Abstract
To understand whether high temperatures and temperature extremes are important for climate change adaptation in Scotland, we place the 2018 heatwave in the context of past, present, and future climate, and provide a rapid but comprehensive impact analysis. The observed hottest day (d), 5 d, and 30 d period of 2018 and the 5 d period with the warmest nights had return periods of 5–15 years for 1950–2018. The warmest night and the maximum 30 d average nighttime temperature were more unusual with return periods of >30 years. Anthropogenic climate change since 1850 has made all these high-temperature extremes more likely. Higher risk ratios are found for experiments from the CMIP6-generation global climate model HadGEM3-GA6 compared to those from the very-large ensemble system weather@home. Between them, the best estimates of the risk ratios for daytime extremes range between 1.2–2.4, 1.2–2.3, and 1.4–4.0 for the 1, 5, and 30 d averages. For the corresponding nighttime extremes, the values are higher and the ranges wider (1.5- >50, 1.5–5.5, and 1.6- >50). The short-period nighttime extremes were more likely in 2018 than in 2017, suggesting a contribution from year-to-year climate variability to the risk enhancement of extreme temperatures due to anthropogenic effects. Climate projections suggest further substantial increases in the likelihood of 2018 temperatures between now and 2050, and that towards the end of the century every summer might be as hot as 2018. Major negative impacts occurred, especially on rural sectors, while transport and water infrastructure alleviated most impacts by implementing costly special measures. Overall, Scotland could cope with the impacts of the 2018 heatwave. However, given the likelihood increase of high-temperature extremes, uncertainty about consequences of even higher temperatures and/or repeated heatwaves, and substantial costs of preventing negative impacts, we conclude that despite its cool climate, high-temperature extremes are important to consider for climate change adaptation in Scotland.
Highlights
Introduction ceClimate change adaptation is essential alongside mitigation given existing climate change (IPCC, 2018), and urgent given the implementation time of measures
In summer 2018 Scotland experienced anomalously high temperatures, and a range of impacts of this heatwave were reported by news media
This study places the 2018 heatwave in the context of past, present, and projected future climate, and provides a rapid but comprehensive analysis of the heatwave impacts to understand the need for Scotland
Summary
We characterise observed temperatures during summer 2018 using near-surface daily minimum (nighttime) and maximum (daytime) temperature from the European gridded observational dataset (E-OBS), version 19.0e spanning 1/1/1950-31/12/2018 at 0.25◦. Resolution (Haylock et al, 2008; ECA&D, 2019). We further use daily minimum and maximum temperature observed at the stations at Eskdalemuir (WIGOS station identifier (WMO, 2015): 0-20000-0-03162; MIDAS source ID (Met Office, 2012): 1023) and Auchincruive (MIDAS source ID: 1005). The atmospheric circulation is shown using daily us cri sea level pressure data at 0.75◦ resolution from the ERA-Interim reanalysis (Dee et al, 2011; ECMWF , 2018)
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