Land use (switching from one land cover to another or changing land management) is known to be important for climate at both global and regional scales. It is a significant source of greenhouse gas emissions for the atmosphere and thus contributes to global warming. At smaller spatial scales it can shape the response of some regions to global warming, by either dampening or enhancing the increase in temperature during summer time (for example). It has also been shown to modulate the intensity, frequency and persistence of heat waves.
The effects of land use on climate, discussed throughout the literature, generally focus on greenhouse gas emissions and on temperature. Those are the two variables that have been assessed in the IPCC special report on Land (published August 8, 2019). Many papers however report significant effect of e.g. tropical deforestation on rainfall in the Amazon, others have looked at the effects of land cover (e.g. afforestation) or management (e.g. irrigation) on african and asian monsoon rains. But there is yet no assessment made on how land use affects the water cycle, in a changing climate, at both the global and regional scales. How are the various components of the water cycle affected by land use? How do those changes compare with the ones induced by global warming?
In addition there is evidence that deep-water resources, used for irrigated agriculture, are becoming or may become more scarce in many regions of the world with both increasing anthropogenic pressure and climate change. There is thus a need to make sure that rainfed agriculture can still be sustained across the world.
We propose, for this PhD work, to assess the respective contributions of anthropogenic land cover change and global warming on past and projected changes in rainfall, with a specific focus on present-day rainfed agriculture areas as well as on present-day irrigated areas. The student will analyze existing simulations carried out in various modeling groups around the world, within the framework of IPCC exercises. Those simulations address past and future climate changes, with and without land use changes, at both global and regional scales.
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Location of the PhD
The PhD will work at LSCE (https://www.lsce.ipsl.fr/), just outside Paris on the Plateau de Saclay. Nathalie de Noblet-Ducoudré works in the team ESTIMR (https://www.lsce.ipsl.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=22) and so will the PhD student.