Health effects of climate change.

HUMANS ARE NOW MAKING UNprecedented changes to the global environment. Economic development has been fostered by the use of fossil fuels but the accompanying accumulation of greenhouse gases, particularly carbon dioxide and methane, has implications for the world’s climate (BOX). Since the 1850s when temperature records began, the world has warmed by approximately 0.6°C, largely in the last 3 decades. The United Nations Intergovernmental Panel on Climate Change (IPCC) projects an increase of between 1.8°C and 5.8°C and an increase in sea levels between 9 and 88 cm during the next century. Warming is likely to be greater at the poles than at the equator. The residence time in the atmosphere of carbon dioxide exceeds 100 years; therefore, our actions affect the prospects of future generations. The IPCC concluded, “There is now good evidence that regional changes in climate, particularly increases in temperature, have already affected a diverse set of physical and biological systems in many parts of the world.” Earlier break-up of ice on rivers and lakes and movements of plant and animal ranges to higher altitudes are some examples. There is also potential for large-scale and potentially irreversible changes in Earth systems, such as slowing of the ocean circulation that transports warm water to the North Atlantic, large-scale melting of the Greenland and west Antarctic ice sheets, and accelerated global warming because of the positive feedbacks of the carbon cycle (eg, methane released from thawing arctic tundra). The probability of these events may be very low but is likely to be affected by the speed and duration of climate change. The potential pathways by which climate change may affect health are shown in the FIGURE.