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GLOBAL WARMING
CLIMATE MODELS
Scientists have studied global
warming with computer models of the climate. These models predict that
the net effect of adding greenhouse gases will be a warmer climate in
the future. However, even when the same assumptions of fossil fuel
consumption and CO2 emission are used, the amount of predicted warming
varies between models and there still remains a considerable range of
climate sensitivity.
Including model and future greenhouse gas uncertainty, the IPCC
anticipates a warming of 1.1 °C to 6.4 °C (2.0 °F to 11.5 °F) between
1990 and 2100. They have also been used to help investigate the causes
of recent climate change by comparing the observed changes to those that
the models predict from various natural and human derived forcing
factors.
Climate models can produce a good match to observations of global
temperature changes over the last century . These models do not
unambiguously attribute the warming that occurred from approximately
1910 to 1945 to either natural variation or human effects; however, they
suggest that the warming since 1975 is dominated by man-made greenhouse
gas emissions.
Most global climate models, when run to predict future climate, are
forced by imposed greenhouse gas scenarios, generally one from the IPCC
Special Report on Emissions Scenarios (SRES). Less commonly, models may
be run by adding a simulation of the carbon cycle; this generally shows
a positive feedback, though this response is uncertain (under the A2
SRES scenario, responses vary between an extra 20 and 200 ppm of CO2).
Some observational studies also show a positive feedback.
The representation of clouds is one of the main sources of uncertainty
in present-generation models, though progress is being made on this
problem. There is also an ongoing discussion as to whether climate
models are neglecting important indirect and feedback effects of solar
variability.
 
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Terminology
History of warming
Causes
Greenhouse gases in the atmosphere
Solar variation
Attributed and
expected effects
Mitigation
Kyoto Protocol
Climate models
Other related issues
Ocean acidification
Relationship to ozone depletion
Relationship to global dimming
Pre-human global warming
Pre-industrial global warming
References |
