What can we learn about climate feedbacks from short-term climate variations?

ABSTRACT

This study examines the radiative feedbacks resulting from changes in the climate over the last 30 yr. These ‘short-term’ feedbacks correspond to both external changes in the forcing [from greenhouse gases (GHGs), aerosols etc.] and internal climate variations [mostly due to El Niño Southern Oscillation (ENSO)]. They differ from the ‘long-term’ (century scale, mainly due to GHG warming) feedbacks both in magnitude (by 24% on the global average) and geographical distribution, according to the Coupled Model Intercomparison Project phase 3 multi-model dataset. In addition, the inter-model spread of the short-term feedbacks is larger than the long-term ones even for the models with the best ENSO performance, which indicates that important aspects of the ENSO variability are still poorly understood and/or simulated. Information from observations and from advanced reanalysis systems can be very useful to improve the model short-term climate responses. However, long and accurate observational records are critical in order to obtain confident results.

• feedbacks
• long-term
• ENSO
• climate change
• radiative kernels

8. Acknowledgements

I am grateful to Lennart Bengtsson for useful discussions on this work. Thanks to two anonymous reviewers for comments and corrections on the original manuscript. I acknowledge the modelling groups, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) and the WCRP's Working Group on Coupled Modelling (WGCM) for their roles in making available the WCRP CMIP3 multi-model dataset. I would also like to acknowledge ECMWF for the use of the ERA-Interim reanalysis data and the Japan Meteorological Agency for the use of the JRA-25 reanalysis data. The Clouds and the Earth's Radiant Energy System (CERES) Energy Balances and Filled (EBAF) dataset were obtained from the NASA Langley Research Center Atmospheric Science Data Center.