Outline climate change and present arguments for and against the scientific evidence for global warming and its effects.


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Josh Bovill 18/06/09
Outline climate change and present arguments for and against the scientific evidence for
global warming and its effects.
Global warming is the increase in the average temperature of the Earth's nearsurface air and
oceans since the mid20th century and its projected continuation.
Global surface temperature increased during the last century.
The Intergovernmental Panel on Climate Change (IPCC) concludes that increasing
greenhouse gas concentrations resulting from human activity such as fossil fuel burning and
deforestation are responsible for most of the observed temperature increase since the middle
of the 20th century.
The IPCC also concludes that natural phenomena such as solar variation and volcanoes
produced most of the warming from preindustrial times to 1950 and had a small cooling
effect afterward.
These basic conclusions have been endorsed by more than 45 scientific societies and
academies of science, including all of the national academies of science of the major
industrialized countries.
Climate model projections summarized in the latest IPCC report indicate that the global
surface temperature will probably rise further during the twentyfirst century.
The uncertainty in this estimate arises from the use of models with differing sensitivity to
greenhouse gas concentrations and the use of differing estimates of future greenhouse gas
Some other uncertainties include how warming and related changes will vary from region to
region around the globe.
Most studies focus on the period up to 2100. However, warming is expected to continue
beyond 2100 even if emissions stop, because of the large heat capacity of the oceans and
the long lifetime of carbon dioxide in the atmosphere.
Increasing global temperature will cause sea levels to rise and will change the amount and
pattern of precipitation, probably including expansion of subtropical deserts.
The continuing retreat of glaciers, permafrost and sea ice is expected, with the Arctic region
being particularly affected.
Other likely effects include shrinkage of the Amazon rainforest and Boreal forests, increases
in the intensity of extreme weather events, species extinctions and changes in agricultural
Political and public debate continues regarding what actions (if any) to take in response to
global warming.
The available options are mitigation to reduce further emissions adaptation to reduce the
damage caused by warming and, more speculatively, geoengineering to reverse global
Most national governments have signed and ratified the Kyoto Protocol aimed at reducing
greenhouse gas emissions.
The Greenhouse Effect is the heating of the surface of a planet or moon due to the presence
of an atmosphere containing gases that absorb and emit infrared radiation.
Greenhouse gases, which include water vapor, carbon dioxide and methane, are almost
transparent to solar radiation but strongly absorb and emit infrared radiation. Thus,
greenhouse gases trap heat within the surfacetroposphere system.
This mechanism is fundamentally different from that of an actual greenhouse, which works by
isolating warm air inside the structure so that heat is not lost by convection. The greenhouse

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Josh Bovill 18/06/09
effect was discovered by Joseph Fourier in 1824, first reliably experimented on by John
Tyndall in 1858, and first reported quantitatively by Svante Arrhenius in 1896.
In the absence of the greenhouse effect and an atmosphere, the Earth's average surface
temperature of 14 °C could be as low as -18 °C, the black body temperature of the Earth.…read more

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Josh Bovill 18/06/09
a 17member team led by Ben Santer noted errors in the Douglass study, and found instead
that the models and observations were not statistically different.
Not all effects of global warming are accurately predicted by the climate models used by the
IPCC. For example, observed Arctic shrinkage has been faster than that predicted.…read more


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