Sherwood Steven C, Huber Matthew
Climate Change Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia.
Proc Natl Acad Sci U S A. 2010 May 25;107(21):9552-5. doi: 10.1073/pnas.0913352107. Epub 2010 May 3.
Despite the uncertainty in future climate-change impacts, it is often assumed that humans would be able to adapt to any possible warming. Here we argue that heat stress imposes a robust upper limit to such adaptation. Peak heat stress, quantified by the wet-bulb temperature T(W), is surprisingly similar across diverse climates today. T(W) never exceeds 31 degrees C. Any exceedence of 35 degrees C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible. While this never happens now, it would begin to occur with global-mean warming of about 7 degrees C, calling the habitability of some regions into question. With 11-12 degrees C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 degrees C are possible from fossil fuel burning. One implication is that recent estimates of the costs of unmitigated climate change are too low unless the range of possible warming can somehow be narrowed. Heat stress also may help explain trends in the mammalian fossil record.
尽管未来气候变化影响存在不确定性，但人们通常认为人类能够适应任何可能的气候变暖。在此我们认为，热应激对这种适应能力施加了一个严格的上限。通过湿球温度T(W)量化的峰值热应激，在当今不同气候条件下惊人地相似。T(W)从未超过31摄氏度。如果长时间超过35摄氏度，人类和其他哺乳动物就会出现体温过高，因为代谢热无法散发。虽然目前这种情况从未发生，但随着全球平均气温上升约7摄氏度，这种情况将开始出现，这使得一些地区的宜居性受到质疑。随着气温上升11 - 12摄氏度，这些地区将扩大到涵盖目前分布的大多数人口。由于燃烧化石燃料，最终气温有可能上升12摄氏度。这意味着，除非能以某种方式缩小可能的变暖范围，否则近期对未减缓气候变化成本的估计过低。热应激也可能有助于解释哺乳动物化石记录中的趋势。
