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CLIMATE ARGUMENT SOLVED?
TECHNICAL ERRORS BLAMED FOR MISMATCH IN TEMPERATURE READINGS.
By Jenny Hogan
Nature
August 11, 2005

http://www.nature.com/news/2005/050808/full/050808-13.html

The end may be in sight for a 15-year argument over a discrepancy in the
data on global warming.

Three papers published in Science today say that temperature trends in the
lower atmosphere are consistent with a warming world, countering earlier
claims to the contrary.

One study deals with satellite measurements, the second with data from
weather balloons and the third with predictions of climate models. "Taken
together, these three results are a major step forward," says Carl Mears of
Remote Sensing Systems in Santa Rosa, California, an author of one of the
papers.

The problems began in 1990, when an analysis of satellite observations
showed the troposphere - the lowest few kilometres of the atmosphere - was
warming too slowly compared to the surface for climate models to be
correct1. Global-warming sceptics seized upon the result.

"It has been the main crutch of the sceptics when it comes to pooh-poohing
global warming, with some success," says Kevin Trenberth, from the National
Center for Atmospheric Research in Boulder, Colorado. Some politicians have
also cited the data as evidence of the uncertainties in global warming.

The 1990 study, headed by John Christy from the University of Huntsville,
Alabama, was criticized for the way it used satellite data. This prompted
multiple rounds of revision, but never really solved the problem. A recent
re-analysis in Nature2, which claimed to solve the debate, also fell short
of being definitive.

Converging work

So why pin any hopes on the new papers? "We are converging, we are
definitely getting closer," says Mears.

He and Frank Wentz, also at Remote Sensing Systems, tackled a problem with
how the satellite data are corrected for the time of day. Although the
satellites nominally pass over the same point at the same time each day, in
practice drag causes their orbits to sink and the time to drift.

Christy's group estimated the temperature at the exact time they wanted,
rather than when the satellite actually was overhead, by looking at
temperature measurements the satellite took to the east and west of its
position. From this they concluded the troposphere was warming by about 0.09
°C per decade.

Mears and Wentz instead used data generated by a complex model of the
atmosphere to adjust the satellite measurements. On doing so, the
troposphere suddenly appears to be warming by almost 0.2 °C per decade, in
agreement with climate models3.

The new work is bound to draw its own criticism, however. "It's going to be
very interesting to see how this reverberates through the climate-sceptic
blogosphere. I expect by Tuesday there will be plenty of articles calling me
a fraud," says Mears.

Burst balloon

The second paper points out problems in the temperature record from weather
balloons. Steven Sherwood and co-authors argue that changes in instruments
have made the records untrustworthy4. The problems arise because different
manufacturers' instruments heat up by different amounts during the day. At
the moment, they say, the errors on this data are so big that one can't pin
down how much the troposphere is warming.

The third piece of research, led by Ben Santer from the Lawrence Livermore
National Laboratory in California, concludes that disagreement between 19
climate models and measurements are more likely to be due to errors in
measurements, rather than models5.

"I don't think this will be the last word," says Phil Jones, a researcher
from the University of East Anglia, UK, who has looked at the new results
for the next assessment of the Intergovernmental Panel on Climate Change.

"Certain people have too much invested to admit they accept all these
reports," Jones says. "But there's quite a bit of agreement in the whole
community that these papers are getting closer to the truth."

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Published by David Sunfellow
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