Is lowering the sun the answer to global warming?

Scientists are proposing an ingenious but not yet proven way to combat climate change: spraying chemicals that tarnish the sun in the Earth's atmosphere.

Research scientists at Harvard and Yale Universities, published in the journal Environmental Research Letters, proposes to use a technique known as aerosol injection into the stratosphere, which they say , could halve the rate of global warming.

The technique would involve spraying large quantities of sulphate particles in the lower stratosphere at altitudes up to 12 miles. Scientists propose to deliver sulphates with specially designed aircraft, balloons or large naval guns.

Despite the fact that the technology has not yet been developed and that no aircraft can be adapted, the researchers say that "the development of a new tanker specially designed for passenger transport and equipped with a large payload capacity would be neither technologically difficult nor as expensive. "

They estimate the total cost of launching a hypothetical system in 15 years at around $ 3.5 billion, with operating costs of $ 2.25 billion a year over a 15-year period.

The report recognizes, however, that the technique is purely hypothetical.

"We are not making any judgment on the desirability of an SAI," the report says. "We are simply showing that a hypothetical deployment program starting in 15 years, while being very uncertain and ambitious, would in fact be technically feasible from an engineering point of view, it would also be extremely cheap."

The researchers also recognize the potential risks: coordination between several countries in both hemispheres would be needed and aerosol injection techniques in the stratosphere could compromise crop yields, drought or extreme weather conditions.

The proposals also do not address the issue of increasing greenhouse gas emissions, which are one of the main causes of global warming.

And despite the belief of the report's authors, other experts were skeptical.

"From the point of view of the climate economy, the management of solar radiation remains a much worse solution than greenhouse gas emissions: more expensive and much more risky in the long term," said Philippe Thalmann of the Ecole Polytechnique Fédérale de Lausanne, expert in the economics of climate change.

David Archer of the Department of Geophysical Sciences at the University of Chicago said: "The problem of technical climate in this way is that it is only a temporary dressing covering a problem that will persist forever, in fact hundreds of thousands of years ago for CO2 fuel fossils to finally leave naturally.

"It would be tempting to continue procrastinating over the cleansing of our energy system, but we would leave the planet on a form of support for life.If a future generation did not pay its climate bill, it would do everything immediately."