Global warming

Global warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-twentieth century and its projected continuation.

The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the hundred years ending in 2005.[1] The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations"[1] via the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.[2][3] These basic conclusions have been endorsed by at least thirty scientific societies and academies of science,[4] including all of the national academies of science of the major industrialized countries.[5][6][7] While individual scientists have voiced disagreement with some findings of the IPCC,[8] the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.[9][10]

Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.[1] The range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.[1]

Increasing global temperature will cause sea level to rise, and is expected to increase the intensity of extreme weather events and to change the amount and pattern of precipitation. Other effects of global warming include changes in agricultural yields, trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors.

Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but there is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.

Controversy

For a more detailed treatment, see Global Warming Controversy.

Since 1989, advocates have clashed on the issue of whether human beings are more responsible than nature for modern periods of global warming; see "greenhouse warming" and global warming theory.

Most scientific support for the global warming theory rests on popular accounts such as Al Gore's An Inconvenient Truth or on reports issued by the UN's IPCC.

Politician Al Gore calls it a moral issue, while psuedo-scientist Richard Lindzen says, "It is probably the most immoral thing you could do to restrain energy so that the billions in the earth who don’t have access to electricity won't conveniently get it." However, it is to be noted that many proponents of the theory propose energy conservation only until 'green' energy generation becomes predominant.^{[Citation Needed]}

The termglobal warming can falsley be used for any upward trend in the global mean temperature, but it is mostly used to refer to the 1° F warming since 1850.

The two sides are divided on whether this warming is a natural recovery from the Little Ice Age or a man-made environmental phenomenon. There are also debates regarding the potential positive or negative effects of a warming.