They are the ultimate technological fixes: schemes that will span our planet and involve scientists in reshaping our world to save it from global warming. Yet only a few years ago, such projects — giant space mirrors, flotillas of artificial cloud makers and ocean fertilisation programmes — were dismissed as the stuff of science fiction.

Today many engineers and researchers — fearful of the rate at which our planet is warming — say geo-engineering projects are now mankind’s only hope of saving itself from the impact of climate change. A major report and a new exhibition at the Science Museum in London starting next week will resurrect the debate.

Despite 10 years of international negotiations aimed at reducing carbon dioxide levels by between 60-80%, global emissions are still rising. The only hope, say geo-engineers, is to change the planet, alter its oceans and reshape its cloud cover. It is a point highlighted by Brian Launder, professor of mechanical engineering at Manchester University, England, who was once ‘neutral’ about these great geo-engineering projects but who has come to believe that current attempts to reduce CO2 emissions are doomed to failure.

“As time has gone on I have become increasingly concerned about the lack of progress on climate change and [although] they once seemed a last resort, I have to say we’re going to need to do this.” Launder is now editing a forthcoming issue of the Philosophical Transactions of the Royal Society in London which will be devoted to the subject of geo-engineering schemes. The latest assessment report by the Intergovernmental Panel on Climate Change considered three major techniques to reduce sunlight reaching the Earth: orbiting mirrors, sulphur particle schemes and projects for enhancing cloud cover.

The ideas “could have beneficial consequences” by increasing agricultural productivity and forestry, the panel concluded. Carbon dioxide would be left in the atmosphere, stimulating plant growth, while reductions in sunlight would stop temperatures from rising even as CO2 levels continued to increase.

“Geo-engineering is one of the types of thing that are worth investigating,” says Ken Caldeira, of the Carnegie Institution of Washington. “If we can generate 100 ideas, and 97 are bad and we land up with three good ones, then the whole thing will have been worthwhile.” Opponents to such schemes point out that it is technology that got mankind in its current fix.

Schemes for fertilising the oceans with iron compounds pose immense risks to marine life, for example. Geo-engineers defend their schemes by pointing out that emissions of greenhouse gases are already bringing huge changes to natural ecosystems. It is a point stressed by the distinguished ecologist James Lovelock: there are dangers in intervening but the risks posed by doing nothing are worse. “There may be all sorts of ecological consequences,” he said. “But then stakes are terribly high.” — The Guardian