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GLOBAL WARMING
Global warming is the observed
increase in the average temperature of the Earth's atmosphere and oceans
in recent decades and its projected continuation. Models referenced by
the Intergovernmental Panel on Climate Change (IPCC) predict that global
temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F)
between 1990 and 2100. The uncertainty in this range results from two
factors: differing future greenhouse gas emission scenarios, and
uncertainties regarding climate sensitivity.
Global average near-surface atmospheric temperature rose 0.74 ± 0.18
°Celsius (1.3 ± 0.32 °Fahrenheit) in the last century. The prevailing
scientific opinion on climate change is that "most of the observed
increase in globally averaged temperatures since the mid-20th century is
very likely due to the observed increase in anthropogenic greenhouse gas
concentrations,"[1] which leads to warming of the surface and lower
atmosphere by increasing the greenhouse effect. Greenhouse gases are
released by activities such as the burning of fossil fuels, land
clearing, and agriculture. Other phenomena such as solar variation and
volcanoes have had smaller and probably negative effects 1950. A small
number of scientists disagree with regard to the nature of the observed
warming. Svante Arrhenius first predicted CO2-induced global warming in
1896.
An increase in global temperatures can in turn cause other changes,
including a rising sea level and changes in the amount and pattern of
precipitation. These changes may increase the frequency and intensity of
extreme weather events, such as floods, droughts, heat waves,
hurricanes, and tornados. Other consequences include higher or lower
agricultural yields, glacier retreat, reduced summer streamflows,
species extinctions and increases in the ranges of disease vectors.
Warming is expected to affect the number and magnitude of these events;
however, it is difficult to connect particular events to global warming.
Although most studies focus on the period up to 2100, even if no further
greenhouse gases were released after this date, warming (and sea level)
would be expected to continue to rise for more than a millennium, since
CO2 has a long average atmospheric lifetime.
Remaining scientific uncertainties include the exact degree of climate
change expected in the future, and especially how changes will vary from
region to region across the globe. A hotly contested political and
public debate also has yet to be resolved, regarding whether anything
should be done, and what could be cost-effectively done to reduce or
reverse future warming, or to deal with the expected consequences. Most
national governments have signed and ratified the Kyoto Protocol aimed
at combating global warming.
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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 |
