Extremely high temperatures pose an immediate threat to humans and ecosystems. In recent years, many regions on land and in the ocean experienced heat waves with devastating impacts that would have been highly unlikely without human‐induced climate change. Impacts are particularly severe when heat waves occur in regions with high exposure of people or crops. The recent 2018 spring‐to‐summer season was characterized by several major heat and dry extremes. On daily average between May and July 2018 about 22% of the populated and agricultural areas north of 30° latitude experienced concurrent hot temperature extremes. Events of this type were unprecedented prior to 2010, while similar conditions were experienced in the 2010 and 2012 boreal summers. Earth System Model simulations of present‐day climate, that is, at around +1 °C global warming, also display an increase of concurrent heat extremes. Based on Earth System Model simulations, we show that it is virtually certain (using Intergovernmental Panel on Climate Change calibrated uncertainty language) that the 2018 north hemispheric concurrent heat events would not have occurred without human‐induced climate change. Our results further reveal that the average high‐exposure area projected to experience concurrent warm and hot spells in the Northern Hemisphere increases by about 16% per additional +1 °C of global warming. A strong reduction in fossil fuel emissions is paramount to reduce the risks of unprecedented global‐scale heat wave impacts.

中文翻译：

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人为气候变化导致 2018 年北半球同时出现极端高温

极高的温度对人类和生态系统构成直接威胁。近年来，陆地和海洋的许多地区经历了热浪，造成了毁灭性的影响，如果没有人类引起的气候变化，这种影响是不可能发生的。当热浪发生在人员或农作物暴露程度较高的地区时，影响尤其严重。2018 年春夏季节出现了几次严重的高温和干燥极端天气。2018 年 5 月至 7 月期间，日均约 22%北纬 30°以北的人口稠密地区和农业地区经历了同时极端炎热的温度。此类事件在 2010 年之前是前所未有的，而 2010 年和 2012 年的北方夏季也经历过类似的情况。地球系统模型对当今气候（即全球变暖+1°C 左右）的模拟也显示出同时发生的极端高温的增加。基于地球系统模型模拟，我们表明几乎可以肯定（使用政府间气候变化专门委员会校准的不确定性语言）如果没有人类引起的气候变化，2018年北半球同时发生的高温事件就不会发生。我们的结果进一步表明，全球变暖每增加 1°C，北半球预计将同时经历暖热期的平均高暴露区域就会增加约 16%。大幅减少化石燃料排放对于降低前所未有的全球范围热浪影响的风险至关重要。