U.S. health report quells fears

Published June 1, 2000

The long-awaited results of the U.S. National Assessment of Potential Consequences of Climate Variability and Change are beginning to see the light of day.

And though we would never have guessed the report’s results would be anything but negative, it’s beginning to look like our own assessment of the report’s potential was overly dour, as some of the early results surface.

Mandated by Congress, the U.S. National Assessment (USNA) is supposed to “assess the risks and opportunities for the United States–its people, its environment, and its economy–associated with the increased climate change.”

From what we are hearing so far, things just don’t sound so bad. About one month ago, for example, in a pre-release press conference, the authors of the USNA’s hydroclimate section presented their analysis, which was fairly even-handed.

Yet the media remained in denial, refusing at first to let this absence of gloom and doom stand in the way of a good scare story.

For instance, the Philadelphia Inquirer on February 21 breathlessly reported that “Global warming is so real and hard to stop that Americans will have to learn to cope with a hotter and quite different lifestyle in coming generations–including harvesting Southern forests to keep them from dying and building higher bridges.” But none of that is in the report, nor was it covered in the news conference. Instead, this inaccurate, sensationalistic “reportage” was based on a conversation the reporter had with a high-level National Assessment administrator in the hallway.

A month later, however, the Inquirer seemed to be getting the idea. A March 30 article on the mid-Atlantic Assessment section toned down the alarmist rhetoric in favor of more balanced coverage, including such commentary as “A warmer region with more carbon dioxide in the air would actually be a boon for agriculture,” “The region will simply adapt to the relatively mild changes in climate,” and lead researcher Ann Fisher’s remark that, “We’re not judging if [climate change] is good or bad. It will just be different.”

The Los Angeles Times was quicker to catch on. The following headline appeared in its March 16 edition: “Study Finds No Support for Global Warming Fears.” Yes, this was a real headline in a major U.S. daily. As Dave Barry says, we are not making this up! Admittedly, the story was buried on page 2 of the Metro section, but minor miracles, such as the press reporting a positive global warming story, are worth celebrating even if they’re carried under “Land Transactions.”

Their tone was correct, as the following phrases, excerpted from the USNA health section’s abstract, attest:

“The levels of uncertainty preclude any definitive statement on the direction of potential future change for [any] health outcomes.

“Although we mainly addressed adverse health outcomes, we identified some positive health outcomes, notably reduced cold-weather mortality.”

Even more remarkable is that the lead author, Jonathan Patz (from Johns Hopkins) and one of his coauthors, Paul Epstein (from Harvard), have in the past been perhaps the two most vocal extremists on how global warming will allegedly increase the spread of death and disease.

This USNA section, which summarizes their health outcomes workshop, appears in the April issue of Environmental Health Perspectives, addressing the following topics: Temperature-related death and disease; extreme weather events; air pollution-related health impacts; water and food-borne diseases; and diseases transferred by insects and rodents.

Heat-related mortality. On the subject of temperatures and deaths, the report states, “There is evidence that heat-related illnesses and deaths are largely preventable through behavioral adaptations including the use of air-conditioning and increased fluid intake, although the magnitude of the mortality reduction cannot be predicted.” By 2050, air-conditioning will be available in nearly every U.S. household.

Extreme weather events. In the section on extreme events, the authors note, “Climate models currently are unable to accurately project changes in extreme events such as floods, hurricanes, and tornadoes, making it difficult to assess future potential health impacts of such events.”

Of course, projections aside, there’s little observational evidence that extremes are increasing, despite the rise in greenhouse gases. It is pretty obvious that fewer people are dying because of weather. How realistic is it to assume that that trend will suddenly take a turn for the worse?

Air quality. Air pollution is a trickier problem, since it is only indirectly related to climate change. Most greenhouse gases are not pollutants, so we are left with theoretical arguments such as higher temperatures’ increasing the reaction rates of certain pollutants. Furthermore, it’s not possible to determine the impact of air pollution on health without first accounting for the weather. Some studies even indicate that weather is far more responsible for deaths than pollution.

Even so, this report properly notes that “ambient levels of regulated air pollutants have generally dropped since the mid-1970s.”

The spread of disease. The focus of the water- and food-borne disease section is on drinking water contaminated by flooding. Although not cited in the report, in a recent comprehensive study of U.S. streamflow in nonurbanized catchments, Lins and Slack (1999) reported that, while low streamflows have generally been increasing, the frequency of flooding conditions has shown no general trend. So it is unfair to insinuate that more drinking water will be flooded and thus contaminated.

The section on insect- and rodent-borne diseases was the responsibility of Paul Reiter of the Centers for Disease Control, who has long explained that applied technology (e.g., hygiene, infrastructure, even window screens) is a better way to control vector-borne disease than attempting to affect the climate. He notes that most of these diseases were long ago eradicated in the United States, “mainly because of changes in land use, agricultural methods, residential patterns, human behavior, and vector control.”

For once, a government global warming report is right on the money, admitting there is no possible way to determine the potential climate impacts on these areas because future climate is not predictable! Despite the multiple millions governments annually pour into global climate models, their output provides zero useful guidance on what the future climate will be like.

So we are left to rely on history to anticipate the future. Overall death rates are declining rapidly; in fact, so few people now die during heat waves that the impact of heat in many cities is almost indistinguishable from the “impact” of pleasant temperatures.

People are less susceptible to severe storms: The major hurricane that hit Galveston in 1900 killed more than 8,000 people in the United States; the similarly intense Hurricane Andrew in 1992 killed only 23 people in the United States.

And if you’re concerned about global warming making rats and insects more infectious, consider the following data: From 1980 to 1996, there were 50,333 dengue fever cases in the three Mexican states that border the Rio Grande–and 43 cases in Texas. The last time we checked, the climate was the same in both places.

The common thread here is that technological improvements have made our country a cleaner, safer, and healthier place to live. Given that fact, it’s hardly surprising that the National Assessment‘s health report concludes that, “In sum, we found that most of the U.S. population is protected against adverse health outcomes associated with weather and/or climate.” And that is the only scientifically defensible conclusion.


Davis, R.E., et al., 1999. Decadal changes in summer mortality in the U.S. Proceedings of the 10th AMS Conference on Applied Climatology, Asheville, NC, 4 pp., forthcoming in May 2000.

Kalkstein, L.S., 1991. A new approach to evaluate the impact of climate on human mortality. Environmental Health Perspectives, 96, 145-105.

Lins, H.F., and J.R. Slack, 1999. Streamflow trends in the United States. Geophysical Research Letters, 26, 227-230.

Patz, J.A, et al., 2000. The potential health impacts of climate variability and change for the United States: Executive summary of the report of the Health Sector of the U.S. National Assessment. Environmental Health Perspectives, 108, 367-376.