New Global Warming Study Ignites Heated Debate

Climate change research is a giant scientific sandbox. The subject is so complex, the data sources spread across so many disciplines, and the analytical tools so new and powerful that just about any scientist can stick in his shovel someplace and come up with a new -- and probably plausible -- result.

There even remains -- in the United States, at least -- controversy over whether global temperatures are rising and, if so, how much.

A recent paper in the British journal Nature claims to have found a way out of at least one dilemma that has plagued climate research for years: the rise in temperatures in the lower atmosphere that is slower than the climate computer models have predicted, at least in relation to data on heating of the surface. This discrepancy has been the linchpin of the arguments by climate skeptics.

A University of of Washington team led by atmospheric researcher Qiang Fu re-analyzed the satellite data underlying the conclusion about the lower atmosphere. After applying some compensating factors, they now argue that temperature trends in the lower atmosphere are, in fact, consistent with the trends on the surface.

Microwave sounding units aboard polar-orbiting satellites run by the National Oceanic and Atmospheric Administration measure radiation emitted at different frequencies and provide temperature and other data for different layers of the atmosphere.

Channel two on those satellites measures tropospheric temperatures, the layer from the surface to about 7.5 miles up, while channel four measures temperatures in the stratosphere -- above 7.5 miles.

One well-known -- albeit counterintuitive -- greenhouse effect is the cooling of the stratosphere. Fu and his team found about one-fifth of the signal from the troposphere on channel two actually was coming from the stratospheric cooling. So they used statistical methods to subtract this phenomenon from the record and recalculated the warming rate of the troposphere.

The team concluded the troposphere was warming at the rate of about 0.2 degrees Celsius (nearly 0.4 degrees Fahrenheit) per decade, a result that fits almost perfectly with the predictions of the climate models.

"If the models agree with what has happened in the real world, that gives them more credence," said Kevin Trenberth, head of global climate analysis for the National Center for Atmospheric Research in Boulder. "The main cry of the skeptics is that the models don't agree with the tropospheric temperature change. What (the journal article) suggests is that the record agrees extremely well in the troposphere."

The finding seems to invalidate the data presented by researchers such as a group at the University of Alabama, Huntsville, one of the originators of the tropospheric anomaly.

"You'll hear an outcry from the skeptics," Trenberth told United Press International.

Indeed, John Christy, a member of the UAH team that compiled the tropospheric temperature record -- from the same satellite data that Fu and colleagues used -- said the University of Washington group subtracted out more cooling than exists and therefore their results are wrong.

Furthermore, Christy said, he and his colleagues previously had tried the method Fu used and found it did not work.

"In 1992 we published a means to eliminate the stratosphere," Christy told UPI. "We indicated in there that we had tried these multichannel methods, but that they were not suitable."

"He can claim whatever he wants," Fu told UPI. "He never showed it in a paper. This method is very effective."

Christy responded that "there was no paper about it because, well, it didn't work. We went down a different road. It wasn't worth showing because it didn't work."

For the method used by Fu's team to be effective, Christy said, there has to be considerable overlap in the signals between satellite channels two and four.

"There is not enough overlap," he added. "There is not enough information in channel four to completely remove the stratospheric part of channel two."

In other words, there has to be enough cooling signal to subtract, and Fu and his colleagues subtracted more cooling than warranted by the data, Christy said.

"I think what bothers me at this point is the lack of attention given to all of the work we did in the early 1990s recognizing that methods such as Fu's were inappropriate," Christy continued. "Everyone knows there is stratospheric influence in channel two, but Fu makes it out as if he discovered this. Our method works, and has also been verified in a large number of published papers by investigators independent of ourselves."

Christy and his colleagues are not entirely entirely skeptical about warming. Their data do find a mean warming trend of 0.08 degrees C per decade. But the 0.2 degrees C per decade from Fu's team -- and from most climate models -- is about 1.5 times higher, which amounts to a considerable difference.

"This kind of mistake would not get published with adequate peer review of manuscripts submitted for publication," said Roy Spencer, principal research scientist at UAH on his climate change Web site. "But in recent years, a curious thing has happened. The popular science magazines, Science and Nature, have seemingly stopped sending John Christy and me papers whose conclusions differ from our satellite data analysis. This is in spite of the fact that we are (arguably) the most qualified people in the field to review them."

NCAR's Trenberth, one of the reviewers of the Fu paper, said, "I think the protests are silly ... I think this is the cleanest indication of what is actually happening in the troposphere from the standpoint of the satellite record."

I love the smell of peer-review in the morning.

Smells something like burnt cowhide, when the rebuttal starts in.

