Investigating the pace of temperature change and its implications over the twenty-first century

Abstract:

In most studies, climate change is approached by focusing on the evolution between a fixed current baseline and the future, emphasizing stronger warming as we move further from the current climate. Under climate conditions that are continuously evolving, human systems might have to constantly adapt to a changing target. We propose here an alternative approach, and consider indicators of the pace of temperature change and its effects on temperature distributions estimated from projections of an ensemble of 18 General Circulation Models. The pace is represented by a rate defined by the difference between two subsequent 20-year periods. Under the strongest emission pathway (RCP 8.5), the warming rate strongly increases over the twenty-first century, with a maximum reached before 2080. Whilst northern high-latitudes witness the highest temperature rise, all other latitudes highlight at least a doubling in the warming rate compared to the current period. The spatial extent of significant shifts in annual temperature distributions between two subsequent 20-year periods is projected to be at least four times larger than in the current period. They are mainly located in tropical areas, such as West Africa and South-East Asia. The fraction of the world population exposed to these shifts grows from 8% to 60% from around 2060 onwards, i.e. reaching 6 billions people. In contrast, low mitigation measures (RCP 6.0) are sufficient to keep the warming rate similar to current values. Under the medium mitigation pathway (RCP 4.5), population exposure to significant shifts drops to negligible values by the end of the century. Strong mitigation measures (RCP 2.6) are the only option that generates a global return to historical conditions regarding our indicators. Considering the pace of change can bring an alternative way to interact with climate impacts and adaptation communities.