Abstract
Concurrent extreme events, i.e. multi-variate extremes, can be associated with strong impacts. Hence, an understanding of how such events are changing in a warming climate is helpful to avoid some associated climate change impacts and better prepare for them. In this article, we analyse the projected occurrence of hot, dry, and wet extreme events’ clusters in the multi-model ensemble of the 6th phase of the Coupled Model Intercomparison Project (CMIP6). Changes in ‘extreme extremes’, i.e. events with only 1% probability of occurrence in the current climate are analysed, first as univariate extremes, and then when co-occurring with other types of extremes (i.e. events clusters) within the same week, month or year. The projections are analysed for present-day climate (+1 °C) and different levels of additional global warming (+1.5 °C, +2 °C, +3 °C). The results reveal substantial risk of occurrence of extreme events’ clusters of different types across the globe at higher global warming levels. Hotspot regions for hot and dry clusters are mainly found in Brazil, i.e. in the Northeast and the Amazon rain forest, the Mediterranean region, and Southern Africa. Hotspot regions for wet and hot clusters are found in tropical Africa but also in the Sahel region, Indonesia, and in mountainous regions such as the Andes and the Himalaya.
Highlights
Compound events, i.e. multivariate extremes, count among the most potentially impactful consequences of human-induced climate change (Zscheischler et al 2018), but have received relatively little attention in the research literature so far
The projections are analysed for present-day climate (+1 ◦C) and different levels of additional global warming (+1.5 ◦C, +2 ◦C, +3 ◦C)
Already for +1 ◦C of global warming (figure 1(a), top), which approximately corresponds to presentday warming, we find more than a doubling of hot extremes compared to +0.61 ◦C in most regions of the world
Summary
I.e. multivariate extremes, count among the most potentially impactful consequences of human-induced climate change (Zscheischler et al 2018), but have received relatively little attention in the research literature so far. Dedicated analyses of projected changes in compound events are very limited, the impacts could be much stronger than those caused by isolated hazards. Some studies investigate the occurrence of compound events in present climate (Martius et al 2016) or in the recent past (AghaKouchak et al 2014), while others have investigated projections of changes in multivariate extreme conditions (Zscheischler and Seneviratne 2017), but without an event perspective. The co-occurrence of hot and dry conditions can intensify the development of summer heatwaves (Seneviratne et al 2010) and can be associated with specific hazards, such as fire risk (Zscheischler et al 2018). There is so far to our knowledge no analyses of projected changes in compound extreme events available based on the new 6 th phase of the Coupled Model Intercomparison Project (CMIP6; Eyring et al 2016), which serves as the basis for the 6 th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6)
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