Much attention has recently been devoted to the environmental and economic effects of climate change. Much less attention, however, has been given to the possible effects of climate change, particularly global warming, on the health of the populations, particularly those from the poorest countries. This is a trend that requires prompt attention if the negative effects of climate change on health are to be avoided or minimized. According to some estimates, at least 1 in 6 people worldwide will suffer the consequences of climate change.

Climate change effects on health

The World Health Organization (WHO) estimates that global warming and rainfall changes cause the loss of at least 150,000 lives every year. This figure could increase significantly if current trends of climate change continue. The WHO also states that the risk of death and disease from climate change will at least double in the next 20 years. Paradoxically, the developing countries that have contributed the least to global warming are the most vulnerable to its negative consequences.

Global warming can affect the health of populations both directly and indirectly. Direct effects can result from heat-related deaths or weather-related disasters such as hurricanes and drought-related wildfires. Indirect effects can result from alterations in complex ecological processes such as changes in the patterns of infectious diseases, in the quantity and quality of domestic food production, and in alterations of potable water supplies. In India, experts predict that receding waters in the Ganges River could affect the lives of 400 million people.

Climate change could also alter the geographic distribution of disease vectors and thus alter the epidemiology of vector-transmitted diseases. Some diseases such as malaria, yellow fever, dengue and encephalitis, which are spread by insects, are sensitive to climatic conditions, since mosquitoes thrive in warmer climates. Other diseases, like cholera, are closely linked to the quality of potable water supplies, which can be seriously eroded by increasing rains, resulting in flooding and contamination by microorganisms.

In addition, prolonged heat waves will likely increase deaths from heart disease, since the cardiovascular system must work harder to keep the body cool. Because the elderly and the sick are more susceptible to the effects of extreme changes in temperature, heat waves will also pose health risks to those populations. A study commissioned by the American Association of Retired Persons (AARP) concluded that hospital admissions and emergency room visits for kidney failure, urinary tract infections and other health problems increase significantly for older adults during heat waves.

Climate change can also have serious effects on people’s mental health, since not only is their quality of life affected, but so is their survival. Climate change can provoke post-traumatic stress disorder (PTSD) anxiety, depression, an increased sense of helplessness, hopelessness and intense feelings of loss that can lead to alcoholism and substance abuse.

Additional effects of climate change

The integrity of the global environment is being increasingly compromised by the deterioration in the ozone layer and ever higher concentrations of the gases responsible for the greenhouse effect. It is believed that to the extent that these factors intensify, they will have serious effects on the health of the population. While some of these negative effects will be direct – for example the impact of rising temperatures on the people’s quality of life, or the rise in skin cancer resulting from the deterioration in the ozone layer — others will be indirect and probably even greater.

Some of these factors also have negative consequences for biodiversity, which will be one of the critical problems affecting humanity. Biodiversity is particularly important because of the role that many species play as sources of food and medicine.

Climate change effects on food production

Climate change will seriously affect food production, since many cereal crops can be affected by higher temperatures. This will have an effect not only on the amounts of food available but also on the economies of the countries affected.

Crop failures will provoke a higher death toll in poor countries, particularly amongst children, as a result of malnutrition. The Food and Agriculture Organization of the United Nations estimates that almost 800 million people in developing countries do not currently have enough to eat, a figure that is bound to increase substantially as a result of climate change.

Climate change and environmental refugees

Increased global warming could exacerbate the frequency and intensity of natural disasters and augment the risk of epidemics and, as a result, increase the number of “climate migrants” or “climate refugees.” While the range of consequences on people’s health is wide and their magnitude difficult to predict, children are amongst the most vulnerable to these changes. Since children constitute almost half of the population in many developing countries, such problems assume in them even greater significance.

Although human populations vary widely in their vulnerability to climatic change, one may reasonably predict that those particularly affected will be the poor and marginal populations that have less access to adequate emergency health services. In this regard, climate change will exacerbate the disparities between the rich and the poor throughout the world. Not only will the poor in developing countries be affected, but even the poor in industrialized societies.

Although nobody can anticipate with any certainty how climate change will affect human population distribution, current estimates vary between 25 million and one billion people by 2050. Norman Myers, of Oxford University, has tried to estimate the numbers of people who will be forced to migrate as a result of climate change. He argues, “When global warming takes hold, there could be as many as 200 million people overtaken by disruptions to monsoon systems and other rainfall patterns, by droughts of unprecedented severity and duration, and by sea-level rise and coastal flooding.”

Are there any benefits of climate change?

It is possible that climate change may bring some benefits, such as fewer deaths in winter in some climates, as well as increased food production in areas free from the rigors of cold weather. Matt Ridley, a British journalist and science writer argues that climate change has done more good than harm, and will continue to do so for the rest of the century. Among the benefits of global warming he includes fewer winter deaths; lower energy costs; better agricultural yields; probably fewer droughts and, at least in some areas, richer biodiversity. However, a careful assessment of its consequences shows that most of them are negative.

Costs of climate change

Climate change impacts negatively on social and environmental determinants of health, such as clean air, safe drinking water, nutritious food and safe shelter. The direct costs of health conditions (excluding costs in health-affecting sectors such as agriculture, and water and sanitation) is considerable, estimated by WHO to be between $2—4 billion dollars by 2030. That figure is considered an underestimate by some public health experts.

Although human populations vary widely in their vulnerability to climate change, one may reasonably predict that those particularly affected will be the poor and marginal populations who have less access to adequate health services to respond to emergencies. In this regard, climate change will exacerbate the existing disparities between the rich and the poor throughout the world. Not only will the poor in the developing countries be affected, but even those in industrialized societies.

Addressing climate change

According to The Lancet, climate change threatens to undermine the past 50 years of development gains in public health. However, an adequate response to climate change can bring immense benefits for human health, with cleaner air, healthier diets, more livable cities, and can reduce the risk factors of future infectious diseases. However, addressing the challenges of climate change requires more than resources and technology. Increased education, advocacy and the creation of legal frameworks to allow people and governments to be better-informed and make sustainable policy decisions. It is also important to develop risk-communication strategies — alerting about the dangers of inaction is necessary.

To avoid many of the negative health effects of climate change it is important to strengthen public health programs so that they can be used to monitor and treat the spread of infectious diseases, and respond more effectively to health emergencies. Climate change is a most serious health risk. Adequate policies are known; what is necessary is the political will to put them into action.