Effects of Spatial Patterns of Ocean Heat Uptake on the CMIP5 inter-model spread of the Transient Climate Response
Abstract
A pressing goal of climate science is to reduce the uncertainty in climate sensitivity to anthropogenic forcing, with far reaching implications for science and policy. Recent advances have shown that feedback processes governing the transient climate response (TCR) are strongly influenced by the spatial pattern of ocean heat uptake (OHU). This work seeks to determine how much of the spread in TCR in the CMIP5 ensemble can be effectively captured by prescribing the inter-model spread of OHU patterns diagnosed from CMIP5 transient warming experiments in a single 2xCO2 model (a slab-ocean version of the Community Earth System Model). We find that our model suite is able to effectively capture both the mean and spread of the CMIP5 response, with the sensitivity spread being predominantly driven by differences in the climate feedbacks excited by the OHU spatial patterns rather than the differences in the global rate of heat uptake. The majority of this feedback spread can be attributed to the degree of Southern Ocean OHU, which works to excite cloud feedbacks both locally and remotely throughout the tropics. Most notably, we find that the large variation in the low cloud response in subtropical cold pool regions bears little relation to the local prescribed forcing patterns, indicating the limited influence of the small scale tropical OHU patterns on the global mean response. This result is further confirmed in a series of idealized model runs in which we are able to effectively capture both the tropical and full global mean temperature and feedback responses while only prescribing the high latitude components of the OHU spatial patterns.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA113.0009R
- Keywords:
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- 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSES;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES