Life, Death, and Climate

Thomas Gale Moore
Senior Fellow
Hoover Institution
Stanford University

Advocates of reducing greenhouse gases typically assert that a warmer climate would increase disease and deaths worldwide. But fortunately those zealots are wrong.

In fact, a warmer world would be world with fewer fatalities. Cold, not heat, is the biggest killer as more and more researchers are finding.

Weather Heats Up, Deaths Drop

A warmer climate would reduce deaths markedly in the United States. The evidence comes from monthly death rates in Washington, DC, from 1987 to 1989 and an analysis of deaths in 89 large counties across the US. Those statistical evaluations showed that warmer weather cut death rates, not only in Washington but throughout the country.

In Washington, as in the rest of the United States, deaths peaked in the winter months and were lowest in the hot months of summer. The study considered whether temperature or increases in the amount of sunlight reduced mortality but found that warm temperatures had a more significant effect than long summer days.

The analysis of the data from 89 counties took into account the age of the local population, the African-American percentage of the county, and the median family income. Each of those variables affects mortality strongly. It also examined whether air pollution, smoking, or latitude had a significant effect on deaths and found that none of these variables was significant. To paraphrase some politicians, "it’s the climate stupid!"

Whether measured by average temperature, maximum summer temperature, minimum winter cold, heating degree days, or cooling degree days, warmth or its lack plays a substantial role in determining a county’s mortality.

Simply put, warmer weather means fewer deaths.

Two studies reached remarkably similar conclusions. Extrapolating those findings to the nation as a whole indicates that a 2.5°C increase in temperatures would cut deaths nationwide from 37,000 to 41,000, approximately the number of people who die annually on our highways.

The prestigious International Journal of Biometeorology published further confirmation of the beneficial consequences of heat earlier this year (WCR Vol. 4 No. 9). That research of Alexander Lerchl of Münster, Germany’ Institute of Reproductive Medicine, shows that colder weather, rather than hotter, is a more significant killer. Lerchl culled information from German mortality statistics gathered between 1946 and 1995, relating them to corresponding air temperatures.

Not only is mortality higher in the winter but a very cold winter produces a higher number of deaths. During the summer, according to Lerchl’s analysis, heat spells do lead to more deaths; but the increase is relatively small compared to deaths from the cold.

Island Climate

Now, a researcher in the United Kingdom has confirmed that those findings apply in his country as well. Prepared for the UK’s Department of the Environment, the report finds that a warmer world would bring even greater health benefits for England and Wales than I found for the United States in the two studies outlined above. Ironically the British research was carried out as part of a study of the impacts of the extraordinarily warm year of 1995.

In his analysis, C.G. Bentham, Director, Centre for Environmental Risk, School of Environmental Sciences, University of East Anglia, looked at the relationship between the mean monthly temperatures and monthly deaths from 1976 to 1995 (with the exception of two years for which no figures exist).

Although heat waves in Britain kill people, cold weather fells more. As the figure 1 shows, a greater number die in the winter months of December, January, and February than leave this world during the hot months of June, July, and August. The highest mortality occurs in January; the lowest, in August.

Bentham’s data show that, for every month except July and August, hotter than normal weather reduces deaths. In July and August, temperature increases of 2 or 3 degrees Celsius, about 3.6 or 5.4 degrees Fahrenheit, boost mortality slightly; but similar increases in other months cut deaths more significantly. In January and December, with a warming of 5.4 degrees Fahrenheit, he estimates deaths would fall by 5 percent.

By the same token, an annual increase in temperatures of 3 degrees Celsius would cut mortality by 3 percent. In England and Wales this means a savings of 17,500 lives for the entire year. For a total population of only about 50 million, this constitutes a significant reduction in fatalities.

The study examined whether lower than expected deaths might occur following heat spells or periods of extraordinary cold. Such a pattern would have been observed if extreme weather simply culled those who would have died shortly in any case. Bentham, however, failed to find any relationship between temperature extremes and deaths in subsequent periods, suggesting that it was not simply the weak and sick elderly who expired.

That 1995 was exceptionally warm in the United Kingdom shows up in Bentham’s figures. In particular, the very mild month of February 1995, tallied fewer deaths than usual for that time of year. Deaths were, however, slightly higher than is typical during the unusually hot summer.

As Bentham puts it, temperatures in England and Wales are sub-optimal for human health. Since humans evolved in Africa in a much warmer climate, it is unsurprising that the cold weather of the northern portions of the globe is less than beneficial for most.


Further Confirmation

Bentham’s results are similar to those I found for the United States, but he actually found a strikingly larger effect. Whereas he estimated that an increase of 3°C would reduce mortality in a population of 50 million by 17,500 while I calculated that, for the U.S. population, a world 2.5°C hotter would save about 40,000 lives annually.

Extrapolating, a 3-degree C boost in temperature would save roughly 48,000 lives out of a population of 275 million. Applying this calculation to the United States, Bentham’s results would indicate that a 3-degree C warmer world would prevent 65,000 deaths, a markedly greater number. The greater effect of temperature in Great Britain may be explicable to a climate cooler in the summer than in the United States.

Consequently the effects of warming would be greater in that country.

In terms of percentages, my Washington DC results imply that a 3°C boost in temperatures would reduce deaths by 2.0 percent; the nationwide county data indicate that the same increase in warmth would cut mortality by 2.2 percent. In England and Wales, 3°C would reduce deaths by 3 percent.

As the data show with increasing clarity, there seems no reason to fear global warming and a number of reasons to welcome it. And aside from population fanatics who fear a drop in mortality, most people would welcome increases in life expectancy.


Figure 1.Percent Change from normal of deaths per Day for England and Wales for given temperature increases

Source: Bentham, 1997, Table 8.4.


C.G. Bentham. 1997. Health, Chapter 8 in Economic Impacts of the Hot Summer and Unusually Warm Year of 1995, eds J.P. Palutikof, S. Subak, and M.D. Agnew. Prepared for the Department of the Environment, February, 1997, pp. 87-95.

T. G. Moore. 1998. The Health and Amenity Benefits of Global Warming, Economic Inquiry, July.

Lerchl, A. 1998. Changes in the seasonality of mortality in Germany from 1946 to 1995: The role of temperature, International Journal of Biometeorology, 42, 84-88.