Human health impacts of climate change as a catalyst for public engagement: Combining medical, economic and behavioural insights Open Access

Formal negotiations for an international climate agreement are currently framing a win–win narrative in the hope of spurring positive engagement from Parties (Rietig, 2014). According to the recent UNEP (2014) Emissions Gap Report, there is an urgency to act now to stay within the 2°C limit.

If one compares environmental issues that are solved with the ones that are not, it is unsurprising that often health is a serious concern and a driver of action. For instance, one of the reasons why the Montreal protocol was so quickly agreed upon is because stratospheric ozone depletion was seen as a serious risk to human health, notably in relation to skin cancer (Sunstein, 2007). This suggests that giving more attention to the human health benefits of curbing greenhouse gas (GHG) emissions might help to strengthen broad support for a climate agreement. With human health benefits, we mean here the main benefits[¹] stemming from an effective climate agreement that reduces the chances of increased global temperatures, thus resulting in less negative human health impacts.

In this respect, it is worthwhile to consider for a moment the recent announcements on emission reductions by the two biggest CO₂ emitters, the USA and China, in the run-up to the United Nations 20th Conference of the Parties (COP) in December 2014 (McGrath, 2014). Local air pollution and its impacts on health were the motivating reasons behind these pledges. In the case of China, dangerous levels of local air pollution, notably fine particles posing serious health risks, were an important incentive (Sheehan et al., 2014). In the case of the USA, the Environmental Protection Agency already since December 2009 uses the Clean Air Act to motivate regulating carbon dioxide and five other GHGs. In this context, it has stated its authority to protect public health from the impacts of climate change (Maibach et al., 2010).

Nevertheless, human health is rather neglected in influential climate discussions. As an important proof of this, note that at the UN Climate Change conference in Bonn (March and June, 2014), human health impacts of climate change received very little attention [International Institute for Sustainable Development (IISD), 2014]. This paper considers the potential role that human health might play in the debate on climate change. This involves examining to what extent there is evidence for considerable human health impacts of climate change, its economic costs and whether better informing citizens and policy makers about these can help to create more support for required climate policies.

There is ample evidence of the health risks associated with climate change. Medical journals have published frequently on the relation between human health and climate change (Cardwell and Elliott, 2013; Frumkin and McMichael, 2008; Frumkin et al., 2008; Patz et al., 2005). A report released by the Lancet and University College London went as far as to say that “climate change is the biggest global health threat of the twenty-first century” (Costello et al., 2009, p. 1693). In addition, a more recent report by the Lancet (2015) makes the similar statement that “tackling climate change could be the greatest global health opportunity of the twenty-first century” (Wang and Horton, 2015). The World Health Organization (WHO) (2008, 2009, 2013) and UNEP (2011) have also published reports stressing the importance of the connection between health and climate change. The health risks associated with climate change vary across people and regions. Scientists agree that developing countries and small-island states may have hit the hardest, and that women, children and the elderly are the most vulnerable (WHO, 2008). An increase in global temperature affects meteorological conditions such as humidity and precipitation. These changes directly affect the onset and intensity of physical health impacts – infectious and non-infectious diseases, as well as non-physical health impacts – such as psychological stresses due to extreme weather events – or in a worst case scenario, civil conflict. Section 2 presents a summary of this literature.

Current economic studies of the costs of climate change generally have not emphasized health-related impacts of climate change in their conclusions (Hutton, 2011). Nevertheless, the main economic studies provide evidence of considerable health costs of global warming. Section 3 of this paper reviews these studies. Section 4 discusses the co-benefits of climate mitigation policy in terms of human health to further strengthen the relevance of climate policy for health. This logically brings us to the next element of our study, namely, examining whether and to what extent behaviour can be changed in a desirable direction by providing information about such health impacts. For this purpose, Section 5 reviews relevant behavioural studies and discusses communication strategies that can increase public support for climate policy. The final section concludes and offers suggestions for further research.

