Warmest year on record for the southern hemisphere

Figures just released by NASA's Global Institute for Space Studies (GISS) show that 2009 was the warmest year on record for the southern hemisphere and the second equal warmest for the world as a whole.

NASA mathematician Reto Ruedy commented to Science magazine before the release of the final official figures that while United States may be experiencing one of the coldest winters in decades, but things continue to heat up in the Southern Hemisphere. Ruedy said Southern Hemisphere temperatures can serve as a trailing indicator of global warming given that that part of the globe is mostly water, which warms more slowly and with less variability than land. Ruedy says 2009 temperatures in the Southern Hemisphere were 0.49°C warmer than the period between 1951 and 1980, with an error of +/- 0.05°C.

Asked if indeed 2009 was the second hottest year on record world-wide, Ruedy said yes, and then quickly clarified that, given the error bars on the temperature record (see figure), it's really best to call it a 3-way tie with 1998 and 2007. In fact, he said, 2005 is "only marginally warmer than" the second hottest years."

This is especially impressive because we're at "the deepest solar minimum in nearly a century." Of 2009 being the warmest ever in the Southern Hemisphere he said:

That's significant because the second-warmest year, 1998, saw the most severe recorded instance in the 20th century of El Niño, a cyclic warming event in the tropical Pacific. During El Niño events, heat is redistributed from deep water to the surface, which raises ocean temperatures and has widespread climatic effects. But last year was an El Niño year of medium strength, which Ruedy says might mean that the warmer temperatures also show global, long-term warming as well as the regional trend.