sitch, Stephen -- Boucher, Olivier -- Huntingford, Chris -- Wild, Martin -- Cox, Peter M -- England -- Nature. 2009 Apr 23;458(7241):1014-7. doi: 10.1038/nature07949.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Ecology and Hydrology, Wallingford OX10 8BB, UK. lmme@ceh.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19396143" target="_blank"〉PubMed〈/a〉
    Keywords: Aerosols/analysis/chemistry ; Atmosphere/*chemistry ; Carbon/*metabolism ; Carbon Dioxide/analysis ; *Darkness ; *Ecosystem ; Greenhouse Effect ; History, 20th Century ; History, 21st Century ; Photosynthesis/*radiation effects ; Plants/metabolism/*radiation effects ; Sulfates/metabolism ; *Sunlight ; Volcanic Eruptions
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
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    Atmospheric science. Climate forcing by aerosol--a hazy picture (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-05-17
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Anderson, Theodore L -- Charlson, Robert J -- Schwartz, Stephen E -- Knutti, Reto -- Boucher, Olivier -- Rodhe, Henning -- Heintzenberg, Jost -- New York, N.Y. -- Science. 2003 May 16;300(5622):1103-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, WA 98195, USA. tadand@u.washington.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12750507" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Climate science: The aerosol effect (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-10-06
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stevens, Bjorn -- Boucher, Olivier -- England -- Nature. 2012 Oct 4;490(7418):40-1. doi: 10.1038/490040a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23038459" target="_blank"〉PubMed〈/a〉
    Keywords: Aerosols/*adverse effects/analysis ; Atmosphere/chemistry ; Carbon Dioxide/analysis/chemistry ; *Climate ; *Climate Change/statistics & numerical data ; *Models, Theoretical ; *Uncertainty
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 6
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    Bounding global aerosol radiative forcing of climate change (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth's radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable and arguable lines of evidence, including modelling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol‐radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol‐driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed‐phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of ‐1.60 to ‐0.65 W m‐2, or ‐2.0 to ‐0.4 W m‐2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted towards more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial‐era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds.
    Print ISSN: 8755-1209
    Electronic ISSN: 1944-9208
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Efficacy of climate forcings in PDRMIP models (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Quantifying the efficacy of different climate forcings is important for understanding the real‐world climate sensitivity. This study presents a systematic multi‐model analysis of different climate driver efficacies using simulations from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP). Efficacies calculated from instantaneous radiative forcing deviate considerably from unity across forcing agents and models. Effective radiative forcing (ERF) is a better predictor of global mean near‐surface air temperature (GSAT) change. Efficacies are closest to one when ERF is computed using fixed sea surface temperature experiments and adjusted for land surface temperature changes using radiative kernels. Multi‐model mean efficacies based on ERF are close to one for global perturbations of methane, sulphate, black carbon and insolation, but there is notable inter‐model spread. We do not find robust evidence that the geographic location of sulphate aerosol affects its efficacy. GSAT is found to respond more slowly to aerosol forcing than CO2 in the early stages of simulations. Despite these differences, we find that there is no evidence for an efficacy effect on historical GSAT trend estimates based on simulations with an impulse response model, nor on the resulting estimates of climate sensitivity derived from the historical period. However, the considerable intermodel spread in the computed efficacies means that we cannot rule out an efficacy‐induced bias of ±0.4 K in equilibrium climate sensitivity to CO2 doubling (ECS) when estimated using the historical GSAT trend.
    Print ISSN: 2169-897X
    Electronic ISSN: 2169-8996
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Carbon dioxide physiological forcing dominates projected Eastern Amazonian drying (2018)
    Wiley
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    Publication Date: 2018-03-13
    Description: Future projections of east Amazonian precipitation indicate drying, but they are uncertain and poorly understood. In this study we analyse the Amazonian precipitation response to individual atmospheric forcings using a number of global climate models. Black carbon is found to drive reduced precipitation over the Amazon due to temperature-driven circulation changes, but the magnitude is uncertain. CO 2 drives reductions in precipitation concentrated in the east, mainly due to a robustly negative, but highly variable in magnitude, fast response. We find that the physiological effect of CO 2 on plant stomata is the dominant driver of the fast response due to reduced latent heating, and also contributes to the large model spread. Using a simple model we show that CO 2 physiological effects dominate future multi-model mean precipitation projections over the Amazon. However, in individual models temperature-driven changes can be large, but due to little agreement, they largely cancel out in the model-mean.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Inter-annual variability in fossil-fuel CO 2 emissions due to temperature anomalies (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-07-05
    Description: It is well known that short-term (i.e. interannual) variations in fossil-fuel CO 2 emissions are closely related to the evolution of the national economies. Nevertheless, a fraction of the CO 2 emissions are linked to domestic and business heating and cooling, which can be expected to be related to the meteorology, independently of the economy. Here, we analyse whether the signature of the inter-annual temperature anomalies is discernible in the time series of CO 2 emissions at the country scale. Our analysis shows that, for many countries, there is a clear positive correlation between a heating-degree-person index and the component of the CO 2 emissions that is not explained by the economy as quantified by the gross domestic product (GDP). Similarly, several countries show a positive correlation between a cooling-degree-person (CDP) index and CO 2 emissions. The slope of the linear relationship for heating is on the order of 0.5...
    Print ISSN: 1748-9318
    Electronic ISSN: 1748-9326
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering
    Published by Institute of Physics (IOP)
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  • 10
    Electronic Resource
    Electronic Resource
    Continental Runoff A quality-controlled global runoff data set (Reply) (2006)
    [s.l.] : Nature Publishing Group
    Nature 444.2006, 7120, E14-, (2 S.) 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Replying to Peel and McMahon Peel and McMahon argue that limitations of the continental runoff data set we use in our study call our main conclusion into question — that is, that changes in twentieth-century continental-scale runoff are partly attributable to the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05481
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    Paper (German National Licenses)
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