While the rewards may one day prove mind blowing, the risks inherent to the development of geo-engineering technologies that many scientists believe are now necessary to combat global warming are so huge that proposed pilot projects are struggling to find funding.

According to a series of papers published today by the Royal Society, the failure to address soaring carbon emissions means that the world should be preparing geo-engineering techniques capable of artificially lowering temperatures, such as dumping iron into oceans to improve plankton's ability to soak up carbon or seeding clouds to bolster their ability to reflect the sun's rays.

Writing in the preface to the collection of papers, Brian Launder of the University of Manchester and Michael Thompson of the University of Cambridge argued that, "While such geo-scale interventions may be risky, the time may well come when they are accepted as less risky than doing nothing."

However, several of the scientists who contributed work for the Royal Society series have today admitted that with no commercial model currently in place to monetise geo-engineering projects, they are struggling to raise the funding required to move beyond the planning stages.

"There is no money to be made from saving the planet," said Stephen Salter, emeritus professor of engineering design at the University of Edinburgh, who is proposing a project to seed marine clouds to increase the amount of energy they reflect. "You can make vast sums from wrecking it, but not the other way round, unfortunately."

Salter claimed that his team could undertake a working pilot project for about £20m, a sum he describes as less than the security budget for the UN's series of international climate change negotiations. But he admitted that attracting the investment was proving difficult.

"At the moment there is no commercial return on these [geo-engineering] projects for bringing the temperature down," he said. "The people working in carbon markets don't want these type of projects included and unless someone works out a way to put a value on cooling, there is no commercial proposition."

Speaking to BusinessGreen.com, Launder agreed that geo-engineering projects were facing huge difficulties in raising the funding necessary to move their proposals into the pilot stage. "The funding could come from government, but it is difficult prising out the necessary development money," he said. "For businesses, we are talking about technologies that have to be ready to go, but you hope you will never have to use… that requires a new business model to anything we have currently."

The commercial risks associated with such projects are simply too large for most investors, according to David Metcalfe, director at independent green business research firm Verdantix. "There is a growing sense among scientists that we will need some of these big bets as part of the portfolio for tackling climate change," he said. "But for most investors, even projects such as carbon capture and storage are too risky a bet, so [geo-engineering] will really struggle [to attract funding]."

The risk associated with geo-engineering projects was highlighted earlier this year when almost 200 countries imposed a moratorium on ocean iron fertilisation projects.

Iron fertilisation is believed to help lower carbon dioxide concentrations in the atmosphere by stimulating the growth of phytoplankton, which trap the carbon dioxide on the ocean floor when they die. However, many environmentalists have criticised the approach, claiming it could do huge damage to delicate marine ecosystems.

The ban on fertilisation projects throws into doubt the future of a number of startups already working on the technology, such as US firm Climos and Australian outfit Ocean Nourishment Corp, which announced plans for a pilot project off the coast of the Philippines earlier this year.

Salter is confident that his proposals for cloud seeding could avoid many of the environmental risks associated with more controversial and costly projects such as ocean fertilisation, and is continuing to seek financial backing.

"The advantage of seeding clouds to make them whiter is that you can try it on a small scale and it is reversible," he said. "You can also use satellites to measure how much energy is reflected and prove it is working."

But Metcalfe warned that commercial backing for geo-engineering projects will remain very difficult to secure. "The problem with any project in the R&D phase is that an investor has to ask when it will start delivering," he said. " And with these projects that is just not clear."