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date: 22 February 2018

Communicating the Public Health Risks of Climate Change

Summary and Keywords

Effective public communication and engagement have played important roles in ameliorating and managing a wide range of public health problems including tobacco and substance use, cardiovascular disease, HIV/AIDS, vaccine preventable diseases, sudden infant death syndrome, and automobile injuries and fatalities. The public health community must harness what has been learned about effective public communication to alert and engage the public and policy makers about the health threats of climate change. This need is driven by three main factors.

First, people’s health is already being harmed by climate change, and the magnitude of this harm is almost certain to get much worse if effective actions are not soon taken to limit climate change and to help communities successfully adapt to unavoidable changes in their climate. Therefore, public health organizations and professionals have a responsibility to inform communities about these risks and how they can be averted.

Second, historically, climate change public engagement efforts have focused primarily on the environmental dimensions of the threat. These efforts have mobilized an important but still relatively narrow range of the public and policy makers. In contrast, the public health community holds the potential to engage a broader range of people, thereby enhancing climate change understanding and decision-making capacity among members of the public, the business community, and government officials.

Third, many of the actions that slow or prevent climate change, and that protect human health from the harms associated with climate change, also benefit health and well-being in ways unrelated to climate change. These “cobenefits” to societal action on climate change include reduced air and water pollution, increased physical activity and decreased obesity, reduced motor-vehicle–related injuries and death, increased social capital in and connections across communities, and reduced levels of depression. Therefore, from a public health perspective, actions taken to address climate change are a “win-win” in that in addition to responsibly addressing climate change, they can help improve public health and well-being in other ways as well.

Over the past half decade, U.S.-based researchers have been investigating the factors that shape public views about the health risks associated with climate change, the communication strategies that motivate support for actions to reduce these risks, and the practical implications for public health organizations and professionals who seek to effectively engage individuals and their communities. This research serves as a model for similar work that can be conducted across country settings and international publics. Until only recently, the voices of public health experts have been largely absent from the public dialogue on climate change, a dialogue that is often erroneously framed as an “economy versus the environment” debate. Introducing the public health voice into the public dialogue can help communities see the issue in a new light, motivating and promoting more thoughtful decision making.

Keywords: climate change, public health, framing, public engagement, communication

Climate Change and Human Health

Climate change is creating a truly unprecedented worldwide public health emergency. The 2015 Lancet Commission on Health and Climate Change concluded: “The effects of climate change are being felt today,” “(these effects) threaten to undermine the last half century of gains in development and global health,” and “future projections (of climate change) represent an unacceptably high and potentially catastrophic risk to human health” (Watts et al., 2015, p. 1861). Similarly, the most recent assessment by the Intergovernmental Panel on Climate Change (IPCC) concludes that human health worldwide is already being harmed by shifts in weather patterns and other aspects of climate change, and that unless there is a dramatic reduction in greenhouse gas emissions, there is likely to be major increases in the magnitude of climate change-related morbidity and mortality by 2050 (Smith et al., 2014).

However, public health action can do much to protect people and places from climate change and from the harms to health that it causes. Effective public communication can be used to alert, engage, and empower the public to respond to climate change and to participate in efforts to mitigate risks. Many of these strategies offer a variety of cobenefits, protecting people not only against the risks posed by climate change but benefiting their health and well-being in other ways as well. Indeed, according to the Lancet Commission: “Tackling climate change could be the greatest global health opportunity of the 21st century. . . . Many mitigation and adaptation responses to climate change are ‘no regret’ options, which lead to direct reductions in the burden of ill-health, enhance community resilience, alleviate poverty, and address global inequity” (Watts et al., 2015, p. 1861).

Direct and Indirect Threats to Human Health

There is widespread agreement among climate scientists that the Earth is warming as a result of human activity (Cook et al., 2016), primarily due to rising levels of carbon dioxide and other heat trapping atmospheric gases created by burning fossil fuels. It is also clear that current trends in energy use, development, and population growth will lead to continuing—and more severe—climate change over the course of this century and beyond (WHO, 2009; Smith et al., 2014).

Although a relatively new area of research, there is a rapidly increasing base of knowledge about the public health implications of climate change (Melillo, Richmond, & Yohe, 2014; Smith et al., 2014; Levy & Patz, 2015). Worldwide, climate change is harming human health by exacerbating health problems that already exist, with the worst health problems taking place in developing nations with high rates of poverty, and this is projected to increase over the next several decades (Smith et al., 2014).

