In May, Rep. Norm Dicks (D-Wash.) sponsored a nonbinding resolution on
global warming, stating that the House of Representatives recognizes that
warming is real and caused by excessive greenhouse gases in the atmosphere.
The resolution reached the floor of the House, but was blocked from a
vote. As with other such climate policy decisions, uncertainty surrounding
climate research was partially to blame for its failure.
Among many uncertainties that global warming skeptics have cited are
past discrepancies between a supposed warming trend at Earths surface
and a supposed cooling trend in the lower atmosphere in the tropics. A
new report, however, issued in April by the U.S. Climate
Change Science Program (CCSP) a White House-sponsored research
program on climate change states that this particular discrepancy
has been resolved. The reconciliation removes one of the biggest uncertainties
used to challenge the reliability of climate models and observations,
says John M. Wallace of the University of Washington in Seattle, who was
involved in both the CCSP report and a 2000 National Academy of Sciences
report on the topic.
Since the late 1970s, scientists have observed rising temperatures both
at Earths surface and in the troposphere, the part of the lower
atmosphere that reaches to about 10 to 15 kilometers (6 to 9 miles) above
the planet. Models predict that temperatures in the troposphere should
rise in step with temperatures at the surface, and that the largest upward
trends should be in the tropics, Wallace says. But in the tropics, the
instruments used to measure tropospheric trends sensors on satellites
and weather balloons called radiosondes have disagreed somewhat
on the relative change, with some even showing a cooling in the troposphere.
A number of reports have come out in the past year that explain this
discrepancy, suggesting that the original analyses of the satellite data
were incorrect, Wallace says (see Geotimes, October
2005). The new CCSP report is the first time these data have been
compiled, however, and is the first report issued by CCSP. The wide variety
of experts involved in the report, most of whom have worked on this issue
for more than a decade, agreed that errors in observations and analyses
were to blame.
The report is important because it is a consensus statement, says Carl
Mears of Remote Sensing Systems in Santa Rosa, Calif., who is a lead author
on the CCSP report. We [scientists] are in much more agreement,
he says. Theres now little disagreement between measurements
Still, although this significant discrepancy no longer exists,
as the authors wrote, it is important to note that more work is necessary,
especially on tropical temperature datasets, says John Christy of the
University of Alabama in Huntsville, who was also a lead author on the
report. While the data quality from the satellites and radiosondes is
good for measuring short time periods (for which it was designed), it
is poor for showing temperature trends over years or decades,
says Jay Gulledge, a senior research fellow at the Pew Center on Global
Climate Change. To figure out what is actually going on in the tropical
atmosphere over the long term, he says, well have to rely
on further measurements.
Many more studies need to be done, including more comparison studies
and new, better observations, Christy says. I hope this will draw
attention to the fact that we need to upgrade our observing system,
in addition to surveying past records in finer detail, Wallace adds.
The authors of the CCSP report steered clear of making any policy statements,
but the reports conclusions will make it harder for Congress
to ignore climate change, Mears says. The observed patterns
of change over the past 50 years cannot be explained by natural processes
alone, the authors wrote, and there is no doubt that humans are
affecting the atmosphere.
Whether that will translate to congressional or administrative action
remains to be seen, says Vicki Arroyo, director of policy analysis for
the Pew Center on Global Climate Change. With each new scientific report
that comes out, such as this one, or 2004s Arctic Climate Impact
Assessment, we keep hoping, expecting that the government will push
something through, Arroyo says, but until the political will
is there, nothing will happen.
Following the reports publication, the White House said it welcomed
the reports conclusions. In terms of actions, a White House spokesperson
says: The president believes that while we improve our understanding
of climate science, we can also act to reduce emissions of greenhouse
gases through investments in cleaner and more efficient energy and technologies.