Kenyan farmers pass by a gully
in Nyakach district, an area where massive land degradation has been exacerbated
by livestock grazing and a rapidly increasing population, in western Kenya
Global temperatures in the future could be much hotter than scientists have predicted
if new computer models on climate change are correct, researchers said on Wednesday.
Improvements in air quality will lead to a decrease in aerosols, small particles
in the atmosphere that act as a brake on the impact of greenhouse gases. As
the effect of aerosols lessen, searing temperatures could follow.
"This new way of integrating the aerosol, greenhouse gas and biosphere
effects changes the picture from one where climate change most likely is a fairly
tolerable thing to one where there is a fairly high risk of change sooner, and
to a higher degree," said Professor Meinrat Andreae.
The Intergovernmental Panel on Climate Change (IPCC) predicts a rise in global
temperatures from a doubling of carbon dioxide could be in the range of 1.5-4.5
degrees Celsius by the end of the century. But according to calculations by
Andreae and his team, the upper figure could be as high as 6 degrees.
"That's quite a lot," the professor from the Max Planck Institute
for Chemistry in Mainz, Germany said in an interview.
Andreae compared greenhouse gases to an accelerator that is speeding up global
warming, while the aerosols act as a type of brake.
"The actual true force of the greenhouse gases has been masked by the
effects of the aerosols. They put a brake on warming and we don't really know
how strong that brake is," said Andreae, who reported his findings in the
Scientists have warned that severe climate change could lead to a rise in sea
levels, flooding, severe droughts and the loss of crop and animals species.
Aerosols are small particles and droplets in the air from combustion processes,
chemicals and smoke. As regulatory agencies issue new air purity controls, the
amount of aerosols will diminish so their cooling effect will be smaller.
Aerosols stay in the atmosphere for about a week but greenhouse gases accumulate
over about 50 years. The aerosol brake is going to come off faster than the
decrease in greenhouse gases.
"Because one is cumulative and the other is not, the cumulative will always
win out in the long run," said Andreae.
He admitted it was a situation of high scientific uncertainty. But if his calculations
are correct, climate change in the 21 century could reach the upper extremes
or exceed the IPCC estimates.
"Such a degree of climate change is so far outside the range covered by
experience and scientific understanding that we cannot with any confidence predict
the consequences for the Earth system," Andreae said in the journal.