Call it the new normal. Last year was the ninth warmest on record across the globe, according to NASA’s annual analysis of surface temperatures. But by recent standards, it was nothing special: all but one of the hottest 10 years have happened since 2000.

The single exception – 1998 – was influenced by a very strong El Niño, in which warm water from the western Pacific spreads to the east, increasing the transfer of heat from the oceans to the atmosphere.

The global average figures from the annual analysis of surface temperatures, released today by NASA’s Goddard Institute for Space Studies in New York, tell only part of the story. Local and regional changes can be even more extreme.

Continental record


Although 2012 was not a record breaker in global terms, it was an extreme year for the Arctic and North America, with temperatures exceeding 3 °C above the average for NASA’s baseline period of 1951 to 1980.

Last week, the US National Oceanic and Atmospheric Administration announced that 2012 was the warmest year on record for the continental US.

NASA’s analysis confirms this conclusion. According to team leader James Hansen, an unusually warm spring dried out the soil across much of the country, leaving little moisture to moderate summer temperatures through evaporative cooling.

Still, the steady rise in global average temperature seems to have levelled off in the past few years. One reason may be that the El Niño conditions that prevailed in the first half of the decade gave way to La Niña, which reduces heat transfer from the oceans. If so, prepare for more record-breaking years when El Niño returns.