The problem:.
Emissions of greenhouse gases have increased dramatically in the last century through fossil fuel burning and land-use changes. Human activity has pushed atmospheric concentrations of carbon dioxide to more than 30 percent above pre-industrial levels. These increases have already brought changes to the earth's climate. Nine of the ten hottest years since 1860 occurred between 1990 and 2000. .
According to the Intergovernmental Panel on Climate Change, without active efforts to reduce emissions, the planet is expected to warm by an unprecedented 2.5 to 10 degrees F during the 21st century. This rate of warming is much larger than the observed changes during the 20th century and is very likely to be without precedent during at least the last 10,000 years.
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Several kinds of health impacts from higher temperatures have been identified. The long term will see the spread of vector-borne infectious diseases that are particularly sensitive to changes in climate. More directly, the frequency of heat-related illness and death is expected to increase. Additional warming in urban areas would accelerate the formation of air pollutants such as smog (largely ozone). In sum, a sizable net increase in weather-related human mortality is expected if the climate warms as the models predict. Sea-level rise will threaten cities and countries worldwide, eroding barrier islands and virtually eliminating some island chains. .
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Continued warming would also lead to shifts in rainfall patterns as global precipitation increases. Unable to migrate fast enough to keep up with the changing climate, whole ecosystems would be lost. Because tropical storms such as hurricanes derive their energy from the oceans, there could be an increase in the number and intensity of such storms.
Distribution of resources between nations: .
While consumption has risen steadily worldwide, there remains a profound disparity between consumption levels in wealthy nations and those in middle-income and low-income nations.
