By Alex Kirby
BBC News Online environment correspondent
Scientists are studying possible ways of using engineering to help the world to adapt to increasing climate change.
Snow and ice influence climate strongly
A conference in Cambridge, UK, has been convened to consider possible options while ignoring "political correctness".
The organisers say many options appear at the moment very unlikely to work, with some even appearing to be "crazy", but insist that they must be evaluated.
They say engineering will probably have to play its part in cutting greenhouse gases by the huge amounts necessary.
The conference organisers are the Tyndall Centre for Climate Change Research, based at the University of East Anglia, and the Cambridge-MIT Institute.
The meeting, on 8 and 9 January, is entitled Macro-engineering Options For Climate Change Management And Mitigation.
One speaker is Professor James Lovelock, begetter of the Gaia Hypothesis, which holds that the Earth functions as a single organism which maintains the conditions necessary for its survival.
The organisers say reducing global greenhouse gas emissions by around 50%, which may be needed to avoid excessive climate change, will be very difficult, and could require even larger cuts by developed countries.
Clouds can reflect the Sun's energy back from Earth
They say: "Many people feel it is very unlikely that such reductions can be achieved just by improving energy efficiency and reducing carbon intensity by using renewable sources of energy."
So they see a need to evaluate possible macro-engineering options before any can be seriously considered as candidates, even if they prove to be only "an insurance".
So the conference is committed to considering all approaches "without preconceptions" and disregarding "potential pressures in relation to political correctness".
It will look at four main sets of possibilities:
- "sequestering" (storing) carbon dioxide, for example in the oceans, by removing it from the air for storage, or by improved ways of locking it up in forests
"insolation management" - modifying the albedo (reflectivity) of clouds and other surfaces to affect the amount of the Sun's energy reaching the Earth
climate design, for example by long-term management of carbon for photosynthesis, or by glaciation control
impacts reduction, which includes stabilising ocean currents by river deviation, and providing large-scale migration corridors for wildlife.
The organisers note: "Many of these possible options are highly speculative at present, and some may even appear to be crazy.
Closing the options
"However, that is precisely why they should be evaluated (and if necessary dismissed) as soon as possible.
"Otherwise politicians may seek to use them as 'magic bullets' either to postpone action, or as prospective solutions for actual implementation, once it becomes clear that the mitigation of climate change is going to be a major and very difficult task."
The conference was planned a year ago, long before acute doubts surfaced over the prospects for the eventual entry into force of the Kyoto Protocol, the international climate treaty.
There are hopes the oceans could absorb carbon
The US has rejected the protocol, and Russia, whose support is vital, has not yet said whether or not it will ratify it.
Professor John Schellnhuber, of the Tyndall Centre, told BBC News Online: "Kyoto is in a very difficult position, and it may be necessary to find other exit strategies.
Chances slipping away
"We may find we're in a cul-de-sac and have to think of other policies which transcend the protocol.
"But we must think about unconventional strategies in any case, because a back-of-envelope calculation shows we're unlikely to do the job without them.
"We may have missed the best time to intervene to protect the climate. Kyoto will reduce global warming by less than a tenth of a degree anyway.
"If it can be rescued, by then it may mean we've lost another 10 years and are simply running out of time."