Several new CMIP6 climate models project stronger future warming and have higher climate sensitivity (ECS) than previous generations of climate models.
These are some of the findings of a study led by CONSTRAIN researcher Kasia Tokarska, published in the journal Science Advances, which shows that most of these high ECS models overestimate observed warming. As a result, their higher future warming projections are less likely.
There is a relationship between the projected future warming in the models and the model-simulated warming trend over recent decades (1981-2014 and 1981-2017), for both CMIP5 (the previous generation) and CMIP6 models. This relationship allows us to constrain future warming by using recent observations on how the climate has changed.
Using these observed global warming trends for the recent period to constrain the model projections reduced the warming in 2050s in CMIP6 models by 16% for high emissions scenarios and 14% for ambitious mitigation scenarios (scenarios such as SSP 2-4.5 are consistent with achieving the Paris Agreement goals). For the 2090-2100 period, warming was reduced by over 14% and 8% respectively, relative to 1995–2014.
This observationally-constrained CMIP6 future warming is also consistent with CMIP5 assessments.
Importantly, these results do not mean climate change is not serious, but they do indicate there is little evidence for future warming being stronger than we thought.
Correlation of the simulated warming trend for the period 1981–2014 with TCR for CMIP6 models