Abstract
We analyze projected changes in climate extremes (extreme temperatures and heavy precipitation) in the multimodel ensembles of the fifth and sixth Coupled Model Intercomparison Projects (CMIP5 and CMIP6). The results reveal close similarity between both ensembles in the regional climate sensitivity of the projected multimodel mean changes in climate extremes, that is, their projected changes as a function of global warming. This stands in contrast to widely reported divergences in global (transient and equilibrium) climate sensitivity in the two multimodel ensembles. Some exceptions include higher warming in the South America monsoon region, lower warming in Southern Asia and Central Africa, and higher increases in heavy precipitation in Western Africa and the Sahel region in the CMIP6 ensemble. The multimodel spread in regional climate sensitivity is found to be large in both ensembles. In particular, it contributes more to intermodel spread in projected regional climate extremes compared with the intermodel spread in global climate sensitivity in CMIP6. Our results highlight the need to consider regional climate sensitivity as a distinct feature of Earth system models and a key determinant of projected regional impacts, which is largely independent of the models' response in global climate sensitivity.
Highlights
Extensive literature is available on the representation of global climate sensitivity in different generations of Earth system models (ESMs) (Forster et al, 2019; Knutti & Hegerl, 2008; Otto et al, 2013)
That we consider a relatively large ensemble of CMIP6 simulations and that while this ensemble does differ from CMIP5 in its global temperature projections, the overall differences are not found to be extremely large in the case of the multimodel mean
Regions with largest increases in regional TXx sensitivity in CMIP6 are found in the South America monsoon (SAM) region, eastern Russia, the Tibetan Plateau (TIB), and eastern Sahara (SAH)
Summary
Extensive literature is available on the representation of global (transient and equilibrium) climate sensitivity in different generations of Earth system models (ESMs) (Forster et al, 2019; Knutti & Hegerl, 2008; Otto et al, 2013). Global climate sensitivity refers to the response of global mean temperature to changes in CO2 concentrations, either in transient simulations ( termed “global transient response”) or at climate equilibrium. These global features are regularly reported prominently in first analyses of new multimodel experiments, such as when the first simulations of the sixth phase of the Coupled Model Intercomparison Project (CMIP6, Eyring et al, 2016) were released in mid-2019 (Forster et al, 2019; Sellar et al, 2019; Swart et al, 2019). For some extremes and regions, these responses can show a large spread: in CMIP5, these were found in some cases to be much
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