Global and European climate response to transient forcings since 1870, as simulated in an atmospheric general circulation model
Predicting and adapting to climate change is one of the major challenges for the twenty-first century. To better understand the future changes in precipitation associated with climate change on the global and regional scale, this thesis investigates, for the past 140 years, the time-varying impact of the major climate forcings on precipitation. To do so, the global climate is simulated between 1870 and 2005 in a transient mode with the atmospheric general circulation model “ECHAM5- HAM”. The model is forced with observationally based time-varying sea surface temperatures (SSTs) and the major climate forcings, which include total solar irradiance, volcanic optical depth, aerosol emissions (natural and anthropogenic), and greenhouse gas concentrations. Sensitivity experiments, holding one or more of these forcings constant throughout the experiments are then used to identify and quantify their time-varying impacts on the hydrological cycle. In a first step, the thesis aims to identify the main climate forcings driving the decadal variability of global land temperature and precipitation between 1870 and 2005. It then investigates the causes driving the wind stilling observed over land after 1970 in many sites over the globe, due to its potential impact on the hydrological cycle and on industries such as wind powered energy. Finally, the high precipitation anomalies observed in central Europe in the late nineteenth century are also investigated, for their potential contribution to the accumulation of destructive floods recorded at the time in central Europe.
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