Geoffrey Lean, RTCC, fair use: https://vimeo.com/54838707

@RichardHCNourse. Thanks. I'm touched. But it looks as if none will have one: Telegraph is pushing me out....

That was the rather modest way in which he announced it. Geoffrey Lean, the world's longest serving specialist environmental journalist, master of the trade for over 40 years, declared this week that the Telegraph had pushed him out.

In a subsequent blog, he outlined part of the significance of the decision.

“In the British press... there, in my estimation, some ten columnists who reject or underplay the dangers of global warming, with precious few columnar voices on the other side. I write with feeling, and declare an interest. Until recently I was perhaps one of such voice but in the summer I lost my half page column in the Daily Telegraph, - while rejectionist columnists across a whole range of newspapers have retained theirs – and I am now being pushed out altogether.”

Lean's role was an important one. In previous jobs at the Observer and the Independent on Sunday, he was able to tell generally left leaning types about another thing they mostly already cared about. But from 2009, when he moved to the Telegraph, he took on a different role.

I don't know exactly which ten columnists he was referring to, but what is certainly the case is that a disproportionate number of them (Charles Moore, Christopher Booker, James Delingpole) wrote for the Telegraph alongside him. He was a counterbalance, taking the arguments for the scientific consensus to the readership of Britain's biggest broadsheet.

We saw this role after the VW scandal this summer. Dr James Le Fanu wrote a column questioning the idea that particulates are particularly bad for us.

“The assertion that diesel fumes cause thousands of deaths a year” he wrote “is similarly contentious, the only evidence being a study demonstrating a marginally increased risk of lung cancer in a group of heavily exposed miners.”

Lean's response was calm and crushing. He outlined the hundreds of studies showing that exhaust fumes are indeed dangerous, some of which have involved more than half a million people. Le Fanu was politely demolished.

Among British journalists I've spoken to at COP, the news of his departure came as a shock: almost like the captain of the team had been sacked with no explanation, the day before the world cup final. A regular feature at the events (and he's said to be covering this one at his own expense), lots of people have stories about him.

Kyla Mandel, deputy editor of the climate website DesmogUK, for example, talks about his rumoured role in the final negotiations of the climate treaty in New York, in 1992. After many hours of fraught back-and-forth, there was a proposal from the chair that the negotiations, which were about to reach agreement, should be stopped so that delegates could refer back to their capitals: a delay which could knock the whole process off the rails. From the press gallery, Lean let forth an involuntary “NO”. The poor chair caved in, and the agreement was accepted without delay.

I hear that this year, at a briefing with the British delegation, Lean asked a question about the ongoing process. The diplomat responded “you'd know better than me”. Another journalist leant over to their neighbour and said “Geoffrey should really be doing these briefings”. Such rumours may or may not be 100% true, but they do show the esteem in which he is held by his peers.

So why has the Telegraph allowed this highly respected journalist to go, right before such a big gig?

In June last year, James Delingpole – climate denier and arch conservative journalist – wrote a piece for Breitbart in which he bemoaned “the studiedly centrist direction (the Telegraph) has taken”.

The centrepiece of his argument? They had appointed as their chief environmental commentator “a left-leaning Fabian called Geoffrey Lean, a man so in thrall to the Greenpeace/Friends Of The Earth/IPCC green narrative he might just as well have been George Monbiot’s favourite uncle”. The paper should instead have given the role to its climate skeptic columnist Christopher Booker, he argued.

A quick Google reveals occasions on which Lean has vocally criticised all three of the organisations mentioned, but it's the proposal that's more interesting. Booker, who normally only appears in the Saturday edition, had a column on the Telegraph website on Tuesday: “10 reasons why we shouldn't worry about man made global warming”. Is this a special for the summit? Or has the paper followed Delingpole's advice, a year and a half later? We'll see.

Lean himself points to a particular trend. “Rejection of the seriousness of climate change” he says, “is growing in the comment pages of British newspapers even as it is retreating everywhere else”. Is this shift what pushed him out? Who knows. But it's a worrying one, and one I'm sure we'll come back to as we dig through the British media in the coming weeks.

In the meantime, you can read Geoffrey Lean's valedictory column for the Telegraph, presumably penned after he knew he was going: "The old white men and their climate scepticism are finally in retreat", and follow his blog from Paris. He may have lost his job, but he certainly hasn't lost his voice.

We're digging through the media to see how climate change is reported over the Paris climate talks and beyond. Sign up to hear what we find out.