Changes

<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." http://data.giss.nasa.gov/gistemp/2005/</ref>

<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." http://data.giss.nasa.gov/gistemp/2005/</ref>

Scientists such as [[Richard Lindzen]] of [[MIT]], [[Sallie Baliunas]] of [[Harvard]] and [[Fred Singer]] (independent) say that the patterns of global warming are naturally caused (see [[climate cycles]]).

Scientists such as [[Richard Lindzen]] of [[MIT]], [[Sallie Baliunas]] of [[Harvard]] and [[Fred Singer]] (independent) have made claims that the patterns of global warming are naturally caused (see [[climate cycles]]).

Assessments by the [[United Nations]] promote the world view that the warming since around 1850 is mostly human-caused.

Assessments by the [[United Nations]] support the consensus of scientists with the view that the warming since around 1850 is mostly human-caused.

In February, 2007, the [[Intergovernmental Panel on Climate Change]], a body of climate change scientists<ref>http://www.chicagotribune.com/news/nationworld/chi-0704280477apr29,1,4275902.story?coll=chi-newsnationworld-hed</ref> established by the [[United Nations]], released their fourth assessment report on climate change. That report concluded that recent global climate change was "very likely" caused by human activity, <ref>http://news.bbc.co.uk/2/hi/science/nature/6321351.stm</ref>.

In February, 2007, the [[Intergovernmental Panel on Climate Change]], a body of climate change scientists<ref>http://www.chicagotribune.com/news/nationworld/chi-0704280477apr29,1,4275902.story?coll=chi-newsnationworld-hed</ref> established by the [[United Nations]], released their fourth assessment report on climate change. That report concluded that recent global climate change was "very likely" (90-95%) caused by human activity, <ref>http://news.bbc.co.uk/2/hi/science/nature/6321351.stm</ref>.

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.

==Natural variability of the climate system==

==Natural variability of the climate system==

Secular scientists think that the Earth has experienced numerous [[Ice Age|ice age]]s over two million years, during which global temperatures dropped approximately 6 degrees Celsius and then returned to normal. The frigid temperatures allowed ice sheets to expand southward, covering much of [[Asia]], [[Europe]], and [[North America]]. The cooling associated with ice ages is gradual, while the terminations are relatively rapid. However, even the rapid terminations of ice ages take centuries to millennia.

Secular scientists think that the Earth has experienced numerous [[Ice Age|ice age]]s over two million years, during which global temperatures dropped approximately 6 degrees Celsius and then returned to normal. The frigid temperatures allowed ice sheets to expand southward, covering much of [[Asia]], [[Europe]], and [[North America]]. The cooling associated with ice ages is gradual, while the terminations are relatively rapid. However, even the rapid terminations of ice ages take centuries to millennia, as opposed to the speed with which global warming is happening.

==Global Warming on other Planets==

==Global Warming on other Planets==

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'')

have claimed that scientists are 90% sure that over 50% of the observed global warming in recent decades is human-caused, and that continued global warming should be expected over at lease the next century. Science published a literature search by Naomi Oreskes concluding that "scientific consensus" supports the IPCC reports. <ref>http://www.sciencemag.org/cgi/content/full/306/5702/1686]</ref>

have claimed that scientists are 90% sure that over 50% of the observed global warming in recent decades is human-caused, and that continued global warming should be expected over at least the next century. Science published a literature search by Naomi Oreskes concluding that "scientific consensus" supports the IPCC reports. <ref>http://www.sciencemag.org/cgi/content/full/306/5702/1686]</ref>

Several prominent scientists have pointed out the [[politicized science]] of the UN's assessment methods. The scientific reports are submitted to a panel of representatives appointed by each country in the IPCC. Several scientists have complained about their work being misrepresented by the U.N.

Several prominent scientists have pointed out the [[politicized science]] of the UN's assessment methods. The scientific reports are submitted to a panel of representatives appointed by each country in the IPCC. Several scientists have complained about their work being misrepresented by the U.N.