Extreme seasonal/annual precipitation, defined here as ranking first, second, or third highest or lowest in the record of at least 100 years, occurred in several continental U.S. regions during 2013. The authors of this study used CMIP5 models to simulate internal climate variability and the response to historical anthropogenic and natural forcings, for the Northern Tier and the Upper Midwest regions of the U.S. This study suggests that, for these two regions, extreme annual or seasonal positive precipitation anomalies over the U.S. were at least partly attributable to a combination of anthropogenic and natural forcing.
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GFDL Research Highlights
In order to produce better seasonal-to-interannual climate predictions, GFDL scientists explored improvements in the method of initializing a high-resolution coupled model. Traditionally, when observations are assimilated into a high-resolution coupled model, small-scale cyclones tend to get filtered out in the process of making corrections to the large-scale background. GFDL scientists pioneered a method of processing the large-scale background and the small-scale perturbations separately in a cyclone-permitting model.
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The goals of this research were to assess the role of AMOC in global climate and identify the predictability of the associated climate impacts. Decadal prediction experiments were conducted as part of CMIP5 using a prototype GFDL-CM2.1 forecast system. The abrupt warming of the North Atlantic subpolar gyre (SPG), observed in the mid-1990s, was used as a case study to evaluate the forecast capabilities of the model, and to better understand the reasons for the observed changes.
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August 13th, 2014 - Seasonal Forecasting of Regional Tropical Cyclone Activity
Tropical cyclones (TCs, which include hurricanes and typhoons) are a major climate hazard across the Northern Hemisphere, and have exhibited variability and change on year-to-year timescales. Understanding and predicting future year-to-year TC activity is central to NOAA’s mission and highly relevant to society. Of particular relevance for decision support is predicting seasonal activity on regional spatial scales (scales smaller than the entire basin) – a goal that has remained elusive.
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Projected changes in the winds circling the Antarctic may accelerate global sea level rise significantly more than previously estimated. Changes to Antarctic winds may have a profound impact on warming ocean temperatures under the ice shelves along the coastline of West and East Antarctic. Projected Antarctic wind shifts were included in a detailed global ocean model, and the authors found water up to 4°C warmer than current temperatures rose up to meet the base of the Antarctic ice shelves. The projected sub-surface warming is twice as large as previously estimated, on average, and it affects almost all of coastal Antarctica. This relatively warm water provides a huge reservoir of melt potential right near the grounding lines of ice shelves around Antarctica. It could lead to a massive increase in the rate of ice sheet melt, with direct consequences for global sea level rise.
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A suite of simulations, done with a new high-resolution climate model (CM2.5) developed at GFDL, were used to study the observed long-term decline of winter rainfall over parts of southern Australia. In response to anthropogenic increases in greenhouse gases and reduction in stratospheric ozone, the model is able to capture many aspects of the observed drying, especially over southwest Australia. The model projects a continued decline in winter rainfall throughout the rest of the 21st century, with significant implications for regional water resources.
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The insensitivity of the global climate response once emissions cease in simplified coupled climate models has been used to argue for lack of committed warming based on past carbon emissions. Additional studies have also demonstrated that the cessation of carbon emissions results in a stabilization or decrease of global mean surface air temperature. Such studies generally assume either a 1%/year increase or an instantaneous doubling/quadrupling of atmospheric CO2.
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The rapid change in summer Arctic sea ice could have significant large scale climatic, ecological, and economic impacts. Understanding the mechanisms for the recent rapid decline in summer Arctic sea ice will help to predict future changes in summer Arctic sea ice and associated climatic, ecological, and economic impacts.
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May 14th, 2014 - The Poleward Migration of the Location of Tropical Cyclone Maximum Intensity
Tropical cyclones (TCs), including hurricanes and typhoons, are a major hazard around the globe, including North America. TCs have exhibited variability and change on a variety of timescales, including multi-decadal changes.
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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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