With summer’s unofficial start looming on Memorial Day, a major environmental group seized the warm-weather occasion last week to try to build support for the Obama administration’s regulation of greenhouse gases at new power plants and to call for such controls at existing plants, too.

The effort took the form of a report, issued by the Natural Resources Defense Council (NRDC), which detailed the increase in heat-related deaths that scientists have projected to occur throughout the 21st century as a result of higher temperatures and other weather changes due to manmade global warming.

The NRDC based its report on a peer-reviewed study [pdf] that was published last October in Weather, Climate and Society, the journal of the American Meteorological Society. One of the study authors, Laurence S. Kalkstein, a research professor at the University of Miami in Florida, reviewed the environmental group’s document to confirm that it accurately reflected the original study’s findings.

The conclusions, which may be somewhat surprising to Texans, included the calculation that in the 40 most populous U.S. cities, including three in Texas, “more than 150,000 additional Americans could die by the end of this century due to excessive heat caused by climate change.”

The cities with the most additional heat-related deaths projected by the study’s scientists through 2099 were Louisville (with 18,988 deaths), Detroit (17,877) and Cleveland (16,600).

And in the considerably hotter climes of Texas? Dallas was the top-ranked city (with 7,271 extra projected deaths over the nearly nine decades through 2099), while the totals for San Antonio (631 deaths) and Houston (1,391) were much lower.

(The NRDC presented statistics from the original study’s projections that incorporated a “business-as-usual” assumption for an “unfettered” increase in greenhouse emissions, but coupled with actions to warn and protect the public during excessive heat, which were expected to reduce the death toll somewhat.)

So what gives with numbers like Detroit’s nearly 18,000 deaths and San Antonio’s 631? Why would hyper-hot Texas cities (also hyper-humid in Houston’s case) have numbers so much smaller than in cities far to the north? (Minneapolis, not generally known for excessive heat, had a fatality projection of 7,516, slightly higher than Dallas, infamous for long strings of 100-degree-plus days in the summertime.)

Texas Climate News asked Kalkstein to address the question.

“First, it’s not just the intensity of heat that kills people, it’s variability of the weather that’s more important,” he said. “More people die of heat-related illness in Toronto than in Phoenix.”

In Florida, where he lives, Kalkstein said, “no one dies from the heat,” due to factors including temperatures staying relatively constant, people being more acclimatized to warmer weather, and buildings (“even the ones that poor people live in”) that are different, with almost universal access to air conditioning.

In more southerly locations, generally speaking, “the consistency of hot weather is something people acclimatize to, not only in themselves physically, but behaviorally and in urban structures as well,” he said.

TCN also asked John Nielsen-Gammon, a Texas A&M University professor of atmospheric sciences and the state climatologist, for his reaction to the lower death projections in Texas, compared to some cities to the north, in the NRDC report and its underlying research findings.

His emailed response:

Texans are largely acclimated to hot weather and are intelligent enough to avoid risky behavior during the heat of the summer. Even high school football teams recognize the danger of hot weather. In that sense, we’re better prepared than places farther north, who don’t have the luxury of very hot summers to prepare them for future climate change. I imagine the projected numbers are overestimates, because people will get used to warmer temperatures, both physiologically and through changes in behavior.

The NRDC report had this to say about matters such as adjustment to hotter conditions, greater use of air conditioning and the like:

The study does not take into account potential acclimatization of individuals because it is difficult to determine the exact degree to which individual behavior will change or how much change can realistically be made. If individuals continue to respond to heat exposure by purchasing air conditioners or avoiding the outdoors during heat waves, mortality will be lower than the estimates produced here. However, there are limits to the extent of behavioral response. Those people living in poverty, who are among the most vulnerable to heat-waves, are constrained in their ability to find access to air conditioning. Likewise, many individuals are required by their job to spend time outside, so their options for reducing exposure may be limited.

Kalkstein, who also works with the National Weather Service in developing heat-warning systems for cities, said he agrees with Nielsen-Gammon that Texans are better adapted to heat than people who live farther north, which is a major reason fewer die of heat in Texas.

Regarding the state climatologist’s suspicion that the heat-death study overestimated future mortality rates, Kalkstein said he “would probably disagree.”

He and fellow researchers have found “gross underestimates” of heat-caused deaths by medical examiners’ offices, Kalkstein said.

Medical examiners typically require criteria such as a core body temperature above 104 F to be met in order to rule that a death was heat-related, he said.

He and his colleagues have found in their research, however, that cases of heart attacks, strokes and respiratory failures “spike considerably during a heat wave,” so they consider a certain portion of such deaths as heat-related.

“Heat is already the leading weather-related killer in the U.S. right now,” he said. “Even if you’re a climate change skeptic, we already have a major heat-related health problem.”

 – Bill Dawson

Image credit: Bierchen