Climate change induces changes in the climate that amplify and increase the range and extent of health risks (Table I). Climate-related health risks can be either physical or non-physical (psychological or mental health). The first category can be divided into infectious and non-infectious illnesses. Infections strongly depend on climate conditions, such as temperature, rainfall and humidity. These in turn affect insect vectors that carry the pathogens transmitting infections like malaria, dengue and other infections. Diarrhoea and cholera are transmitted mainly through contaminated water (WHO, 2008). Furthermore, vector-borne diseases are extremely temperature sensitive. Rapid warming can have catastrophic implications for non-immune populations living in tropical areas (Sutherst, 2004). In addition, frequent or severe droughts, floods and storms due to climate change represent important mechanisms that increase the chances of being infected, as they make access to safe drinking water and sanitation systems difficult. This issue is of particular concern to developing countries in tropical and sub-tropical climate zones (Patz et al., 2005).

Climate change can also affect allergic respiratory diseases. Recently, Ziello et al. (2012) presented empirical evidence and suggested that anthropogenic rise of atmospheric CO₂ levels may be even more influential than temperature rise. Climate change has extended the period of seasonal growth of many flowering trees and grasses, both starting earlier and ending later than 10 or 20 years ago (WHO, 2013). This has caused an increase in the total amount of pollens in the air, contributing to a rise in the number of allergy cases.

Non-infectious health impacts include cardiovascular and respiratory diseases. Extreme heat and air pollution are important causes of these health risks, especially in urban areas of both developed and developing nations. These especially affect young and old people (WHO, 2013p. 40). Furthermore, more frequent and intense droughts, storms and floods due to climate change may damage sources of drinking water and destroy agricultural crops. All the more, such damages may increase food insecurity leading to malnutrition among more vulnerable populations in poor countries, notably in Africa where already 3.5 million die each year due to malnutrition (Black et al., 2008). On the basis of experiments, Myers et al. (2014) found that levels of zinc, iron and protein are likely to be reduced by up to 10 per cent in wheat and rice at expected CO₂ levels in the atmosphere by 2050. Zinc and iron are vital nutrients which contribute to the human immune system and the formation of haemoglobin (a protein in blood cells) which distributes oxygen throughout the human body. The study states that two billion people already suffer from dietary deficiencies in zinc and iron, representing a global health problem. Climate change will further add to such global health challenges.

Next, non-physical health impacts include immediate and long-term negative psychological health consequences that are generally difficult to quantify. This encompasses psychological disorders such as depression, post-traumatic stress and a reduction in cognitive functioning. They are especially triggered by extreme weather events and catastrophes, including droughts, floods and storms. Psychological disorders may produce prolonged human suffering which means they deserve serious attention in the assessment of climate change (Willox et al., 2013; Portier et al., 2010). The impact of climate change on armed conflict, though uncertain, can have profound impacts on psychological well-being. Based on modelling and scenario analysis of climate change, civil war and economy calibrated to sub-Saharan Africa, Devitt and Tol (2012) demonstrate that despite rapid economic growth in Africa, climate change and civil war are able to retain these African countries in poverty with a high probability, causing prolonged negative psychological implications. Another study in this vein (Gleditsch, 2012) assesses the likelihood of the relationship between increased food insecurity and water contamination, population displacement and a worst case scenario of civil conflict.

Next, we illustrate how various diseases become more common under various temperature scenarios. A series of reports produced by the World Bank (2012), entitled “Turn down the heat”, portrays the increased health risks under various temperature scenarios across different regions. Béguin et al. (2011) examined climate impacts on malaria under the IPCC’s A1B scenario of a 3.5°C world relative to pre-industrial levels. They estimate that the population at risk of contracting malaria in 2050 is over 200 million. Relative to pre-industrial levels, 2.5, 3.9, 4.1 and 5.4°C temperature rise scenarios show an annual mortality increase caused by heat in Europe between 60,000 and 165,000 by the 2080s, if there are no adaptation measures and physiological acclimatization (Ciscar et al., 2011). Malnutrition in sub-Sahara Africa is expected to increase by 25-90 per cent under warming of 1.2-1.9°C by 2050 compared to the present. Table I presents an overview of the different diseases, climate mechanisms involved and the regions most exposed to such diseases.

Certain groups are particularly vulnerable to the negative health effects of climate change, notably the elderly, children and those already predisposed to specific diseases. In addition, indigenous people, especially in Australia and the Arctic, are found to be very vulnerable because of their reliance on natural landscapes that are undergoing rapid change (Ford, 2012). Children suffer a large portion of the existing disease burden. There are various reasons for this. In comparison with adults, young children have a less effective heat adaptation capacity and a higher exposure to diseases, as they breathe more air, drink more water and eat more food per unit of body weight than adults. In addition, children spend more time outdoors, making them more susceptible to environmental risks (Landrigan, 2005). Moreover, children are expected to live longer than adults, so they are likely to live under future conditions affected by climate change (Landrigan and Garg, 2005). Of the estimated global disease burden attributable to climate change, 88 per cent concerns children aged under five years (Zhang et al., 2007). These figures are noticeably higher than the paediatric proportion of the total burden of diseases, which for children aged under five years is 5 per cent in high-income countries and 31 per cent in low- and medium-income counties (Sheffield and Landrigan, 2011).

