2A. Global Surface Temperature Trends
The global average surface temperature fluctuates over time, but recently it has increased dramatically. From 1920 to the present, the earth’s average surface temperature has increased by 1.4 °F. According to the National Academy of Sciences, this change is the largest global temperature rise in at least the last 2,000 years and, possibly, the last 5,000 years.
The sharpest rise occurred between 1975 and 2005, when temperature rose steadily by about 1 °F. To see the relationship between surface temperature and the concentration of CO2 in the atmosphere, go to figure 2B.
