Children conceived during heatwaves receive more schooling, are more literate and have lower rates of disability as adults, according to research by Benedicte Apouey and Joshua Wilde to be presented at the Royal Economic Society's 2015 annual conference.
Their study examines the health and educational records of children born in sub-Saharan Africa, nine months after a period of hot weather. They advance two reasons why heatwave babies are smarter and stronger:
• Reduced sexual activity: poorer parents are less likely to have air conditioning, meaning that a higher proportion of heatwave babies have wealthy parents. The decline in sexual activity during heatwaves is especially prevalent among mothers with low levels of education.
• Natural selection: extreme heat can result in higher rates of miscarriage. Weaker foetuses have a higher likelihood of perishing, so only the most biologically fit children survive.
The second explanation might imply that global warming is a 'good thing', though the authors do not agree:
'These benefits come at a real human cost. Miscarriage often comes with a high psychological and biological cost to parents, especially if these lost pregnancies were wanted. It is hard to imagine that society is better off as a result.'
A study from the Paris School of Economics and the University of South Florida finds that in sub-Saharan Africa, children conceived during heatwaves receive more schooling, are more literate and have lower rates of disability as adults. Although this may seem to imply that global warming could be beneficial, one reason behind this result may be slightly less positive: natural selection.
'Studies have shown that when a mother faces environmental stressors such as hunger or disease, or even psychological stresses, there is a higher probability she will miscarry her unborn child', says Joshua Wilde, one of the authors of the study. 'As a result, extreme heat can result in higher rates of miscarriage.'
The authors note that relatively weaker foetuses have a higher likelihood of perishing, so only the most biologically fit children survive. As a result, those born nine months after a heat wave do better later in life – not because temperature in utero makes them stronger, but because their weaker peers do not survive.
Another reason behind their result could be that temperature changes the sexual behaviour of parents. If sexual activity is less pleasant in extreme heat, then fewer children will be conceived during heat waves – especially among parents who can't afford air conditioning. And if lower income parents aren't conceiving children, then those children who are born nine months later are more likely to have mothers with more education and higher wages and hence be better off.
To test this hypothesis, the authors use data on sexual activity to show that fewer women report being sexually active during heatwaves. In addition, they show that the reduction in sexual activity is larger for women with low levels of education. They also use Google data to show that searches for pornography and other sexually-themed words decrease when the temperature goes up.
If higher temperatures lead to a better educated and healthier population, this may be evidence that global warming is actually a good thing. But the authors take the opposite view.
'These benefits come at a real human cost'. says Benedicte Apouey, another author of the study. 'Miscarriage often comes with a high psychological and biological cost to parents, especially if these lost pregnancies were wanted. It is hard to imagine that society is better off as a result.'
Their study provides insight into these heretofore undiscussed consequences of global warming, and joins the chorus of researchers touting the benefits of policies that slow climate change.
Benedicte Apouey, Joshua Wilde