The trillion-tonne challenge

What should come after the end of the first round of the Kyoto Protocol in 2012? Fred Pearce makes a

There is a dangerous pessimism abroad which says no. Gaia guru James Lovelock and government chief scientist David King have both succumbed. Yet I say we can, and I'll tell you how. But first, some simple science and arithmetic. The atmosphere's temperature is largely set by the amount of the greenhouse gas carbon dioxide it contains. In the last ice age, when most of Britain was covered by a kilometre of ice, the atmosphere contained about 400 billion tonnes of the stuff. Then planetary process switched some 200 billion tonnes from the oceans to the atmosphere, and the world warmed up.

That's where things rested until the industrial revolution, when we started burning fossilised carbon fuels such as coal and oil. So far we have added another 200 billion tonnes, making about 800 billion tonnes in all, and raised temperatures by almost another 1ºC. More will come once time-lags unwind. To prevent irreversible events, such as runaway warming or collapsing ice sheets, we have to stop this accumulation of carbon dioxide. Some scientists say the ceiling should be 850 billion tonnes. Most agree that, at the worst, we should keep below 1,000 billion tonnes. And, because most of our emissions stick around for centuries, that means we will ultimately have to virtually halt our emissions. That is the trillion-tonne challenge.

Technically, we can do it. Take your pick from wind or nuclear power; solar energy or hydrogen; carbon burial or investment in energy efficiency. The world could quite quickly start reducing emissions and, eventually, kick the carbon habit entirely. Economically, most options are already competitive with likely future oil prices. But politically? There's the rub. How do we get organised? And how do we share out the task?

Right now, developing countries such as China would be entitled to point out that the rich world has already used up half the available "space" in the atmosphere for carbon dioxide, so it should stop emissions forthwith to allow the poorer nations some of what is left. But because they fear changing climate will derail their own development, they are being generous and have not played the historical card.

They just want the rich world to take a lead. Quite right, too. Current annual global emissions work out at a bit over one tonne of carbon per head. But the US emits around five tonnes a year for every citizen, Europe averages under three tonnes, China is still below one tonne, and India and Africa are below half a tonne. So the route to progress is a more equitable share-out of the remaining pollution "space" - based on population.

This brings us to "contraction and convergence" (C&C). Advocated by a small British group called the Global Commons Institute, which is seeking a trademark for the term, this formula for future global emissions could, without exaggeration, save the world. The contraction half of the formula cuts global emissions year on year so we never go above the critical trillion-tonne threshold of carbon dioxide in the atmosphere. The convergence half brings about a gradual convergence of national emissions entitlements, according to population.

So, to meet the trillion-tonne challenge, national carbon-emissions targets might begin at about one tonne per person and then fall to half a tonne by 2050 and virtually nothing by 2100. Trading would be allowed, even encouraged. Especially early on, rich nations would buy permits from poor nations with spares. Corporations would trade their government-conferred entitlements, too. Trading would reward countries and companies with clean-up technology.

The logic is compelling, but some say it is fantasy politics. Big environment groups such as Greenpeace see the formula as a political dead end. I think they are profoundly wrong. For one thing, the business incentives for C&C are strong. Carbon trading, based around the existing Kyoto Protocol targets, is already functioning well. So well that some US fossil-fuel companies want their government to sign up to Kyoto so they can join in. The idea of being excluded from a trading system where they can make money is anathema to them. C&C provides a fixed and predictable emissions formula ideal for making long-term business decisions. And its tough targets would mean more trading and more profit potential.

Politicians still don't like it. But a coalition of the willing to fight a war against climate change could develop very fast after, say, a rapid succession of Katrina-style hurricanes along the US coastline, or the catastrophic collapse of Antarctic ice sheets. And how else will every nation be persuaded to join in? There may soon, as someone once said, be no alternative.

Fred Pearce is an editor and writer at the New Scientist. His new book, The Last Generation: how nature will take revenge for man-made climate change, will be published by Eden Project Books in June

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