Changes

Politicians who support the [[Kyoto Protocol]] have made the claim that there is a cause and effect relationship between increases in atmospheric concentrations of [[greenhouse gas]]es and air temperature.

Politicians who support the [[Kyoto Protocol]] have made the claim that there is a cause and effect relationship between increases in atmospheric concentrations of [[greenhouse gas]]es and air temperature.

Hansen's group at the Goddard Institute wrote, "Global warming is now 0.6°C [1.0°F] in the past three decades and 0.8°C [1.4°F]in the past century." <ref>http://data.giss.nasa.gov/gistemp/2005/</ref>

Hansen's group at the Goddard Institute wrote, "Global warming is now 0.6&nbsp;°C [1.0&nbsp;°F] in the past three decades and 0.8&nbsp;°C [1.4&nbsp;°F]in the past century." <ref>http://data.giss.nasa.gov/gistemp/2005/</ref>

==Natural variability of the climate system==

==Natural variability of the climate system==

==Politics of global warming==

==Politics of global warming==

The global average surface temperature warmed about 0.5°C (0.9°F) over the second half of the 20th Century,{{Fact-science}} and to some the warming appears to be related to increases in carbon dioxide and other greenhouse gases. The possibility of adverse consequences has become a major concern for environmentalists.

The global average surface temperature warmed about 0.5&nbsp;°C (0.9&nbsp;°F) over the second half of the 20th Century,{{Fact-science}} and to some the warming appears to be related to increases in carbon dioxide and other greenhouse gases. The possibility of adverse consequences has become a major concern for environmentalists.

Assessments of climate science by the United Nations (see [[IPCC]] - ''Intergovernmental Panel on Climate Change'')

Assessments of climate science by the United Nations (see [[IPCC]] - ''Intergovernmental Panel on Climate Change'')