Mar 14 2001 2:29PM
Greenhouse gas rise found in satellite data
LONDON (Reuters) - Scientists dispelled any lingering doubts about the
increase of greenhouse gases in the atmosphere Wednesday with new evidence
from satellites orbiting the Earth.
Until now researchers have depended on ground-based measurements and
theoretical models to gauge the change in greenhouse gases, believed by
scientists to be the cause of global warming and major climate disruption.
New sets of data taken 27 years apart from two satellites orbiting the Earth
have now provided the first observational evidence from space of a rise in
greenhouse gases.
"We've seen greenhouse gas increases that we can link to a change in
outgoing long-wave radiation, which is believed to force the climate
response," said Dr. Helen Brindley, an atmospheric physicist at Imperial
College in London.
By comparing the two sets of data, Brindley and her colleagues have shown a
change in greenhouse gas emissions from Earth over 27 years which is
consistent with ground-based measurements.
REAL DIFFERENCES OVER 27 YEARS
The comparison of the data, reported in the science journal Nature, shows
real differences over 27 years in the outgoing long-wave radiation which can
only be due to greenhouse gases.
The scientists compared data for a region over the Pacific Ocean and the
entire globe to calculate the differences in the levels of atmospheric
methane, carbon dioxide (CO2), ozone and chlorofluorocarbons.
"Because we know where in the spectrum certain greenhouse gases are
observed, when we look at the changes between the two periods we can say
that change is due to changes in CO2 or methane," Brindley said in a
telephone interview.
"There has been quite a significant change over the past 30 years,
particularly in methane."
One of the most powerful greenhouse gases, methane, is emitted from landfill
sites and disused mines.
The scientists took into account the influence of clouds and seasonal
variations, so the changes they observed could only be explained by
long-term changes in greenhouses gases, they said.
"It's the first time that we have seen observationally that these changes
are really having an effect on the radiative forcing of the climate," said
Brindley.
Radiative forcing is the measure of the climate effects of greenhouse gases.
"Since these are the models used to predict future climate and influence
policy decisions, it is imperative that they can accurately simulate
measurements of what is considered to be the driving mechanism behind
climate change," said Professor John Harries, the first author of the Nature
study.
Without significant reductions in greenhouse gas emissions, scientists
estimate the Earth's temperature and sea levels will rise, leading to
increased flooding and drastic climate changes.
Industrialized nations agreed to cut their emissions of greenhouse gases
under a plan agreed in Kyoto, Japan in 1997 but talks in the Hague in
November to finalize details broke down.