Changes

'''Global warming''' is the term ascribed to an increase in global average surface temperature. Average [[Earth]] surface air temperature has risen just over one degree since 1850.  

'''Global warming''' is the term ascribed to an increase in the [[global mean temperature]]. Average [[Earth]] surface air temperature has risen just over one degree 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>

==The Hockey Stick Reconstruction==

==The Hockey Stick Reconstruction==

[[Image:Hockey stick chart ipcc.jpg|right|thumb|300px|The Hockey stick graph as shown in the 2001 IPCC report.]]

[[Image:Hockey stick chart ipcc.jpg|right|thumb|300px|The Hockey stick graph as shown in the 2001 IPCC report.]]

One of the main arguments for anthropogenic global warming during the 3rd IPCC report was a temperature reconstruction done by climatologist Michael Mann.  The resulting graph of the [[global mean temperature]] is shaped like a hockey stick, and it is used as evidence for the unusualness of the earth's temperature in the past few decades.  However, Stephen McIntyre and economist Ross McKitrick later discovered serious flaw in the statistical methods used to construct the hockey stick graph.  Because of this, the 4th Assessment Report of the IPCC included several different temperature reconstruction methods instead of favoring just one hypothesis.

One of the main arguments for anthropogenic global warming during the 3rd IPCC report was a temperature reconstruction done by climatologist Michael Mann.  The resulting graph of the temperature is shaped like a hockey stick, and it is used as evidence for the unusualness of the earth's temperature in the past few decades.  However, Stephen McIntyre and economist Ross McKitrick later discovered serious flaw in the statistical methods used to construct the hockey stick graph.  Because of this, the 4th Assessment Report of the IPCC included several different temperature reconstruction methods instead of favoring just one hypothesis.

==Natural variability of the climate system==

==Natural variability of the climate system==