Abstract
Over the first half of 2020, Siberia experienced the warmest period from January to June since records began and on the 20th of June the weather station at Verkhoyansk reported 38 °C, the highest daily maximum temperature recorded north of the Arctic Circle. We present a multi-model, multi-method analysis on how anthropogenic climate change affected the probability of these events occurring using both observational datasets and a large collection of climate models, including state-of-the-art higher-resolution simulations designed for attribution and many from the latest generation of coupled ocean-atmosphere models, CMIP6. Conscious that the impacts of heatwaves can span large differences in spatial and temporal scales, we focus on two measures of the extreme Siberian heat of 2020: January to June mean temperatures over a large Siberian region and maximum daily temperatures in the vicinity of the town of Verkhoyansk. We show that human-induced climate change has dramatically increased the probability of occurrence and magnitude of extremes in both of these (with lower confidence for the probability for Verkhoyansk) and that without human influence the temperatures widely experienced in Siberia in the first half of 2020 would have been practically impossible.
Highlights
Since the beginning of 2020, anomalously high temperatures were repeatedly reported in Siberia
The observational analysis plays two roles, giving us an assessment of changes that is independent of numerical climate models as well as providing validation criteria that must be satisfied by all models included in the subsequent model-based attribution analysis
A large, rapid multi-method attribution study, supported by observational and large ensemble model analyses, indicates with high confidence that extremely warm periods such as the 6 months of January–June 2020 over the Siberian region would have been at least 2 °C cooler in a world without human influence
Summary
Since the beginning of 2020, anomalously high temperatures were repeatedly reported in Siberia. On the 23rd of June, the World Meteorological Organization (WMO) announced that it was ‘seeking to verify a reported new record temperature north of the Arctic Circle [of] 38°C on 20th June in the Russian town of Verkhoyansk amid a prolonged Siberian heatwave and increase in wildfire activity’ (WMO 2020). This event happened in the month prior to that of the climatologically expected peak daily maxima. This article is based on a rapid attribution study performed by the World Weather Attribution consortium and the scientific report underlying that study
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