Two closing remarks are in order. First, impacts of climate change on health follow different routes, e.g. through water, agriculture, ecosystems and insect vectors, such as that responsible for malaria (Piontek et al., 2013). This means that focusing on only one or a subset of these is likely to result in an underestimation of health impacts. Second, not all health impacts of climate change are negative. For example, climate change in countries with colder temperatures can lead to a reduction in cold-related stress diseases (Patz et al., 2005). Nevertheless, negative impacts are widely regarded to outweigh positive impacts.

Here, we consider the economic costs of health impacts of climate change. This will allow not only for gauging the economic relevance of them but also for a comparison with other climate induced impacts, and thus an assessment of the relative economic importance of health impacts. Here, we will look at how the three most commonly used economic models for assessing global damage costs of climate change have dealt with health impacts. These models are Framework for Uncertainty, Negotiation and Distribution (FUND) by Richard Tol; Dynamic Integrated Climate-Economy (DICE), and its regionally disaggregated version Regional Integrated Climate-Economy (RICE), by William Nordhaus; and Policy Analysis of the Greenhouse Effect (PAGE) by Chris Hope, which was used in the famous Stern (2006) review.

A number of specific studies have served as the basis for the assessment of health impacts by these models. Tol (2002) used data for vector-borne diseases from Martens et al. (1995, 1997), Martin and Lefebvre (1995) and Morita et al. (1994) and associated mortality figures from Murray and Lopez (1996). Martens et al. (1997) estimated the increase in the epidemic potential of malaria and dengue to be 12-27 per cent and of shistosomiasis 31-47 per cent. Martin and Lefebvre (1995) and Morita et al. (1994) suggested a close-to-linear relationship between global warming and malaria. RICE estimations in Nordhaus and Boyer (2006) used data from Murray and Lopez (1996) who provided global disease estimates for years of life lost (YLLs) and disability-adjusted life years (DALYs) lost. Climate-related diseases include malaria, a broad group of tropical diseases, dengue and diseases due to pollution. Murray and Lopez show YLLs due to climate change to be rather small in established market economies (0.63 per cent of YLLs) and to be large in sub-Saharan Africa (11.76 per cent of YLLs).

FUND (Tol, 2002) measures direct impacts on human health in a 1°C warming world. Basic health care and ability to purchase medicine are found to strongly correlate with vulnerability to vector-borne diseases. Regions that are seen to be affected the most are Latin America, Africa, South and South East Asia. Extrapolating mortality rates of cardiovascular and respiratory diseases from Martens (1998), Tol (2002) calculates that climate change may help to avoid nearly 2.5 million deaths in colder regions but can cause an additional million deaths in other regions. To compare the total impact between regions, Tol (2002) asserts that the positive impact on OECD countries does not exceed 4 per cent of their gross domestic product (GDP), while the negative effect on Central and Eastern Europe and other former Soviet Union countries exceeds 8 per cent of its GDP. Climate-related health impacts can be either positive or negative depending on the region and time scale one is looking at. Generally, poorer regions are affected negatively. As time progresses, the positive impacts on richer countries are seen to diminish and become predominantly negative.

DICE is a globally aggregated climate model that allows the weighing of costs and benefits to reduce GHG emissions (Nordhaus and Boyer, 1999). We could not find any information about DICE estimates on health-related damages of climate change. However, the related RICE-99 model, which calculates climate damages for eight world regions and provides explicit estimates of climate-related health damages. Diseases included were based on Murray and Lopez (1996). The RICE-99 estimates are for climate-related diseases in a 2.5°C warming world. Different regional vulnerabilities are reflected by variation in values of YLLs as a percentage of GDP. High market economies YLLs are valued at 0.04 per cent of GDP, India at 0.79 per cent of GDP and sub-Saharan Africa at 8.78 per cent of GDP. The impact on high-income countries is mostly through pollution effects on health rather than tropical diseases. Sub-Saharan Africa shows the highest vulnerability to climate change impacts on tropical diseases such as malaria and dengue, while this vulnerability is lower in India and other low income countries (Nordhaus and Boyer, 1999, p. 83). Health damages in a 2.5°C warming scenario were estimated to be 0.10 per cent of global output (of 1.50 per cent relative total damage) for output weighted and 0.56 per cent (of 1.88 per cent) for population weighted, as shown in Table II (Nordhaus and Boyer, 1999 p. 91)[²]. Countries with a lower GDP have a higher number of people distressed.