Climate change harms human health, both directly and indirectly, in a variety of important ways. Direct effects can include Earth system changes, including rising temperatures, increasing climate variability, increased rainfall and snowfall in some areas and drought in others, and more frequent severe weather events, all of which have considerable potential to harm human health. Heat waves, for example, can cause direct effects such as dehydration, heat exhaustion, heat stroke, and death (CDC, 2009).

Indirectly, climate change brings new challenges to the control of infectious diseases. Climate-related ecosystem changes can increase the range, seasonality, and infectivity of some vector-borne diseases (Smith et al., 2014). Many of the world’s most prodigious deadly infectious diseases are highly climate sensitive (via changes in temperature and rainfall) including cholera and other diarrheal diseases, and insect-borne diseases including malaria and dengue. Downpours can trigger sewage overflows, contaminating ground water that is often used for crop irrigation and drinking water. In the United States, these consequences will be particularly severe in the roughly 770 cities and towns, including New York, Chicago, Washington, DC, Milwaukee, and Philadelphia, that have “combined sewer systems;” an older design that carries storm water and sewage in the same pipes (IPCC, 2007).

Perhaps most seriously, the changing global climate is also affecting the basic requirements for maintaining health (i.e., clean air and water, sufficient food, and adequate shelter) and placing other pressures on the natural, economic and social systems that sustain health, which can contribute to poverty, population dislocation, and civil conflict (WHO, 2009; Smith et al., 2014; Watts et al., 2015). For example, mass environmental displacement and migration has the potential to disrupt the lives of hundreds of millions of people, intensifying the growing issues associated with urbanization and reverse successes in development; economic downturns and collapse erode both population health and societal development. Armed conflicts can result from resource scarcity and competition, and migration and clashes between host and migrant groups can lead to large scale loss of life and morbidity (Costello et al., 2009). The burden of all of these conditions is expected to increase as climate change advances.

In total, the direct and indirect health effects of climate change threaten to slow, halt, or in some cases reverse—possibly dramatically so—the progress made in enhancing public health worldwide over the past several decades (Watts et al., 2015). Climate change is expected to adversely affect the health of large numbers of Americans as well (TFAH, 2009; USGCRP, 2016). In fact, many communities across the United States are already experiencing the negative health effects associated with climate change (NIEHS, 2010; USGCRP, 2016).

Extreme heat can directly cause illness and death. Extreme heat events pose serious danger to people throughout the United States and abroad, yet virtually all heat-related illnesses and deaths are preventable if communities and individuals implement appropriate preventive measures. Studies conducted by the U.S. Centers for Disease Control and Prevention (CDC, 2009) have shown that exposure to extreme heat can increase discomfort and fatigue, can cause heat cramps, can increase emergency room visits and hospitalizations, and can even lead to death. Between 1999 and 2009, more than 7,800 deaths were associated with exposure to excessive heat in the United States alone (Kochanek, Xu, Murphy, Minino, & Kung, 2011). A particularly intense European heat wave in 2003 helped cause probably the hottest summer in Europe since 1500 ad and led to a reported death toll exceeding 70,000 (Stott, Stone, & Allen, 2004; Robine et al., 2008). Extreme heat is a real danger to human health that will become worse with time. The latest report from the IPCC declared that due to climate change, not only is it likely that heat waves have increased across large parts of the world, but in the future, it is very likely that heat waves will last longer and occur more often (Smith et al., 2014). By the end of this century, extremely high temperatures that currently occur once every 20 years could occur as often as every 2 to 4 years.

Allergens and air pollution can aggravate respiratory problems and disease. The prevalence and severity of respiratory diseases in the United States and other countries has increased sharply in recent decades (WHO, 2007). Many respiratory diseases are sensitive to climate conditions. Respiratory diseases with an allergic component are climate sensitive because climate change can increase the level and duration of pollens and other air-borne allergens. Extreme heat also contributes to elevated levels of ground-level ozone (a component of smog), which results in short-term decreases in lung function and damages lung tissue. Elevated ground-level ozone also increases the incidence of asthma-related hospital visits and premature deaths (Confalonieri et al., 2007).

Extreme precipitation can cause injury, illness, and death. Heavy downpours (which can cause flooding) have increased in recent decades and are projected to increase further as the nation continues to warm (Gutowski, 2008; Kunkel et al., 2008). Extreme precipitation and flooding can cause injury, illness, and deaths. For example, 2,000 Americans were killed as a result of hurricanes in 2005—more than double the average number of lives lost to hurricanes in the United States over the previous 65 years—and stomach and intestinal illnesses increased among evacuees (Ebi et al., 2008). Extreme weather events can also lead to serious indirect health effects, including mental health consequences such as depression and posttraumatic stress disorder (Ebi et al., 2008).

