As the rain in Southern California poured down, yesterday NASA's Goddard Institute for Space Studies, GISS, in New York announced that January 2000 to December 2009 was the warmest decade on record. But, West Orange County congressman Dana Rohrabacher, long known as a global warming skeptic, was incredulous and called the numbers “fraudulent”. A NASA spokesperson acknowledged the data come from a small sample of all monitoring stations, but they stick by their numbers.

While NASA reported 2009 was not quite the hottest year on record, and “2008 was the coolest year of the decade”, it pointed to the longer term trends as supporting the conclusion of global warming. "There's always interest in the annual temperature numbers and a given year's ranking, but the ranking often misses the point," said James Hansen, GISS director. "There's substantial year-to-year variability of global temperature caused by the tropical El Nino-La Nina cycle. When we average temperature over five or ten years to minimize that variability, we find global warming is continuing unabated."

NASA reported “although 2008 was the coolest year of the decade because of a strong La Nina that cooled the tropical Pacific Ocean, 2009 saw a return to a near-record global temperatures as the La Nina diminished.”

According to NASA, “the near-record global temperatures of 2009 occurred despite an unseasonably cool December in much of North America. High air pressures from the Arctic decreased the east-west flow of the jet stream, while increasing its tendency to blow from north to south. The result was 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. This left North America cooler than normal, while the Arctic was warmer than normal.”

"The contiguous 48 states cover only 1.5 percent of the world area, so the United States' temperature does not affect the global temperature much," Hansen said.

The analysis of global surface temperatures by NASA scientists finds average global temperatures have increased by about 1.5 degrees F since 1880. But, most of that increase has come during the last three decades which averaged a 0.36 degree F increase per decade.

GISS climatologist Gavin Schmidt explained the trend in average temperatures from 1870 until the 1930’s was modestly up, but with a lot of variation. Then, it leveled off until the 70’s when it really started to shoot up.

But, even though the strong upward trend has only been present for the last few decades, Schmidt said “The pattern of how things are changing is very consistent with a warming that is being driven externally by greenhouse gases.”

A common criticism of the claim of manmade global warming is that the temperature increase is just natural fluctuation. NASA’s Schmidt said “The natural variability can account for plus or minus about .2 degrees, but the overall trend is not something we can explain by the random meanderings of the climate system.”

But, Congressman Rohrabacher accuses NASA of a long list of problems, including “inaccurate instruments, faulty computer models, fraudulent numbers, and cherry-picking data.”

NASA’s Schmidt acknowledged the information used by the GISS scientists is from samples. He explained the data that is analyzed by GISS is not compiled by them and NASA does not operate weather monitoring stations. The information comes in from the various national weather services and is compiled by the National Climate Data Center, part of the National Oceanic and Atmospheric Administration, NOAA.

In referring to the various national weather services from around the globe which feed the data to the World Meteorological Organization, WMO, Schmidt said “They generally don’t send all of their data to WMO.” He said, For example, “Canada has a thousand stations, they only report a few dozen to WMO. They generally report the same stations every month, but it’s the national weather services that decide what to report.”

The sample data flows from the WMO to NASA and this of course, could easily lead to manipulating the data, or to use a phrase from Congressman Rohrabacher , “cherry-picking the data”—just send in data from the stations which tell the story you want to tell. But, Schmidt said “They don’t change the stations, they just report a certain subset of the stations. When you sample the weather stations, you actually don’t need that many stations to get a good estimate of what the global or hemispheric mean is.

Schmidt said only “60 to 100 stations is all you would need to get the precision we need for the hemispheric mean. We’re actually sampling much more heavily than that, so mostly it doesn’t matter that people are giving us a subset of the data.”

Here is the statement we received from congressman Rohrabacher about yesterday’s NASA/GISS report: “With last week's reports about NASA GISS and NOAA cherry-picking data, Dr. Hansen's known bias, and the world in a global freeze, it is hard for me to understand how these alarmists expect people to continue believing in man-made global warming with their inaccurate instruments, faulty computer models, and fraudulent numbers."

In response to this skepticism, Schmidt said “If you don’t want to believe these temperature data, just go and look at all the different glaciers—they’re melting all over the place. You don’t need to believe in your heart of hearts the temperature estimates are accurate to .1 degrees globally before you can see that there’s a problem. This insistence that some people have that it must all be somehow a mistake, or a scam—the balance of evidence that the planet is warming doesn’t rely on our work. You can look in the oceans—the oceans are warming up; you can look at the sea ice—the sea ice is going away; you can look at the mountain glaciers—the mountain glaciers are receding; all the different things that tell us the planet is warming--it’s absolutely unequivocal.”