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GFDL Research Highlights

August 23rd, 2021 - The Alaskan summer 2019 extreme heat event: the role of anthropogenic forcing, and projections of the increasing risk of occurrence

An extreme heat event, breaking all previous records, occurred over southwestern Alaska in the summer of 2019. Extreme heat can have significant societal and economic effects, including damaging roads and infrastructure, displacing marine ecosystems, and increasing wildfire risk, with disproportionate costs to Alaska’s rural and indigenous communities. The authors examined the extent to which human-driven climate change played a role in increasing the likelihood of experiencing such an extreme event. Read More…

July 28th, 2021 - Anthropogenic forcing and response yield observed positive trend in Earth’s energy imbalance

The observed trend in Earth’s energy imbalance, a measure of the acceleration of heat uptake by the planet, is a fundamental indicator of perturbations to climate. The study found that it is exceptionally unlikely (< 1% probability) that this observed trend can be explained by natural variations in the climate system alone. Using climate model simulations and by conducting a hierarchy of GFDL CM4/AM4 experiments, the authors estimated the anthropogenic and internal variability contributions to the observed trend during 2001-2020. The study concludes that the satellite record provides clear evidence of a human-influenced climate system. Read More…

June 16th, 2021 - Horizontal circulation across density surfaces contributes substantially to the long-term mean northern Atlantic Meridional Overturning Circulation

The Atlantic Meridional Overturning Circulation (AMOC) has profound impacts on many aspects of climate, including temperature and precipitation. How and why the AMOC changes remains a challenging issue. The Greenland Sea is often viewed as the northern terminus of the AMOC and it has been suggested that the shutdown of open-ocean deep convection in the Labrador or Greenland Seas would substantially weaken the AMOC. This study suggests that the Arctic Ocean, not the Greenland Sea, is the northern terminus of the mean AMOC. Open-ocean deep convection, in either the Labrador or Greenland Seas, contributes minimally to the mean AMOC, hence it may not be weakened substantially by a shutdown of open-ocean deep convection. Meanwhile, horizontal circulation contributes more than 40% to the maximum mean northeastern subpolar AMOC. Read More…

March 30th, 2021 - Climate change is probably increasing the intensity of tropical cyclones

This ScienceBrief presents a summary of the state of the science on tropical cyclones (tropical storms, hurricanes, and typhoons) and climate change. The authors assessed more than 90 peer-reviewed scientific articles, with a focus on articles describing observations of, or projected future changes to, the frequency and intensity of tropical cyclones (TCs) globally or in key regions, as well as changes in tropical cyclone-related rainfall and storm surge. Read More…

February 19th, 2021 - Assessing the influence of COVID-19 on Earth’s radiative balance

The ongoing COVID-19 pandemic led to a worldwide reduction in aerosol emissions. Anecdotal effects on air quality and visibility were widely reported. Less known are the impacts on the planetary energy balance, and by extension, on weather and climate. By separating the impacts from meteorology and emissions with model simulations, the authors found that about one‐third of the clear‐sky anomalies can be attributed to pandemic‐related emission reductions, and the rest to weather variability and long‐term emission trends. Read More…

December 22nd, 2020 - Increasing risk of another Cape Town’s Day Zero drought in twenty-first century

Three consecutive dry winters (2015-2017) in southwestern South Africa (SSA) resulted in the Cape Town “Day Zero” drought in early 2018. Combined with management practices and infrastructure shortcomings, the drought caused one of the most serious water crises ever experienced in any heavily populated metropolitan area, with extensive economic impacts. The authors of this study applied a high-resolution (0.5◦×0.5◦) large ensemble, generated from the newly developed Seamless System for Prediction and EArth System Research (SPEAR) global climate model developed at GFDL, to investigate regional hydroclimatic risk. Read More…

December 15th, 2020 - Ocean Biogeochemistry in GFDL’s Earth System Model 4.1 and its Response to Increasing Atmospheric CO2

The Geophysical Fluid Dynamics Laboratory’s newest Earth System Model, ESM4.1, was developed to study the past, present, and future evolution of the Earth system under scenarios for natural and anthropogenic drivers of earth system change, including greenhouse gases and aerosols. The response of the ocean’s vast carbon and heat reservoirs to accumulating greenhouse gases greatly reduces their atmospheric and terrestrial impacts, but also puts ocean environments and the marine resources they support at risk. This paper describes, evaluates, and discusses the ocean biogeochemical component of ESM4.1. Read More…

December 10th, 2020 - The GFDL Global Atmospheric Chemistry-Climate Model AM4.1: Model Description and Simulation Characteristics

The atmospheric model documented in this study, AM4.1, marks the culmination of GFDL’s 4th-generation model development effort that included comprehensive revisions of atmospheric dynamics, physics, and chemistry, and biogeochemical coupling to land and ocean. These efforts were merged into a single atmospheric configuration in support of NOAA’s first coupled carbon-chemistry-climate Earth system model (ESM4.1) with state-of-the-art representation of each component, along with comprehensive interactions between components. The final coupled ESM4.1 configuration is described in a separate manuscript (Dunne et al.). Read More…

November 12th, 2020 - The GFDL Earth System Model version 4.1 (GFDL-ESM4.1): Model description and simulation characteristics

The Earth system model documented in this study, ESM4.1, marks the culmination of GFDL’s 4th generation model development effort that included comprehensive revisions of atmospheric dynamics, physics and chemistry, ocean physics, biogeochemistry and ecosystems, sea ice, and land physics, biogeochemistry and ecosystems. These efforts were merged into NOAA’s first coupled carbon-chemistry-climate model with state-of-the-art representation of each, along with comprehensive interactions between components. Read More…

November 6th, 2020 - Sea Level Pressure Trends: Model-based Assessment of Detection, Attribution, and Consistency with CMIP5 Historical Simulations

With anthropogenic climate change becoming evident, it is imperative to provide reliable scientific information to society on causes of emerging trends. Sea level pressure (SLP) is a key variable, relevant for impacts and extremes (e.g., steering flows for storms, storm track changes), for which trends and other changes must be monitored and understood. This study explores how the atmospheric circulation may be changing regionally in response to anthropogenic forcing, based on an analysis of sea level pressure trends in observations and models. Read More…

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