Markku Rummukainen

The present day global climate change is fueled by our use of fossil fuels and land use change. The already observed warming and other distinct changes in the climate system stem from these human influences and are ongoing. Due to climate system inertia, a part of the climate system's response to this historical forcing remains to manifest itself, which it will do over time. At the same time, socio-economic forces and trends imply some amount of additional emission and land use change, which compounds our commitment to even more substantial climate change. Cumulative carbon dioxide emissions are the basic determinant of the ultimate amount of anthropogenic climate change. Climate system properties, such as climate sensitivity and the carbon cycle, and also possible initiation of non-linear changes, further shape the amount and nature of the long-term change for any set amount of greenhouse gas emissions. While a changed climate is, in practice, now unavoidable, our commitment to continued climate change can be constrained by reductions of global carbon dioxide emissions, their cessation and/or negative emissions. These alternatives have different implications for the long-term unfolding of these changes, but can all considerably reduce the possibility of very large amounts of change, the need for adaptation and responses to negative impacts.