Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1
Abstract Climate forcing, sensitivity, and feedback metrics are evaluated in both the United Kingdom's physical climate model HadGEM3‐GC3.1 at low (‐LL) and medium (‐MM) resolution and the United Kingdom's Earth System Model UKESM1. The effective climate sensitivity (EffCS) to a doubling o...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
American Geophysical Union (AGU)
2019-12-01
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| Series: | Journal of Advances in Modeling Earth Systems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2019MS001866 |
| _version_ | 1798045975663607808 |
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| author | Timothy Andrews Martin B. Andrews Alejandro Bodas‐Salcedo Gareth S. Jones Till Kuhlbrodt James Manners Matthew B. Menary Jeff Ridley Mark A. Ringer Alistair A. Sellar Catherine A. Senior Yongming Tang |
| author_facet | Timothy Andrews Martin B. Andrews Alejandro Bodas‐Salcedo Gareth S. Jones Till Kuhlbrodt James Manners Matthew B. Menary Jeff Ridley Mark A. Ringer Alistair A. Sellar Catherine A. Senior Yongming Tang |
| author_sort | Timothy Andrews |
| collection | DOAJ |
| description | Abstract Climate forcing, sensitivity, and feedback metrics are evaluated in both the United Kingdom's physical climate model HadGEM3‐GC3.1 at low (‐LL) and medium (‐MM) resolution and the United Kingdom's Earth System Model UKESM1. The effective climate sensitivity (EffCS) to a doubling of CO2 is 5.5 K for HadGEM3.1‐GC3.1‐LL and 5.4 K for UKESM1. The transient climate response is 2.5 and 2.8 K, respectively. While the EffCS is larger than that seen in the previous generation of models, none of the model's forcing or feedback processes are found to be atypical of models, though the cloud feedback is at the high end. The relatively large EffCS results from an unusual combination of a typical CO2 forcing with a relatively small feedback parameter. Compared to the previous U.K. climate model, HadGEM3‐GC2.0, the EffCS has increased from 3.2 to 5.5 K due to an increase in CO2 forcing, surface albedo feedback, and midlatitude cloud feedback. All changes are well understood and due to physical improvements in the model. At higher atmospheric and ocean resolution (HadGEM3‐GC3.1‐MM), there is a compensation between increased marine stratocumulus cloud feedback and reduced Antarctic sea‐ice feedback. In UKESM1, a CO2 fertilization effect induces a land surface vegetation change and albedo radiative effect. Historical aerosol forcing in HadGEM3‐GC3.1‐LL is −1.1 W m−2. In HadGEM3‐GC3.1‐LL historical simulations, cloud feedback is found to be less positive than in abrupt‐4xCO2, in agreement with atmosphere‐only experiments forced with observed historical sea surface temperature and sea‐ice variations. However, variability in the coupled model's historical sea‐ice trends hampers accurate diagnosis of the model's total historical feedback. |
| first_indexed | 2024-04-11T23:30:03Z |
| format | Article |
| id | doaj.art-8836074b18d347a2b938df6f6a6a788b |
| institution | Directory Open Access Journal |
| issn | 1942-2466 |
| language | English |
| last_indexed | 2024-04-11T23:30:03Z |
| publishDate | 2019-12-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj.art-8836074b18d347a2b938df6f6a6a788b2022-12-22T03:57:09ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662019-12-0111124377439410.1029/2019MS001866Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1Timothy Andrews0Martin B. Andrews1Alejandro Bodas‐Salcedo2Gareth S. Jones3Till Kuhlbrodt4James Manners5Matthew B. Menary6Jeff Ridley7Mark A. Ringer8Alistair A. Sellar9Catherine A. Senior10Yongming Tang11Met Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKNCAS University of Reading Reading UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKMet Office Hadley Centre Exeter UKAbstract Climate forcing, sensitivity, and feedback metrics are evaluated in both the United Kingdom's physical climate model HadGEM3‐GC3.1 at low (‐LL) and medium (‐MM) resolution and the United Kingdom's Earth System Model UKESM1. The effective climate sensitivity (EffCS) to a doubling of CO2 is 5.5 K for HadGEM3.1‐GC3.1‐LL and 5.4 K for UKESM1. The transient climate response is 2.5 and 2.8 K, respectively. While the EffCS is larger than that seen in the previous generation of models, none of the model's forcing or feedback processes are found to be atypical of models, though the cloud feedback is at the high end. The relatively large EffCS results from an unusual combination of a typical CO2 forcing with a relatively small feedback parameter. Compared to the previous U.K. climate model, HadGEM3‐GC2.0, the EffCS has increased from 3.2 to 5.5 K due to an increase in CO2 forcing, surface albedo feedback, and midlatitude cloud feedback. All changes are well understood and due to physical improvements in the model. At higher atmospheric and ocean resolution (HadGEM3‐GC3.1‐MM), there is a compensation between increased marine stratocumulus cloud feedback and reduced Antarctic sea‐ice feedback. In UKESM1, a CO2 fertilization effect induces a land surface vegetation change and albedo radiative effect. Historical aerosol forcing in HadGEM3‐GC3.1‐LL is −1.1 W m−2. In HadGEM3‐GC3.1‐LL historical simulations, cloud feedback is found to be less positive than in abrupt‐4xCO2, in agreement with atmosphere‐only experiments forced with observed historical sea surface temperature and sea‐ice variations. However, variability in the coupled model's historical sea‐ice trends hampers accurate diagnosis of the model's total historical feedback.https://doi.org/10.1029/2019MS001866Climate SensitivityClimate feedbackRadiative forcingCMIP6RFMIPCFMIP |
| spellingShingle | Timothy Andrews Martin B. Andrews Alejandro Bodas‐Salcedo Gareth S. Jones Till Kuhlbrodt James Manners Matthew B. Menary Jeff Ridley Mark A. Ringer Alistair A. Sellar Catherine A. Senior Yongming Tang Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1 Journal of Advances in Modeling Earth Systems Climate Sensitivity Climate feedback Radiative forcing CMIP6 RFMIP CFMIP |
| title | Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1 |
| title_full | Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1 |
| title_fullStr | Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1 |
| title_full_unstemmed | Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1 |
| title_short | Forcings, Feedbacks, and Climate Sensitivity in HadGEM3‐GC3.1 and UKESM1 |
| title_sort | forcings feedbacks and climate sensitivity in hadgem3 gc3 1 and ukesm1 |
| topic | Climate Sensitivity Climate feedback Radiative forcing CMIP6 RFMIP CFMIP |
| url | https://doi.org/10.1029/2019MS001866 |
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