How may low-cloud radiative properties simulated in the current climate influence low-cloud feedbacks under global warming?
Article first published online: 23 OCT 2012
©2012. American Geophysical Union. All Rights Reserved.
Geophysical Research Letters
Volume 39, Issue 20, 28 October 2012
How to Cite
2012), How may low-cloud radiative properties simulated in the current climate influence low-cloud feedbacks under global warming?, Geophys. Res. Lett., 39, L20807, doi:10.1029/2012GL053265., and (
- Issue published online: 23 OCT 2012
- Article first published online: 23 OCT 2012
- Manuscript Accepted: 16 SEP 2012
- Manuscript Revised: 10 SEP 2012
- Manuscript Received: 25 JUL 2012
- MSE budget;
- climate sensitivity;
- low-cloud feedback;
- model hierarchy;
- model tuning;
- observational constraints
 The influence of cloud modelling uncertainties on the projection of the tropical low-cloud response to global warming is explored by perturbing model parameters of the IPSL-CM5A climate model in a range of configurations (realistic general circulation model, aqua-planet, single-column model). While the positive sign and the mechanism of the low-cloud response to climate warming predicted by the model are robust, the amplitude of the response can vary considerably depending on the model tuning parameters. Moreover, the strength of the low-cloud response to climate change exhibits a strong correlation with the strength of the low-cloud radiative effects simulated in the current climate. We show that this correlation primarily results from a local positive feedback (referred to as the “beta feedback”) between boundary-layer cloud radiative cooling, relative humidity and low-cloud cover. Based on this correlation and observational constraints, it is suggested that the strength of the tropical low-cloud feedback predicted by the IPSL-CM5A model in climate projections might be overestimated by about fifty percent.