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Nairobi - If the sun warms the Earth too dangerously, the time
may come to draw the shade.
The "shade" would be a layer of pollution deliberately spewed into the atmosphere to help
cool the planet. The proposal comes from prominent scientists, among them a Nobel laureate. The reaction here at the annual
UN conference on climate change is a mix of caution, curiosity and some resignation to such "massive and drastic" operations,
as the chief UN climatologist describes them.
Nobel Prize-winner Paul Crutzen, who made the proposal is himself "not
enthusiastic about it". "It was meant to startle the policymakers," said Crutzen, of Germany's Max Planck Institute. "If they
don't take action much more strongly than they have in the past, then in the end we have to do experiments like this."
Serious
people are taking Crutzen's idea seriously. Moffett Field, California, Nasa's Ames Research Centre, is to host a high-level
workshop on the global haze proposal.
When he published his proposal in the journal Climatic Change in August, Crutzen
cited a "grossly disappointing international political response" to warming.
The Dutch climatologist, awarded a 1995
Nobel in chemistry for his work uncovering the threat to Earth's ozone layer, suggested that balloons bearing heavy guns be
used to carry sulphates aloft and fire them into the stratosphere.
While carbon dioxide keeps heat from escaping Earth,
substances such as sulphur dioxide reflect solar radiation, helping cool the planet.
Tom Wigley, a US government climatologist,
agreed with Crutzen and cited the precedent of the huge volcanic eruption of Mount Pinatubo in the Philippines in 1991. Pinatubo
poured so much sulphurous debris into the stratosphere that it is believed it cooled the Earth by 0.5 degrees Celsius for
about a year.
Wigley ran scenarios of stratospheric sulphate injection - on the scale of Pinatubo's estimated 10 million
tons of sulphur - through supercomputer models of the climate, and reported that Crutzen's idea was likely to work. Even half
that amount per year would help, he wrote.
A massive dissemination of pollutants would be needed every year or two,
as the sulphates precipitate from the atmosphere in acid rain.
The American scientist said a temporary shield would
give political leaders more time to reduce human dependence on fossil fuels - main source of greenhouse gases. He said experts
must more closely study the feasibility of the idea and its possible effects on stratospheric chemistry.
American geophysicist
Jonathan Pershing, of Washington's World Resources Institute, said the idea might be worth considering "if down the road 25
years it becomes more and more severe because we didn't deal with the problem". - Sapa-AP
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