Anja Katzenberger, Universität Potsdam

Abrupt Monsoon Transitions

As an integral element of the global circulation system, the monsoon influences the livelihood of more than 70% of the world’s population. Paleoclimatic records have shown, that monsoon systems have the capacity to alternate between an active (wet) and nonactive (dry) monsoon state. Since transitions between these states change the climatic conditions that people have adapted to throughout centuries, even small changes in the  the characteristics of the monsoon can bring substantial change to the lives of millions of individuals.

In my PhD project, I want to focus on such transitions particular of those with a non-linear abrupt character. For this purpose, I first focus on the physical and climatological background of such non-linear transitions and conduct a conceptual study of an idealized planet designed in such a way that the analysis of complex monsoon dynamics is facilitated. In this context, we use the Atmospheric Model GFDL-AM2 that was developed in Princeton University and perform simulations with different CO2 as well as aerosol concentrations.

In the second phase, we want to examine the possibility of a non-linear transition in the first half of the 21st century for the Sahel region. General climate models from the last generation have indicated the possibility of an abrupt transition in this region but there is no agreement between the different climate models. Recently, the latest generation of the Coupled Model Intercomparison Project (CMIP) has become available with significant improvements in the processes regarding the monsoon systems. Thus, analyzing the projections in these models for the 21st century is of high interest. Such transitions and the associated substantial change of available water in the region would be an enormous change with potential influences even reaching Europe due to climate induced migration and geopolitics.

During the third phase of my PhD, I want to focus on the impacts of the changes found e.g. in the second phase on agriculture and thus food-security in the monsoon regions. In this context, I want to use the agricultural yield data of the International Crops Research Institute for the semi-arid tropics and examine the impact of weather extremes during past monsoon seasons on crop yield in India.