I'd never imagined a career move that would see me stepping gingerly between the crevasses of the Greenland ice sheet, let alone covering a topic like climate change. In fact, when the job of environment and science correspondent first came up, the Iraq invasion was on the horizon and I wondered if I could face leaving my position in foreign news.
It had been on assignments abroad that I'd had some of my most formative experiences: East Berlin for the fall of the Wall, with a family who'd watched the barrier being assembled in the 1960s; a golden summer evening in Bosnia scarred when two children, familiar from a house close to the BBC's, were shot by a sniper. Part of me worried that the environment brief would feel tame. Was I that interested in farms and fish? Most significantly, if I thought about it, I'd have described myself as cynical about the green agenda. In the heat of Disneyland in California, I'd loved the chill of outdoor air-conditioning.
A colleague identified my dilemma: he'd never seen me as someone instinctively comfortable with things ecological, joking that he didn't see me as "one of us bunnyhuggers". He was right.
But then my editor came up with a line so persuasive that I'd have been a fool to hesitate: the job would be to report on the planet and its changes – to cover anything I might see on the front of National Geographic or even imagine seeing there.
And so I found myself in places like Greenland meeting researchers worrying about climate change. It was a new field for me but in every subject I've covered the practitioners have been skilled at scaring themselves to death. In the 1980s, in a bunker beneath Nebraska, a US Air Force colonel, pointing to a picture of a smiling Gorbachev, warned that he could be the front man for a devious Communist plot. After the Cold War, analysts urged me to grasp the new threat of Islamist terrorists. The warnings about the Russians were wrong but those about al-Qa'ida were right. So what about global warming? Was it plausible that melting ice would drown London?
Instinct told me it must be easy to exaggerate environmental threats. Either the timescales are too long for a news reporter to keep up, or the threat never materialises and those who warned about it claim credit for heading it off.
As the job developed, some issues emerged as more obvious than others. Illegally-felled trees in the Amazon rainforest? No quibbling there: I touched the fresh sap dripping from severed trunks. The ozone hole? In Chile, under the hole, I saw the cancer scars on an old man's face.
But it's a much bigger step to say that the warm period we're in now is being made warmer by us. Are we really endangered by relatively tiny quantities of carbon dioxide? People assumed I was a green convert. An old friend of my father's, dismissing global warming, smiled pityingly as he described me as "a believer" when, like any reporter, I just wanted the facts. Some were found in the polar regions where projects to extract ice cores, which are marked like tree rings with each year's accumulation of snow, reveal the patterns of the ice ages and changing levels of CO2.
My immediate thought on seeing the graphs was that the gas has fluctuated on a huge scale without any hand from us. I then ran my finger along the carbon dioxide data over the past 800,000 years: with all the natural changes, its level never got above 300 parts per million. Now it's 387ppm. This is what the fuss is all about.
After a year or two in the job, the subject was gaining profile. But it was attracting criticism. One letter-writer, complaining about green taxes, called me a "seething shite". I was accused of doing the Government's bidding by hyping climate change to make it easier for ministers to punish motorists.
The doyen of climate sceptics was Michael Crichton, author of ER and Jurassic Park. In his thriller State of Fear, environmentalists staged disasters to hide the fact that climate change was a hoax. Crichton has since died of cancer but one day in 2005 I had the chance to meet him over lunch. With a presidential aura, he was on impressive form. Over starters, he explained that he was environmentally aware – he and his wife had used cloth nappies on their babies instead of throwaway ones. But studying the research on carbon dioxide and warming left him unconvinced of the link; the evidence, as defined by the usual rules of science, wasn't there.
I described how I'd seen researchers go about their work carefully and methodically. These weren't campaigners, they were genuinely interested in the truth. His answer? That climate change has become such a guiding principle that researchers can unwittingly distort findings.
