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Climate change


Key impacts: Human health, economic impacts, and impacts for North America

Human Health

Climate change poses serious risks to human health.  According to the Intergovernmental Panel on Climate Change (IPCC), global warming is expected to increase the risk of illness and death due to poorer air quality, increased urban heat waves, disease, and extreme weather-related events. Some effects of climate change upon human health may be positive. For example, studies in temperate areas have shown that climate change is projected to bring some benefits, such as fewer deaths from cold exposure. But the balance of positive and negative health impacts will vary from one location to another, and it is expected that these benefits will be outweighed by the negative health effects of rising temperatures worldwide.


Deer ticks can carry Lyme disease, and incidents of Lyme disease in North America are spreading as temperatures warm. Image: Scott Bauer/USDA

The IPCC predicts that climate change will affect the health of millions of people worldwide in a number of ways. For example, warmer temperatures may increase the risk of mosquito-borne diseases such as Malaria and West Nile Virus. According to Harvard Medical School’s

“Climate Change Futures” report, Lyme disease is the most widespread vector-borne diseases in the US, and it is spreading in North America as winters warm. Continued warming is likely to increase the suitable range for deer ticks that can carry the disease.

Health risks also occur from decreases in air quality, especially in urban environments. For example, increased ozone levels and allergens may lead to higher incidence of asthma and other respiratory ailments. Also, extreme weather events like heat waves will likely increase mortality rates. In its most recent report, the IPCC lists a number of health-related concerns from climate change, including: increases in malnutrition; increased deaths, disease and injury due to heat waves, floods, storms, fires, and droughts; increased frequency of cardio respiratory diseases due to higher concentrations of ground-level ozone; altered spatial distribution of some infectious disease vectors; and increased burden of diarrhoeal disease. Although all are at risk, the elderly, chronically sick, very young and socially-isolated are most vulnerable.



According to the IPCC, the economic impacts of climate change will vary regionally, but, aggregated and discounted to the present, they are very likely to impose net annual costs which will increase over time as global temperatures rise. In fact, it is very likely that all regions will experience either declines in net benefits or increases in net costs for increases in temperature greater than about 2-3oC. For the most detailed discussion to date on the possible global economic impacts of climate change, see the Stern Review on the Economics of Climate Change.

Deer ticks can carry Lyme disease.


Projected Impacts on North America:

In its most recent assessment report, the IPCC lists a number of broad projected impacts on North America from continued climate change and global warming. As discussed in the human health section, heat waves are projected to increase in number, intensity, and duration.


The IPCC figure above shows that average temperatures in North America are on the rise. What impacts will increased temperatures bring?

Warming in western mountains is projected to impact freshwater resources by causing decreased snowpack, more winter flooding, and reduced summer flows, thereby exacerbating competition for already over-allocated water resources. Disturbances from pests, diseases and fire will increasingly impact forests, resulting in an extended period of high fire risk and larger areas burned. Although moderate climate change in the early decades of the century is projected to increase aggregate yields of rain-fed agriculture by 5-20%, major challenges will exist for farmers who plant crops that are near the warm end of their suitable range or which depend on highly utilized water resources.



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