While we’re thinking about global warming.

The National Snow and Ice Data Center has a tool which allows you to compare the extent of sea ice in any two years from 1978 to 2009.

Here are figures for sea ice in May of three different years:

1980 Southern Hemisphere = 9.5 million sq km
1980 Northern Hemisphere = 14.0 million sq km
Total = 23.5 million sq km

2008 Southern Hemisphere = 11.5 million sq km
2008 Northern Hemisphere = 13.2 million sq km
Total = 24.7 million sq km

2009 Southern Hemisphere = 11.4 million sq km
2009 Northern Hemisphere = 13.4 million sq km
Total = 24.8 million sq km