The atmosphere acts just like a blanket around the Earth through the action of greenhouse gases, which absorb the sun's radiation: without them it would bounce off into space.
Higher concentrations of GHGs in the atmosphere mean that more solar energy is trapped, so raising the planet’s surface temperature.
Throughout the Earth's history there have been large changes in the concentrations of various greenhouse gases. These changes, particularly when they have happened over a relatively short period of time, have brought profound changes to all living things. The potential impact of the current rapid rise in GHG concentrations, which has happened since the Industrial Revolution, are a significant cause for concern.
Feedback processes can enhance the greenhouse effect, a striking example being the melting of the polar ice sheets. The reduced ice cover exposes a much darker surface (water or land), which in turn absorbs yet more heat, speeding the melting process still further. Click on the diagram to the right for a schematic view of the greenhouse effect.
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