Extreme Heat vs. Extreme Cold: Which is the Greatest Killer?

In an impressive study published in The Review of Economics and Statistics, Deschenes and Moretti (2009) analyze the relationship between weather and mortality, based on "data that include the universe of deaths in the United States over the period 1972-1988," wherein they "match each death to weather conditions on the day of death and in the county of occurrence," which "high-frequency data and the fine geographical detail," as they write, allow them "to estimate with precision the effect of cold and hot temperature shocks on mortality, as well as the dynamics of such effects," most notably, the existence or non-existence of a "harvesting effect," whereby the temperature-induced deaths either are or are not subsequently followed by a drop in the normal death rate, which could either fully or partially compensate for the prior extreme temperature-induced deaths.

So what did they find?

The two researchers say their results "point to widely different impacts of cold and hot temperatures on mortality." In the later case, they discovered that "hot temperature shocks are indeed associated with a large and immediate spike in mortality in the days of the heat wave," but that "almost all of this excess mortality is explained by near-term displacement," so that "in the weeks that follow a heat wave, we find a marked decline in mortality hazard, which completely offsets the increase during the days of the heat wave," such that "there is virtually no lasting impact of heat waves on mortality [italics added]."

In the case of cold temperature days, they also found "an immediate spike in mortality in the days of the cold wave," but they report that "there is no offsetting decline in the weeks that follow," so that "the cumulative effect of one day of extreme cold temperature during a thirty-day window is an increase in daily mortality by as much as 10% [italics added]." In addition, they say that "this impact of cold weather on mortality is significantly larger for females than for males," but that "for both genders, the effect is mostly attributable to increased mortality due to cardiovascular and respiratory diseases."

In further discussing their findings, Deschenes and Moretti state that "the aggregate magnitude of the impact of extreme cold on mortality in the United States is large," noting that it "roughly corresponds to 0.8% of average annual deaths in the United States during the sample period." And they estimate that "the average person who died because of cold temperature exposure lost in excess of ten years of potential life [italics added]," whereas the average person who died because of hot temperature exposure likely lost no more than a few days or weeks of life. Hence, it is clear that climate-alarmist concerns about temperature-related deaths are wildly misplaced, and that halting global warming - if it could ever be done - would lead to more thermal-related deaths, because continued warming, which is predicted to be greatest in earth's coldest regions, would lead to fewer such fatalities.

Interestingly, the two scientists report that many people in the United States have actually taken advantage of these evident facts by moving "from cold northeastern states to warm southwestern states." Based on their findings, for example, they calculate that "each year 4,600 deaths are delayed by the changing exposure to cold temperature due to mobility," and that "3% to 7% of the gains in longevity experienced by the U.S. population over the past three decades are due to the secular movement toward warmer states in the West and the South, away from the colder states in the North."

It's really a no-brainer. An episode of extreme cold can shave an entire decade off one's life, while an episode of extreme warmth typically hastens death by no more than a few weeks. If you love life, therefore, you may want to reconsider the so-called "morality" of the world's climate-alarmist's perverse prescription for planetary health.