The Obama administration last week released The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. The 333-page report “significantly advances what we know about the impacts of climate change on public health, and the confidence with which we know it,” according to the White House FACT SHEET. The report’s basic message: “climate change is a significant threat to the health of the American people not just in the future but right now.”
The report’s scariest claims are that by 2030, climate change will significantly increase U.S. deaths due to heat-related illness and ozone pollution (because higher temperatures increase the rates at which ozone is formed). Let’s examine each scare in turn.
The report projects an additional 11,000 heat-related deaths in 209 American cities during summer 2030 compared to a 1990 temperature baseline. However, the report acknowledges that the “U.S. population has become less sensitive to heat over time,” and that “future changes in adaptive capacity [are] expected to reduce the future increase in mortality.” It even concedes that “historically adaptation has outpaced warming.” Yet the administration wants us to believe that, over the next 15 years, warming will exceed our ability to adapt.
That is implausible. As U.S. urban air temperatures increased, heat-related mortality declined, decade-by-decade, during the 1960s-1990s, and declined further during the 2000s. In all likelihood, additional warming would spur additional adaptation, again decreasing Americans’ vulnerability to excessive heat.
Calling the report’s dire assessment “overheated,” environmental researcher Bjorn Lomborgcontends the administration “ignores inconvenient evidence—like the fact that cold killsmany more people than heat.” The administration claims climate change will increase heat-related deaths by more than it reduces cold-related deaths, but its evidence includes a study that “flat-out disagrees with this assertion, projecting that cold deaths will fall more than heat deaths will rise.”
The report also claims that by 2030, warming-induced increases in summer ozone levels will “result in tens to thousands of additional ozone-related illnesses and premature deaths per year.” That is problematic on several counts.
First, unlike exposure to excessive heat or cold, no coroner’s report lists ozone as a cause of death. At today’s historically-low levels, a link between ozone and mortality cannot be directly observed, only inferred from weak statistical associations that may be a product of data mining (researchers selecting data to get the results they want) or confounding variables (coincidental factors unrelated to ozone levels). With roughly 2.5 million Americans dying each year from major illnesses, it is anyone’s guess whether ozone exposure is an aggravating factor in “thousands” of deaths, let alone in “tens.”
Second, the report’s high-end mortality estimate assumes an improbable warming scenario in which peak summer temperatures increase by 4°C (7.2°F) between now and 2030—almost three times as much warming as the continental United States experienced in the past 40 years.
Third, what we indisputably know is that, despite roughly 2.5°F of warming during the past 40 years, ozone levels declined by 33%. That is because ozone precursor emissions—nitrogen oxides and volatile organic compounds—declined by 55% and 53%, respectively. Federal and state regulations already being implemented or in the pipeline will continue to reduce precursor emissions over the next 15 years.
Citing Fann et al. (2015), the administration claims warming will increase ozone formation by more than current and planned regulations will reduce ozone precursor emissions. However, in discussing the “limitations” of their study, Fann et al. write: “To the extent that climate change increases ambient ozone concentrations (and/or other criteria pollutants) above the health-based air quality standards, the Clean Air Act directs states and municipalities to attain the standard by developing policies to reduce these ambient levels.”
In other words, even if climate warming starts to increase ozone formation faster than current emission controls reduce it, the Clean Air Act will require states to cut emissions as necessary to “protect public health” with an “adequate margin of safety.”