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→The Modern Warm Period
==The Modern Warm Period==
==The Modern Warm Period==
[[Image:Artic 1979.jpg|left|thumb|275px|A computer projection comparing the Polar Ice Mass in 1979 (left) and 2000 (right).]]
[[Image:Artic 1979.jpg|left|thumb|275px|A computer projection comparing the Polar Ice Mass in 1979 (left) and 2000 (right).]]
Average [[Earth]] surface air temperature has risen about 1° F since 1850.
Average [[Earth]] surface air temperature has risen about 1° F since 1970.
<ref>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." http://data.giss.nasa.gov/gistemp/2005/</ref> How much of this is due to contamination of the temperature record from the [[urban heat island]] effect is hard to assess. Efforts are currently underway to detect and remove this bias. Spurious warming trends that might be considered as global warming can occur almost anywhere. <ref>http://climatesci.colorado.edu/2006/01/29/do-urban-areas-have-larger-long-term-temperature-trends-than-other-locations/feed/</ref>
<ref>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." http://data.giss.nasa.gov/gistemp/2005/</ref> How much of this is due to contamination of the temperature record from the [[urban heat island]] effect is hard to assess. Efforts are currently underway to detect and remove this bias. Spurious warming trends that might be considered as global warming can occur almost anywhere. <ref>http://climatesci.colorado.edu/2006/01/29/do-urban-areas-have-larger-long-term-temperature-trends-than-other-locations/feed/</ref>
Nonetheless, controversy has persisted over the influence of urban warming on reported large-scale surface-air temperature trends. <ref>http://climatesci.colorado.edu/2006/01/29/do-urban-areas-have-larger-long-term-temperature-trends-than-other-locations/feed/</ref>
Nonetheless, controversy has persisted over the influence of urban warming on reported large-scale surface-air temperature trends. <ref>http://climatesci.colorado.edu/2006/01/29/do-urban-areas-have-larger-long-term-temperature-trends-than-other-locations/feed/</ref>