Climate Change

Sources of uncertainty in climate projections and their relative importance for different variables, regions and seasons
June 29, 2020

A new collection of single model initial-condition large ensembles (SMILEs) can test statistical assumptions with a cleaner separation between sources of uncertainty in climate projections. In particular, the potential bias at regional scales or for variables with a lot of internal variability can be greatly reduced.

Time of emergence of the anthropogenic signal in storm-related extreme sea level at New York in the GFDL CM4 simulations.
June 1, 2020

Yin and coauthors use the new GFDL CM4 and CM4HR models to consider a series of climate change experiments under the CMIP6 protocol to study characteristics of extreme sea level events and their future evolution in a fully coupled weather, climate, sea level, and storm surge modeling system. They found that even in the absence of global warming, the Gulf Coast is most vulnerable to hurricane-induced storm surge.

Zonally averaged multi-model average shortwave low cloud feedbacks
March 25, 2020

Zelinka and coauthors compared ECS values derived from CO2 quadrupling experiments conducted with CMIP6 and CMIP5 models and found that the latest models warm more than their predecessors by about 0.5˚C. The primary culprit for the enhanced warming was shown to be clouds.

Multi-model mean evolution of the Hadley cell edge (defined by streamfunction at 500 hPa) in the 1 percent CO2 increase simulations. Copyright AGU.
January 14, 2020

Under exclusive CO2 forcing, climate models predicted twice as much Hadley cell expansion in the Southern Hemisphere as in the Northern Hemisphere. The finding was robust across models and all seasons except boreal fall.

Schematic representation of proposed dynamical mechanisms in summer
September 13, 2018

Researchers conduct a comprehensive review of research on summer weather stalling, focusing on the influence of Arctic amplification and how it could interact with other factors influenced by climate change.

linear model accounting for changes in drying ratio and mean source distance
September 4, 2018

A new study shows that a simple linear model that accounts for changes in mean source distance, as well as the local drying ratio, can successfully replicate water isotopic variations in space and time.

The Observational Large Ensemble (Obs-LE) can be used to assess the relative roles of internal variability and anthropogenic influence on 50-year trends in (a-b) temperature and (c-d) precipitation over land.
August 29, 2018

Researchers have developed a complementary approach to creating ensembles for seasonal-average temperature and precipitation over land that can also be used to study internal variability.

trends in the latitude of the (left) Northern Hemisphere and (right) Southern Hemisphere tropical edg
August 8, 2018

Observed Southern Hemisphere summer and fall trends of tropical expansion are well captured in model simulations of the late 20th and early 21st centuries, consistent with the roles of increasing greenhouse gases and stratospheric ozone depletion in driving poleward circulation shifts during these seasons.

Hurricane Harvey and Louisiana flood
June 18, 2018

Regional model simulations suggest that post-1980 warming in both the ocean and atmosphere resulted in an estimated 20% increase of the accumulated precipitation for Hurricane Harvey. 

sensible heat and evaporation fluxes in the Arctic Ocean
April 19, 2018

Researchers conclude that changes in sensible heat transfer and evaporation fluxes — in response to strong regional trends in sea ice cover — are becoming increasingly consequential to Arctic climate variability and change. 

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