Atmospheric changes can exacerbate vector-, food-, and waterborne diseases.

Certain vector-, food-, and waterborne diseases are expected to occur more often and to affect new populations as a result of changes in temperature and precipitation that enable pathogens to expand into new geographic regions. People living in mountain states, for example, may become more susceptible to certain insect-borne diseases as a result of warming temperatures that enable mosquitos and other vectors to live and reproduce at higher elevations. Heavy rains and flooding can contaminate food crops with feces from nearby livestock or wild animals, increasing the likelihood of food-borne disease associated with fresh produce and spurring outbreaks of waterborne Cryptosporidium and Giardia (Ebi et al., 2008).

Wildfires can cause injury and death. Climate change has already contributed to increasing wildfire frequency. Wildfire smoke contains particulate matter, carbon monoxide, nitrogen oxides, and various volatile organic compounds that can significantly reduce air quality. Smoke exposure increases respiratory and cardiovascular hospitalizations, emergency department visits for asthma, bronchitis, chest pain, chronic obstructive pulmonary disease, respiratory infections, and medical visits for lung illnesses. Smoke exposure has been associated with hundreds of thousands of global deaths annually. Future climate change is project to contribute to wildfire risks and associated emissions, with harmful impacts on health.

A core principle of the practice of public health is that the public should be informed about threats to their health and well-being (Kass, 2001; Scutchfield & Keck, 2009). Individuals require sufficient knowledge to understand how they are at risk, to take actions to reduce their risk, and to participate in meaningful public discourse about collective actions that can be taken to reduce public health risks (Maibach, Roser-Renouf, & Leiserowitz, 2008). Informing members of the public, and the full range of other decision makers, about climate change health risks and response options creates important opportunities to protect prior gains in public health—locally and globally—and to further advance the health of the public worldwide (Watts et al., 2015).

Public Awareness of Health Consequences Remains Low

Despite the well-documented current and future threats to human health, public understanding of climate change varies greatly among countries. For example, Ray and Pugliese (2011) found that among the five countries with the most greenhouse gas emissions, the percentage of people who were familiar with climate change in 2010 varied dramatically (a) in Japan (98%), (b) in the United States (96%), (c) in Russia (83%), (d) in China (62%), and (e) in India (37%).

The proportion of people who were completely unaware of global warming also varied greatly (a) in developed countries in Asia, Canada, and the United States (4%); (b) in developing countries in Asia (48%); (c) in countries in the Middle East and North Africa (49%); and (d) in countries in sub-Saharan Africa (54%).

In 2013, a poll conducted in 39 countries by the Pew Research Center found that climate change was perceived as a major national threat by 65% of people in Latin America; 56% in Asia and the Pacific; 54% in Canada, Europe, and Africa; but only 40% in the United States.

Relatively little research, however, has been done to assess public understanding of the human health relevance of climate change. Surveys conducted in Canada, Malta, and the United States in 2008 and 2009 found that many people answer closed-ended survey questions in ways that suggest some recognition of the health relevance of climate change, but relatively few people answer open-ended questions in a manner that suggests clear top-of-mind associations between climate change and health (Akerlof et al., 2010). A 2014 survey found that most Americans (61%) have given little or no thought to how global warming may affect people’s health and that relatively few could, in response to open-ended questions, name a single heath harm (27%) or a group of people whose health is most at risk (25%; Maibach et al., 2015).

Similarly, little research has been done on why many in the public seem not to understand the health implications of climate change. One study found that the American news media rarely reported on this subject, and when they did, the reporting was often inaccurate (Weathers & Kendall, 2015). When news stories mention impacts on human health, they are typically reported in an episodic context, embedded in a story about a specific heat wave, storm, flood, or fire—rather than in a broader context that explains the long-term consequences of climate change. Many government agencies and nongovernmental organizations attempt to educate the public about climate change, but they typically focus on scientific aspects, harm to nonhuman forms of life (e.g., plants, penguins, and polar bears), or impacts to the environment (Nisbet, 2009). The public’s lack of understanding about the health implications of climate change creates an opportunity—and a responsibility—for health professionals and others to provide this information. The opportunity is facilitated by people’s concerns about health threats in general and actions that they can take to benefit their health.

Public health professionals have some unique opportunities to help the public and other decision makers better understand the human implications of climate change, and the scientific consensus about it. Public health professionals are uniquely positioned to explain how the rapidly emerging threats associated with climate change are connected with individual and community health. By communicating the potential of global climate change to harm human health—locally and elsewhere—and by conveying the potential to improve human health through actions that limit climate change and prevent human harm, health professionals can enhance public understanding of the full scope of the problem and help enable appropriate responses by individuals and communities.