Synopsis of John Christy's comments regarding the the Fu et.al. Nature article,

http://www.techcentralstation.com/050504H.html

When Is Global Warming Really a Cooling?

By Roy Spencer

Published

05/05/2004

Much media attention is focusing on the forthcoming big-budget climate disaster movie "The Day After Tomorrow" and how much scrutiny the "science" on which it is based deserves. But there are some developments in the world of serious climate science that certainly deserve greater scrutiny.

A new paper¹appearing today in the journal Nature purports to solve the long standing "problem" of the satellite-based global temperature record not showing much warming over the last 25 years (only +0.085 deg C/decade -- about a third of what is expected from climate models for the troposphere). Instead, all it does is help answer the question: "is the quality of peer review in the popular science journals getting worse?" (The answer is "yes.")

By way of background, the Microwave Sounding Units (MSU) on the NOAA polar orbiting satellites measure deep layers of the atmosphere, with each instrument channel measuring the average temperature of a different layer (see Fig. 1). John Christy, a professor of atmospheric science at the University of Alabama, Huntsville, and I discovered in 1990 that these instruments were so stable in their calibration that we have been using them ever since for climate monitoring of tropospheric and lower stratospheric temperatures since the satellite record began in 1978.

The lowest layer (the troposphere) is measured by channel 2, and this is where global warming is supposed to occur. The lower stratospheric layer is measured by MSU channel 4. Christy and I have measured substantial cooling (-0.47 deg. C/decade) in this layer over the same 25 year period.

But because the layers measured by the satellite are so thick, there is a intermingling of the warming and cooling signals. This means that warming in the tropospheric channel would be partly cancelled by stratospheric cooling occurring in the upper portion of this layer. Because of this problem, we devised a lower tropospheric retrieval² based upon different Earth viewing angles from the MSU tropospheric channel. As can be seen in the accompanying figure, this removes the stratospheric influence and so allows us to monitor the lower and middle troposphere for signs of global warming.

Fig. 1 Microwave Sounding Unit weighting functions for channels 2 and 4, along with derived weighting functions meant to remove the influence of lower stratospheric cooling on MSU channel 2 by Spencer & Christy (1992, "TLT") and Fu et al. (2004). The Fu et al. weighting function shows substantial negative weight above 100 hPa, a pressure altitude above which strong cooling has been observed by weather balloon data. This leads to a misinterpretation of stratospheric cooling as tropospheric warming.

Enter the new Nature study. The authors, noticing that channel 4 measures the extreme upper portion of the layer that channel 2 measures (see Fig. 1), decided to use the MSU channel 4 to remove the stratospheric influence on MSU channel 2. At first, this sounds like a reasonable approach. We also tried this thirteen years ago. But we quickly realized that in order for two channels to be combined in a physically meaningful way, they must have a large percentage of overlap. As can be seen in Fig. 1, there is very little overlap between these two channels. When a weighted difference is computed between the two channels in an attempt to measure just the tropospheric temperature, an unavoidable problem surfaces: a large amount of negative weight appears in the stratosphere. What this means physically is that any attempt to correct the tropospheric channel in this fashion leads to a misinterpretation of stratospheric cooling as tropospheric warming. It would be possible for their method to work (through serendipity) if the temperature trends from the upper troposphere to the lower stratosphere were constant with height, but they are not. In this instance, the negative (shaded) area for the Fu et al. weighting function in Fig. 1 would be cancelled out by its positive area above about 200 millibars. Unfortunately, weather balloon evidence suggests the trends change from warming to strong cooling over this altitude range.

This kind of mistake would not get published with adequate peer review of manuscripts submitted for publication. But in recent years, a curious thing has happened. The popular science magazines, Science and Nature, have seemingly stopped sending John Christy and me papers whose conclusions differ from our satellite data analysis. This is in spite of the fact that we are (arguably) the most qualified people in the field to review them. This is the second time in nine months that these journals have let papers be published in the satellite temperature monitoring field that had easily identifiable errors in their methodology.

I will admit to being uneasy about airing scientific dirty laundry in an op-ed. But as long as these popular science journals insist on putting news value ahead of science, then I have little choice. The damage has already been done. A paper claiming to falsify our satellite temperature record has been published in the "peer reviewed" literature, and the resulting news reports will never be taken back. This is one reason increasing numbers of scientists regard Science and Nature as "gray" scientific literature.

1. Fu, Q., C.M. Johanson, S.G. Warren, and D.J. Seidel, 2004: Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends. Nature, 429, 55-58.

2. Spencer, R.W., and J.R. Christy, 1992: Precision and radiosonde validation of satellite gridpoint temperature anomalies, Part II: A tropospheric retrieval and trends during 1979-90. J. Climate, 5, 858-866.

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