RQ1: How do health professionals perceive the health impacts of climate change?
We identified a total of 12 studies conducted with health professionals in English-speaking nations: seven with public health department personnel (six in the USA [11,12,13,14,15,16] and one in Canada ), four with physicians (three in the USA [18,19,20] and one in Australia ), and one with dieticians in the USA . On the whole, a large majority of both clinical and population health professionals with whom research has been conducted understand that climate change is occurring, and that it is already harming or has the potential to cause harm to the public’s health in the near future.
In health departments, different groups of professionals—specifically directors, environmental health directors, and nursing directors—appear to have largely similar views of the public health relevance of climate change, but some differences are evident both within and between groups.
Most public health department directors see climate change a potentially serious public health problem in their jurisdiction, although this is not universally the case. In 2008, a majority (69%) of American local public health department directors perceived climate change to be occurring in their jurisdiction—whereas only 11% did not—while 78% felt their jurisdiction would experience climate change over the next 20 years . However, a 2012 replication of the 2008 study found that polarization may have occurred, with most directors becoming more certain that climate change is already occurring in their jurisdiction (an increase of 9.3%), while other directors became more certain it is not happening in their jurisdiction (an increase of 11.3%); the proportion who were not sure either way had declined .
Similarly, by 2012, more directors had become more certain that over the next 20 years, their jurisdiction would experience one or more serious public health problems as a result of climate change (an increase of 17.8%), while more directors also became more certain their jurisdiction would not (an increase of 9.3%). Two state-based surveys of health department directors showed divergent profiles: in 2008, nearly all directors in California (94%) perceived climate change to be a threat to public health , whereas in 2009, only a minority of directors in New York State (32%) perceived climate change to be occurring yet in their jurisdiction .
Most environmental health directors nationwide feel that climate change will have serious health impacts globally (65%) and in the USA (56%); however, fewer than half (46%) believe their jurisdiction will experience serious impacts . Similarly, nearly all public health nursing directors nationwide (90%) perceive that human-caused climate change is happening (90%), and most (65%) feel its health-related impacts will be a serious public health issue in the next 20 years .
The specific public health risks of greatest concern to public health personnel appear to be heat-related impacts, displacements, disruptions in health care due to storms and floods, vector-borne illness, air quality-related conditions, and mental health problems [11, 12, 14, 17]. Relatively few health departments have developed programs to address these problems, and most respondents indicated their department will need assistance (including expertise, additional people, and finances) to make significant progress [11,12,13,14, 16, 17].
Among physicians, a similar profile emerged. Most clinicians are convinced that climate change is happening and is already beginning to affect the health of some of their patients. Three physician surveys—of African-American physicians, thoracic specialists, and asthma and allergy specialists—all found that a sizable majority of respondents felt they had patients whose health was already being harmed by climate change in a variety of ways. The health impacts most commonly identified were air pollution-related increases in severity of chronic disease, such as asthma, COPD, and cardiovascular disease; allergic symptoms; heat-related effects; vector-borne illnesses; diarrheal diseases from food-/water-borne agents of infection; and injuries due to extreme weather [18,19,20].
Despite their experiences to date with health impacts of climate change, most physicians feel they lack knowledge about the topic, and large majorities support increased education on the health aspects of climate change in the form of continuing medical education, undergraduate medical education, patient education materials, and medical association policy statements. Large majorities also say that physicians and their associations should be involved in advocacy pertaining to the health effects of climate change [18,19,20].
Six surveys of health professionals’ perceptions of and knowledge about climate change have been done in non-English-speaking nations. They include Ethiopian health science students , Indian medical residents , Cambodian health professionals , Chinese hospital-based nurses , and Chinese public health professionals [27, 28]. In all cases, a large majority of respondents perceived that climate change is harmful to health, but their self-assessed knowledge was low, and their perceived need to learn more was high.
In addition, one study conducted in the European Economic Area, including all European Union countries as well as Norway, Iceland, and Lichtenstein, found that a large majority of national infectious disease experts agreed that climate change would affect vector-borne (86%), food-borne (70%), water-borne (68%), and rodent-borne (68%) diseases in their countries .
RQ2: How does the public perceive the health impacts of climate change?
Ten studies have been done to assess public understanding of the health impacts of climate change in English-speaking countries; most of this research has been conducted in Canada [30,31,32,33] and the USA [8, 11, 31, 34,35,36]. Overall, it appears that relatively few Canadians and Americans associate climate change and health harms; most report they have given little thought to the issue [31, 37]. The depth of participants’ knowledge and risk perceptions is difficult to assess because people’s answers to open-ended questions give the impression of relatively little knowledge and risk perception [31, 34, 35, 38], whereas people’s answers to closed-ended questions demonstrate much higher level of risk perception [31, 34, 35, 39]. Specifically, only a minority of survey participants answer open-ended questions in ways that suggest they know anything about how climate change harms health, or who is most likely to be harmed [11, 38]. However, when asked specific closed-ended questions, a majority of respondents answer in a manner indicating that they do perceive climate change to be harmful to health [31, 37].