One way to do this is through a public health frame. When climate change is framed as a public health issue, the need to invest in adaptation efforts to protect people and their communities becomes an important and unavoidable part of the story. The specific climate-related health risks vary by region, but the risks in most communities include reduced air quality and more extreme storms, floods and storm surges, heat events, wildfires, vector-borne diseases, and allergic reactions. Unlike limiting climate change, which is inherently a global challenge, actions to protect against health risks are inherently local. Public health officials can help citizens prioritize and choose among responses to these threats. A focus on adaptation can help move the community dialogue about climate change from the realm of global abstraction to the realm of local reality.

Framing Climate Change as a Public Health Problem May Enhance Public Engagement

Research over the past several decades has shown that how experts, policy makers, and journalists “frame” an issue (i.e., how they mentally organize and discuss the issue’s central ideas) greatly influences how the public understands the nature of the problem, the personal relevance or societal importance 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 (Scheufele, 1999; Price, Nir, & Capella, 2005; Nisbet, 2009). However, the way climate change has traditionally been framed—as an environmental problem—tends not to engage members of the public, at least not adequately. 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 (Maibach, Nisbet, Baldwin, Akerlof, & Diao, 2010). For example, information about climate change that is framed as an environmental problem is likely to engage people who see themselves as environmentalists (about one third of Americans) but it is likely to be totally dismissed by people who believe that environmentalists are misguided (another one third of Americans; Sarfaty & Maibach, 2015).

The frames that have dominated U.S. public discourse on climate change have included an environmental frame, a political frame, and an economic frame—all of which have been highly polarizing—as well as a scientific frame, which most resonates with few people. In addition, other frames of climate change that have recently been introduced in U.S. public discourse include the following:

  • A national security frame, as illustrated by military strategists who inform the public that climate change can lead to global instability, which will threaten U.S. national security

  • An energy frame, as illustrated by entrepreneurs who highlight the benefits of clean renewable forms of energy—in contrast to the costs of fossil fuels

  • A moral frame, as illustrated by leaders in civic society and the faith community who assert that some (mostly high-income) countries are harming people in other (mostly low-income) countries—and harming future generations in all countries

  • A stewardship frame, as illustrated by leaders of the faith community who assert that people have responsibility to protect God’s creation

  • A human health frame, as illustrated by health professionals who point to increased morbidity and

  • mortality due to heat-related disorders, respiratory disorders, and vector-borne diseases

Framing, then, is a central process by which public health professionals can link messages and recommendations about climate change to their audience members’ deeply held values and beliefs. By defining or “framing” the relevance of climate change in ways that connect to the core values of specific audience segments—and repeatedly reinforcing that information through a variety of trusted sources and networks of recruitment—purposive communication can foster enhanced public engagement with the issue.

A public health frame for climate change (i.e., making the case that climate change is a major threat to people’s health and well-being) has potential to engage a much broader cross section of the American public than has previously been engaged in the issue. Suggesting a frame that resonates with peoples’ broadly shared values—such as health—helps people ground their understanding of an issue in the context of their previously existing, carefully considered, and deeply held belief systems and motivations (Price & Tewksbury, 1997; Scheufele & Tewksbury, 2007). The health frame also helps connect the complex and poorly understood topic of climate change to risks that the public already understand and accept as important, such as asthma and other respiratory problems, vulnerability to extreme heat, food-borne illness, and infectious disease. The health frame also has the potential to shift the climate dialogue from one based on environmental values to public health values, which tend to cut across ideology and partisanship (Maibach, Roser-Renouf, & Leiserowitz, 2009; Akerlof et al., 2010). The public health frame also enables a new and highly respected group of voices—which includes doctors, nurses, and public health officials—to engage new segments of the public. And finally, the frame moves the location of impacts closer to home, emphasizing the risks to vulnerable people, such as children, the elderly, and the poor.

A public health frame can convey local relevance. To most people, the problem of climate change is distant and abstract, while human health impacts are local and concrete. About half of Americans, for example, believe that global warming will cause great harm to the natural environment (51%), and future generations of people (51%). Fewer, however, believe the world’s poor (36%), people in developing countries (34%), people in the United States (23%), or they themselves (14%) will be harmed a great deal (Leiserowitz, Maibach, Roser-Renouf, Feinberg, & Rosenthal, 2015). In other words, people are more likely to perceive climate change impacts as a threat to plants and animals, to people in other parts of the world, and to future generations, but not as a local issue affecting themselves, their family, and their community.

