Report  In a basement in London, in probably the smallest office in the world, an american television crew is demanding to know what the weather will be like on april 29, the day Prince William marries Kate Middleton. any mainstream meteorologist would tell them their question is unanswerable so far in advance. But Piers Corbyn is not mainstream.  "It looks like being a cool day with blustery showers, although we do have to see if there will be a blocking high pressure to keep things away. But to do it properly we need a little more time."  Corbyn, who is the brother of the Labour MP Jeremy Corbyn, has the air of a Dickensian clerk - crazy hair, disordered clothes, and he sniffs persistently through a giant nose. "He comes across," muses one climate scientist, "as mad as a hatter, but he's not daft."  Not being daft makes him, to the vast majority of climate scientists, a very dangerous man indeed and one in serious need of a good slap.  "He is... an utter prat."  That was Professor Philip Jones of the University of East anglia Climate Research Unit. His view of Corbyn appeared in one of the leaked emails in the "Climategate" scandal, which proved to global warming sceptics that scientists like Jones were prepared to rig the evidence to advance their case. Corbyn, you see, thinks that global warming is a scam, a fraud, bad science, you name it. "There is no evidence whatsoever," he says, "for any long cycle connected with carbon dioxide, absolutely none."  Later, over breakfast at his club, Brooks's, the 3rd Viscount Monckton of Brenchley - pinstripe suit, clashing shirt and tie - tells me that he also thinks warming is a scam, a fraud, etc. "Selfsustaining nonsense," he calls it, "where anybody who wishes to be part of the establishment dare not stand up and say it's nonsense."  Christopher Monckton, joint deputy leader of Ukip, the anti-immigration party, is perhaps the most high-profile warming sceptic on the planet. Though not a scientist, he is highly scientifically informed. "If it were him versus al Gore or him versus David Cameron, he's vastly better scientifically qualified," says Richard Lindzen, professor of meteorology at Massachusetts Institute of Technology.  Monckton is lapped up by sceptical americans for two reasons. First, he has a plummy English accent and he peppers his talk with classical references. Secondly, he has a habit of suggesting that warming is a quasi-communist plot. The believers, he says, are those who once would have been communists. They are intent, he claims, on a form of world government capable of overruling democratically elected leaders. He is very self-conscious and aware that he might be taken as bonkers. at one point, in the middle of a long story about a cold war Soviet plot, he stops and looks at me. "I watched your face and you looked as if you were thinking, 'Oh, my God, what kind of a nutter am I talking to?'" There are good reasons to treat Corbyn and Monckton with caution. Corbyn bases his weather forecasts and his carbon denial on a system he will not divulge; he maintains that climate change is the result of solar activity rather than manmade.  "The thing about Piers," says Professor Chris Rapley of University College London, one of our most distinguished climate scientists, "is that he will not reveal his methodology and therefore cannot be taken seriously as a scientist."  Monckton, meanwhile, has a nasty habit of rewriting his own story. To me, for example, he denies he advocated quarantining those infected with HIV in an article in the american Spectator in 1987. He says he simply said they should be warned about the dangers. In fact, he was very specific about quarantine. The infected, he wrote, should be "isolated compulsorily, immediately, and permanently... Carriers need not be isolated from each other... and carefully supervised visits from uninfected people would be possible."  Both of them tend to alienate other sceptics. One anti-warmist had doubts about Monckton when he argued that coal was as clean as wind and solar.  and Corbyn's assertion that there is no carbon effect is dismissed by even hard sceptic scientists. Neither man, in short, is strictly credible. But they are on a roll, both making regular appearances on american TV. The question is: what should the reasonable person now think? Since I wrote about being converted to warmism in this magazine just over a year ago, the greens - and I - have been on the run. They are so much on the run that, on key issues, they have fallen silent. The last few months have seen a series of spectacular weather events - floods in Pakistan, Brazil and australia, cyclones hitting australia, huge snowfalls on the eastern coast of america, and two very cold winters in Britain.  Such extreme events were, in fact, predicted by global warming models. But nobody has dared to claim them for the climate change case.  "Not a single climatologist," says Rapley, "has even dared to discuss the possibility that these events are linked to climate change... The truth is you cannot attribute any one of these things to human-induced climate change, but they represent a series of coincidences that seem very unlikely."  The climate scientists have been demoralised by a series of heavy blows to their credibility - among them the Climategate affair. The Labour MP Graham Stringer was on the select committee that questioned Dr Philip Jones about his emails. "It was quite a shock," Stringer says. "It was not just the emails, which were probably over the top, but when you look below at what they were actually doing, they weren't doing science."  Stringer, a scientist by training, is one of the few politicians to come out as a warming sceptic. But there are plenty of closet sceptics. "With Labour MPs, it's become more of an issue like racism: 'Of course you're against it, and if you're not, you're not going to be invited to my dinner party.' " There was also the 2009 Copenhagen climate conference, at which world leaders got together to do almost nothing, and then last year's Cancun summit, at which the poor accused the rich of failing to deliver the $30 billion promised to help mitigate the effects of warming. and, finally, the science itself turned weird. after decades of temperatures increasing steadily, the trend levelled off in the noughties. It did not, as some sceptics claimed, go flat. It was still the warmest decade on record, but the rise had dropped to one-tenth of what climate models had predicted.  