Addressing Global Warming Will Pay Huge Dividends in Protecting Public Health
Could global warming make you sicker? In an era when an emergent disease can cross continents in the span of a day and the word “pandemic” is on everyone’s lips, it’s a timely question. The simple answer is yes, but the reasons behind that conclusion are complex. While scientists generally agree that some parts of the world will become more vulnerable to disease outbreaks and other health risks as a result of rising sea levels and warming temperatures, they are unsure of the exact impacts—and their potential severity.
The Human Toll of Climate Change: Health Impacts Around the Globe
A look at some of the latest research on health impacts around the world plotted on the interactive Human Toll of Climate Change map.
But the recommendations from existing research are relevant now more than ever, and what we know already about the relationship between health and climate is invaluable as communities in the United States and around the world adapt to a warming world.
Researchers first began to speculate that global warming could facilitate the spread of infectious diseases during the 1990s. Scientists understood that malaria, dengue fever, and other vector-borne diseases—those carried by mosquitoes, ticks, sandflies and other organisms—were endemic to tropical and subtropical regions, and thought their transmission rates were particularly sensitive to slight fluctuations in temperature and humidity. They theorized that rising temperatures and humidity, among other shifting climate patterns, could increase the number of cases by expanding the diseases’ reach.
Several studies done at the time examined the effects of global warming on disease transmission in Africa and found strong temperature dependencies in the correlations between disease rates and weather variations over spans of both weeks and years, and in the close geographic associations between major climate indices and the distributions of the diseases. Though most of these studies ultimately failed to pinpoint the exact causes of the increase in disease spread, the researchers involved concluded that continued warming would have a strong impact on pathogen development and disease transmission, increasing the risk of future outbreaks.
In 1997, the U.S. Global Change Research Program commissioned the creation of the National Assessment of the Potential Consequences of Climate Variability and Change to study the future impacts of climate change on the country and on several major national sectors, including health, over two periods-through 2030 and through 2100. The report, published in 2001, concluded that the number of deaths and illnesses resulting from extreme weather events, air pollution, and water- and foodborne diseases would likely increase, and that certain populations—particularly the poor, the elderly, and children—would face the most severe consequences.
Heat waves would become more common and more severe, as would natural disasters like floods and storms. The combined effects of higher temperatures and increased pollutant emissions in urban areas could worsen air quality by enhancing the formation of ground-level ozone and spurring the use of air conditioning and other fossil fuel-dependent technologies. Changes in temperature, rainfall, and humidity could affect water quality by increasing the flow of urban and agricultural run-off to coastal waters and freshwater bodies, making it easier for waterborne disease agents like bacteria and viruses to spread. Similarly, weather variations could increase the number of cases of vector- and rodentborne illnesses by creating conditions amenable to the disease agents’ growth.
They cited the example of hantaviruses, a group of viruses carried by several rodent species and transmitted to humans through contact with feces and through the air, which caused an outbreak of Hantavirus Pulmonary Syndrome in the southwest when a previously undocumented strain, called Sin Nombre (“Without a Name”), emerged in 1993. The outbreak was attributed to a surge in the local mouse population that was caused by an increase in their food supply; this, in turn, was attributed to unusually high precipitation brought about by the 1991-1992 El Niño event.
To counter these trends and prepare for the worst, the authors recommended a series of adaptive responses. These included weather watch systems, improved disease monitoring and prevention programs, more vaccines, more robust sanitation systems, and better targeted research, among others. “Vigilance in the maintenance and improvement of public health systems and their responsiveness to changing climate conditions and to identified vulnerable subpopulations should help to protect the U.S. population from any adverse health outcomes of projected climate change,” they concluded.
Though the report may now seem dated, many of its conclusions and recommendations are as relevant ever. As its authors predicted, the United States has since experienced more heat waves and extreme weather events, including the devastating Hurricane Katrina (which a warmer Gulf of Mexico helped strengthen), though the federal and state governments have yet to implement many of their suggested adaptive responses.
In 2005, Paul R. Epstein of Harvard Medical School, one of the foremost experts on the relationship between climate and health, warned in an editorial in The New England Journal of Medicine that the consequences of further warming could be devastating to human well being worldwide. Floods, like those that followed Hurricane Katrina, often create “disease clusters” by forming new mosquito-breeding sites, driving rodents from their burrows, and dumping large amounts of pathogens, nutrients, and chemicals into waterways. Prolonged droughts and heat waves, like those seen in the southwest, lay the ground for more wildfires, which can result in deaths from burns and respiratory illness, and draw on the region’s already overdrawn water supplies. One of the greatest threats to human health could come from an increase in the number of illnesses affecting wildlife, livestock, crops, and other organisms-illnesses that we’ve now realized can sometimes make the leap over to humans.
His conclusion echoed many of the points made in the 2001 report:
All in all, it would appear that we may be underestimating the breadth of biologic responses to changes in climate. Treating climate-related ills will require preparation, and early-warning systems forecasting extreme weather can help to reduce casualties and curtail the spread of disease. But primary prevention would require halting the extraction, mining, transport, refining, and combustion of fossil fuels-a transformation that many experts believe would have innumerable health and environmental benefits and would help to stabilize the climate.
The United States is on its way to enacting the country’s first meaningful climate legislation, which could, as Epstein and other scholars have noted in more recent work., pay some of its largest dividends in the area of health. Moreover, the Environmental Protection Agency’s decision to regulate carbon dioxide and other greenhouse gases as dangerous pollutants under the Clean Air Act signals the new administration’s intent to take the joint matters of climate change and health seriously.
As a recent study co-published by The Lancet and the University College London Institute for Global Health Commission, entitled “Managing the health effects of climate change” noted: “The move to a low-carbon economy will have global health benefits from both a reduction in the health effects of climate change and improvement in human lifestyles, and these must be emphasized.” The Obama administration’s embrace of this goal will jumpstart a clean-energy economy and simultaneously ensure a healthy society.
 Patz, J.A. et al, “The Potential Health Impacts of Climate Variability and Change for the United States: Executive Summary of the Report of the Health Sector of the U.S. National Assessment,” Journal of Environmental Health 64(2)(2001): 20 – 28.
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