Risk communication research has shown that an individual’s personal sense of risk as the most powerful motivator of behavioral change (Hale & Dillard, 1995; Witte & Allen, 2000); people are more likely to recognize and act on risks that are perceived to be close to home. Public health organizations are well positioned to demonstrate that the health risks of climate change are indeed close to home, wherever that home may be. National public health organizations can highlight the current impacts of climate change on human health in each region of the country. State and local public health organizations, in turn, can localize this information to the greatest extent possible.

By framing climate change as a local public health issue, it is possible to replace people’s mental associations of climate change as being geographically and socially distant with more proximate and relevant mental associations such as the risks to children, the elderly, and the poor in their own communities and across the United States. Americans who understand that climate change is harming people here in the United States (rather than only in nations far away) and now (rather than at some time in the future, if at all), are more engaged in personal actions and more supportive of climate change policies (Roser-Renouf, Elligers, Maibach, Colon, & Li, 2012). A focus on the local health consequences of climate change is likely to enhance—and sustain—public engagement on the issue, and thereby facilitate meaningful public dialogue about the problem and opportunities for solutions. Conveying local health relevance may be particularly important in encouraging public support for adaptation measures to avoid health risks associated with climate change.

In addition to enhancing public engagement, elucidating the local health risks associated with climate change is likely to engage journalists as well. Nisbet et al. (2010) found that when experts and their institutions pursued basic media agenda-building strategies focused on public health threats, especially when localized, the strategies lead to substantive reporting. These strategies include the release of a locally or regionally tailored study or report; the sponsorship of regional meetings; or a news conference on the part of a public health-related coalition or professional group.

A public health frame can convey additional benefits of taking action. Many actions taken to address climate change create “win-win” situations in that they create important public health benefits. For example, urban reforestation helps limit the urban heat-island effect, making cities safer for vulnerable people (and more pleasant for everyone) during extreme heat events, thereby reducing heat deaths and illness. Other steps taken to address climate change also work to reduce leading causes of death and illness including obesity, physical inactivity, unhealthful diets, asthma and other chronic conditions including heart disease and cancer, transportation-related injuries, and death. Examples include programs and policies that make it easier for people to walk, cycle, and take public transportation (Maibach, Steg, & Anable, 2009).

People across the continuum of climate beliefs respond positively to the concept of health cobenefits associated with taking action to limit global warming (Maibach et al., 2010; Myers et al., 2013). For example, most Americans endorse the following statements: (a) “Taking actions to limit global warming – by making our energy sources cleaner and our cars and appliances more efficient, by making our cities and towns friendly to trains, buses, and bikers and walkers, and by improving the quality and safety of our food – will improve the health of almost every American.” (b) “Cleaner energy sources and more efficient use of energy will lead to healthier air for children and adults to breathe.” (c) “Improving the design of our cities and towns in ways that make it easier to get around on foot, by bike and on mass transit will reduce the number of cars and help people become more physically active, lose weight.”

A focus-group–based research study conducted by the CDC also found that individuals embraced information about climate change that used a health cobenefits frame (Sapru, Telfer, Luber, Price, & Ryan, 2010). Recommended behaviors were seen to benefit the individual as well as convey specific information about what the individual could do to mitigate the effects of climate change. A focus on the cobenefits of climate change prevention behaviors contained messages that convey the ways that climate change mitigation behaviors—such as driving less, eating less processed food, and using energy saving light bulbs—can have benefits like reduced stress, improved health, and cost savings.

Moreover, people tend to respond better to positive information than negative information (Monahan, 1995). Therefore, highlighting the health benefits associated with taking action against climate change—including benefits that have nothing to do with climate change per se—is a useful way of accentuating the positive, giving people important additional reasons to support helpful programs, policies, and individual actions. For example, the American Lung Association (2010) in California has documented the significant public health gains that Californians will enjoy if their state implements the Vision California “mixed growth” and “growing smart” initiatives. Their data show that the sustainable community and transportation development options proposed for the next two decades will help clean the air, reduce pollution-related illness and death, and avoid significant health costs, benefits that are broadly supported by all Californians.

A public health frame can elicit support for mitigation and adaptation. When asked what questions they would pose to a global warming expert, if given the chance, many Americans expressed an interest in asking what harms global warming will cause (74%) and when it will begin to harm people (71%; Leiserowitz, Maibach, Roser-Renouf, & Smith, 2011). Therefore, the public health perspective on climate change is likely to be useful to a wide range of audiences, especially audiences in the middle of the climate change belief continuum who are most interested in learning more about the potential impacts of climate change.