It should be noted that the separation of health impacts from other damage categories, as shown in Table II, is difficult. The reason is that several of the other categories, notably sea level rise, agriculture and catastrophes, also involve health impacts. In other words, the health impacts are likely to be considerably higher than the percentages mentioned in the table. If we consider the Population weighted percentages (the most relevant from an ethical perspective), we see that only catastrophic effects have a higher percentage than “health”. If one quarter or more of the catastrophic effects equals health (and mortality) impacts, then shifting these to the health category in the table would make this the largest percentage, that is, the most important damage category. This illustrates the relevance of health impacts of climate change[³].

The Stern (2006) Review used results from the PAGE 2002 model, which demonstrate climate-related health damages to be an important part of global climate change damage costs. The PAGE model allows for an integrated assessment of a wide range of risks and uncertainties, formalized through probabilities associated with a rise in temperature of 1°C to 5°C. Health impacts include vector-borne diseases, malnutrition and cardiovascular diseases, each linked to the particular temperature scenarios. For example, globally, a 1°C increase in temperature is calculated to cause 300,000 more people to die globally each year from climate-related diseases (mainly diarrhoea, malaria and malnutrition). A 3°C increase is estimated to cause 1 to 3 million more to die from malnutrition globally, while it exposes 40 to 60 million more people to malaria in Africa. Additionally, in a 4°C increase scenario, the number of people exposed to malaria goes up to 80 million. Moreover, a U-shaped curve in temperature is found for heat-related human mortality: a decrease in cold-related mortality especially for old people in cold regions and a sharp increase in mortality once human tolerance for high temperatures is exceeded (The Stern (2006) Review, p. 60).

Table III summarises the climate-related diseases included in the three mentioned economic models. Results from these models are difficult to compare because of distinct temperature scenarios used and different climate-related diseases included.

Effects on human health are not only restricted to the above-mentioned diseases but can further involve indirect consequences, such as changes in labour productivity and demand for health care. Bosello et al. (2006) examined such indirect impacts of climate change focusing on changes in morbidity and mortality due to cardiovascular and respiratory diseases, diarrhoea, malaria, dengue fever and schistosomiasis. They found that the indirect economic effects of climate-related health impacts follow the same pattern as direct impacts on health itself, being either positive or negative depending on the region, sector and time scale. For instance, climate-induced health impacts in 2050 were predicted to increase GDP by 0.08 per cent in richer countries (with on average relatively cold climates) and reduce GDP by 0.07 per cent in poorer regions.

A recent study by Heal and Park (2013) further underpins the unequal effects of higher temperatures between warmer countries (generally poorer) and colder countries (generally richer). It estimates that in a 1°C warmer world lower output per person results for countries with a relatively warm climate and a higher output for countries with a colder climate. Warmer countries tend to have a lower productivity and GDP in general, namely, 1.2 to 1.9 per cent for each degree Celsius of higher than average temperature (Dell et al., 2009). This adds to the fact that the economic impacts of climate impacts may be felt more strongly by the world’s poorest regions. Monetary valuation of mortality and morbidity in economic studies of climate change varies with income per capita. This has been criticized (Ackerman and Stanton, 2007). However, as stated in the footnote[¹], it is fair to say that this can be, and in some studies has been partly, corrected for by applying distributional (population based) weights (Table II). Other problems when estimating economic costs of health impacts of climate change include, next to lost productivity as discussed above, higher health care expenditure (Hutton, 2011), and the use of high discount rates which underestimates future welfare impacts including those associated with health effects.

