Second warmest year on record
NASA recently released an article regarding temperature, weather, and global warming and cooling. The article, entitled, "2009: Second Warmest Year on Record; End of Warmest Decade", provides a rather detailed look at global warming trends due to several causes. From the article:
"'There’s always an interest in the annual temperature numbers and on a given year’s ranking, but usually that misses the point,' said James Hansen, the director of Goddard Institute for Space Studies (GISS). 'There's substantial year-to-year variability of global temperature caused by the tropical El Niño-La Niña cycle. But when we average temperature over five or ten years to minimize that variability, we find that global warming is continuing unabated.'"
While pretty technical, I found the article interesting; particularly the segment on "Decoding the Temperature Record."
"Climate scientists agree that rising levels of carbon dioxide and other greenhouse gases trap incoming heat near the surface of the Earth and are the key factors causing the rise in temperatures since 1880, but these gases are not the only factors that can impact global temperatures."
Three others key factors -- including changes in the sun’s irradiance, oscillations of sea surface temperature in the tropics, and changes in aerosol levels -- can also cause slight increases or decreases in the planet's temperature. Overall, the evidence suggests that these effects are not enough to account for the global warming observed since 1880."
You can also check out their Surface Temperature Analysis page to find (and customize in some instances) graphs and maps on temperature trends.