In america the Republicans' success in the midterm elections has given the sceptics' cause what it does not have here: important mainstream representation. But that could be about to change.  Down in the leafy lanes, something is stirring.  "We prefer not to use the word 'sceptic'," says Fay Kelly-Tuncay. "We prefer 'realist'." She is the Surrey housewife organising a campaign to repeal the 2008 Climate Change act, which commits the UK to cutting carbon emissions by 80% by 2050.  "We've become very aware that data has been manipulated, and the most annoying thing is the closing down of debate. There have been complaints about the BBC having meetings to decide that all scientists agree, so let's stop talking to sceptics. I think that's undemocratic... "We've had a scare story running since the 1970s. It started off as global cooling. Then they said the Earth was warming and it would be catastrophic, there would be tipping points - and those things just haven't happened."  Zeroing in on the 2008 act potentially gives the campaigners real political traction. "We think MPs rushed to judgment on global warming and made a catastrophic policy blunder," she continues. "We feel energy subsidies will be too high. Wind farms and solar, they're uneconomic. also, the government is ignoring gas from shale and shale oil, which is very cheap and in plentiful supply... We don't really understand why."  Graham Stringer adds the jobs issue into the anti-act mix. "Gradually, those MPs who take the global warming arguments at face value are beginning to realise they'll have to explain to their constituents why industries are closing down and why their domestic fuels bills are going up. Making renewable energy three times as profitable as traditional energy, and making my constituents pay for it - that's a very bad idea."  Finally, there is the moral issue. The Rev Philip Foster is now retired from his job as vicar of St Matthew's, Cambridge. about 10 years ago he was talking to a scientist who asked him how much he thought temperature had risen in the last 120 years. "I said about two or three degrees. He said about half a degree." Foster was shocked that so much was being made of so little, and in retirement he has immersed himself in warming science. He is now a card-carrying realist. He does not believe rising carbon dioxide levels cause warming, rather that warming causes rising CO2.  I ask him why he thinks the warmists believe otherwise. "Scientists of a certain kind say, 'There's a problem. Will you give us money to research it?' It then becomes a self-fulfilling prophecy."  But the real issue for Foster is moral. "If africa is told it mustn't touch its coal, mustn't touch its oil, when it desperately needs electricity to run basic services, that's morally shocking. This western obsession is actually killing people. It is Christian charities pushing this, and it distresses me."  Repeal the act, the campaign to overturn the 2008 Climate Change act, will be launched formally at a meeting in St Ives, Cambridgeshire on March 19. This immediately precedes Climate Week, which runs from March 21 to 27.  Climate Week, and green politics in general, show that, if sceptics rely on dubious science, warmists rely on bad politics. The week is, as the website says, "a supercharged national occasion that offers an annual renewal of our ambition and confidence to combat climate change". Nothing damages a cause in secular Britain like quasi-religious language; it spreads suspicion.  Well, there is one thing even more damaging, and that is the pursuit of clearly unattainable goals. Caroline Lucas is the Green party leader and our first Green MP. She recently came up with the idea of the New Home Front initiative. Based on our performance during the second world war - when we cut coal use by 25%, we saved waste to feed pigs, car use plummeted and so on - it calls for Britain to get onto a war footing again to combat climate change. The glaringly obvious objection to this is that slowly rising temperatures do not have quite the same persuasive power as the Luftwaffe and massed panzer divisions on the French coast. So I asked Lucas how on earth she expected people to be talked into joining the new Home Front. The answer is leadership.  "If you think of the political capital that Tony Blair expended on persuading people there was a genuine threat from Iraq, if he had used that same political capital he had back in 1997, that charisma, that leadership, around the issue of climate change... you could communicate in a clear way what the threat is, what the benefits are of acting, and you could galvanise people."  This is the Greens shooting themselves in both feet prior to standing on a rake. If evoking the war as a model for our response to climate change is a mistake, then evoking Iraq is an egregious blunder. Blair did not get us into that war on the basis of his popular leadership skills; he got us in against massive popular resistance and on the basis of wrong intelligence and extremely dodgy dossiers.  So, torn between bad politics, grass-roots unease, eccentric deniers, terrible weather and unbelievably complicated science, what should you, the reasonable person, think? First, the heart of the matter is science, not politics. The kneejerk right-winger who embraces hard-ass scepticism as a necessary political accessory is as stupid as the kneejerk left-winger who embraces radical, back-toausterity warmism for the same reason. These people are pre-programmed ideologues.  Nevertheless, the science says that global warming is happening and that human activity is almost certainly the cause. There are important arguments to be had about the rate of warming, about its impact, and about "climate sensitivity", the degree to which the climate responds to small changes. But the simple truth is, unless some staggering new development reveals factors at work that have concealed themselves for 40 years from the best scientists in the world, denying the basics of the case is irrational, mere prejudice. Piers Corbyn claims to have such a revelation but, since he refuses to share his methods, he need not trouble the reasonable person.  Secondly, that rational formulation of the issue does not in itself solve any of the political problems. Our uncertainties about rate and impact entail profound uncertainties about action. How much should we spend, how much should we change our lives? The short answer is neithe