What are the top ten hottest years on record?

Answer 1

Scientists take the average temperature of the years from 1951 to 1980 as a baseline. Then they measure the anomaly, or the difference, between each year's average temperature and the baseline.

There are tiny differences between one year and the next. Many major organizations measure these differences, and their ranking may vary just slightly.

See the graph (Four Agencies...) at the link below.

1. 2010 (+1.13˚F higher than the baseline) and 2005
2. 2005 tied with 2010 as the two hottest years ever
3. 2009
4. 2007
5. 2006
6. 1998
7. 2002
8. 2003 The maximum difference between these six years is a mere 0.03°C (0.01˚F)
9. 2001
10. 1997

The differences between one year and the rest are not important. What is important to realize is that "average global temperatures have increased by about 0.8°C (1.5°F) since 1880" (NASA)

Worldwide, the top ten hottest years have all occurred since 1997. Check the animated world map link below (it takes a moment to download) and see how the hot spots increase in the last ten years.