There are a number of other studies that have measured the potential health impacts of climate change. A study for the 27 member states of the European Union (at the time) quantitatively estimated climate-related health impacts for 2011-2040 and 2071-2100 (Watkiss and Hunt, 2012). This covered temperature-related mortality effects, salmonellosis and mental health impacts of coastal flooding. Mortality costs for the second period can reach €100bn annually. Costs of Salmonellosis related to climate change are estimated at several hundreds of million € annually, and the cost of depression due to flooding is estimated to be €1.5bn annually. Aggregating climate change-induced health impacts on a global scale (McMichael et al., 2004) reveals the health impacts of climate change to be distributed very unevenly among regions. Estimated DALYs burdens per capita are several hundred times higher in poorer regions of Africa, parts of the Eastern Mediterranean region and South-East Asia than in Western Europe, North America and the more developed regions of the Western Pacific.

So far, we have been talking about the direct health impacts of climate change. If we were to implement serious climate policies, then as a result, we would create considerable (main) health benefits, namely, by avoiding such direct health impacts. In addition, it is widely recognized that action on reducing GHG emissions can generate various co-benefits including for human health (McCollum et al., 2013; McCollum and David, 2011; Bell et al., 2008). In a thorough overview of co-benefits, Smith (2013) identifies three major categories, namely, cleaner air, cleaner and safer energy and energy security. Each of these involves health-related benefits. In fact, health is often seen as a main aspect of co-benefits that stem from climate mitigation policy (Olsthoorn et al., 1999).

In the case of cleaner air, less fossil fuel use to reduce CO₂ emissions will at the same time reduce emissions of fine particles, sulphur dioxide and nitrogen dioxides (the latter two causing acid rain), ozone-forming volatile organic compounds and others like toxic heavy metals and dioxins and carcinogenic polycyclic aromatic hydrocarbons. All of these have moderate to severe health implications. In the case of cleaner and safer energy, less reliance on fossil fuels will generate various health-related benefits, especially related to less coal mining (such as less water pollution, fewer accidents and lower propensity of cancer) (West et al., 2006). The third category of co-benefits associated with energy security involves improved health conditions for isolated communities or villages (notably in developing countries) through access to renewable energy (Dudek et al., 2003; van Vuuren et al., 2003).

This does not exhaust all the health-related co-benefits of climate mitigation policy. Other examples are found in relation to transport and low-carbon lifestyles. For transport, climate policies might stimulate less use of motorized transport – resulting in reduced congestion, noise and accidents – and more walking and cycling, directly contributing to a healthier life. In addition, other elements of a low-carbon lifestyle, such as eating less meat and less consumerism, notably in richer countries, will arguably contribute to a healthier life and improved psychological well-being (Howell, 2013).

For a fair and complete assessment, one should also take into account what one might call “health co-costs”, that is, the negative health impacts of renewable energy (e.g. noise from wind turbines) and of other alternatives of fossil fuels, such as nuclear energy (accidental leakage of radioactive substances) (Panwar et al., 2011). Estimating the health co-benefits and co-costs surely is not an easy task. Finally, rather than enjoying health-related co-benefits, there could be a conflict between climate mitigation goals and health aims. For example, gas or electric stoves could improve indoor air quality of households in developing countries that currently use coal, kerosene or traditional biofuels. However, such stoves could increase GHG emissions (Smith, 2013, p. 42).

The previous sections support the case that the health impacts of climate change deserve serious attention in policy and public debate on policy. Relatively few studies have examined public knowledge and perception of such impacts. Even fewer have studied the willingness to support climate policy by citizens using public health frames.

Public health officials in certain countries are aware of the mounting health threats associated with climate change (Akerlof et al., 2010). A survey among local health department directors in the USA found that almost 70 per cent of them believe that climate change will affect the health of members of their jurisdiction within the next 20 years (Maibach et al., 2008b). A survey among Ministries of Health in the British Commonwealth found that of the 31 responses –of a total of 53 commonwealth states – all were concerned about current or future health impacts of climate change, particularly on children and the elderly (Commonwealth Secretariat, 2009).

Findings of studies assessing public perception and understanding of global climate change show that health is more important for the public than environmental issues (Poortinga and Pidgeon, 2003; Bord et al., 2000). In addition, a worldwide survey found respondents to mention human health impacts of climate change as the most important category, followed by droughts and water shortages, species loss and extreme weather events (Leiserowitz, 2006). Moreover, some of these other categories often mentioned involve serious health impacts (except species loss).

