Senate Democrats

The Cost of Inaction: The Impacts of Climate Change on Global Health

Climate change is affecting human health around the globe, with most of the severe impacts in low-income countries, which are the least able to adapt.  While most models suggest modest changes to human health over the next few decades, larger increases are expected by mid-century.  Climate change is predicted to increase malnutrition; the number of people affected by heatwaves, floods, storms, fires, and droughts; the burden of diarrheal diseases; and deaths associated with ground-level ozone.[1]

The World Health Organization (WHO) estimates that climatic changes caused more than 150,000 deaths due to diarrheal disease, malaria, malnutrition, flooding, and other effects in a single year (2000).[2]  Unfortunately, inaction from Bush Republicans on efforts to reduce greenhouse gas emissions has jeopardized the health of millions of people.  This Fact Sheet, the third in a series to be published by the Democratic Policy Committee, will highlight the cost that inaction on climate change is expected to have on global health.

Health Impacts

The WHO has conducted regional and global comparative risk assessments which quantify the impacts that climate change (and a range of other factors) are having on premature morbidity and mortality.  The study also estimated the benefit of interventions to remove or reduce these risk factors.  The WHO study estimated that climate change was responsible for the loss of over 150,000 lives and 5,500,000 disability adjusted life years in 2000.[3]

Heat waves.  The number of people suffering death and disease from heatwaves is expected to rise due to climate change.  Hot days, hot nights, and heatwaves have already become more frequent, and these heatwaves have been associated with short-term increases in mortality.  A heatwave in France during the summer of 2003 led to more than 14,800 deaths, (60 percent of those deaths occurred in persons aged 75 and over).  Belgium, the Czech Republic, Germany, Italy, Portugal, Spain, Switzerland, the Netherlands and the United Kingdom reported excess deaths during the same heatwave, with total mortalities of around 35,000.[4]

Recent studies show an overall increase of about 70 percent in the annual number of heatwave days for the Midwestern portion of the United States by the late 21st century, and these extreme days will be hotter on average than at present.  Another study predicted that the number of heat-related deaths in Los Angeles would increase two- to three-fold under a low greenhouse gas emission scenario and five- to seven- fold under a high emission scenario by 2070-2099.[5]

Floods.  Storm surges and rising sea levels from global warming are expected to lead to increased flooding around the world.  For example, in China in 2003, 130 million people were affected by floods.  In 1999, storms followed by floods and landslides killed 30,000 in Venezuela.  Areas with high incidence of infectious disease and poor sanitation infrastructure often experience increased rates of diarrheal diseases after flooding.  Water reservoirs may also become contaminated with dangerous chemicals, heavy metals, or other hazardaous substances following flooding.  For example, chemical contamination, and including oil spills from refineries and storage tanks, pesticides, metals and hazardous waste, occurred in the United States following Hurricane Katrina.[6]

Malnutrition.  For areas at lower latitudes, especially seasonally dry and tropical regions, crop productivity is expected to decrease as local temperatures rise.  A decrease in available crops would increase the risk of hunger, creating significant health problems for sub-Saharan Africa. The Fourth Assessment Report released by the Intergovernmental Panel on Climate Change (IPCC) found with high confidence that overall climate change increases the number of people at risk of hunger.  The IPCC report found that Climate change will probably increase the number of undernourished people to between 40 million and 170 million…  By 2080, about 75 percent of all people at risk of hunger are estimated to live in Sub-Saharan Africa.”[7]

Drought.  The loss of livelihoods from drought is a major trigger for population movements, specifically rural to urban migration.  Population displacement can lead to increases in communicable diseases resulting from overcrowding, and a lack of safe water, food and shelter.  Rural to urban migration has also been associated with increased transmission of HIV.[8]

Disease.  Several food and waterborne diseases are climate sensitive, suggesting that climate change may affect their incidence and distribution.  For example, studies report a correlation between temperature and common forms of foodborne diseases such as salmonellosis, so rising temperatures would increase the incidence of those diseases.

Despite improvements, childhood mortality due to diarrhea remains high in low-income countries, especially sub-Saharan Africa.  Overall, the effects of climate change on the burden of diarrheal diseases are expected to be negative.  For example, climate change is expected to increase the burden of diarrheal diseases in low-income areas by 2 to 5 percent in 2020. The range and incidence of cholera, an acute diarrheal infection, are affected by climate change.

