In a recent article, New York Times reporter Sabrina Tavernise asks: “Is climate change a serious threat to human health?” To my surprise, this was not a rhetorical question but the opener for an inquiry assessing the balance of evidence.
Tavernise even suggests that a recent White House report exaggerates climate change health effects to “build support” for the President’s domestic and international climate policy agenda.
As summarized by Tavernise, the report predicts that “Asthma will worsen, heat-related deaths will rise, and the number and traveling range of insects carrying diseases once confined to the tropics will increase.” But, she comments, those “bullet points convey a certainty that many scientists say does not yet exist.”
For one thing, some health effects attributed to climate change may actually be due to social factors:
For example, scientists note that global travel and trade, not climate change, brought the first cases of chikungunya, a mosquito-borne tropical disease, to Florida.
Sometimes even when climate change may affect health, it is difficult to quantify how important a factor it is. For example, Lyme disease is spreading into Canada — a development apparently linked to climate change because warmer weather lengthens tick breeding seasons. “But,” Tavernise points out, “Lyme disease is also an example of just how difficult it is to draw broad conclusions about how climate change affects health.”
The disease is also moving south, with large sections of Virginia and parts of North Carolina now inundated with ticks that carry the disease. But that pattern appears to have little to do with climate.
Dr. C. Ben Beard, associate director for climate change at the Centers for Disease Control and Prevention, said reforestation in the eastern United States and the expanding populations of deer and people appear to be factors.
What’s more, wealth and technology can greatly diminish climate-related health risks:
A study comparing Laredo, Tex., and a city just across the border in Mexico found the incidence of dengue fever was far higher in Mexico, even though the mosquitoes that carry it were more abundant in Texas. Researchers attributed the Texan advantage to economics — air conditioning and windows that shut — not climate.
Tavernise also notes that, despite global warming, heat-related deaths in the United States are not increasing:
Temperatures may be rising, but overall deaths from heat are not, in part because the march of progress has helped people adapt — air conditioning is more ubiquitous, for example, and the treatment of heart disease, a major risk for heat-related mortality, has improved.
In fact, U.S. heat mortality risk is declining:
A recent review of heat mortality in the United States found that the rate of heat-related deaths declined by more than half from 1987 to 2005. (For more on this topic, see these previous posts.)
Tavernise even seems to recognize some additional warming may have net health benefits because far more people die from extreme cold than extreme heat:
A study in The Lancet in May analyzed 74 million deaths from 1985 to 2012 in more than 10 countries, including the United States, and found that about 8 percent of the deaths had been caused by abnormal temperatures. Of those, the rate of death from cold — more than 7 percent — far outnumbered that from heat, about 0.42 percent. [click to continue…]