Studies measuring the perception and knowledge of the human health threats of climate change on Canadian citizens reveal that although six in ten Canadians surveyed mentioned at least one potential health risk of climate change, few did so without being prompted (Environics Research Group, 2008, Berry et al., 2009). This indicates that health consequences of climate change can alter the urgency of climate policy in public opinion. Studies explicitly measuring the effect of human health frames generally found public engagement with climate change and policy to increase (Cardwell and Elliott, 2013; Maibach et al., 2010; DeBono et al., 2010; Myers et al., 2012). Maibach et al. (2010) was one of the first to carry out an exploratory study on public reactions of climate-related health impacts. This study builds upon an earlier study which used statistical (latent class) analysis to cluster individuals according to their knowledge, beliefs and attitude towards climate change into six groups, or audience segments as they call it (Leiserowitz et al., 2008): Alarmed (18 per cent), Concerned (33 per cent), Cautious (19 per cent), Disengaged (12 per cent), Doubtful (11 per cent) and Dismissive (7 per cent). The first two groups responded clearly positively to climate mitigation policy framed as a public health issue, while the Cautious, Disengaged and Dismissive groups showed a weaker but still positive response. The Doubtful group showed no clear response. Further analysis comparing how respondents reacted to the health benefits associated with mitigation policy and to the health threats associated with no policy showed that all groups responded more positively to the statements on health benefits. It should be noted that the results obtained did not take into account any “order effect”; that is, the influence on the results of respondents first reading about health threats and then about benefits. A follow-up study was conducted (Myers et al., 2012) based on the same six groups assigned to three experimental conditions emphasizing three different frames comparable with climate change: environmental risks, public health and national security. Its results show that for all groups, the public health frame triggered emotions in line with giving more support to climate policy.

A study by DeBono et al. (2010) for Malta indicates that the perception of climate change impacts like diseases, a reduced standard of living and potential deaths may well be the strongest driver of support for climate policy. Another study investigating options for dengue fever prevention in Trinidad and Tobago; and St Kitts and Nevis, concluded that health impacts of climate change can be used to increase the support for dengue prevention issues (Rawlins et al., 2007). Cardwell and Elliott (2013) seek to go beyond the perceived risk of climate change as a factor of behaviour by focusing on the facilitators and barriers – what they call it the attitude-action link – to understand behaviour change towards more support for climate mitigation. Health risks of climate change were not identified by respondents without being prompted. When asked about “global environmental change”, 77 per cent of the respondents mentioned health effects of possible impacts, such as air pollution, sunburn cancer, heat stress and natural disasters. This study reinforces the insight of earlier studies that the public perceives climate change as a temporally and spatially distant phenomenon, which explains the lack support given to climate policy (Leiserowitz, 2006; Bord et al., 1998). The previous studies all indicate that reframing the climate debate to one of public health has the potential to transform climate change into a current and local issue.

An important question is whether human health frames can change the opinion of sceptics on climate change and policy. In studying the effects of how one’s predispositions interact with characteristics of information in science messages, Hart and Nisbet (2012) found political beliefs and social identity to influence policy support more than scientific knowledge about global warming. Respondents were asked to identify themselves as a Democrat or Republican supporter and were presented scenarios of potential victims of climate change to be either from their local area of upstate New York (so-called “low social distance identity cues”) or further away, such as the state of Georgia or France (“high social distance identity cues”). Results show support for climate policy among Republicans to become even lower under the first scenario, or as the authors put it to “boomerang” when presented with scenarios of those being affected by climate change to be socially distant. On the other hand, support improved under the second scenario. This suggests that communicating the health impacts of climate change as being personally relevant may trigger self-interested concerns in people who are sceptical about climate change which then might increase support for climate policy.

Using evidence from communication science and social marketing can help increase the relevance of public health concerns in climate debates. Frumkin and McMichael (2008) and Maibach et al. (2008a) found that communicating the health benefits instead of health threats increased support for climate policy. As Maibach et al. (2008a) have suggested, fear appeals are needed to motivate people to consider a problem worthwhile to solve and thus look for solutions. Others instead argue that fear messaging must be combined with tangible solutions (Witte and Allen, 2007). The reason is that people are likely to engage in actions they believe they can influence, known as perceived self-efficacy (Bandura, 1977). Otherwise, feelings of hopelessness or even anger can boomerang when communicating the negative elements of climate change, as observed by Myers et al. (2012) and Maibach et al. (2010). This is particularly important when communicating the health impacts of climate change, as its consequences, mostly negative, are already felt at a local level.

