The Noughties were hotter than anything ever measured. Plus, according to NASA's latest analysis of global surface temperatures, 2009 was tied for the second warmest since 1880. In the Southern Hemisphere, it was the warmest year on record.
Apparently 2008 confused a lot of people. It was the coolest year of the decade because a strong La Nina was cooling the tropical Pacific Ocean. Via NASA:
"There's always interest in the annual temperature numbers and a given year's ranking, but the ranking often misses the point," says James Hansen, director of NASA's Goddard Institute for Space Studies. "There's substantial year-to-year variability of global temperature caused by the tropical El Nino-La Nina cycle. When we average temperature over five or ten years to minimize that variability, we find global warming is continuing unabated."
Modern monitoring began in 1880. A clear warming trend has been present ever since, although temps leveled off briefly between the 1940s and 1970s.
In the last three decades, the surface temps have increased ~0.36 degrees F (0.2 degrees C) per decade. In total, average global temperatures have increased by about 1.5 degrees F (0.8 degrees C) since 1880.
The year 2009 nearly busted the hottest-year-on-record record—despite an unusually cold December in much of North America. The conditions that made North America so cold however warmed the Arctic above normal. James Hansen explains via NASA:
"The contiguous 48 states cover only 1.5 percent of the world area, so the United States' temperature does not affect the global temperature much."
Too bad the United States' political temperature does affect global temperature so much. Between the Republican Senate win in Massachusetts, and today's Supreme Court ruling on corporate campaign funding, expect the Teens to get even hotter.