LEADING ARTICLE:Sharper, clearer, greener, better

There are two international conferences to choose from next week. In Berlin, the Global Climate Protection Conference will look at progress made on saving the world from global warming since the 1992 Earth summit in Rio. Meanwhile, Granada, in Spain, will host an "International Conference on Car-Free Cities". Visitors will appreciate the irony of this. In Granada only the toilets are free of traffic.

But then, according to several recent works, the whole area of environment and greenery is rife with hypocrisy, exaggeration and wrong-headedness. Wilfred Beckerman's Small is Stupid and Richard North's Life on a Modern Planet take issue with just about every aspect of the traditional green agenda. North argues that "for 20 years it is the campaigners that have been manipulative, conspiratorial and desperately economical with the truth".

Given the apocalyptic visions conjured up over the years of over-population, cooking-pot temperatures and rivers of filth, nothing is more tempting than to settle back, exhale gently and feel relieved. You can look the kids in the eye after all.

This relief will be temporary. The conference in Berlin will be discussing evidence from careful and conservative sources, which suggests that global warming is indeed happening, and may start to accelerate. Not, of course, at the rate that some on the fringes of the green movement once claimed. Those futuristic magazine illustrations of London under water were, of course, fanciful. Nevertheless, Met Office calculations predict that average temperatures will have risen by 1C by 2040, the fastest warming since the end of the ice age.

The emergence of the enviro-sceptics and first evaluation of progress since the Rio summit show that we are at an important moment in the debate about the future of the planet. The truth is that this a complex area, which has been too full of people who enjoy the sound of their own assertions. Understanding what is happening to the earth and why; mapping actions to be taken and their consequences, call for scrutiny, maturity and carefulness. Increasingly, there are signs that the green debate is, indeed, growing up.

A new consensus is starting to emerge that rather dates criticisms made by the Beckermans and the Norths. Policy-makers and campaigners now know that they must be more careful about calculating what is likely to happen. They are also learning not to claim more than is known. For instance, they accept that it is impossible to be sure how much of the rise in the world's temperature is caused by man-produced greenhouse gases and how much may be down to natural climatic fluctuations. Finally, there is a more practical attitude developing towards adopting policies to improve our environmental prospects.

In the best sense greenery is becoming political. It is no longer reliant upon the shock effect of millennarian predictions to gain attention, but has entered the real world of cost-benefit analysis. In that world nothing is certain and clear-cut decisions must often be taken that are partial, or are a hedge against the future.

The most obvious result of this maturity is the advocacy of so-called "no-regret" policies - ones that could do no harm under any circumstances - and might do much good. Such policies include a substantial push on energy conservation. Whatever the contribution of CO2 (from power stations and other sources) to global warming, fuel efficiency is bound to be cheaper and cleaner than profligacy. Afforestation is also relatively cheap, leads to CO2 absorption and commands political support around the world. Likewise, policies that help the development of efficient public transport at the expense of the car make sense under almost all circumstances.

None of this is an argument for complacency. Just because we cannot be sure of the future does not mean that we have any right to be sanguine about it. There are plenty of things going on, from car pollution in Western cities to the great migrations of China, which give rise to fears about life in the 21st century. But clear heads and sharp minds are the best tools we possess to ensure hope for our children.