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Home » Climate Change (2001) » Level 2 » Question 8
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2013 IPCC Assessment Report on Climate Change

Climate Change 2001 Assessment

8. Do man-made greenhouse gases matter compared to water vapor?

  • 8.1 How do gases affect the earth's temperature?
  • 8.2 What is the human contribution?
  • 8.3 How could water vapor amplify global warming?
  • 8.4 What is the role of clouds?

8.1 How do gases affect the earth's temperature?

The earth's surface temperature would be about 34°C (61°F) colder than it is now if it were not for the natural heat trapping effect of greenhouse gases like carbon dioxide, methane, nitrous oxide, and, the most important one, water vapor. More...

8.2 What is the human contribution?

Greenhouse gases concentrations have been stable over the past 10 000 years until several of them started increasing with industrialization. Without control measures, these man-made gases are expected to produce over the next 50 to 100 years a heat-trapping effect equivalent to more than a doubling of the pre-industrial carbon dioxide level. More...

8.3 How could water vapor amplify global warming?

Warmer air contains more water vapor. Since water vapor is itself a greenhouse gas, global warming could be further enhanced by the increased amounts of water vapor. More...

8.4 What is the role of clouds?

Clouds affect the heat balance of the Earth by reflecting sunlight (a cooling effect) and trapping infrared radiation (a heating effect). Their response to global warming remains a major uncertainty in determining the magnitude and distribution of climate change. More...


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