This still image from an animation shows the temperature
anomalies that were present during 2007. Note the Arctic.
Source: NASA GISS
With January’s chill comes the season of the annual temperature scorecards for the home planet. Both the NASA Goddard Institute for Space Studies and the National Climate Data Center say 2007 delivered some of the warmest average temperatures on record for the globe and United States. Each agency produced slightly different results.
Was 2007 the second warmest year on record? Or the fifth? And what about the United States?
Here’s one answer, from the NCDC:
The average U.S. temperature for 2007 was 54.2 °F; 1.4 °F warmer than the 20th century mean of 52.8 °F. NCDC originally estimated in mid-December that 2007 would end as the eighth warmest on record, but below-average temperatures in areas of the country last month lowered the annual ranking.
For Alaska, 2007 was the 15th warmest year since statewide records began in 1918.
One thing’s for sure. The trend line has continued to lurch upward. For up, and for those of us at the high latitudes, where the sun never abandons June yet hardly shines in December, 2007 clearly was another sign that climate change continues its acceleration.
From the GISS story:
The greatest warming in 2007 occurred in the Arctic, and neighboring high latitude regions. Global warming has a larger affect in polar areas, as the loss of snow and ice leads to more open water, which absorbs more sunlight and warmth.
Snow and ice reflect sunlight; when they disappear, so too does their ability to deflect warming rays. The large Arctic warm anomaly of 2007 is consistent with observations of record low geographic extent of Arctic sea ice in September 2007.
Using temperatures gathered from land-based weather stations plus satellite measurements of sea ice since 1982 and data from ships for earlier years, the climate gurus at NASA caculated that 2007 tied with 1998 as the second warmest year in a century.
“It is unlikely that 2008 will be a year with truly exceptional global mean temperature,” said GISS director James Hansen. “Barring a large volcanic eruption, a record global temperature clearly exceeding that of 2005 can be expected within the next few years, at the time of the next El Nino, because of the background warming trend attributable to continuing increases of greenhouse gases.”
Here’s more discussion:
The eight warmest years in the GISS record have all occurred since 1998, and the 14 warmest years in the record have all occurred since 1990. …
In the contiguous 48 states, the statistical tie among 1934, 1998 and 2005 as the warmest year(s) was unchanged. In the current analysis, in the flawed analysis, and in the published GISS analysis, 1934 is the warmest year in the contiguous states (but not globally) by an amount (magnitude of the order of 0.01°C) that is an order of magnitude smaller than the certainty.
The NCDC, using a different mix of stations and methods, rated 2007 not quite as high on the scale, a detailed analysis posted on line this week. With the Northern land masses logging their warmest average temperatures on record, the home planet simmered to the fifth warmest. The United States registered 10th warmest.
An excerpt:
For 2007, the global land and ocean surface temperature was the fifth warmest on record. Separately, the global land surface temperature was warmest on record while the global ocean temperature was 9th warmest since records began in 1880. Some of the largest and most widespread warm anomalies occurred from eastern Europe to central Asia.
Including 2007, seven of the eight warmest years on record have occurred since 2001 and the 10 warmest years have all occurred since 1995. The global average surface temperature has risen between 0.6 °C and 0.7 °C since the start of the 20th century, and the rate of increase since 1976 has been approximately three times faster than the century-scale trend.
The greatest warming has taken place in high latitude regions of the Northern Hemisphere. Anomalous warmth in 2007 contributed to the lowest Arctic sea ice extent since satellite records began in 1979, surpassing the previous record low set in 2005 by a remarkable 23 percent.
According to the National Snow and Ice Data Center, this is part of a continuing trend in end-of-summer Arctic sea ice extent reductions of approximately 10 percent per decade since 1979.