Changes

The '''global warming''' warming issue is a political battle over the science of climate change. Liberals and conservatives in the U.S. are evenly split on the issue: 75% of Democrats believe that the science supports the [[anthropogenic global warming]] theory, while only 23% of Republicans believe the science supports it.

The '''global warming''' warming issue is a political battle over the science of climate change. Liberals and conservatives in the U.S. are evenly split on the issue: 75% of Democrats believe that the science supports the [[anthropogenic global warming]] theory, while only 23% of Republicans believe the science supports it.

In the general, the term ''global warming'' can 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.

In the general, the term ''global warming'' can 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 benevolent and natural recovery from the [[Little Ice Age]] or a man-made "[[climate crisis]]" (see also [[runaway greenhouse effect]]).

The two sides are divided on whether this warming is a benevolent and natural recovery from the [[Little Ice Age]] or a man-made "[[climate crisis]]" (see also [[runaway greenhouse effect]]).

==The modern warm period==

==The modern warm period==

Average [[Earth]] surface air temperature has risen a little less than 1 °C since 1850.  

Average [[Earth]] surface air temperature has risen about 1° F since 1850.  

<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>

==Natural variability of the climate system==

==Natural variability of the climate system==

Evolutionary scientists who believe in global warming 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.

Evolutionary scientists who believe in global warming think that the Earth has experienced numerous [[Ice Age|ice age]]s over two million years, during which global temperatures dropped approximately 11° F 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.

==Global Warming on other Planets==

==Global Warming on other Planets==

Since the [[Viking spacecraft]] reached [[Mars]] in the 1970s until recent readings were taken, the average temperature on Mars has risen 1.1 degrees Fahrenheit just as the average temperature on the earth has risen.  Since human industrialization is clearly not to blame for the change on Mars, other causes are being considered.  One possibility is that dust storms are changing the albedo of the planet, allowing it to warm, while another possibility is that solar variations from the sun are causing the warming.<ref>http://www.space.com/scienceastronomy/070404_gw_mars.html</ref><ref>http://www.heartland.org/Article.cfm?artId=17977</ref>

Since the [[Viking spacecraft]] reached [[Mars]] in the 1970s until recent readings were taken, the average temperature on Mars has risen 1.1° F just as the average temperature on the earth has risen.  Since human industrialization is clearly not to blame for the change on Mars, other causes are being considered.  One possibility is that dust storms are changing the albedo of the planet, allowing it to warm, while another possibility is that solar variations from the sun are causing the warming.<ref>http://www.space.com/scienceastronomy/070404_gw_mars.html</ref><ref>http://www.heartland.org/Article.cfm?artId=17977</ref>

Recently, it has also been found that similar to the Earth and Mars, [[Neptune]] is also undergoing global warming.  Measurements taken at the Lowell observatory in [[Arizona]] have shown an increase in Neptune's brightness and temperature since 1980 following the same pattern seen on Earth and Mars.  The researchers who discovered this warming suggest there may be a correlation between the warming and solar variations.<ref>http://www.agu.org/pubs/crossref/2007.../2006GL028764.shtml</ref>

Recently, it has also been found that similar to the Earth and Mars, [[Neptune]] is also undergoing global warming.  Measurements taken at the Lowell observatory in [[Arizona]] have shown an increase in Neptune's brightness and temperature since 1980 following the same pattern seen on Earth and Mars.  The researchers who discovered this warming suggest there may be a correlation between the warming and solar variations.<ref>http://www.agu.org/pubs/crossref/2007.../2006GL028764.shtml</ref>

==Politics of global warming==

==Politics of global warming==

The global average surface temperature warmed about 0.5&nbsp;°C (0.9&nbsp;°F) over the second half of the 20th Century, 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 0.9&nbsp;°F over the second half of the 20th Century, 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'')