Alexander is a Senior Scientist at the Potsdam Institute for Climate Impact Research (PIK) where he leads a research group on land-use management as well as the PIK activity on land-use modelling.
Alexander coordinates the development of the global land-use model ‘Model of Agricultural Production and its Impacts on the Environment’ (MAgPIE), which is one of the world’s leading integrated global land and water use modelling systems. He contributes to several international climate and land-use assessments such as IPCC (e.g. Lead author for Special Report on Land, Lead author for AR6). He also plays a leading role in the assessment of land-based climate change mitigation for the Stanford Energy Modeling Forum as well as in BES-SIM, coordinates the land-use group for the development of the new scenario framework ‘Shared Socioeconomic Pathways’ (SSPs) and works on The World in 2050 (TWI2050) and FABLE projects on Sustainable Development Goals.
Since 2019, Alexander has been an Associate Deputy Editor of the journal Climatic Change, has published numerous peer reviewed scientific articles and is ranked by Web of Science among the 1% most influential scientists in the world.