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> 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>

<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 Karl et al. (1993) 'Global and Hemispheric Temperature Trends: Uncertainties Related to Inadequate Spatial Sampling' in Journal of Climate, 7(7); 1144 - 1168</ref>