Climate change is already taking a toll on human health in the United States [1
] and other nations worldwide [2
]. Unless greenhouse gas emissions worldwide are sharply curtailed - and significant actions taken to help communities adapt to changes in their climate that are unavoidable - the human toll of climate change is likely to become dramatically worse over the next several decades and beyond [3
]. Globally, the human health impacts of climate change will continue to differentially affect the world's poorest nations, where populations endemically suffer myriad health burdens associated with extreme poverty that are being exacerbated by the changing climate. As stated in a recent British Medical Journal
editorial, failure of the world's nations to successfully curtail emissions will likely lead to a "global health catastrophe" [4
]. In developed countries such as the United States, the segments of the population most at risk are the poor, the very young, the elderly, those already in poor health, the disabled, individuals living alone, those with inadequate housing or basic services, and/or individuals who lack access to affordable health care or who live in areas with weak public health systems. These population segments disproportionately include racial, ethnic, and indigenous minorities [5
While legislation to reduce U.S. greenhouse gas (GHG) emissions has stalled in Congress, in December 2009 the Environmental Protection Agency (EPA) moved toward regulating carbon dioxide and five other of the gases under the Clean Air Act, citing its authority to protect public health and welfare from the impacts of global warming [5
]. The agency found that global warming poses public health risks - including increased morbidity and mortality - due to declining air quality, rising temperatures, increased frequency of extreme weather events, and higher incidences of food- and water-borne pathogens and allergens.
This finding comes as a relatively small group of public health professionals are working rapidly to better comprehend and quantify the nature and magnitude of these threats to human health and wellbeing [6
]. This new but rapidly advancing public health focus has received minimal news media attention, even at internationally leading news organizations such as the New York Times
[unpublished data]. It is not surprising therefore that the public also has yet to fully comprehend the public health implications of climate change. Recent surveys of Americans [7
], Canadians [8
], and Maltese [9
] demonstrate that the human health consequences of climate change are seriously underestimated and/or poorly understood, if grasped at all. About half of American survey respondents, for example, selected "don't know" (rather than "none," "hundreds," "thousands," or "millions") when asked the estimated number of current and future (i.e. 50 years hence) injuries and illnesses, and death due to climate change. An earlier survey of Americans [10
] demonstrated that most people see climate change as a geographically and temporally distant threat to the non-human environment. Notably, not a single survey respondent freely associated climate change as representing a threat to people. Similarly, few Canadians, without prompting, can name any specific human health threat linked to climate change impacts in their country [8
Cognitive research over the past several decades has shown that how people "frame" an issue - i.e., how they mentally organize and discuss with others the issue's central ideas - greatly influences how they understand the nature of the problem, who or what they see as being responsible for the problem, and what they feel should be done to address the problem [11
]. The polling data cited above [7
] suggests that the dominant mental frame used by most members of the public to organize their conceptions about climate change is that of "climate change as an environmental problem." However, when climate change is framed as an environmental problem, this interpretation likely distances many people from the issue and contributes to a lack of serious and sustained public engagement necessary to develop solutions. This focus is also susceptible to a dominant counter frame that the best solution is to continue to grow the economy - paying for adaptive measures in the future when, theoretically, society will be wealthier and better able to afford them - rather than focus on the root causes of the environmental problem [13
]. This economic frame likely leaves the public ambivalent about policy action and works to the advantage of industries that are reluctant to reduce their carbon intensity. Indeed, it is precisely the lack of a countervailing populist movement on climate change that has made policy solutions so difficult to enact [13
Significant efforts have been made over the past several years by public health organizations to raise awareness of the public health implications of climate change and prepare the public health workforce to respond, although as noted above, it is not clear the extent to which public health professionals, journalists, or most importantly, the public and policy makers have taken notice. In the United States, National Public Health Week 2008 was themed "Climate Change: Our Health in the Balance," the Centers for Disease Control and Prevention created a Climate Change and Public Health program, and several professional associations assessed the public health system's readiness to respond to the emerging threat [15
]. Globally, World Health Day 2008 was themed "Protecting Health from Climate Change," and the World Health Organization has developed a climate change and health work plan, the first objective of which is "raising awareness of the effects of climate change on health, in order to prompt action for public health measures" [18
]. Several prominent medical journals have released special issues on climate change and health [19
], and these and other medical journals [4
] have issued strongly worded editorials urging health professionals to give voice to the health implications of climate change.
An important assumption in these calls to action is that there may be considerable value in introducing a public health frame into the ongoing public - and policy - dialogue about climate change. While there is indeed solid theoretical basis for this assumption, to the best of our knowledge there is not yet empirical evidence to support the validity of the assumption [22
The purpose of this study therefore was to explore how American adults respond to an essay about climate change framed as a public health issue. Our hypothesis was that a public health-framed explanation of climate change would be perceived as useful and personally relevant by readers, with the exception of members of one small segment of Americans who dismiss the notion that human-induced climate change is happening. We used two dependent measures in this hypothesis: a composite score based on respondent reactions to each sentence in the essay, and the overall valence of respondents' general comments made after reading the essay.
Our study builds on previous research that identified six distinct segments of Americans, termed Global Warming's Six Americas
]. These six segments of Americans - the Alarmed (18% of the adult population), the Concerned (33%), the Cautious (19%), the Disengaged (12%), the Doubtful (11%), and the Dismissive (7%) - fall along a continuum from those who are engaged on the issue and looking for ways to take appropriate actions (the Alarmed) to those who actively deny its reality and are looking for ways to oppose societal action (the Dismissive; see Figure ). The four segments in the middle of the continuum are likely to benefit most from a reframing of climate change as a human health problem because, to a greater or lesser degree, they are not yet sure that they fully understand the issue and are still, if motivated to do so, relatively open to learning about new perspectives.
Global Warming's Six Americas. A nationally representative sample of American adults classified into six unique audience segments based on their climate change-related beliefs, behaviors and policy preferences.