This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Marine low clouds over the world's eastern subtropical oceans strongly influence Earth's temperature by reflecting sunlight back to space. How these clouds change as the planet warms is one of the biggest uncertainties in predicting the severity of future warming.
However, Earth system models have had difficulty simulating these clouds because the small-scale turbulence and rain processes that shape them must be approximated. A study headed by University of Wyoming researchers used 250 experimental configurations of an existing climate model to investigate how clouds respond to changes in their environment. The researchers found that similar changes in cloud coverage can have very different climate effects depending on how reflective the clouds are to begin with.
They also identified a persistent problem in how the simulated clouds respond to winds moving air across ocean regions with different temperatures. The findings identify opportunities to improve cloud simulations, although the study did not implement or test those improvements. "The findings highlight why evaluating climate models requires examining both how clouds change and how reflective they are before changing, with implications for assessing cloud feedback and future warming," says Timothy Myers, an associate research scientist in the UW Department of Atmospheric Science.
"To understand how clouds affect warming, we need to know both how their coverage changes and how strongly they reflect sunlight." Myers was the lead author of a paper, titled "Cloud Controlling Factor Analysis Reveals E3SMv3 Structural Bias and Mean State Controls on Stratocumulus Radiative Sensitivity," that was published Oct. 18 in Geophysical Research Letters. Associate research scientists Travis Aerenson and Jacqueline Nugent; Hunter Brown, a postdoctoral research associate; and Daniel McCoy, an associate professor, all in the UW Department of Atmospheric Science, contributed to the paper, along with Mark Zelinka, an atmospheric scientist at Lawrence Livermore National Laboratory. The study, conducted from February through August, builds on Nephele, a UW-led effort to explore uncertainty in cloud processes through hundreds of climate model simulations.
Nephele involves 250 Earth system model simulations with systematically varied cloud, convection and aerosol parameters, Myers says. The main simulations and satellite observations analyzed cover the period from 2010 to 2016. Researchers used the Energy Exascale Earth System Model version 3 (E3SMv3) for testing cloud simulations.
E3SMv3 is a computer representation of Earth's climate system developed by the U.S. Department of Energy (DOE). It simulates interactions among the atmosphere, oceans, land and ice to investigate how climate works and how it may change.
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