Editing IPCC:AR6/WGI/Chapter-10 (section)

==== 10.6.4.8 Storyline Approaches ====

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The atmospheric circulation is influenced by large-scale, often slowly varying components of the climate system, such as ocean, sea ice and soil moisture. Historical and future changes of the atmospheric circulation depend, among other factors, on how these drivers have changed and will change. [[#Zappa--2017|Zappa and Shepherd (2017)]] have analysed this for the Mediterranean region and developed a set of storylines based on different plausible evolutions of those drivers and their impact on the Mediterranean winter climate. Important identified drivers during winter are tropical and polar amplification of global warming and the polar stratospheric vortex ( [[#Manzini--2014|Manzini et al., 2014]] ; [[#Simpson--2018|Simpson et al., 2018]] ), with implications for precipitation. [[#Zappa--2019|Zappa (2019)]] discusses the relative amplitude of tropical and Arctic warming, response of the AMOC, patterns of Pacific SST change, and changes in stratospheric vortex strength as possible drivers of the Mediterranean summer climate and stresses that given the present state of knowledge, alternative storylines based on these drivers should be considered as equally plausible future manifestations of regional climate change. Brogli et al. (2019a, b) and [[#Kröner--2017|Kröner et al. (2017)]] have revealed thermodynamic processes, lapse rate, and circulation as important drivers for Mediterranean summer climate.

Low-likelihood high-impact events might affect future Mediterranean climate. An example of such an event is the collapse of the AMOC ( [[#Weijer--2019|Weijer et al., 2019]] ), that would bring widespread cooling over the Northern Hemisphere. For the Mediterranean this is estimated to be a few degrees Celsius during summer in the case of a total collapse ( [[#Jackson--2015|Jackson et al., 2015]] ).

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