NICOSIA: A slowdown in the world economy may give the planet a breather from the excessively high carbon dioxide (CO2) emissions responsible for climate change, a Nobel Prize winning scientist said on Tuesday.

Atmospheric scientist Paul J Crutzen, who has in the past floated the possibility of blitzing the stratosphere with sulfur particles to cool the earth, said clouds gathering over the world economy could ease the earth's environmental burden.

Slower economic growth worldwide could help slow growth of carbon dioxide emissions and trigger more careful use of energy resources, though the global economic turmoil may also divert focus from efforts to counter climate change, said Crutzen, winner of the 1995 Nobel Prize in Chemistry for his work on the depletion of the ozone layer.

"It's a cruel thing to say ... but if we are looking at a slowdown in the economy, there will be less fossil fuels burning, so for the climate it could be an advantage," Crutzen said.

"We could have a much slower increase of CO2 emissions in the atmosphere ... people will start saving (on energy use) ... but things may get worse if there is less money available for research and that would be serious."

CO2 emissions, released by the burning of fossil fuels in power stations, factories, homes and vehicles, are growing at almost 3.0 percent a year.

The U.N. Panel on Climate Change estimates that world temperatures may rise by between 1.8 and 4.0 degrees Celsius (3.2-7.2 degrees Fahrenheit) this century. The Group of Eight industrial nations agreed in July to a goal of halving world emissions by 2050.

Crutzen was in Cyprus for a lecture organized by the Cyprus Institute, a research foundation.

He caused a stir with the publication of a paper in 2006 suggesting that injecting the common pollutant sulfur into the stratosphere some 10 miles above the earth could snuff out the greenhouse effect.

He believes that dispersing 1 million tons of sulfur into the stratosphere each year, either on balloons or in rockets, would deflect sunlight and cool the planet.

Scientists observed that world temperatures dropped by 0.5 degrees centigrade on average when Mount Pinatubo in the Philippines erupted in 1991, spewing sulfur dioxide into the atmosphere, and Crutzen said the idea originated with a Russian scientist about 30 years ago.

"I am not saying we should do it, but it is one of the options if we continue under present conditions. We should study it," he said. "If you look beyond a decade, two decades, and nothing has been done (to counter warming) then we will have a very serious problem on our hands."

Sulfur is a component of acid rain, which has harmful effects on plants and fish.

"Acid rain is caused by sulfur dioxide emissions from the ground, from the chimneys, and it's 50m tons per year. The experiment in the stratosphere would be one million tons of sulfur per year. It's negligible," he said.

It would be an extreme endeavor, but for extreme circumstances, he said.

In a 2007 report, the U.N. climate change panel said such geo-engineering options were largely speculative and unproven, with the risk of unknown side effects. Reliable cost estimates had not been published, it said.