Thursday, May 7, 2009



The Earth's climate changes in response to external forcings, including changes in greenhouse gas concentrations, variations in Earth's orbit around the Sun,changes in solar luminosity, and volcanic eruptions. The thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels a further warming of about 0.5 °C (0.9 °F) would still occur.

Global dimming, a gradual reduction in the amount of global direct irradiance at the Earth's surface, may have partially counteracted global warming during the period 1960-1990. Human-caused aerosols likely precipitated this effect. Scientists have stated with 66–90% confidence that the effects of human-caused aerosols, along with volcanic activity, have offset some of the warming effect of increasing greenhouse gases.

Ozone depletion, the steady decline in the total amount of ozone in Earth's stratosphere, is sometimes cited in relation to global warming. Although there are a few areas of linkage the relationship between the two is not strong.

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