I have many years of experience in global climate and carbon cycle research. My research focuses on the interactions between terrestrial ecosystems and climate, including biogeophysical and biogeochemical feedbacks. I have developed global dynamic vegetation models and used them for pioneering studies on the stability of climate-vegetation systems. I have used models of varying complexity to study the dynamics of the Quaternary carbon cycle, including the last glacial cycle and the Holocene. My group's research now focuses on understanding the role of high-latitude ecosystems in the climate system, with an emphasis on terrestrial and marine permafrost processes. I have contributed as lead author to the Millennium Ecosystem Assessment and IPCC WGI AR5 (carbon cycle chapter) and as review editor to IPCC WGI AR6 (carbon cycle chapter).