© 2008 American Thoracic Society doi: 10.1164/rccm.200801-052ED
Global Warming: A Challenge to All American Thoracic Society Members
New York University School of Medicine
Center for Health and the Environment
National Institute of Environmental Health Sciences
Rome E Health Authority Global warming results from the greenhouse effect caused by infrared radiation passing through the earth's atmosphere, reaching the earth's surface, and then being reflected back to the earth's surface by greenhouse gases accumulating in the troposphere 10 to 15 km above the earth. Increased infrared radiation raises the earth's surface temperature. The average global annual temperature has risen from 14.5°C in 1886, when records began, to 15.4°C in 2005. The warmest year on record was 2006, and 11 of the past 12 years have broken records for global average temperatures. Moreover, warming around the earth's poles has exceeded the average increase. Greenhouse gases consist primarily of CO2 and methane. CO2 is the major greenhouse gas that accumulates in the troposphere and has a residence time of approximately 400 years. Real-time measurements of CO2 atop Mauna Loa in Hawaii show a rise from 315 ppm in 1959 to 383 ppm in 2007. In contrast, Antarctic ice cores show that CO2 levels ranged from 200 to 280 ppm over the past 400,000 years (1). While methane is a smaller component of greenhouse gas than CO2, methane has 20 times the greenhouse warming effect of CO2. Methane measurements are currently over 1,700 ppb, whereas ice core measurements show that methane ranged from approximately 400 to 700 ppb. The International Panel on Climate Change concluded in its fourth report that global warming was unequivocal and that human activity was the main driving force very likely causing most of the rise in temperatures since 1950 (2). More than 27 billion metric tons of CO2 are emitted each year, primarily from electric power generation (coal) and transportation (gasoline and diesel). These sources of CO2 are the same as for other air pollutants, including PM2.5 and ozone. The U.S. Environmental Protection Agency (EPA) has not regulated CO2 in its National Ambient Air Quality Standards because of the lack of direct health effects. In contrast, the U.S. Supreme Court ruled in Massachusetts v. EPA in 2007 that the Clean Air Act defines CO2 as a pollutant and that the health and welfare of plaintiffs were adversely affected due to climate change from global warming (3). Dr. Margaret Chan, Director-General of the World Health Organization, remarked at the National Institutes of Health on December 10, 2007, that "climate change will ride across this landscape as the fifth horseman. It will increase the power of the four horsemen that rule over war, famine, pestilence, and death" (18). This fifth horseman will directly impact our patients with lung disease through the direct effects of heat, extreme weather events, air pollution, allergic diseases, water- and food-borne infections, and vector-borne and zoonotic diseases (4, 5). Mortality will most likely increase due to heat waves; in addition, heat waves will likely be accompanied by increases in air pollutants, such as PM2.5 and ozone (6). Higher surface temperatures, especially in urban areas with the "heat island" effect, promote the formation of ground-level ozone, and have been demonstrated to further increase all-cause mortality (7, 8). With higher temperatures, there is a greater effect on mortality in women as compared with men, as well as among the aged, widowed, single, divorced, and those living in retirement institutions (9). Hospitalized patients with chronic obstructive pulmonary disease (COPD) without appropriate climate control are at severe risk of death (10). Currently, allergic rhinitis (hay fever) affects approximately 40 million Americans and asthma prevalence is estimated by the Centers for Disease Control and Prevention to be 16 million (11). The self-reported prevalence of asthma rose 75% from 1980 to 1994 in both adults and children, but increased by 160% in preschool-aged children (12). Climate change has resulted in phenologic changes in plants advancing the spring allergenic pollen season. Ragweed grown at twice the ambient CO2 has greater biomass and 40 to 60% more pollen (13). The fifth horseman of climate change will no doubt wreak the most havoc among the poor in the developing world. The burning of biomass fuels in homes is the way of life for more than 3 billion of the poorest people on the planet. Recent reports suggest that this may well be part of an emerging epidemic of COPD, especially in women (14–16). Increased surface temperatures have predictable and potentially catastrophic health effects from air pollutants; yet, poor women and infants exposed to indoor air pollution in the developing world are most vulnerable. Mitigation of the consequences of global warming and climate change will require dedication and prioritization by the public, governments, and professional and scientific societies, such as the American Thoracic Society (ATS). The United States emits 25% of CO2 and other greenhouse gases and has 4% of the world's population. The Kyoto Treaty has been ratified by all of the major nations of the world except the United States; it mandates the United States to reduce CO2 to levels 7% below 1990 levels by the time period 2008–2012 (2). Promotion of environmentally sound policies in the energy, transportation, land development, and agriculture sectors has great potential both to mitigate climate changes and improve public health for all (17). To avoid the worst impacts of global warming, the United States needs to achieve an 80% reduction of greenhouse gas emissions from 1990 levels by 2050. This requires transforming our economy to one that is efficient and green compared with the present carbon-based economy. The post-Kyoto era needs vision and political activism across the political spectrum to achieve ambitious goals of reducing CO2. In addition to advocacy for local, state, and national policies to mitigate CO2 emissions, we need to reduce our own individual and worksite carbon footprints, and educate our patients and colleagues of the public health and societal threats posed by climate change. Our roots as ATS members go back to the beginning of the previous century in the care of patients with tuberculosis, a disease of the industrial revolution that exploded as a result of overcrowding, malnutrition, and poverty. As climate change inevitably appears to be part of our future, the ATS should focus on helping those who are at most risk and use our skills and networks to advance the importance of lung health in this changing but highly vulnerable world. FOOTNOTES Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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