How will heat and cold deaths change over the coming century with global warming? Let us for the moment assume—very unrealistically—that we will not adapt at all to the future heat. Still, the biggest cross-European cold/heat study concludes that for an increase of 3.6 degrees Fahrenheit in the average European temperatures, “our data suggest that any increases in mortality due to increased temperatures would be outweighed by much larger short-term declines in cold-related mortalities.” For Britain, it is estimated a 3.6°F increase will mean 2,000 more heat deaths but 20,000 fewer cold deaths. Likewise, another paper incorporating all studies on this issue and applying them to a broad variety of settings in both developed and developing countries found that “global warming may cause a decrease in mortality rates, especially of cardiovascular diseases.”
Mind you, this benefit of warmer weather might not be found in Africa, the Middle East, the Indian subcontinent, or other already very warm places.
In industrialized countries air conditioning appears to have decreased deaths from heat.
Yet something great happened in the decades following. Death rates in Philadelphia and around the country dropped in general because of better health care. But crucially, temperatures of 100°F today cause almost no excess deaths. However, people still die more because of cold weather. One of the main reasons for the lower heat susceptibility is most likely increased access to air-conditioning. Studies seem to indicate that over time and with sufficient resources, we actually learn to adapt to higher temperatures. Consequently we will experience fewer heat deaths even when temperatures rise.
Indeed humans live longer in warmer weather and cold weather seems to wear us out more quickly if we believe a paper by Olivier Deschenes and Enrico Moretti and published by the National Bureau of Economic Research:, Extreme Weather Events, Mortality and Migration.
We estimate the effect of extreme weather on life expectancy in the US. Using high frequency mortality data, we find that both extreme heat and extreme cold result in immediate increases in mortality. However, the increase in mortality following extreme heat appears entirely driven by temporal displacement, while the increase in mortality following extreme cold is long lasting. The aggregate effect of cold on mortality is quantitatively large. We estimate that the number of annual deaths attributable to cold temperature is 27,940 or 1.3% of total deaths in the US. This effect is even larger in low income areas. Because the U.S. population has been moving from cold Northeastern states to the warmer Southwestern states, our findings have implications for understanding the causes of long-term increases in life expectancy. We calculate that every year, 5,400 deaths are delayed by changes in exposure to cold temperature induced by mobility. These longevity gains associated with long term trends in geographical mobility account for 8%-15% of the total gains in life expectancy experienced by the US population over the past 30 years. Thus mobility is an important but previously overlooked determinant of increased longevity in the United States. We also find that the probability of moving to a state that has fewer days of extreme cold is higher for the age groups that are predicted to benefit more in terms of lower mortality compared to the age groups that are predicted to benefit less.
Global warming, by decreasing exposure to cold weather, should therefore increase life expectancies of people who now live in colder climates.
I wonder whether the real benefit of a southward migration is reduced exposure to the cold or increased exposure to the rays of the sun. Greater sunlight exposure reduces depression and also increases vitamin D production and therefore reduces incidence of cancer and other diseases. But even if life expectancy benefit comes from more sunlight exposure a warming of northern climes will get people outside sooner in springtime and hence up their vitamin D production.
Cold weather also probably reduces levels of exercise. Plus, in warmer climes locally grown vegetables and fruits are available more of the year. So diets might be better in warmer areas of industrialized countries.
|Share |||Randall Parker, 2007 September 02 11:46 PM Aging Studies|