News analysis: Climate Change

We are now standing on the threshold of the carbon age. Throughout the rest of our lifetimes, and far into the future as global warming takes hold, we will progressively measure our actions in the stuff.

Already the rules for the new age are beginning to emerge. We are beginning to learn that we should reduce our "carbon footprint" - the amount of greenhouse gases we each produce - to tread more lightly on the Earth. Companies are taking up "carbon trading". Ministers are even starting to consider carbon rationing (except that they dare not use the words), where each of us will be entitled to cause only a limited, and diminishing, amount of pollution. It has all come a long way since the element was known mainly as the "lead" in a pencil.

Carbon - which combines so readily with other elements that it is known to form nearly 10 million different compounds - is the most important building block of life. We exhale it with every breath, eat it in every meal. And, since the Industrial Revolution, we have used it, laid down over eons in underground "fossil fuels" - coal, oil and gas - to power our ever more prosperous and mobile lives.

Yet it is our very use of these fuels and the felling of forests that are causing our carbon crisis. Each emits carbon dioxide, the main cause of global warming. Thanks to us, concentrations of the gas are higher than they have been at any time in the past 650,000 years, and they are rising. Carbon dioxide in the atmosphere traps some of the energy that reaches Earth from the sun, preventing it from escaping back into space; thus, like an invisible blanket, it warms the planet. We know this happens because natural levels of the gas keep in enough heat to make the world habitable - without it, ours would be a freezing planet. It is little more than common sense that adding more carbon dioxide will make the blanket thicker, heating the world up more.

The warming effect of the gas was first pointed out in 1827 by the French scientist Jean-Baptiste Fourier. And on Christmas Eve 1896w Svante Arrhenius, a depressed 35-year-old Swedish chemist trying to take his mind off the collapse of his marriage to his beautiful research assistant, sat down and started a year-long mathematical calculation. This concluded that doubling the concentration of carbon dioxide in the atmosphere would raise global temperatures by some 5C to 6C.

And ever since, the basic physics has never been seriously challenged. So why the much-touted scientific debate over global warming? The truth is that there really isn't one. A recent survey of 928 scientific papers found not one that disputed the reality of climate change. Last year, the scientific academies of the G8 countries, plus India, China and Brazil, issued a joint statement confirming it.

Yet a handful of much-publicised contrarians create the illusion of a debate. Few are climatologists. Even fewer publish any research. Some openly admit to being funded by the oil industry.

They flourish because of the media's love of controversy and newspaper columnists' understandable desire to be provocative. This "debate" provides politicians with excuses for inaction, but the public seems to have made up its mind - 85 per cent of Britons now recognise that climate change is already taking place.

Since the Industrial Revolution, carbon dioxide levels in the atmosphere have risen by more than a third, from around 280 parts per million to above 380, and the rise is accelerating. Emissions from transport are growing particularly fast.

Other greenhouse gases add to the warming: methane, released by fuels and paddy fields; nitrous oxides, mainly from fertilisers; and a few manufactured chemicals. Now at last, the world is beginning to try to restrain them, before climate change runs out of control.

Some Western European countries, including Britain, have reduced emissions by policy changes. Eastern Europe and Third World nations have seen them fall through economic decline.

In other developing countries they are rising rapidly, often from a low base. A small increase in the US, which emits a quarter of the world's carbon dioxide, is much more damaging than a big one in Bangladesh.

This month, the massive Stern report concluded that emissions will have to be cut by 25 per cent by 2050, to give the world a chance. As natural justice and political reality dictate that poor countries must be allowed to burn more fuel to grow, rich ones will have to cut their emissions by 60 per cent.

This week, ministers from around the world will fly to Nairobi to join the latest negotiations on how to achieve this. One of the favoured means is by "carbon trading", whereby nations and companies are given pollution allowances; those that wish to exceed them have to buy spare permits from those producing less.

The most sophisticated such system, "contraction and convergence", was dreamed up by a former London busker, Aubrey Meyer, who runs the Global Commons Institute. Under it everyone on Earth would be entitled to the same carbon footprint. National emissions would have to "converge" until each country emitted the same amount of pollution per person. Rich ones would cut back while poor ones increased, within a "contracting" and ever-reducing world total.

Politically difficult though it may be, it is attracting growing support. David Miliband, the Secretary of State for the Environment, has recently endorsed an even more controversial proposal - that each person should be given a steadily reducing carbon allowance. Those who want to exceed this permitted footprint, such as by driving more or flying frequently, would have to buy permits from those who live more modestly.

Experts think it would be the best way to bring down emissions fast and it should mean that the poor get wealthier by selling part of their allowances to the rich. Then we will be in the carbon age indeed.