Leading article: Pretty green kinda guys

It has been David Cameron's first worst week. There will be many more. Alastair Campbell used to mock journalists for describing every setback as Tony Blair's worst week, and soon lost count. But it really has been a bad week for the Conservative leader. After a long phoney peace, a shadow minister has resigned and his MPs are mutinous. Many of them are baffled by his opposition to grammar schools; emboldened by Thursday's partial U-turn; unsettled by the claim to be more New Labour than Gordon Brown; and alarmed by the hiring on a huge salary of a controversial former tabloid editor as press secretary.

That sense of nothing going right for Mr Cameron carries through the interview with him that we publish today. Before he went to Crete on his half-term break, he allowed The Independent on Sunday into his refurbished house in west London to see how he personally was helping to save the planet. The windmill has come down because the roof was not strong enough. The composter does not work because it kept filling with water. And the gardener grows the prize-winning vegetables of which he is so proud. He describes himself as an "imperfect environmentalist" and says, disarmingly: "You'll find lots of holes."

On green issues, however, his charm is persuasive. He deftly lets slip that Samantha, his wife, was a member of Greenpeace. In other words, the Camerons are just like his target voters: right-on, wanting to do the right things for the environment but finding some of the practicalities a bit daunting. It is easy to dismiss Mr Cameron's green conversion as tactical and recent. But this newspaper applauds him wholeheartedly for two things.

First, it is in part down to him that climate change has become such a foreground issue in British politics. He set the pace and made the space. Tony Blair achieved much in recent years, bringing together the biggest and fastest-growing polluters, the US, China and India, to agree that something must be done. But he was too cautious in making the case that our lives must change.

Second, Mr Cameron thinks it is important for politicians to try to set a personal example. Mr Blair has never had much time for that sort of thing. Now Mr Brown and Sir Menzies Campbell, with a little prompting from this paper, feel that they have to follow Mr Cameron's example and set an example themselves. Mr Brown seems to have pulled it off with least fuss, although his interest seems even more recent.

There is a danger in Mr Cameron's self-deprecating sincerity - "we're still in the learning phase" - as it comes close to parody of Mr Blair's long-disbelieved "pretty straight kinda guy" theme tune. But it should be apparent that leaders cannot urge people to adopt a low-carbon lifestyle unless they are prepared to do so themselves. Nor will it be possible to build consent for green taxes and restrictive laws, such as the ban on high-energy light bulbs, unless politicians are seen to be part of a rising wave of green consciousness.

So far, so good, even if Mr Cameron is a greenie-come-lately. But the test is cutting greenhouse gas emissions at home and abroad, and it is a test in which the Conservative leader is not yet performing so well. Conservative local councillors have opposed restrictions on cars. His MPs have voted against legislation introduced by Labour that will cut emissions. The most recent example was the doubling of air passenger duty, which will cut British air travel by 4 per cent. The Liberal Democrats voted against it on the grounds that the increase was not enough - but Mr Cameron boldly abstained while allowing his MPs to vote against because it was too much.

This matters because it is only by measures such as these that the nations of the world have any hope of turning down the thermostat in the global greenhouse. At the G8 summit in Germany on Friday, a deal could be done to limit the world's production of carbon dioxide. George Bush has instead tried to divert the talks into a US-led voluntary process. As one of Mr Blair's final acts, he has adopted the familiar posture of welcoming the change in US rhetoric, claiming that such constructive engagement will encourage President Bush to go further. But experience suggests, as Geoffrey Lean, our environment editor, argues on page 38, that isolating the US is the more effective form of leverage.

We do not know where Mr Brown, Mr Cameron and Sir Menzies stand on this question. We should. Mr Cameron has made a start on green issues: now he needs to follow it through. He needs to join up the apparent sincerity of his personal commitment to a greener lifestyle with local government, national government and international policy. Where he leads, Mr Brown, the supreme calculator of political positioning, is bound to follow.

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