NOAA released "Re-Analyses of Historical Climate Data for Key Atmospheric Features: Implications for attribution of causes of observed change" in December 2008. According to the report, from 1951 to 2006 the yearly average temperature for North America increased by 1.6° Fahrenheit, with virtually all of the warmingsince 1970. During this period, the average temperature has warmed approximately 3.6 °F over Alaska, the Yukon Territories, Alberta, and Saskatchewan, but no significant warming occurred in the southern United States or eastern Canada. More than half of the warming of North America is likely (more than 66 percent chance) to have resulted from human activity.