Maibach et al. (2010) conducted a study to systematically understand how segments across the climate belief spectrum respond to information about the health risks of climate change and the benefits to health that may result from societal action on the problem. Respondents were asked to read “a brief essay about global warming” designed to frame climate change as a human health issue. The health benefits mentioned included cleaner air to breathe and cleaner water to drink, healthier food to eat, fewer cars on the road, and more pedestrian- and bicycle-friendly communities. All audience segments responded positively to the benefits section of the essay, rating this information on average as compelling and useful.

In a randomized message test experiment, Myers et al. (2012) asked more than 1,000 nationally representative survey participants to read uniquely framed news articles about climate change that emphasized either environmental, public health, or national security aspects of climate change. Across all of the audience segments, the news article about the public health implications of climate change was the most likely to elicit emotional reactions consistent with support for climate change mitigation and adaptation. Recent research by McCright et al. (2016), however, found that exposure to competing climate denial messages has the potential to negate the benefit of public health–framed messages.

More recent research has examined how to effectively reframe the connections between climate change, human health, and ocean health. In this research involving 500 subjects recruited from among passengers on a ferry boat in Seattle, Washington, participants were randomly assigned to two frame conditions in which they read presentations that defined the impact of climate change on oceans. In the first condition, the consequences of climate change were framed in terms of their risks to marine species such as oysters. In the second condition, climate change was framed in terms of risks to humans who may eat contaminated oysters. The framing of ocean impacts in terms of risks to human health appeared to depoliticize perceptions. In this case, the human health framing condition had no discernable impact on the views of Democrats and Independents, but it did influence the outlook of Republicans; right leaning subjects in the human health condition were significantly more likely to support various proposed regulations of the fossil fuel industry (Schuldt, McComas, & Byrne, 2016).

Communicating About Climate and Health

To enhance public engagement in climate change, health professionals should be informing people about its health relevance. Understanding that climate change is harmful to people—not just to the natural environment—is strongly associated with supporting societal responses to addressing climate change, and with political (Roser-Renouf, Maibach, Leiserowitz, & Zhao, 2014) and consumer advocacy (Roser-Renouf, Atkinson, Maibach, & Leiserowitz, 2016) to encourage societal responses. In fact, understanding that climate change is harmful to people is one of five key climate change beliefs that are strongly associated with likelihood to support a societal response and to personally take actions that encourage a societal response (Sarfaty & Maibach, 2015):

  • It’s real—i.e., climate change is real.

  • It’s us—i.e., climate change is human-caused.

  • Experts agree—i.e., there is consensus among climate scientists that human-caused climate change is happening.

  • It’s bad—i.e., climate change is harmful to people.

  • There’s hope—i.e., human actions can limit climate change.

In addition, people who feel they have directly experienced the consequences of climate change are more likely to hold firm convictions that it is real (Akerlof, Maibach, Fitzgerald, Cedeno, & Neuman, 2013; Myers et al., 2013). Health professionals can play an important role by communicating these key concepts through the following three simple, important messages.

There is scientific consensus about human-caused climate change. The majority of the public is unaware that there is a scientific consensus about human-caused climate change. While recent studies have shown that 90% to 99.9% of active climate scientists are convinced that the planet is warming as a result of human activity (Cook et al., 2016; Powell, 2016), only about half of American adults believe that “most scientists think global warming is happening,” and only 12% estimate the consensus at 90% or higher (Leiserowitz et al., 2015).

Although more research is needed, several studies suggest that when people are told that there is a consensus among scientists about human-caused climate change, their understanding changes (Lewandowsky, Gilles, & Vaughan, 2013; Myers, Maibach, Peters, & Leiserowitz, 2015; van der Linden, Leiserowitz, Feinberg, & Maibach, 2015). For example, a presentation of the following statement increases the proportion of people who believe there is a consensus from about 60% to about 80%: “Based on the evidence, more than 97% of climate experts are convinced that human-caused climate change is happening” (Myers et al., 2015). By presenting information about this consensus, rather than explaining the facts of human-caused climate change, health professionals can avoid conversations about areas of climate science with which they themselves may not be familiar.

Climate change is harming people’s health everywhere. People process threat information more easily when it is explained in a way that reflects their own experience or that of others in their community. Since personal and community experience varies, specific content of messages needs to be tailored for specific communities. For example, in communities where air quality is poor, relevant stories may refer to the way that more-severe heat waves due to climate change are contributing to poor air quality and resulting in increased occurrence of serious respiratory disease.

