Impact projections refer to the future and address questions such as “Will coral reefs die because of increasing water temperatures?”, “Do we have to expect more coastal flooding because of climate induced sea level rise”, “Will heatwaves become more often and more dangerous for human health?”.
The answers to these questions depend on human greenhouse gas emissions. So they can only be addresses in an “if-then” context such as “If CO2 emissions continue to rise as currently observed then…” or “If we manage to limit global warming to 2°C, then…”. That means that projections depend on the underlying assumptions about greenhouse gas emissions, the potential emission scenarios. In ISIMIP2 impact modelling teams have agreed on two scenarios, one reaching about 3°C of global warming at the end of the century (RCP6.0) and another one that is more in line with the Paris agreement reaching about 2°C of global warming. To project impacts according to associated climate change we also have to make assumption about socioeconomic developments (e.g. population increase). In ISIMIP2 we also asked modelling teams to make the same assumptions regarding these socioeconomic changes. So all the projections you can find here are based on this agreement.