Nature - Satellite Data Confirms Climate Change

"For years, climate researchers have struggled with an apparent discrepancy in the data on global warming: temperatures in the lower atmosphere have been rising far slower than models predict, given how fast the Earth’s surface is heating.

The discrepancy has been central to the arguments of sceptics about global warming. But according to a study in this issue of Nature1 it can be explained by interactions between the troposphere - the first 11 km of the atmosphere - and the stratosphere above it.

In the study, a team from the University of Washington at Seattle and the Air Resources Laboratory of the National Oceanic and Atmospheric Administration (NOAA), based in Maryland, analysed microwave emissions from the atmosphere. The emissions were recorded between 1979 and 2001 by NOAA’s polar orbiting satellites. The data can be used to deduce temperatures in different layers of the atmosphere. And the study finds that stratospheric cooling, a known effect of greenhouse gases,appears to account for discrepancies between temperature trends on the ground and in the troposphere.

The team, led by Qiang Fu, an atmospheric researcher at the University of Washington, subtracted the impact of such cooling from data on the stratosphere and performed a statistical analysis, which found temperature trends consistent with observed warming on the surface and the predictions of climate models. The finding is “a stunningly elegant and accurate method of clarifying global trends”, says Kevin Trenberth, head of the climate analysis section at the National Center for Atmospheric Research in Boulder,Colorado."

EDIT

http://www.nature.com/nsu/040503/040503-5.html

Nature 429, 55 - 58 (06 May 2004)

Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends

QIANG FU, CELESTE M. JOHANSON, STEPHEN G. WARREN & DIAN J. SEIDEL

From 1979 to 2001, temperatures observed globally by the mid-tropospheric channel of the satellite-borne Microwave Sounding Unit (MSU channel 2), as well as the inferred temperatures in the lower troposphere, show only small warming trends of less than 0.1 K per decade (refs 1–3). Surface temperatures based on in situ observations however, exhibit a larger warming of 0.17 K per decade (refs 4, 5), and global climate models forced by combined anthropogenic and natural factors project an increase in tropospheric temperatures that is somewhat larger than the surface temperature increase. Here we show that trends in MSU channel 2 temperatures are weak because the instrument partly records stratospheric temperatures whose large cooling trend offsets the contributions of tropospheric warming. We quantify the stratospheric contribution to MSU channel 2 temperatures using MSU channel 4, which records only stratospheric temperatures. The resulting trend of reconstructed tropospheric temperatures from satellite data is physically consistent with the observed surface temperature trend. For the tropics, the tropospheric warming is 1.6 times the surface warming, as expected for a moist adiabatic lapse rate.

he's obviously pissed off. But he does go into an explanation of why he thinks the new analysis is wrong, which is interesting.

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

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.

now that he's come over from the dark side.

There's a brief article in this week's Science citing testimony supporting the Fu work.

"Now, in this week’s issue of Nature, a group of researchers describes a way to correct a long-standing problem in the satellite readings caused by the ongoing cooling of the stratosphere. Once adjusted, satellite temperatures show much the same warming in the lower atmosphere as do thermometers at the surface. “Within the uncertainty of reasonable methods of analysis of the satellite data, this paper essentially reconciles the satellite surface temperature trend debate,” says meteorologist Thomas Vonder Haar of Colorado State University in Fort Collins. “Our disparate observing systems are in agreement.”

-snip-

Fu and colleagues’ approach “is a fairly simple but illuminating way of looking at the problem,” says meteorologist David Karoly of
the University of Oklahoma in Norman. “I don’t see any fundamental problem with the analysis.” That would leave researchers with
the uncertainties evident in the spread of the three published estimates, but for now satellite temperatures can no longer be used to portray a feeble greenhouse effect."

http://www.sciencemag.org/cgi/reprint/304/5672/805a.pdf
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is exactly what Spencer thinks should be done with weather balloon measurements to weight the readings, and what Fu et al have done. Spencer said you need to use them, because the temperature gradient isn't constant; but this section of the news release implies Fu did:

Stratosphere temperatures are measured by channel 4 on the microwave units. Fu's team used data from weather balloons at various altitudes to develop a method in which the two satellite channels could be employed to deduce the average temperature in the troposphere. The scientists correlated the troposphere temperature data from balloons with the simulated radiation in the two satellite channels to determine which part of the channel 2 measurement had come from the cooling stratosphere and should be removed.

http://www.newswise.com/articles/view/504769/

is the weighting of the two MSU channels which is derived from balloon measurements (radiosonde). His objection is not that Fu's team didn't use baloon radiosonde, but that the weighting they derive from the baloon measurements doesn't add up.

Although referring gratuituously to his own work, Spencer's TechCentral piece neglects to mention the forthcoming article on which Fu's team heavily relies in this area.

Seidel, D. J. et al. Uncertainty in signals of large-scale climate variations in radiosonde and satellite upper-air temperature datasets. J. Clim. (in the press)