Background
In light of historic linkages between high temperatures and human deaths, IPCC-inspired projections of CO2-induced global warming have led many scientists and public health officials, in the words of Davis et al., "to forecast significant increases in mortality from greenhouse warming in the United States in the early twenty-first century (Kalkstein and Greene, 1997; Chestnut et al., 1998; NAST, 2000)."  However, as they note, "most, if not all, of the forecasts of increasing mortality are based on steady-state weather-mortality models that implicitly assume that weather-mortality relationships have not varied significantly over time."  Hence, it was their objective to evaluate this assumption with data from the United States.

What was done
The authors calculated and evaluated "annual excess mortality on days when apparent temperatures - an index that combines air temperature and humidity - exceeded a threshold value for 28 major metropolitan areas in the United States from 1964 through 1998."

What was learned
Davis et al. report that "for the 28-city average, there were 41.0 ± 4.8 (mean SE) excess heat-related deaths per year (per standard million) in the 1960s and 1970s, 17.3 ± 2.7 in the 1980s, and 10.5 ± 2.0 in the 1990s."  In further analyzing these results together with various types of ancillary data, they conclude that "this systematic desensitization of the metropolitan populace to high heat and humidity over time can be attributed to a suite of technologic, infrastructural, and biophysical adaptations, including increased availability of air conditioning."

What it means
Because "all-causes mortality during heat stress events has declined despite increasingly stressful weather conditions in many urban and suburban areas," Davis et al. but state the obvious when noting that "heat-related mortality in the United States seems to be largely preventable at present."   Indeed, it is patently obvious that technologic and infrastructural advancements made possible by the economic progress of the past few decades have more than compensated for the increasingly stressful conditions induced during this period of what climate alarmists typically describe as "unprecedented" global warming.

Clearly, unimpeded economic progress readily trumps unimpeded global warming in matters of life and death.  Therefore, we should concentrate on encouraging the former, over which we clearly have significance influence (indeed, humanity creates it), and leave the latter, over which there is general agreement we have but little influence (Kyoto's impact, for example, would be miniscule), to the normal course of nature.

References
Chestnut, L.G., Breffle, W.S., Smith, J.B. and Kalkstein, L.S.  1998.  Analysis of differences in hot-weather-related mortality across 44 U.S. metropolitan areas.  Environmental Science & Policy 1: 59-70.

Gaffen, D.J. and Ross, R.J.  1998.  Increased summertime heat stress in the US.  Nature 396: 529-530.

NAST (National Assessment Synthesis Team).  2000.  Climate Change Impacts on the United States.  The Potential Consequences of Climate Variability and Change.  U.S. Global Change Research Program, Washington, DC, USA.