On the increased climate sensitivity in the EC-Earth model from CMIP5 to CMIP6
<p>Many modelling groups that contribute to CMIP6 (Coupled Model Intercomparison Project Phase 6) have found a larger equilibrium climate sensitivity (ECS) with their latest model versions compared with the values obtained with the earlier versions used in CMIP5. This is also the case for the...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-08-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/13/3465/2020/gmd-13-3465-2020.pdf |
| Summary: | <p>Many modelling groups that contribute to CMIP6 (Coupled
Model Intercomparison Project Phase 6) have found a larger equilibrium
climate sensitivity (ECS) with their latest model versions compared with the
values obtained with the earlier versions used in CMIP5. This is also the case for
the EC-Earth model. Therefore, in this study, we investigate what developments since
the CMIP5 era could have caused the increase in the ECS in this model. Apart
from increases in the horizontal and vertical resolution, the EC-Earth model has also substantially changed the representation of aerosols; in
particular, it has introduced a more sophisticated description of aerosol
indirect effects. After testing the model with some of the recent updates
switched off, we find that the ECS increase can be attributed to the more
advanced treatment of aerosols, with the largest contribution coming from
the effect of aerosols on cloud microphysics (cloud lifetime or second
indirect effect). The increase in climate sensitivity is unrelated to model
tuning, as all experiments were performed with the same tuning
parameters and only the representation of the aerosol effects was
changed. These results cannot be generalised to other models, as their CMIP5
and CMIP6 versions may differ with respect to aspects other than the aerosol–cloud
interaction, but the results highlight the strong sensitivity of ECS to the
details of the aerosol forcing.</p> |
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| ISSN: | 1991-959X 1991-9603 |