Malaria is one of the most common infectious diseases and causes about one million child deaths annually.  Currently, 70 percent of all malaria cases are in Africa, and that percentage is expected to rise in the future.  Climate change is expected to have mixed effects on malaria, affecting both geographical range and incidence.  In some areas, the geographical range of infection will contract, while elsewhere it will expand.  The season during which transmission takes place may also evolve in response to climate change.

Dengue is a flu-like viral illness that is sensitive to climate, and is considered by some experts the world’s most important vector-borne viral disease.  It is transmitted by mosquitoes, and climate change effects are expected to increase the number of people at risk of dengue.  By the 2080s, climate change and population increase are expected to put 5 to 6 billion people at risk of dengue, compared with only 3.5 billion people if the climate does not change.[9]

Ozone.  Studies have also predicted that expected changes in climate will lead to an increase in deaths associated with ground-level ozone.  Ground-level ozone is naturally occurring and, as the primary constituent of man-made urban smog, is also a secondary pollutant formed in the presence of bright sunshine and high temperatures.  In urban areas, cars, buses, and other modes of transportation are the key sources of the pollutants that lead to ozone.  Concentrations of ozone are typically highest during the summer months because ozone formation is dependent on sunlight.  Summer ozone-related mortality is projected to increase by 4 percent in the New York area by the 2050s based on global warming-induced climatic changes alone.5

Fighting Climate Change

Co-benefits.  Reducing greenhouse gas emissions will prevent negative health impacts from climate change, but it will also have an immediately positive effect on human health due to air pollution.  The same fossil fuels that contribute to climate change also contribute to air pollution, and the heath co-benefits from cleaner air will offset some fraction of mitigation costs. Fine particle pollution from U.S. power plants, principally coal plants, cuts short the lives of nearly 24,000 people each year, including 2,800 from lung cancer.  Power plant pollution is also responsible for 38,200 non-fatal heart attacks per year, and tens of thousands of emergency room visits, hospitalizations, and lost work days.[10]  Reducing the amount of gasoline burned in major metropolitan areas will also improve the air breathed by millions of Americans and reduce respiratory illnesses.

Taking action.  A wide variety of policy options exist for reducing greenhouse gas emissions.  Implementing a cap-and-trade policy to control such emissions, for example, would promote energy efficiency and renewable energy development as alternatives to continuing to expand inefficient fossil fuel resource use.  Energy efficiency regulations would reduce demand for energy, and thus reduce consumption and emissions.  Tax incentives for advanced vehicles and renewable electricity production and technology development would result in substantially less emissions per unit of energy consumed.  All of these options would help to reduce greenhouse gas emissions and, therefore, the threat to human health from climate change.


[1] Confalonieri, U., Menne, B., et al. Climate Change 2007. Impacts, Adaptation, and Vulnerability. Contribution of Working Group II (WG II) to the Fourth Assessment Report (FAR) of the Intergovernmental Panel on Climate Change (IPCC).  Cambridge, England: Cambridge University Press; 2007. Chapter 8, page 393.  Available at

[2] Campbell-Lendrum, D., A. Pruss-Ustun and C. Corvalan, 2003: How much disease could climate change cause? Climate Change and Human Health: Risks and Responses, A. McMichael, D. Campbell-Lendrum, D. Corvalan, K. Ebi, A. Githeko, J. Scheraga and A. Woodward, Eds., WHO/WMO/UNEP, Geneva, 133-159.

[3] IPCC FAR WGII, Section 8.4 page 407

[4] IPCC FAR WGII, Section 8.2, pages 396-397.

[5] Testimony of Kristie L. Ebi to the U.S. Senate Committee on Health, Education, Labor, and Pensions.  April 10, 2008.

[6] IPCC FAR WGII, Section 8.2 page 398.

[7] IPCC FAR WGII, Section 5.8 pages 299-300.

[8] IPCC FAR WGII, Section 8.2 page 399.

[9] IPCC FAR WGII, Section page 408.

[10] ABT Associates “Dirty Air, Dirty Power” 2004