The decade 2000-2009 is the warmest on record, says NASA.
According to NASA's Goddard Institute for Space Studies (GISS) , the decade January 2000 to December 2009 was the warmest on record. 2005 was the warmest year, while 2009 came in second in a tie with four more years (2002, 2003, 2006 & 2007) in the same decade. However, in 2009 the Southern Hemisphere was the warmest, since 1880, when temperatures were recorded for the first time.
GISS director James Hansen said, "There's always interest in the annual numbers and a given year's ranking, but the ranking often misses the point. There's substantial year-to-year variability of global temperature caused by the tropical El-Niño-La Niña cycle. When we average temperature over five or ten years to minimize the variability, we find that global warming is continuing unabated."
Though 2008 was the coolest year in the decade due to the La Niña event over the Pacific Ocean, warm temperatures made a comeback in 2009. "Of course, the contiguous 48 states cover only 1.5 per cent of the world area, so the US temperature does not affect the global temperature much," Hansen said. Though the winter may have been colder in the United States, China and Europe, the Southern Hemisphere and the Arctic remained notably warm.
Climatologists have recently emphasized on the importance of understanding the difference between weather, i.e. day-to-day local events, and climate, i.e. long term global trends. According to NASA, the average global temperatures have been seeing a rise by 0.2 °C or 0.36 °F in the past three decades. In entirety, an increase by about 0.8 °C or 1.5 °F was seen in the average global temperatures since 1880.
The analysis was based on data sourced from meteorological stations around the world, satellite observations and Antarctica research station, NASA said.