Weather Balloons'
1970s Design Caused Climate Spat
August 12, 2005 — By Reuters
WASHINGTON — A dispute over whether
global warming is really happening may have been caused by the placement
of sensors on weather balloons when studies were done in the 1970s,
researchers said Thursday.
Very few scientists now dispute that the Earth's temperature is rising,
and that this is caused by human activity, including burning fossil
fuels such as coal and oil.
But there have been some discrepancies that have troubled experts. For
instance, some measurements show that atmospheric temperatures have been
unchanged since the 1970s, while temperatures at the Earth's surface are
rising.
"Even though models predict a close link between atmospheric and surface
temperatures, there has been a large difference in the actual
measurements," said Steven Sherwood, an associate professor of geology
and geophysics at Yale University in Connecticut, who led the study.
"This has muddied the interpretation of reported warming."
Working with a team at the National Oceanic and Atmospheric
Administration, Sherwood and colleagues said they found the key to the
differences lay in where the sensors were placed on equipment.
With exposed sensors used in earlier designs, measurements taken in
daylight read too warm. Later equipment reduced this effect.
"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,"
Sherwood said in a statement.
"We can't hang our hats on the old balloon numbers."
Writing in the journal Science, Sherwood and colleagues said this helps
explain why temperatures in the troposphere -- the lower atmosphere --
appear not to have risen.
After taking this problem into account, they estimate there has been an
increase of 0.2 degree Celsius (0.36 degree F) in the average global
temperature per decade for the last thirty years.
"Unfortunately, the warming is in an accelerating trend -- the climate
has not yet caught up with what we've already put into the atmosphere,"
Sherwood said. "There are steps we should take, but it seems that
shaking people out of complacency will take a strong incentive."
Two other papers published in Science support this conclusion.
Source: Reuters |