measurement of global warming
The effect of the sun's heat on weather balloons largely accounts for a data discrepancy that has long contributed to a dispute over the existence of global warming, according to a report by scientists at Yale and the National Oceanic and Atmospheric Administration (NOAA).
The report, to be published in the journal Science, says that direct heat of the sun on temperature probes of the weather balloon (radiosonde) probably explains the discrepancy between reports showing that atmospheric temperatures have been unchanged since the 1970s, while temperatures at the Earth's surface are rising.
For the last 40 years radiosonde temperature information has been collected twice each day from stations around the world at local times that correspond to 00:00 and 12:00 Greenwich Mean Time. Some measurements were taken in daylight, others in darkness.
"Even though models predict a close link between atmospheric and surface temperatures, there has been a large difference in the actual measurements," says Steven C. Sherwood, associate professor of geology and geophysics at Yale, and lead author of the study. "This has muddied the interpretation of reported warming." Most scientists have concluded the surface warming has partly resulted from a buildup of greenhouse gases in the atmosphere.
The key to the error in climate change estimates lay in instrument design, according to this study. With exposed sensors, measurements taken in daylight read too warm, and while solar heating had a measurable impact on the earlier designs, the effect became negligible in more recent designs.
"It's like being outside on a hot day -- it feels hotter when you are standing in the direct sun than when you are standing in the shade," says Sherwood. "We can't hang our hats on the old balloon numbers."
After taking this problem into account, the researchers estimate there has been an increase of 0.2 degree Celsius (°C) in the average global temperature per decade for the last 30 years. Over the next century, global surface temperatures are expected to increase by 2°C to 4°C. However, year-to-year and region-to-region increases may vary considerably, say the scientists, with a smaller increase in the tropics but with a 10-degree or higher hike possible in some polar regions.
"Unfortunately, the warming is in an accelerating trend -- the climate has not yet caught up with what we've already put into the atmosphere," says Sherwood. "There are steps we should take, but it seems that shaking people out of complacency will take a strong incentive."
Co-authors on the paper were Cathryn Meyer at Yale and John Lanzante at the NOAA/ Geophysical Fluid Dynamics Laboratory at Princeton. The research was funded by the NOAA Climate and Global Change Program and the National Science Foundation.
-- By Janet Rettig Emanuel
T H I S
W E E K ' SS T O R I E S
University greets its newest freshmen
Freshman Address by President Richard C. Levin
Freshman Address by Yale College Dean Peter Salovey
President of China to speak at Yale Sept. 8
New dean to promote 'values' seminars at SOM
Scientists correct key error in measurement of global warming
ENDOWED PROFESSORSHIPS
Joel Podolny named Beinecke Professor of Management
Emilie Townes is appointed to Andrew Mellon Professorship
Thomas Troeger is designated as the Cox Lantz ProfessorGrant to support research into reducing pain of pediatric surgery
Invitation to Yale community: Meet the new World Fellows
University celebrates Sterling Library's 75th anniversary
Conference will focus on role of religion in public life
Yale engages in special community projects during 'Days of Caring'
Yale hockey star Helen Resor is picked for U.S. Women's National Team
Descendents of John Davenport to converge on campus
The Cinema at Whitney, a new film society, begins weekly screenings
Heart-attack patients seeking after-hours care . . .
While You Were Away: The Summer's Top Stories Revisited
Cell biologist named Bayer Fellow
IN MEMORIAM
Abraham Goldstein, former dean and criminal law scholar
John-Michael Montias, economist and expert on Vermeer
Drama school hosts a memorial tribute to . . . Benjamin MordecaiCampus Notes
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