The report, dubbed “Countdown 2017,” represents the first coherent attempt to unify many of the different climate-related threads in medical and global-health research. In 2015, a commission of researchers—also convened by The Lancet—warned that climate change could “undermine the last 50 years of gains in public health.” They also called for more comprehensive tracking of important climate signals.
This report, which will now be updated annually, is the result. The coauthors have pulled together figures and estimates from across the medical literature and attempted to tabulate single, worldwide figures for many values.
Some of its techniques may have significant weaknesses. The Lancet report makes an eye-popping assertion about the global economy, arguing that climate change has already significantly harmed labor capacity around the world. Between 2015 and 2016—which are the second- and first-hottest years ever recorded—it argues that “outdoor-labor capacity” fell by 2 percent. Since the year 2000, outdoor-labor capacity has fallen by 5.3 percent overall, it claims.
Academic economists who study climate change were very doubtful of this estimate. “I would back way off the claim that [the data] show any of these things, since they don’t have or use any actual data on labor,” said Solomon Hsiang, a professor of public policy at the University of California, Berkeley, and a member of the Climate Impact Lab.
The Lancet authors, he said, used a technique drawn from a 2013 Nature Climate Change article to estimate “labor capacity.” They effectively interpolated temperature data with conclusions from U.S. military and industrial experiments, from 1996 and 2003, that researched how much work soldiers could do in different temperature conditions. But their findings do not align to a type of labor measurements that economists usually track.
“The numbers presented are (in the most generous interpretation) actual measurements (although still not sure what kind) from a few military lab experiments using U.S. soldiers as subjects and then extrapolated to people across Africa, Latin America, the Middle East, and South Asia,” Hsiang told me in an email.
He continued: “There’s lots of ways this could go wrong, since we don’t know if people adapt, we don’t know if U.S. soldiers are good proxies for normal people in Indonesia, and we don’t have any idea how the “labor-capacity” index these guys put together actually connects to “labor productivity” or earnings as any economist would recognize it.”
Climate change will almost certainly harm global labor output, but a lack of empirical observations around the world makes the kind of measurement The Lancet is attempting difficult. The controversy points to one of the most difficult aspects of finding climate change’s effects on human life: While scientists can measure weather worldwide, measuring the fingerprint of climate change on all human activity is far more complicated.