气候变化领域集成服务门户(CCPortal): Equilibrium climate sensitivity above 5 °C plausible due to state-dependent cloud feedback

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DOI	10.1038/s41561-020-00649-1
	Equilibrium climate sensitivity above 5 °C plausible due to state-dependent cloud feedback
	Bjordal J.; Storelvmo T.; Alterskjær K.; Carlsen T.
发表日期	2020
ISSN	17520894
起始页码	718
结束页码	721
卷号	13 期号:11
英文摘要	The equilibrium climate sensitivity of Earth is defined as the global mean surface air temperature increase that follows a doubling of atmospheric carbon dioxide. For decades, global climate models have predicted it as between approximately 2 and 4.5 °C. However, a large subset of models participating in the 6th Coupled Model Intercomparison Project predict values exceeding 5 °C. The difference has been attributed to the radiative effects of clouds, which are better captured in these models, but the underlying physical mechanism and thus how realistic such high climate sensitivities are remain unclear. Here we analyse Community Earth System Model simulations and find that, as the climate warms, the progressive reduction of ice content in clouds relative to liquid leads to increased reflectivity and a negative feedback that restrains climate warming, in particular over the Southern Ocean. However, once the clouds are predominantly liquid, this negative feedback vanishes. Thereafter, other positive cloud feedback mechanisms dominate, leading to a transition to a high-sensitivity climate state. Although the exact timing and magnitude of the transition may be model dependent, our findings suggest that the state dependence of the cloud-phase feedbacks is a crucial factor in the evolution of Earth’s climate sensitivity with warming. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.
英文关键词	air temperature; climate modeling; CMIP; equilibrium; global climate; numerical model; radiative forcing; reflectivity; warming; Southern Ocean
语种	英语
来源期刊	Nature Geoscience
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/206750
作者单位	Department of Geosciences, University of Oslo, Oslo, Norway; Nord University, Bodø, Norway; Center for International Climate and Environmental Research–Oslo (CICERO), Oslo, Norway
推荐引用方式 GB/T 7714	Bjordal J.,Storelvmo T.,Alterskjær K.,et al. Equilibrium climate sensitivity above 5 °C plausible due to state-dependent cloud feedback[J],2020,13(11).
APA	Bjordal J.,Storelvmo T.,Alterskjær K.,&Carlsen T..(2020).Equilibrium climate sensitivity above 5 °C plausible due to state-dependent cloud feedback.Nature Geoscience,13(11).
MLA	Bjordal J.,et al."Equilibrium climate sensitivity above 5 °C plausible due to state-dependent cloud feedback".Nature Geoscience 13.11(2020).