On January 16, 2008, Dr. James Hansen of NASA’s Goddard Institute for Space Sciences (GISS) released the summation of temperature data for 2007 with apparently very little fanfare. Given the data collected by Dr. Hansen, the lack of fanfare itself might well be notable. But regardless, the data itself bears more public attention that it’s had.

2007 is now tied with 1998 as the second hottest year for global temperature in a century.

According to the the GISS 2007 summation press release online, all eight of the hottest years for global temperature have been since 1998, and 14 of the hottest years have been since 1990. The global temperature map (shown in image above – larger version available), the Arctic and Siberia had the greatest temperature increase, between 3 and 4 degrees Celsius. This heating was responsible for, or a direct result of, the smallest Arctic ice cap since records have been kept.

If you look closely at the eastern Pacific ocean in that map, though, you’ll notice a horizontal strip of blue right about the equator, indicating a strip of cooling. The 1998 temperature spike was caused by one of the hotter and bigger El NiÃ±os recorded – 2007 was as hot even though the Pacific Ocean had a La NiÃ±a cooling event instead. Not only that, but in 1998, total solar output was on its way up toward its solar maximum (a result of the solar sunspot cycle) instead of being pretty much at minimum solar irradiance (for this solar cycle) in 2007.

In other words, we had the second hottest year in the last century even though the sun’s output was low and the Pacific had a cooling La NiÃ±a event. Any bets what will happen in the next 5 years or so as the solar irradiance goes up, we have our next El NiÃ±o, and while greenhouse gas concentrations continue increasing?

Global heating skeptics said last year that the earth had already started cooling down – the data doesn’t support this conclusion. Skeptics have also said this year that the unusually cool January put the lie into global heating – given that 2007 was so hot even though there were cooling events, the data suggests that a cooler 2008 is entirely reasonable and even expected. And it’s not like a single year, or even two or 5 years of below average temperatures negate the fact that, as the image above shows, there has been a 30-year heating trend globally.