Séminaire
Weather induced extreme events such as crop failure, river floods, tropical cyclones, heatwaves and droughts represent an immediate threat to communities. In spite of their different characteristics they all have a joint potential to cause (long-term) economic losses, displacement, persistence of poverty, or social de-stabilisation. According to newly released synchronized climate impact simulations, climate change from pre-industrial conditions to today’s 1°C global warming has about tripled the fraction of the global population annually exposed to extreme events. In comparison, reference simulations that account for socio-economic change but assume stable pre-industrial climate conditions show that historical changes in population distribution, land use and – to a limited extent – other direct human influences alone have reduced the fraction of the global population annually exposed to extreme events by about 10%. Assuming fixed year 2005 socio-economic conditions the global population exposed to spatially confined events (river floods, tropical cyclones, wildfires, and crop failures) shows a purely climate change-driven increase of 69 million people at 1.5°C, and 91 million people at 2°C global warming compared to pre-industrial climate conditions. The population exposed to spatially extensive events (droughts and heatwaves) increases by 507 mio people at 1.5°C and 824 mio people at 2°C. The new repository of harmonized multi-impact model data is intended to evolve in parallel to the climate modelling exercise CMIP and provide the basis for new event-based approaches to estimating the societal impacts of climate change.
philippe.ciais@lsce.ipsl.fr