Abstract
Abstract. Climate changes observed in 1850–2014 are modeled and studied on the basis of seven historical runs with the climate model INM-CM5 under the scenario proposed for the Coupled Model Intercomparison Project Phase 6 (CMIP6). In all runs global mean surface temperature rises by 0.8 K at the end of the experiment (2014) in agreement with the observations. Periods of fast warming in 1920–1940 and 1980–2000 as well as its slowdown in 1950–1975 and 2000–2014 are correctly reproduced by the ensemble mean. The notable change here with respect to the CMIP5 results is the correct reproduction of the slowdown in global warming in 2000–2014 that we attribute to a change in ocean heat uptake and a more accurate description of the total solar irradiance in the CMIP6 protocol. The model is able to reproduce the correct behavior of global mean temperature in 1980–2014 despite incorrect phases of the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation indices in the majority of experiments. The Arctic sea ice loss in recent decades is reasonably close to the observations in just one model run; the model underestimates Arctic sea ice loss by a factor of 2.5. The spatial pattern of the model mean surface temperature trend during the last 30 years looks close to the one for the ERA-Interim reanalysis. The model correctly estimates the magnitude of stratospheric cooling.
Highlights
Noticeable climate changes were observed during the last century
Fast warming in 1920– 1940 similar to observations can be seen in four model runs, while the other three runs show warming earlier or later. These results suggest that the observed acceleration of warming in 1920–1940 is probably due to a combination of external forcing and natural variability
Our results suggest that the rapid decrease in Arctic sea ice extent near year 2000 was partially induced by external forcing; the role of internal variability can be very important
Summary
The main feature of these changes is global warming and it is widely accepted that its most probable cause is an increase in the anthropogenic greenhouse gas concentration (Bindoff et al, 2013). There are two wellknown periods of acceleration in 1920–1940 and 1980–2000 and two periods with a stabilization of the global mean temperature in 1950–1975 and 2000–2014. The reason for this oscillatory behavior is still debated. The ensemble of CMIP5 model runs (with all the mentioned aspects of aerosol and greenhouse gas forcing taken into account) continues to raise global temperature in 2000–2014 albeit at a slower rate (Checa-Garcia et al, 2016)
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