In addition, people tend to understand life through the stories of individuals and families rather than through statistics. Stories of people who have experienced the health consequences of climate change can powerfully influence people’s beliefs and actions—stories about old people who have died during heat waves, children with asthma that has been exacerbated by air pollution, people with increased allergy symptoms because of longer pollen seasons, and children who have become malnourished because of drought induced by climate change.

Health professionals are in a unique position to educate the public about the health relevance of climate change. In a recent study of Americans (Maibach et al., 2015), primary care physicians were found to be the most trusted sources for health information related to global warming, with 49% of respondents reporting that they “strongly” or “moderately” trusted their doctor, and the CDC was the next most-trusted source—tied with friends and family members at 41%. As trusted members of the community, health professionals can convey the ways in which climate change is already causing human health effects and how these effects are likely to worsen unless actions are taken to address climate change. They can also communicate about the cobenefits to public health resulting from actions that address climate change.

Actions will limit climate change and make communities healthier. Focusing on solutions can bring people together, even when the underlying ways of thinking may differ (Johnson, 2012). The belief that taking action will make a difference can bolster individual self-efficacy and collective efficacy and motivate people to act. Absence of belief in the efficacy of action—a barrier to action to address climate change—is associated with a sense of helplessness, denial, and avoidance (Roser-Renouf et al., 2014).

Invoking the value of protecting people from harm can help to engage people in responding to climate change. Most people feel that protective behavior is worthwhile and sensible. When people learn about potential harm, they are more likely to take effective action to reduce the risk of that harm. For example, encouraging people to walk or bicycle rather than drive improves their health and reduces use of fossil fuels. Buying locally grown fresh produce helps reduce both fat intake and long-distance food transportation using fossil fuels.

Getting the Message Out

Health professionals can improve their communication effectiveness by attending to a simple formula in their public communication efforts: simple clear messages, repeated often, by a variety of trusted sources (Maibach, in press). Each of the three elements of this formula offers important communication guidance based on extensive empirical evidence and has been shown to be practical for a broad range of health and environmental issues and for a broad range of professionals.

Simple clear messages. Effective external communication—with journalists, policymakers, and members of the public—begins with simple clear messages that have been developed specifically to help people understand and appropriately simplify the issue at hand. The most important information will help members of the audience answer three key questions: What is the risk?; What is causing the risk?; What are the options for managing the risk? When the situation allows, such messages can be pretested to ensure that they are clear and helpful to audience members. Even in situations that do not allow for message testing, health professionals can use their best professional judgment in crafting simple messages aimed at providing clear, proactive answers to the questions that people are most likely to have.

Repetition. Repetition increases message persuasiveness both cognitively, by increasing the salience and availability of the information, and affectively, by increasing positive feelings about the message (Chong & Druckman, 2013; Pechman & Stewart, 1988). Typically, messages must be repeated often before most members of the intended audience will hear them, consider them, and potentially accept them. Health professionals—and other communicators—should convey the same simple clear messages to extend communication effectiveness. Simple clear messages are easy for communicators to embrace, and use, whereas long, complicated messages are not. Ideally, climate change messages should be simple and clear enough that members of the target audience begin to communicate them for us.

Trusted messengers. Trust is the most important factor in effective public communication; where there is no trust, there can be no learning. Fortunately, health professionals as a group are highly trusted, even though trust has declined in “leaders” of the medical profession (Blendon, Benson, & Hero, 2014). While public trust in other professional groups tends to wax and wane, trust in health professionals has remained relatively high over the decades in which these data have been collected.

When members of the target audience do not know the communicator—personally or by reputation—their trust is likely to be superficial, provisional, and vulnerable. As such, effective communicators find other trusted people, individuals who are known personally or by reputation to members of the target audience, to repeat and validate their simple clear messages. As implied above, the ultimate aim is to have members of the target audience convey our message to one another, because people typically trust most the people they know the best—family members, friends, and coworkers (Leiserowitz, Maibach, & Roser-Renouf, 2009).

Public Health Professionals as Climate Change Communicators

A representative national survey of local public health officers conducted in 2008 found that the majority of local public health officials in the United States are aware of the growing human health risks associated with climate change (Maibach et al., 2008). Specifically, many of these health officers reported that they are already seeing the human health impacts of climate change in their jurisdiction and that they expect these impacts will get worse over the next 20 years. The most commonly reported current climate change health impacts were heat-related illnesses (56%), storm- and flood-related health impacts (47%), drought- and fire-related health impacts (47%), and vector-borne infectious diseases (42%). More than half of the health officials (56% to 73%) indicated that they anticipate these health problems will become more common in the 2020s and 2030s in their jurisdiction as a result of climate change. Overall, 60% reported that their jurisdiction would experience serious public health problems as a result of climate change over the next two decades. Relatively few of these health officials, however, had begun communicating about these risks with members of their community.

