Updated climate models beset by scientific bias, researchers find

Updated climate models beset by scientific bias, researchers find

Cloud Southern Ocean shows an improved radiation budget in the latest IPCC climate model, but there are still significant biases in simulated cloud physical properties over SO. Those biases are largely canceled out when they combined affect the cloud radiation effect. The cloud image is captured by the FY-3D Satellite. credit: National Satellite Meteorological Center of China Meteorological Administration

Clouds can cool or warm the planet’s surface, a radiation effect that contributes significantly to the global energy budget and can be changed by human-caused pollution. The world’s southernmost ocean, aptly named the Southern Ocean and far from human pollution but subject to abundant ocean gases and aerosols, is about 80% covered by clouds. How does this body of water and its relationship with clouds contribute to the world’s changing climate?

Researchers are still working to figure this out, and they are now one step closer, thanks to an international collaboration that identified compensation errors in the widely used climate model protocol known as CMIP6. known as. The researchers published their findings on 20 September Advances in Atmospheric Science,

“Cloud and radiation bias over the Southern Ocean has been a long-standing problem in previous generations of global climate modelsaid corresponding author Yuan Wang, who is now an associate professor in the Department of Earth, Atmospheric and Planetary Sciences at Purdue University. “After the latest CMIP 6 models were released, we were curious to see how they performed and whether there were chronic problems. Still there.”

CMIP6, a project of the World Climate Research Programme, allows for the systematic evaluation of climate models based on how they compare to each other and to real-world data. In this study, Wang and researchers analyzed five of the CMIP6 models, which are intended to serve as standard references.

Wang said the researchers were also inspired by other studies in the area that point to Southern Ocean cloud coverage as a contributing factor to the higher sensitivity of some CMIP6 models when simulations predict surface temperatures that increase. For the rate of radiation increases very rapidly. In other words, if simulated improperly, the Southern Ocean clouds Could cast a shadow of doubt on the trajectory of future climate change.

“This paper emphasizes compensating errors in cloud physical properties, despite the overall improvement of radiation simulations in the Southern Ocean,” Wang said. “With space satellite observations, we are able to quantify those errors in simulated cloud microphysical properties, including cloud fraction, cloud water content, cloud droplet size and more, and further reveal how each cloud has a radiative effect in the total.” How that contributes to prejudice.”

The cloud radiation effect – how clouds impede radiation to heat or cool the surface – is largely determined by the physical properties of the cloud. “The cloud irradiation effects in CMIP6 are comparable with satellite observations, but we found that there are large compensating biases in the cloud fraction liquid water path and droplet effective radius,” Wang said. “The major implication is that even though the latest CMIP models improve their simulation of average states, such as the radiation flux at the top AtmosphereThe detailed cloud processes are still under great uncertainty.”

According to Wang, this discrepancy also partly explains why model climate sensitivity assessments do not perform well, as these assessments rely on model detailed physics to evaluate the overall impact on climate – rather than on average state performance. .

“Our future work will aim to reduce the individual standards responsible for these biases,” Wang said. “Hopefully, we can work closely with model developers to solve them. Ultimately, the ultimate goal of any model evaluation study is to help improve those models.”

Other contributors include Lijun Zhao and Yuk L. Yung, Department of Geology and Planetary Sciences, California Institute of Technology; Chuanfeng Zhao, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University; and Zikan Dong, Department of Hydrology and Atmospheric Sciences, University of Arizona.

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more information:
Compensating errors in cloud radiative and physical properties over the Southern Ocean in the CMIP6 climate model, Advances in Atmospheric Science (2022). DOI: 10.1007/s00376-022-2036-z

Citation: Updated climate models covered with scientific biases, researchers find (2022, September 20) Retrieved on September 21, 2022 from https://phys.org/news/2022-09-climate-clouded-scientific-biases.html Gone.

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