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NASA makes it official: 2000s were the hottest decade on record, 2009 tied for second warmest year

“In total, average global temperatures have increased by about 0.8°C (1.5°F) since 1880.”

“There’s a contradiction between the results shown here and popular perceptions about climate trends,” [NASA’s James] Hansen said. “In the last decade, global warming has not stopped.”

NASA Goddard Institute for Space Studies (GISS) released its final report on 2009 surface temperatures Thursday, concluding:

2009 was tied for the second warmest year in the modern record, a new NASA analysis of global surface temperature shows. The analysis, conducted by the Goddard Institute for Space Studies (GISS) in New York City, also shows that in the Southern Hemisphere, 2009 was the warmest year since modern records began in 1880….

January 2000 to December 2009 was the warmest decade on record. Throughout the last three decades, the GISS surface temperature record shows an upward trend of about 0.2°C (0.36°F) per decade.

This is especially impressive because we’re at “the deepest solar minimum in nearly a century.” The point is, notwithstanding the all-too-effective disinformation campaign of the anti-science crowd, it’s getting hotter “” thanks primarily to human emissions.

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I usually show the combined global temperature record, but the split figure above for the hemispheres is interesting for two reasons. First, we see that 2009 set the record for the southern hemisphere, which is dominated by water.

Second, the figure suggests one reason why Americans have softened their views on global warming in the face of a well funded disinformation campaign pushing the “global cooling” myth — and general lame media coverage on the subject. Both 2008 and 2009 were not close to record-breaking for temps in the northern hemisphere. And indeed, during those years, parts of North America saw relatively cool temperatures. GISS and Hansen comment on this very point in the report:

The near-record temperatures of 2009 occurred despite an unseasonably cool December in much of North America. High air pressures in the Arctic decreased the east-west flow of the jet stream, while also increasing its tendency to blow from north to south and draw cold air southward from the Arctic. This resulted in an unusual effect that caused frigid air from the Arctic to rush into North America and warmer mid-latitude air to shift toward the north.

“Of course, the contiguous 48 states cover only 1.5 percent of the world area, so the U.S. temperature does not affect the global temperature much,’ said Hansen.

In total, average global temperatures have increased by about 0.8°C (1.5°F) since 1880.

“That’s the important number to keep in mind,” said Gavin Schmidt, another GISS climatologist. “In contrast, the difference between, say, the second and sixth warmest years is trivial since the known uncertainty “” or noise “” in the temperature measurement is larger than some of the differences between the warmest years.”

You can see NASA scientist Gavin Schmidt’s official interview here and a NASA video here. Schmidt explains why NASA shows slightly higher temperatures than the Met Office:

NASA: Why does GISS get a different answer than the Met Office Hadley Centre [a UK climate research group that works jointly with the Climatic Research Unit at the University of East Anglia to perform an analysis of global temperatures]?

Schmidt: It’s mainly related to the way the weather station data is extrapolated. The Hadley Centre uses basically the same data sets as GISS, for example, but it doesn’t fill in large areas of the Arctic and Antarctic regions where fixed monitoring stations don’t exist. Instead of leaving those areas out from our analysis, you can use numbers from the nearest available stations, as long as they are within 1,200 kilometers. Overall, this gives the GISS product more complete coverage of the polar areas.

NASA: Some might hear the word “extrapolate” and conclude that you’re “making up” data. How would you reply to such criticism?

Schmidt:The assumption is simply that the Arctic Ocean as a whole is warming at the average of the stations around it. What people forget is that if you don’t put any values in for the areas where stations are sparse, then when you go to calculate the global mean, you’re actually assuming that the Arctic is warming at the same rate as the global mean. So, either way you are making an assumption.

Which one of those is the better assumption? Given all the changes we’ve observed in the Arctic sea ice with satellites, we believe it’s better to assume the Arctic Ocean is changing at the same rate as the other stations around the Arctic. That’s given GISS a slightly larger warming, particularly in the last couple of years, relative to the Hadley Centre.

Even the Met Office now admits it is low-balling actual warming (see Finally, the truth about the Hadley/CRU data: “The global temperature rise calculated by the Met Office’s HadCRUT record is at the lower end of likely warming”).

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