Fast forward to Wembley, July 2007, and the scene could not have been more different. Al Gore's Live Earth campaign was in full swing and my role in the BBC's coverage of the Wembley concert was to be Mr Impartial. Razorlight had come by the studio, Genesis were due on soon, Madonna was to appear later. In a surreal twist, when the Pussycat Dolls arrived – dressed for an orgy – they'd just been briefed by a Met Office scientist who was bowled over. "They're across far more of the science than I'd expected," he blushed.
Ushered onto a sofa beside Jonathan Ross, the music deafening, I said that I'm a correspondent not a campaigner, there are things the scientists know and quite a lot they don't, that the science has never been firmer on the basic idea that our greenhouse gases are having some effect on the climate but, whatever people say, we don't know what the impact will be. The organisers of Al Gore's campaign won't have liked it.
And as climate change became more political, I found myself under fire from some environmentalists. Reporting on a protest outside a coal-fired power station, a woman with spiky blonde hair accused me of "obeying establishment orders" by not telling the public about the dangers of climate change.
Two years later and, with Copenhagen approaching, negotiations on a new climate treaty were faltering. Was I optimistic or pessimistic, an earnest woman at a seminar wanted to know. I said that sometimes it felt like we were on the cusp of a low-carbon revolution – if Warren Buffett invests $250m in China's largest electric car maker something must be up. But quite often, the opposite looked more realistic.
I was thrilled at the wheel of a battery-powered Tesla sports car – the ultimate in green chic – but I was also relieved that on a filming trip across the Arizona desert our hire car had a petrol engine. Ahead of a cousin's wedding in France, I shunned the train and chose the quicker 99p seats on a budget airline instead.
By the time of Copenhagen itself there was a more fundamental question: how reliable was the science? The emails from the University of East Anglia's Climatic Research Unit had burst onto the scene. And while the UN conference was underway, climate sceptics, newly invigorated by the doubts raised by the emails, had gathered in the centre of Copenhagen. "About time you're here," said one man as we arrived. "I thought the BBC was banned from criticising climate change."
This was a meeting in a parallel universe. Up the road, negotiators at the UN conference were struggling over greenhouse gases. By contrast in here, carbon dioxide was a good thing: plants like it. Mainstream scientists were corrupted and too scared to challenge the orthodoxy. And governments would use any excuse to raise taxes – in the name of saving the planet.
The big question was whether the doubts about climate science would influence the negotiations. A key figure to ask was Arnie Schwarzenegger: a green Republican. In a media scrum, I got the chance to throw him a question: what do you say to those in the US who don't believe global warming is man-made?
This seemed to throw him at first, but then he got into his stride. "Global warming is a huge obstacle and if we don't spend the money now it'll cost us five times as much later."
I put a similar question to another famous right-wing politician, one never to pass up an opportunity to bash fashionable causes: Boris Johnson, Mayor of London. Fresh from the cold, his blond mop was wilder than usual, his cheeks redder. I asked what he made of fellow Conservatives like Lord Lawson who were saying the jury was out on man-made warming.
"The jury is definitely back," Boris declared, "and the evidence is overwhelming." Even if it wasn't, he said, it made sense to use energy more efficiently. In the conference itself, only one delegate mentioned the emails: the man from Saudi Arabia. Nevertheless the event ended not with the bang of a treaty but the whimper of an "accord". The biggest powers were not prepared to make the scale of commitments the experts said was needed. The final 24 hours were the most dysfunctional I'd experienced at any international forum. Confusion, exhaustion and distrust undermined the outcome.
I was one of the last broadcasters left. The crowds had vanished and the ice on the glass roof looked grey. The man operating the live camera was from an agency and I hadn't met him before. We chatted about the conference.
Didn't do a lot, he suggested. I agreed.
Connected to the studio in London, we both listened to the story before mine: Eurostar trains were paralysed by freezing conditions. And I knew what the cameraman would say next: "Not much global warming anyway."
Reporting Live from the End of the World by David Shukman is published by Profile Books (£12.99). To order a copy for the special price of £10.99 (free P&P) call Independent Books Direct on 08430 600 030, or visit independentbooksdirect.co.uk