Now a new study by researchers at Stanford, the University of California, Berkeley, and the U.S. Department of the Treasury suggests that even short periods of extreme heat can carry long-term consequences for children and their financial future. Specifically, heat waves during an individual’s early childhood, including the period before birth, can affect his or her earnings three decades later, according to the paper, published on Monday in Proceedings of the National Academy of Sciences. Every day that temperatures rise above 32 ˚C, or just shy of 90 ˚F, from conception to the age of one is associated with a 0.1 percent decrease in average income at the age of 30.
The researchers don’t directly tackle the tricky question of how higher temperatures translate to lower income, noting only that fetuses and infants are “especially sensitive to hot temperatures because their thermoregulatory and sympathetic nervous systems are not fully developed.” Earlier studies have linked extreme temperatures during this early life period with lower birth rate and higher infant mortality, and a whole field of research has developed around what’s known as the “developmental origins of health and disease paradigm,” which traces the impacts of early health shocks into adulthood.
There are several pathways through which higher temperatures could potentially lead to lower adult earnings, including reduced cognition, ongoing health issues that increase days missed from school or work, and effects on non-cognitive traits such as ambition, assertiveness, or self-control, says Maya Rossin-Slater, a coauthor of the study and assistant professor in Stanford’s department of health research and policy.
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The bigger danger here is that global warming will mean many more days with a mean temperature above 32 ˚C—specifically, an increase from one per year in the average U.S. county today to around 43 annually by around 2070, according to an earlier UN report cited in the study.