GFI/BCCR Seminar | Giuseppe Zappa: The importance of remote drivers of atmospheric circulation for European and Mediterranean climate change
Giuseppe Zappa (University of Reading)
The importance of remote drivers of atmospheric circulation for European and Mediterranean climate change
Future changes in the atmospheric circulation could cause substantial socio-economic impacts, particularly by modulating storminess and precipitation patterns. However, the confidence in the atmospheric circulation response remains low, and multi-model ensemble projections cannot be interpreted in a probabilistic way. This presentation will analyse some of the causes of low confidence and point to the key role of three remote drivers of European atmospheric circulation, i.e. the tropical and polar amplification of global warming and the strength of the stratospheric vortex, in shaping the European hydro-climate response to climate change. This will be explored using two complementary approaches. First, a storyline approach is introduced by analysing the inter—model spread in the CMIP5 models future projections, whereby regional climate change is analysed as a function of carbon emissions conditional on the response in the three identified remote drivers. For a given amount of global warming, a worst case scenario of European climate change, characterised by a strong drying of the Mediterranean region, is found for a large tropical amplification and a strengthening of the stratospheric vortex. In the second approach, the impact of the CO2 direct radiative forcing, SST warming and sea ice reduction are separated using additional simulations from the CMIP5 archive. Results indicate a robust impact of sea ice loss on the Euro-Atlantic jet shift in late winter, and suggest that part of the uncertainty in the stratospheric vortex response could result from the sea ice loss itself.