There are at least two possible explanations for the discrepancy between people’s answers to open-ended versus closed-ended answers about climate and health. One is that many people are more knowledgeable and perceive more risk than their open-ended responses suggest, but because the issue has low salience to them, specific health impacts and risk groups do not come to mind unless specifically prompted (by follow-on or closed-ended questions). Another possibility—made plausible by the fact that the majority of people surveyed hold negative views about global warming—is that many people do not have prior perceptions about the health relevance of climate change, but when asked closed-ended questions about the topic, they draw on their preexisting negative views about the issue in general to generate answers to specific questions about climate and health. Which explanation(s) best account for the discrepancy between the findings resulting from open-ended and closed-ended questions is not yet clear.
Another important finding is that in studies in the USA and UK, people have a strong tendency to see climate change as less threatening to their health and to their family’s health than to other people’s health—with escalating levels of health threat accorded to people in their community, to Americans in general, and to people worldwide [8, 36, 40].
The one clear exception to finding that few people can identify specific health harms from climate change comes from a study of Inuit elders and seniors in Nunatsiavut, Canada. The majority of Inuits interviewed felt that climate change is harming their health through reduced physical activity (due to a shorter ice season), compromised nutrition (due to reduced catch of wild game), and increased stress and substance use .
In summary, a majority of people in Canada (except possibly Inuit elders) and the USA appear to know relatively little about the health impacts of climate change, but many hold negative views of the health impacts of climate change regardless, or they appear willing to accept that climate change is harmful to human health.
Eight studies have assessed public understanding of the health harms associated with climate change in the non-English-speaking world. Three of these studies have been conducted in Africa (two in Tanzania and one in Nigeria [41,42,43]) and four in Asia (Bangladesh, Nepal, Tibet, and Vietnam) [43,44,45,46], with one additional study in Malta . In all cases but one (Malta), this research has focused on especially vulnerable regions and populations.
Awareness of climate change per se tends to be low—with Hanoi, Vietnam serving as an exception (at approximately 75% )—but all of the studies found very high rates of perceived changes in climatic conditions that are consistent with climate change, including changes in precipitation and temperature. All of the studies also show very high rates of awareness of health harms due to these changing climatic conditions. These include increases in food insecurity (Tanzania, Nigeria, Bangladesh [42, 43, 48]) and water insecurity (Nigeria, Bangladesh [43, 48]); illness (Malta, Nigeria, Nepal, Vietnam [31, 46,47,48]) and stress (Nigeria ); injuries from extreme weather events (Bangladesh ); and heat risk (Tibet ).
RQ3: How does the public react to information about the health implications of climate change?
Eleven studies have assessed public reactions to information about the health implications of climate change [10, 49,50,51,52,53,54,55,56,57,58]. All but one was done in American populations. The exception, a study conducted in 24 nations , included the following nations in addition to the USA: Australia, Brazil, Chile, China, France, Germany, Ghana, Iceland, Israel, Japan, Mexico, Netherlands, New Zealand, Norway, Poland, Russia, South Africa, South Korea, Spain, Sweden, Switzerland, Venezuela, and the UK. No firm conclusions can be reached, but some tentative conclusions seem defensible.
Americans across the political and climate change opinion spectra appear receptive to information about the health aspects of climate change [49,50,51]. Other studies, however, suggest limitations. One study found a small beneficial effects of providing health-framed climate information, but also found that the effect was neutralized by climate change denial counter-messaging . Another found no differential impact of a health-framed message , and a third found positive effects for self-identified Democrats, but negative effects (i.e., a boomerang effect) among self-identified Republicans . Conversely, one small study with people who were particularly vulnerable to the health impacts of climate change (based on their health and SES status) found that participants responded favorably to simple information about climate and health, becoming more certain that climate change is happening and that it may affect their health, and they gained knowledge about who is most vulnerable to such impacts .
One study—which examined how likely various types of information about climate change are to be shared from person to person—found that information about the health impacts of climate change was shared with greater frequency than information about several other types of climate impacts .
A small field study of homeowners found that information about the environmental and public health externalities of electricity production, such as childhood asthma and cancer, was more effective at motivating home energy-saving behavior than information about saving money, especially among households with children .
A series of studies conducted by Levine and Kline , however, provides a cautionary note. In three experiments—field experiments and web-based experiments—they found that climate messages intended to make people concerned about their own health successfully heighten people’s concerns about climate change, but paradoxically they also reduce people’s rate of political participation (e.g., signing a petition, or joining a climate advocacy organization) to express their concern. The hypothesized mechanism of the paradoxical finding is that when people feel their material resources are threatened (in this case, their health), their response is to conserve their resources by avoiding additional commitments (presumably so as to better withstand resource constraints that may be forthcoming).
The only research conducted beyond the USA was a 24-nation study of university students that also included community samples in 10 of the nations. Participants were not presented with information about climate and health, but rather were asked to imagine what their country will look like in the future—in 2050—when people have taken action aimed at preventing climate change. They were then asked how much better, or worse, various conditions in their society would be at that time, including disease and pollution. Participants who believed that climate change action would reduce dysfunction in society, including realizing the health benefits of reducing disease, were significantly (albeit weakly) more likely to intend to perform climate change-relevant citizenship actions (e.g., contact an elected official) and household actions (e.g., install products to save energy) over the next 12 months, and to donate to an environmental organization .