We are not making quick enough progress towards an international climate agreement needed to reach safe concentrations of GHGs in the atmosphere. The reason is that public support for serious climate policy is still weak, despite all available evidence on climate change and its consequences. This article has examined whether emphasizing the human health impacts of climate change, or the (main and co) health benefits of climate policy, is warranted, and whether this can increase public support for climate mitigation policy.

Medical studies provide a firm basis for insights about the direct and indirect impacts of health as a consequence of climate change. Floods, droughts, storms, heat waves and more variation in humidity and precipitation are important climate mechanisms that induce negative health impacts. This involves infectious and non-infectious diseases as well as psychological disorders, lower labour productivity and, in the worst case scenarios, injury and death due to catastrophes and civil conflict induced by climate change. Health effects will be particularly detrimental for the poorer regions of the world where many people already lack proper access to health care. Moreover, a large portion of the global climate-related disease burden will fall, and already falls, upon young children aged below five years.

Economic studies have assessed climate-related health damages. This holds for influential economic model exercises, such as with FUND, RICE and PAGE. They reveal significant health damage costs in a world of higher global temperatures. We have argued that these costs are in fact higher than model results as commonly presented indicate because several health impacts are hidden in other cost categories, namely, sea-level rise, agricultural/food impacts and catastrophes such as extreme weather events. Moreover, indirect impacts of climate change on labour productivity and demand for health care are expected to be substantial but have not been specifically addressed in these model studies. Hence, they tend to underestimate the true health damages. Other economic assessments of the costs of climate-related health impacts provide further support for considerable health costs of climate change.

We touched briefly on the health co-benefits of climate mitigation policy. These include three types, namely, cleaner air, cleaner and safer energy and energy security. Health benefits due to a reduction of local pollutants associated with CO₂ emissions are especially important to developing countries while also relevant to developed countries. In addition, low-carbon lifestyles such as choosing alternatives to motorized transport, eating less meat and even consuming less, can contribute to improved human health. It is good to note that climate mitigation policy does not only produce health co-benefits but also “health co-costs”. For example, renewable energy and alternatives to fossil fuels like nuclear power can cause particular harmful effects on human health, such as noise, visibility losses or harmful radiation. To ensure an unbiased and fair assessment of climate mitigation policy, both co-benefits and “co-costs” should be considered. Moreover, potential conflicts between climate mitigation goals and health benefits should not be ignored as seen in the case of using gas or electric stoves instead of fuelwood (biomass), which improves air quality and human health but simultaneously may result in higher CO₂ emissions. All in all, accounting more explicitly for the various health impacts of climate change in climate debates will lead to a more balanced perspective on the importance and effectiveness of climate policy.

Behavioural studies portray an increase in public engagement with climate policy when health frames are used. This is found for various groups of people who have different opinions and beliefs about the importance and urgency of climate policy. Given the few studies available, it is not possible to draw very general conclusions yet, also as studies have produced distinct results on certain issues. For instance, some studies find climate change sceptics to respond more positively to climate policy when public health frames are used, while others show the opposite effect. The latter finding may relate to the fact that such sceptics tend to view those being affected by climate change as socially distant to them. In addition, studies suggest that emphasizing threats of, versus benefits of avoiding, health-related impacts of climate change generates different responses, which suggests that the way of communicating information is relevant.

Available natural science, medical and economic studies warrant giving the health consequences of climate change more attention in public debate. Behavioural studies imply the potential for the health impacts of climate change to spur support for climate policy, depending on the way it is communicated. For informed decision-making, further research is needed to determine the specific factors that play a role in potentially translating health information into action or policy support, particularly for people showing disinterest, an unclear opinion or scepticism regarding climate change. Relevant stakeholders in the decision-making community, such as national governments, municipalities, the private sector and civil society, will benefit from understanding better the implications of the human health impacts of climate change. This includes information about medical insights, the types of health impacts and the associated economic costs.

This study suggests that giving more attention to the human health consequences of climate change in public debate may further help to overcome the “issue fatigue” that currently characterizes public opinion on climate change. More research is needed on the exact health costs of climate change and on how to best communicate these to a wider public.

The authors would like to declare no conflicts of interests. The authors are grateful to Stefan Drews and two anonymous referees for their useful comments.