If there’s one thing you should get used to with climate change—apart from the heat waves, droughts, and intense storms—it’s hot, uncomfortable nights. Worldwide, there will be somewhere around two weeks of higher nighttime low temperatures. In some places, winter nights may be unseasonable warm, or in others summer nights could grow more sweltering and sleepless.
But it’s not just our comfort that’s at stake. Plants are uniquely sensitive to nighttime low temperatures. If they’re too high, plant respiration rates tend to increase. (Yes, plants respire just like us. Unlike us, they’re able to grow without eating because, during a typical day, the rate of photosynthesis greatly outpaces the rate of respiration, meaning they’re making more food than they are consuming.) When respiration rates rise in plants, they consume more of the carbohydrates they made through photosynthesis during the day. With less energy available, they might grow more slowly or put less energy into producing seeds. It happens that many staple crops, like rice and corn, are seeds, so warm nights are one way climate change could slash crop harvests.
Not only will more people be going to bed sweating, they’ll be doing so on empty stomachs.
Historical climate: Climate Research Unit (Mitchell et al, 2003). Projected changes: Climate Systems Analysis Group, University of Cape Town 2009, calculated from Meehl et al, 2007. Available from the World Bank.