A replication of this survey in 2012 showed that little had changed over 4 years: rates of health impacts from climate change remained high, while little public health programming had been developed to address the issue (Roser-Renouf et al., 2012). Specifically, public health departments have significantly fewer programs now than they did 4 years ago in the programmatic areas that are likely to be impacted by climate change. The average number of programs within the health department addressing the health issues associated with climate change impacts decreased from 7.7 programs to 5.8 programs—a 24% decrease. Mitigation efforts have also decreased: In 2008, two-thirds of public health departments offered at least one program that promoted mitigation actions, such as conserving energy, using mass or active forms of transportation, or consuming sustainable foods; in 2012, the proportion had decreased to 45%.

An unpublished survey of public health information officers (Maibach, 2010)—conducted during a plenary presentation at the 2010 annual meeting of the National Public Health Information Coalition—showed that more than three quarters of the information officers reported that they expect to see one or more serious public health problem as a result of climate change in their jurisdiction over the next 20 years (77%), and they feel that it is appropriate for their organization to communicate with external audiences about the public health implications of climate change (76%). However, fewer than one third reported having communicated with external audiences about the public health implications of climate change over the past 12 months (30%), or that the issue was likely to become a higher priority in their organization over the next 12 months (29%). Among the minority who were communicating about climate change with external audiences, the most commonly reported were other government agencies (13.6%), the general public (11.2%), elected/appointed government officials (9.6%), news media (4%), and members of the business community (1.6%).

Clearly, public health professionals understand the human health implications of climate change and, to some extent, are already engaged in addressing this problem. However, much more is needed. Public health professionals are uniquely well positioned to explain how the rapidly emerging threats associated with climate change are connected with individual and community health and well-being. By communicating the potential of global climate change to harm human health, and by conveying the potential to improve human health through actions that limit climate change, they can enhance public understanding of the full scope of the problem, and help enable appropriate responses by individuals and communities.

Incorporating the results of our research, a climate change communication primer was developed to serve as a training resource and guide for public health professionals. The primer makes the case that public health professionals are uniquely qualified and professionally obligated to engage the public and other stakeholders in their communities on the health risks posed by climate change and the actions that can be taken to adapt to and manage these risks. A range of strategic and tactical recommendations are then systematically reviewed. These include (a) with whom public health professionals should communicating (journalists, bloggers, and community media outlets); (b) decision makers in government, businesses, and NGOs; (c) other professionals whose work is or will be affected by climate change; and (d) the public, especially members of the most vulnerable communities); (e) how to get “the message” right (framing on health; localizing; emphasizing benefits; key messages); and (f) how to get the message out (through internal and external communication; effective partnerships; regional meetings; social media; opinion leaders; public testimony and other means).

Public health professionals should view their work on climate change as a form of civic education and engagement, empowering, enabling, motivating, and educating the public around not just about the technical but also the political and social dimensions of climate change. Importantly, civic education and engagement is as much about informing the public as it is about also informing experts and decision makers. Education should be viewed as a two-way process in which experts and decision makers seek input and learn from the public about preferences, needs, insights, and ideas relative to climate change solutions and policy options. There is also a need to recruit and train opinion leaders, highlight new participatory models for gathering and disseminating climate change news, and for investment in deliberative contexts such as public meetings where citizens can learn, debate, and connect (see Nisbet, 2010). With limited budgetary resources in mind, these initiatives are best focused on states, regions, or segments of the public that have the greatest need for information about climate change, either because of their political context and/or because of their vulnerability to specific climate change impacts.


The activities described in this chapter are best considered an exploration of the premise that public health professionals should engage in climate change for a variety of reasons, not the least of which is that climate change represents a profound threat to human health and well-being. Framing theory suggests—and research supports—the value of public communication that clarifies the public health implications of climate change. Given the magnitude of the public health threat and the relative lack of action by our nation’s leaders to address it, there is a pressing need for further research and evaluation focused on how to motivate and enable public health leaders to embrace this issue in a manner commensurate with the threat, and the opportunity.


We wish to thank The Robert Wood Johnson Foundation and the Energy Foundation for supporting our research. This article draws on our previous publications focused on communicating the health relevance of climate change.

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