Once again, the press is in a tizzy over the Bush administration’s “censoring” of science. It is claimed that the Bush administration edited testimony presented to the Senate Environment and Public Works Committee by Julie Gerberding, director of the Centers for Disease Control and Prevention (CDC). The testimony, originally 14 pages, was cut to six.
However, the narrative of a scientific cover-up is overwrought to say the least. The hearing was on the potential impact of global warming on human health, an exercise in speculation. It appears, if press accounts are correct, that what the Bush administration cut from the director’s testimony was more speculative than settled science.
According to an account of the hearing by Fox News, Senator Barbara Boxer, EPW committee chairman,
produced a CDC chart listing the broad range of health problems that could emerge from a significant temperature increase and sea level rise. They include fatalities from heat stress and heart failure, increased injuries and deaths from severe weather such as hurricanes; more respiratory problems from drought-driven air pollution; an increase in waterborne diseases including cholera, and increases in vector-borne diseases including malaria and hantavirus; and mental health problems such as depression and post-traumatic stress.
When asked about this, Gerberding agreed, “These are potential things you can expect. In some of these areas it’s not a question of if, it’s a question of who, what, how, and when.”
But what is the basis for these claims? Does the CDC have evidence of a link between past climate change and harm to human health? After all, levels of greenhouse gases in the atmosphere are already three-quarters of the way towards an effective doubling of carbon dioxide concentrations, the benchmark typically used in making global warming predictions. And the global average temperature has risen. If global warming predictions are true, and such a link exists, then the harms mentioned by Senator Boxer should already be evident in the data. However, the data fail to reveal such a link. Indeed, the available data on each of the harms mentioned show that in each case, the harms to human health seem to be decreasing.
Heat-related mortality: A study of 28 major U.S. cities, published in Environmental Health Perspectives, found that in nearly every case, the population’s sensitivity to extremely high temperatures has been declining over time despite a general rise in summertime temperatures. This desensitization is attributed to better medical practices, increased access to air-conditioning, and improved community response programs. In some cities heat-related mortality is virtually non-existent.
Infectious Disease: In a study published in Emerging Infectious Diseases, Paul Reiter wrote, “Until the second half of the 20th century, malaria was endemic and widespread in many temperate regions, with major epidemics as far north as the Arctic Circle.” In a subsequent study, in Environmental Health Perspectives, Reiter wrote, “It is…inappropriate to use climate-based models to predict future [disease] prevalence.” With regard to Hantavirus, a study appearing in Emerging Infectious Diseases failed to find a consistent association between El Nino-induced climate changes and risk for Hantavirus.
Pollution: Ground-level ozone levels can increase in response to rising temperature. However, despite an increase in U.S. summertime temperatures from 1980 to 2006, EPA data show that ground-level ozone has fallen substantially.
Hurricanes: According to a study by Roger Pielke, Jr. published in Oceanography, there are no trends in hurricane damages due to Atlantic hurricanes in the U.S. over the last century.
Tornadoes: According to data available from the University of Nebraska, tornado deaths in the U.S. have fallen throughout the century.
Drought: According to data from the National Climate Data Center (NCDC), there is no evidence of an increase in the frequency of dry spells in the U.S. over the last century.
Floods: NCDC data also show that there is no evidence of an increase in the frequency of wet spells in the U.S. over the last century. Moreover, Pielke found that flood damages in the U.S. have fallen over the last several decades.
The claim that the Bush Administration censored science is without merit. What it seems to have done, is cut the portions of the testimony that were based in expert speculation about the future. According to the scientific literature on forecasting, expert opinion is the least reliable source for accurate predictions.
A new paper by Professors Scott Armstrong and Kesten Green, leading experts on forecasting, argues that “Comparative empirical studies have routinely concluded that judgmental forecasting by experts [rather than scientific forecasting] is the least accurate of the methods available to make forecasts.” They also show that, “Agreement among experts is weakly related to accuracy,” when it comes to forecasting.
The media storyline is backwards. Rather than censoring science, the Bush Administration responsibly removed baseless speculation from the CDC’s testimony. If the purpose of congressional hearings is “fact finding,” then such speculation is inappropriate and the Administration acted appropriately.