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.
Tavernise does, however, give an alarmist the last word:
Health risks from climate change are fundamentally local. The dangers of heat are greater in New Delhi than in New York, not only because it is hotter in the Indian city, but because fewer people have electricity, sturdy houses and modern medical care. That makes drawing broad conclusions tricky. But it does not mean the risks are not there. As Dr. Kinney noted, “if we wait for the health evidence to be ironclad, it may well be too late.”
Too late for what? The broad conclusions are easy to draw. Wealth and technology supported by modern commercial energy make people less vulnerable to climate-related risks.
Consider drought, historically the most lethal form of extreme weather because it limits access to food and water. In the 1920s, drought killed an estimated 472,000 people worldwide. What’s happened since then?
From 1930 to the present, roughly 90% of all industrial CO2 emissions since 1750 entered the atmosphere, atmospheric CO2 concentrations increased by about 30% (from ~ 307 parts per million in 1930 to 402 ppm today), and average global temperatures rose by about 0.8ºC. Yet deaths and death rates related to drought declined by a spectacular 99.8% and 99.9%, respectively.
This stunning achievement would have been impossible absent fossil fuels, which dramatically improved the efficiency of food production, transport, and storage, and support the wealth creation and physical assets on which modern early warning systems and emergency relief programs depend.
One other issue is worth mentioning. The White House report predicts global warming will worsen asthma by increasing the formation of ozone smog. Specifically, the report projects a 7.3% increase in “the number of ozone-related emergency room visits for asthma” in the New York metropolitan area “in the 2020s, compared to the 1990s.” No information is given on the warming and emission scenarios underpinning that projection.
EPA’s more recent report, Climate Change in the United States: Benefits of Global Action, lets us peer into the black box. EPA estimates future ozone levels in 2050 and 2100 by modeling the impact of higher-than-observed rates of warming on current air pollution emissions. That makes no sense except as a scare tactic.
Despite global warming, U.S. air quality has been improving for decades as ozone-precursor and other common air pollutant emissions have declined. All significant sources of U.S. air pollution will likely be gone by 2050 or before.
As for the 2020s, U.S. air quality should be better in U.S. cities than in the 1990s as newer vehicles and equipment compliant with EPA regulations already on the books or in the pipeline replace older fleets and capital stock.
Besides, if ozone were the big asthma risk factor EPA assumes it is, asthma prevalence should have declined since the 1980s as air quality improved. Instead, asthma prevalence rates for children increased by 4.6% per year from 1980 to 1996 and then plateaued at historically high levels through 2007, according to Centers for Disease Control data.
Whatever has increased asthma rates, it’s not air pollution or any increment thereof potentially attributable to global warming.