The monsoons are defined by a seasonal reversal of winds that brings more than 80% of annual precipitation to India and the Sahel, which are largely dependent on them. Predicting their evolution under the influence of man – the so-called anthropogenic response – is therefore of the utmost importance, all the more so as these two regions will be home to two billion people by 2100. However, the monsoon projections we are currently able to provide are accompanied by major uncertainties concerning the amplitude and sometimes the very sign of these changes.

I’ll start with an introduction for non-climate specialists, covering the basics of the climate system and how monsoons fit into it. Then, we’ll take a quick look at the anatomy of a climate model, that serve as our crystal ball for seeing the future, and the reasons why the visions they offer may differ. Then, using recent simulations carried out for the 6th report of the Intergovernmental Panel on Climate Change (IPCC), we will attempt to answer the million-dollar question(s): what are the sources of uncertainty in the forced response of Indian/Sahelian monsoons within projections?

Lieu
École normale supérieure – PSL
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