Many cost also strong including that of the heat shield

Of many scientists in the world are worried about both the consequences of human climate... activity and inertia Governments to effectively combat climate change. A concern reinforced by the disappointing results of the Copenhagen Summit, which has not led to binding commitments on the part of the most polluting countries. Therefore, some researchers think about an extreme solution: exploit techniques to directly modify the climate, or the "cool", is to eliminate greenhouse gases already positioned above our heads. For a long time.

These techniques are grouped under the term "climate engineering" or "geo-engineering". They are not new, but interest in growing on the part of the scientific community. It is as well as last March, at Asilomar (Northern California), nearly 200 climate scientists and science of the Earth from 15 different countries have worked on this theme for five days. They are not alone. In October 2009, the Massachusetts Institute of Technology (MIT) in Boston organized a symposium on the subject. A month earlier, the Royal Society of London, composed of recognized scholars, had made public a report of almost 200 pages on these different techniques ("Les Echos" on September 7, 2009).

In none of these cases, it is a rallying suddenly and without nuances. "We are not necessarily hardcore advocates of climate engineering, but we feel the need to explore this route, as there is a policy of insurance", summarizes John Sheperd, Professor of the science of the Earth system at the University of Southampton, who headed the panel of experts of the Royal Society. David Keith, of the University of Calgary, did not say anything at the symposium of MIT: "nothing says that we need to employ these techniques, but at least we should make sure to have the ability to do so."

The railway to boost plankton

Several technologies exist, more or less spectacular. A first approach is to "whiten the clouds", so that they reflect more sunlight and thus contribute to a certain cooling of temperatures. Stephen Salter, Professor at the University of Edinburgh, proposes to perform this operation on the clouds over the oceans, by deploying up to 1,500 boats on their surface. They would aspire sea water, and then projecting it as tiny droplets in the atmosphere with powerful turbines, thereby increasing significantly the amount of cloud... Stephen Salter estimated the cost of construction of these vessels to about $ 5 billion. So far, the validity of the process has not yet been proven - it is even questioned by some researchers American HP, specialists of the micro-gouttelettes of ink invented by the computer manufacturer. Worse, climate effects on the planet itself, related to the increase of this amount of clouds, have not been assessed.

A second option plans to disperse massive amounts of iron particles on the surface of some oceans. They would stimulate the growth of this plant plankton in these waters, the latter having the ability to transform carbon dioxide into oxygen. A start-up in Silicon Valley, Climos, launched a few years in this way. But his current CEO Dan Whaley says now that the company performs Council missions in this area rather than laboratory research and refuses to mention its mysterious customers. In any event, the Royal Society of London issues more vivid reserves on this approach, especially because no one can say what long-term effects would have for wildlife and marine life the addition of this iron filings in their ecosystem...

Create an artificial "shield"

If one really wants to fight climate change, why not try to reduce the amount of heat that the Sun sends to our planet Roger Angel, an astronomer at the University of Tucson in Arizona, specialist in the large space mirrors, suggested sending in the space of billions of small discs ceramic, thus constituting an artificial "shield" which would remain in orbit around the Earth. "I know that this looks like a crazy project, but we live in a mad world," justifies in a recent article published by the magazine "the atlantic", in Washington. Here again, this is not say that technology is not ready, not to mention that, if the project appears pharaonic, the cost would be in some way.

There is an alternative to this approach, just less utopian. It is based on the observation of a natural phenomenon: volcanic eruptions. After that of Mount Pinatubo, which occurred in the Philippines in 1991, temperature had declined by an average of a Celsius demi-degré in the region, for several years. Explanation for the climate scientists: sulphur particles released by the volcano in the atmosphere, which remained long enough altitude so alter the climate. Hence the project to artificially spray particles at very high altitude sulphur dioxide to permanently achieve the same effect.

Capture CO2 particles

If the main problem of the greenhouse gases that warm the planet, why not get rid It is the idea of Professor David Keith, specialist of energy technologies at the University of Calgary, in the Canada. He imagines giant covered construction of filters coated with a chemical solution capable to capture CO2 particles which pollute our atmosphere. Is to develop the method that will retrieve the carbon dioxide to treat... without consuming too much energy.

A team of Columbia University, led by the specialist of Geophysics Klaus Lackner, imagine a Variant: a kind of synthetic tree"able to absorb 1,000 times more CO2 than natural trees. In reality, it is rather small plants - that could be deployed anywhere on the planet designed to suck this carbon dioxide then liquify it into fuel.

None of the proposed solutions is today reliable technical. Many cost also strong, including that of the heat shield. Finally, point is need to be Nobel Prize to be convinced that most of them would effects on the climate or the environment, we know not anticipate to this day.