Harvard Men's Health Watch

Climate change and your health

The debate is over; nearly all scientists (and politicians) agree that climate change is real, is here, and is the result of human activity. Experts also agree that the consequences of global warming are serious and far reaching. All too often, though, these consequences are framed in terms of the threat to polar bears, exotic wildlife, and beautiful glaciers. Without minimizing the value of stately bears and snow-covered peaks, many people find it hard to make lifestyle changes and economic sacrifices to protect such distant assets. But climate change threatens more than the earth's vistas. It also threatens human health — and it's already causing problems here in the United States.

Our planetary greenhouse

Sunshine warms the earth. When solar radiation enters the atmosphere, a portion is bounced back into space, and another portion is absorbed by clouds and water vapor, but the majority strikes the planet's surface. This solar energy warms the earth, but it's also reflected back into the atmosphere in the form of infrared radiation. Some of the infrared penetrates through the atmosphere into space, but some bounces off atmospheric gases and heads back to earth, where it adds warmth (see figure).

The atmospheric gases that reflect infrared radiation back to earth are known as greenhouse gases. Without them, too much solar energy would be lost, and the earth would be ice cold. But since the industrial revolution, the concentration of atmospheric greenhouse gases has increased, and the increase has accelerated in the past 50 years. That means more infrared energy is reflected back to earth, where it produces global warming. Scientists report that the earth's temperature increased by 0.6° C (1.1° F) during the 20th century, and they project an additional rise by as much as 4.4° C (6.1° F) during this century.

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