Updating climate models clouded by scientific biases, researchers find – Are you interested in that?
ATMOSPHERIC INSTITUTE OF PHYSICS, CHINA ACADEMY
Clouds can cool or warm the planet’s surface, a radiative effect that contributes significantly to the global energy budget and can be altered by anthropogenic pollution. The world’s southernmost ocean, aptly named the Southern Ocean, and far from human pollution but rich in marine gases and aerosols, is about 80% covered by clouds. How does this body of water and its relationship to clouds contribute to the world’s climate change?
The researchers are still working to figure it out, and they’re now one step closer, thanks to an international collaboration that identifies offset errors in widely used climate modeling protocols known as CMIP6. They published their findings on September 20 in Advances in Atmospheric Science.
Corresponding author Yuan Wang, now an associate professor in the Department of Earth, Atmospheric and Planetary Sciences at Purdue University, said: “Cloud and radiation biases over the Southern Ocean have been a problem for a long time. in previous generations of global climate models. . “Once the latest CMIP6 models are released, we can’t wait to see how they perform and if the old problems persist.”
CMIP6, a project of the World Climate Research Program, enables a systematic review of climate models to shed light on how they compare with each other and real-world data. In this study, Wang and researchers analyzed five of the CMIP6 models intended to serve as standard references.
Wang said the researchers are also motivated by other studies in the field that indicate that cloud coverage in the Southern Ocean is a contributing factor to the high sensitivity of some CMIP6 models. when simulations predict that the surface temperature rises too quickly, resulting in an increased radiation rate. . In other words, if modeled incorrectly, Southern Ocean clouds can cast doubt on future climate change projections.
“This paper emphasizes compensating for errors in cloud physical properties despite the overall improvement of radiation simulations over the Southern Ocean,” said Wang. “With space satellite observations, we were able to quantify those errors in the simulated cloud microphysics properties, including cloud fraction, cloud water content, droplet size, etc. clouds, etc.”
The radiative effect of clouds – the way clouds impede radiation to warm or cool the surface – is largely determined by the physical properties of the cloud. “The radiation effects of the cloud in CMIP6 are comparable to those of satellite observations, but we found that there are large offset biases in the liquid water path and effective radii of the clouds,” said Wang. droplet. “The main implication is that, although the latest CMIP models improve their simulations of average states, such as the radiation flux at the top of the atmosphere, the detailed cloud processes are still great uncertainty.”
According to Wang, this discrepancy also partly explains why the model’s climate sensitivity assessments don’t perform well, as those assessments are based on the detailed physics of the model – not the model’s performance. mean state pressure – to assess the overall impact on climate.
“Our future work will aim to identify the individual parameterizations responsible for these deviations,” says Wang. “Hopefully, we can work closely with model developers to address them. After all, the ultimate goal of any model evaluation study is to help improve those models.”
Other contributors include Lijun Zhao and Yuk L. Yung, Division of Geology and Planetary Science, California Institute of Technology; Chuanfeng Zhao, Department of Atmospheric and Oceanic, Department of Physics, Peking University; and Xiquan Dong, Department of Hydrology and Atmospheric Sciences, University of Arizona.
JOURNEYS
Advances in Atmospheric Science
DOI
ARTICLE TITLE
Compensating for errors in the physical and radiation properties of clouds over the Southern Ocean in CMIP6 Climate Models
ARTICLE PUBLICATION DATE
September 20, 2022
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