04 atmospheric CO is expensive to retrieve

The man showed his genius to manipulate the climate in the sense of global warming. Perhaps reverse the infernal machine, consider the Royal Society. The British institution of science, the equivalent of the French Academy, has just published a fatalistic report on climate engineering: "there are major doubts about its effectiveness, its cost and its environmental consequences but it could be useful." This is taking a stand that legitimizes a strategy against greenhouse very polemical and long regarded as of science fiction.

For a century, scientists test techniques of climate change, to trigger rain in agriculture, to divert the hurricanes in the United States. Usually without success. In recent years, some promote new approaches to force more generally the climate machine in the sense of a cooling. The report classifies these techniques into two categories. The first is to increase albedo, i.e. the reflection of solar radiation into space. The most spectacular technology offers space orbit of reflective panels. It could also cover the deserts of films reflecting, to mimic the volcanoes by injecting large amounts of dust in the sky. A far more modest register, have the obligation already on Californians to paint their roofs white.

The second category is to avoid the CO to the atmosphere. In this context, some wish to seeding the oceans with particles to increase the proportion of plankton and thus their absorption of CO. Of geochemists dream to accelerate the production of carbonate by capture of CO in the silicates.

This process, which takes place on land and at sea over thousands of years, is one of the most powerful pumps CO of the Earth. The study noted that the integration of silicates crushed in agricultural soils may operate, for example, but the consequences on soil biology are unknown. Similarly, she considered feasible to use industrial processes to capture the CO in the air. But with low concentrations of 0.04, atmospheric CO is expensive to retrieve.

Risk of destabilization

Climate engineering shines most climatologists and scientists, who see a risk of destabilizing an already well shaken Earth System. The international group of experts on climate (IPCC) found in its latest report, very speculative. Environmentalists complain more fundamentally a new inclination of man playing with fire. "Geo-engineering and its consequences are the price we might have to pay for our failure to act on climate change," replied the Professor John Shepherd, at the University of Southampton, who chaired a panel of 12 scientists.

These experts believe that the reflection of solar radiation is the way to act quickly, in only a few years. They do not address the causes of the greenhouse effect, but could be used in an emergency to avoid exceeding critical thresholds.

Among the different technologies, the dispersal of aerosols in the stratosphere is the most promising for researchers. It should be more effective than local measurements of reflection and could be implemented more rapidly than space techniques. Researchers favour despite the use of the capture of the CO, the only geo-engineering can bring back the climate system to its natural state. These methods generate also less collateral effects on the environment.

Before all the uncertainties surrounding this engineering, the Royal Society insists to enable research in this area. Some work has already begun, as the French Oceanographic campaign Keops, which was tested in 2005 fertilization of the oceans.