The impact of the late 20th century changes of anthropogenic aerosols from local (i.e., South Asia) and remote (i.e., outside South Asia) sources on the South Asian summer monsoon is a rather unexplored topic. It has important implications for strategies to control regional pollution and understand its effect in climate. GFDL scientists investigated the impact of this change in aerosols on the South Asian monsoon. This work provides new insights into the pathway by which global anthropogenic aerosols affect long-term variations of the monsoon hydroclimate, which is still uncertain and largely debated in the scientific community.
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GFDL Research Highlights
February 14th, 2014 - Changing Ocean may Challenge Atlantic Cod
This study uses climate projections from GFDL’s Earth system model (ESM2.1) to force an individual-based model for the larval stages of North Atlantic Cod at each of 5 cod spawning sites across the North Atlantic. The behavioral and physiological state of thousands of cod larvae is modeled in response to ESM projected physical and biological changes. The ESM-IBM coupling provides a unique means of exploring the mechanistic response of cod larvae to climate forcing.
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February 6th, 2014 - Solving the mystery of Hawaiian ozone changes
A potent greenhouse gas and biological irritant, ozone near the Earth surface is also a health-damaging air pollutant, regulated by the U.S. Environmental Protection Agency. Shifts in atmospheric circulation have caused Asian ozone pollution reaching Hawaii to rise unexpectedly in autumn since mid-1990s, according to this study. The findings, published in Nature Geoscience, imply that decade-long variability in climate must be considered when attributing observed ozone changes to human-induced trends in precursor emissions.
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This study advances our understanding of the physical processes controlling the dynamics of ice streams – pathways for ice discharge from the interior of ice sheets to surrounding oceans – and the leading source of uncertainty in projections of global sea level rise in the 21st century.
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The authors compared observations to model results, using 23 different CMIP5 models to simulate internal climate variability and the response to anthropogenic and natural forcing. The models were used to investigate the causes of the unusual warmth during March-May 2012 that occurred over the eastern U.S. The 20thcentury warming trend that was observed in this region is consistent with the CMIP5 multi-model ensemble results of All-Forcing runs but not consistent with model runs that did not include external forcing. The long-term trends in the models are predominantly due to anthropogenic forcing. Therefore, we interpret the extreme warmth of March-May 2012 over the eastern U.S. as very likely attributable, at least in part, to anthropogenic forcing. The CMIP5 models’ central estimate of the contribution of anthropogenic forcing to the March-May 2012 anomaly is about 35% in terms of magnitude. Moreover, the model results suggest that the risk of a warm anomaly in the eastern U.S. as large as that seen in March-May 2012 has now increased by about a factor of 10 due to long-term climate warming—primarily anthropogenic in origin.
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Planktonic food web dynamics shape biogeochemical cycles and global patterns of ocean productivity across trophic levels. Primary production alone, for example, is a poor predictor of cross-ecosystem differences in fisheries yields. Predictive capability improves only after consideration of factors such as the number and efficiency of trophic links separating phytoplankton and fish. Limited representation and validation of planktonic food web dynamics within the present generation of Earth System Models limits both their resolution of biogeochemical processes and their utility for assessing climate impacts on living marine resources.
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Evaluating climate simulations against observational data is a fundamental step in the evaluation and eventual improvement of models. Models can also help test our understanding of the causes of past variations of climate seen in the historical record. This analysis shows how current climate models, including those developed by NOAA, compare with observations in terms of their regional surface temperature trends since 1901.
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The impacts of climate change on the North America-North Atlantic-Europe sector are studied using a coupled general circulation model (CM3) and a high-resolution atmosphere-only model (HiRAM), both developed at the Geophysical Fluid Dynamics Laboratory. Long-term changes in surface temperature, precipitation and storminess patterns over Europe and the North Atlantic are projected.
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This study investigates the impact of the late 20th century increase of anthropogenic aerosols on the onset of the Indian summer monsoon. Aerosols are likely responsible for the observed earlier onset, resulting in enhanced June precipitation over most of India. This shift is preceded by strong aerosol forcing over the Bay of Bengal and Indochina, mostly attributable to the direct effect, resulting in increased atmospheric stability that inhibits the monsoon migration in May.
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The authors explored the influence of anthropogenic climate change on Atlantic hurricane activity in the 21stcentury, using dynamical climate models. The results of experiments using multi-model climate change scenarios were compared, with one scenario taken from CMIP3 (A1B), and one from CMIP5 (RCP4.5). A significant reduction in the frequency of tropical storms and hurricanes is projected for both CMIP3 and CMIP5 ensembles. However, the authors found significantly increased frequency of category 4 and 5 hurricanes in experiments with the CMIP3 ensemble. Experiments with the CMIP5 ensemble showed a smaller increase in the strongest storms. In addition, tropical cyclone-related rainfall rates, increased significantly–by about 30% in the hurricane inner core (within 50 km of the storm center) with a smaller increase of about 10% for rainfall rate averaged within 200 km to 400 km of the storm center.
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