Changes

Average [[Earth]] surface air temperature has risen about 1° F since 1970.  

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&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> 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; however, it seems unlikely that this effect has a significant, or even moderate effect on the statistics quoted by environmentalists<ref>http://gristmill.grist.org/story/2006/10/26/224634/48</ref>. Spurious warming trends that might be considered as global warming can occur almost anywhere. <ref name="col">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&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> Studies have ruled out the possibility that errors in the measurements and sampling significantly affect the temperature trends detected over the past century. This accounts for spatial errors in the sampling and thus also incorporates errors associated with the urban-heating effect. According to Karl et al. (1993) ''"Results imply that the errors associated with century-scale trends of temperature are probably an order of magnitude smaller than the observed global warming of nearly 0.5°C per 100 years since the late nineteenth century"'' <ref>http://adsabs.harvard.edu/abs/1994JCli....7.1144K</ref>

 

According to temperature reconstruction made within an [[Old Earth]] paradigm, there have been many cycles of naturally-caused global warming and cooling over many millions of years (see [[climate cycles]]). Some scientists, including [[Richard Lindzen]] of [[MIT]], [[Sallie Baliunas]] of [[Harvard]] and [[Fred Singer]] (independent), say that the recent warming could be part of another natural cycle or random fluctuations in the atmosphere. However, many scientists also think that human activities were most likely the cause of the the planet's recent warming.{{cn}}

According to temperature reconstruction made within an [[Old Earth]] paradigm, there have been many cycles of naturally-caused global warming and cooling over many millions of years (see [[climate cycles]]). Some scientists, including [[Richard Lindzen]] of [[MIT]], [[Sallie Baliunas]] of [[Harvard]] and [[Fred Singer]] (independent), say that the recent warming could be part of another natural cycle or random fluctuations in the atmosphere. However, many scientists also think that human activities were most likely the cause of the the planet's recent warming.{{cn}}