Abstract
Abstract. Extreme temperatures were experienced over a large part of the Northern Hemisphere during the 2018 boreal summer (hereafter referred to as “NH2018 event”), leading to major impacts on agriculture and society in the affected countries. Previous studies highlighted both the anomalous atmospheric circulation patterns during the event and the background warming due to human greenhouse gas emissions as main drivers of the event. In this study, we present Earth system model experiments investigating different storylines of the NH2018 event given the same atmospheric circulation and alternative background global warming for no human imprint, the 2018 conditions, and different mean global warming levels 1.5, 2, 3 and 4 ∘C. The results reveal that the human-induced background warming was a strong contributor to the intensity of the NH2018 event, and that resulting extremes under similar atmospheric circulation conditions at higher levels of global warming would reach dangerous levels. Compared to 9 % during the NH2018 event, about 13 % (34 %) of the inhabited or agricultural area in the investigated region would reach daily maximum temperatures over 40 ∘C under 2 ∘C (4 ∘C) of global warming and similar atmospheric circulation conditions.
Highlights
During the 2018 boreal summer, large parts of the Northern Hemisphere experienced extreme temperatures, leading to major impacts on agriculture and society in the affected countries (Vogel et al, 2019)
We present an analysis of scenario storylines building on the extreme 2018 Northern Hemisphere summer (“NH2018 event”)
The event is alternatively simulated in a natural setting without human imprint on the climate system (“natural”), for the present-day climate conditions and for four scenarios at different levels of global warming (1.5, 2, 3 and 40 ◦C under ◦C (4 ◦C))
Summary
During the 2018 boreal summer, large parts of the Northern Hemisphere experienced extreme temperatures, leading to major impacts on agriculture and society in the affected countries (Vogel et al, 2019). The event (hereafter referred to as “NH2018 event”) was associated with near-simultaneous heatwaves on three continents, including North America, western and northern Europe, as well as Japan and the Korean Peninsula (Kornhuber et al, 2019b; Vogel et al, 2019) Previous studies highlighted both the anomalous atmospheric circulation patterns during the event and the background global warming due to human greenhouse gas emissions as main drivers of the event (Drouard et al, 2019; Kornhuber et al, 2019b; Toreti et al, 2019; Vogel et al, 2019). These experiments are of particular relevance since events associated with the type of circulation patterns from the NH2018 events could lead to high risks of crop failures across several breadbasket regions of the world (Kornhuber et al, 2019a)
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