What if Copenhagen fails?

The Copenhagen summit this Autumn is hugely important. It will, it is to be hoped, create a new climate change treaty to replace Kyoto.

The summit represents the culmination of months of negotiations - negotiations that are taking place right now between civil servants of the world's leading and emerging powers. We have some inkling of how those negotiations are going.

Not very well.

But even if the negotiations were going perfectly and in December the world signs up to the Copenhagen Treaty, it might not be enough to deliver the massive cuts in carbon emissions scientists say are needed to avert catastrophic climate change. After all, Kyoto promised much and delivered not enough.

It would be negligent beyond words for the world's leaders to put all their eggs in the basket of a Copenhagen deal. And it would be unrealistic to believe that a deal of the extent needed is deliverable. Not because politicians are weak, or short-sighted, or fail to grasp the scale of the problem - though some are, some will be and some do. No; simply because the scale of the action - and the amount it will cost, is probably going to be too great for their - and our - electorates to swallow.

As much as politicians need to recognise the catastrophe of climate change, so too must the most fervent environmentalists recognise that politics is about the art of the possible (and I mean possible in a democracy); and what's possible is - I suspect - less than what is actually needed. The full extent of the sacrifice required of the developed world is not likely to be tolerated by its voters. And the developing world, where carbon emissions are rising exponentially, will not tolerate a curtailment of their massive growth. On that basis the most likely outcome of Copenhagen is failure - albeit that it will be presented as a success.

So what happens next? This doesn't necessarily have to be the end of the world as we know it, though many will claim it to be and if nothing else is done, that will be the consequence.

The Royal Society - Britain's UK Academy of Science - published a report recently looking at what they call geo-engineering - using science to combat climate change. One option being investigated isn't as speculative as some other options that have been considered and is relatively low risk. We know this because it has already worked. It's called "stratospheric aerosols".

You may remember the eruption of the Philippine volcano Pinatubo in 1991. It was by all accounts a remarkable sight - the second largest eruption of the 20th century. It lasted several weeks and in the process it pumped millions of tonnes of dust and ash high into the atmosphere. These were stratospheric aerosols: a giant spraycan clouding the outer atmosphere in dust fine enough so as not to obscure the sun but substantial enough to act as a block to a proportion of its rays.

In the year immediately following that eruption, the world's climate cooled by half a degree centigrade because of that one event. Because remember: greenhouse gases in themselves do not cause global warming - the damage they do is in trapping heat; preventing it from rebounding back out into space. And that's why the world is gradually warming.

We know that injecting particles of ash high into our atmosphere works in cooling global temperatures. Second, its subsidiary impact on our climate systems is short-term and minor if it exists at all. Third, it's viable to replicate that volcano effect without the mass destruction that accompanies natural eruptions. And finally, it's possible to do it without blowing the bank.

We should continue reducing carbon emissions radically - if for no other reasons than carbon-based fuels are finite, are concentrated in unstable regions governed by hostile, erratic regimes, and are damaging in all sorts of ways, not just climactically.

But isn't there a better way than simply insisting that the only way we can combat climate is by vast sacrifices that will dramatically curtail the quality of life the developed world has come to enjoy and the developing world is growing to expect? Wouldn't a far better way be to make carbon reductions part of a package that includes safe geo-engineering?

And even if you think we should continue to meet the climate change targets the world has set solely by carbon reduction, wouldn't it be wise to have a fall-back in case the scientists' forecasts are wrong and we need to go even further - a far from implausible scenario?

I can't see a downside to investing in this option. If you're cynical about politics and politicians it deserves backing. If you're a climate change sceptic it deserves backing. If you baulk at the vast costs of climate change it deserves backing. And most importantly, if you want to save the planet it deserves backing.