Science —


NOAA has now analyzed the last year's temperature data, and found that 2010 …


NOAA has released its annual State of the Climate report for the year 2010, and it goes down in the record books as another hot one, in a statistical tie with 2005 as the warmest year on record. But what's most striking about this past year's data is how it fits into the larger trend. The list of the 10 warmest years since NOAA's records started now features nine years from the last decade, and we haven't seen a year with temperatures below the 20th century average since 1976.

NOAA has a temperature record that goes back to 1880, and calculates the annual results relative to the average temperature in the 20th century. By this measure, 2010's global mean surface temperature is 0.62°C (1.12°F) above the previous century's average. That places it in a tie with 2005 as the warmest year NOAA has recorded. The Northern Hemisphere experienced its warmest year on record, while land areas (which more people are likely to perceive as the temperature) tied with the same year as the second warmest on record. By any measure, it was an unusually hot year, despite the winter chills that struck many areas in December.

This came even as the major driver of short-term variability, the El Niño-Southern Oscillation, experienced a mixed year. The equatorial Pacific started the year in its warm, El Niño state, which helped drive up global temperatures. But less than halfway through the year, it began to shift, and by July a cool, La Niña phase had started. This kept global temperatures down, and undoubtedly contributed to the fact that 2010 had to share its record.

We're now several decades into the current warming trend, and it seems safe to say that elevated temperatures have become the planet's new normal. Although there were only minor temperature differences among the years of the past decade, all the years were hot. Only 2008 failed to make it to the top-10 list of the warmest years in NOAA's records, bumped out by 1998, which remains in third place thanks to a strong El Niño. As mentioned above, It has now been 34 years since the last time the planet experienced an annual temperature that was below the 20th century average.

This data comes from a series of surface monitoring stations, but NOAA also tracks the temperature trends in the lower atmosphere using both satellites and balloon-based instruments. Since these records don't go back as far, the temperature differences are calculated relative to the 1971-2000 mean (balloon records start in 1958). That mean incorporates a number of very warm years, but 2010 was 0.78°C (1.40°F) above the mean, and the warmest year yet recorded. Satellite measurements still rank 1998 as the hottest, but 2010 comes in as a clear second.

Two different satellite records show atmospheric trends similar to those registered on the surface.

NOAA also notes that, in general, the trends apparent in surface, satellite, and balloon measurements are roughly in agreement, with the trend being about 0.15°C per decade since 1960.

In contrast, stratosphere temperatures continue to be low. NOAA ascribes this to two influences: the loss of ozone (a greenhouse gas) in the stratosphere, and the enhanced retention of heat in the lower atmosphere caused by rising greenhouse gasses there.

NOAA creates its temperature records using data that is entirely within the public domain, and has described the process by which it calculates its results.

UPDATE:  NASA agrees.

Latest Ars Video >

The Greatest Leap, Episode 3: Triumph


You must to comment.