There's nothing like a glacier crumbling into the sea in front of your eyes to remind you that climate change is more than an abstract reason to recycle egg boxes and wine bottles.
Right now, I'm writing from a small ship's cabin in one of the most isolated, desolate places on earth: the northern tip of Svalbard in the high Arctic, where I have come on an expedition, part of the point of which was to see what I've just seen. Which was a shelf of translucent blue ice the height of a house falling into the water like wet cake.
It's not that I didn't believe in climate change before this. On the contrary: I am of the background and generation that grew up in the mid-1990s with the notion of environmental destruction as an inevitability.
I was raised on the animation FernGully: the Last Rainforest and traumatic colouring books full of sad baby seals and herons choking on plastic bags. This gentle indoctrination was supposed to motivate us to grow up and save the planet, but by the time we were old enough to object, the forests were disappearing and the oilfields burning fast enough for it all to seem too late.
I now realise that, even before the Copenhagen Summit 2009 put paid to the prospect of a green international deal, I had decided that there was nothing I could do. At some point, I decided that my special fight was simply to make sure, to the best of my limited ability, that whatever society is left after the floodwaters settle is as fair and free as possible. I have this luxury, of course, because I grew up in a hilly place in England and my house is not going to be underwater for a while yet.
This, for the generation that grew up after the collapse of communism, is the way the world ends: not with a bang, but a bonfire. When I tried to explain the sense of finality to a friend who is old enough to have collected vinyl records before they were niche, he laughed at me. "Don't talk to me about Armageddon," he said, "when I was your age, we had the bomb to worry about."
The bomb, however, was a very different apocalypse from the inevitable, collective entropy of climate change and it demands an entirely different sort of complicity.
The greatest threat to the future of humanity is now not political brinkmanship, but paranoid indifference: the certainty that the future is both finite and short and that all we can do is burn what little of the remaining money we have and hope civilisation outlasts us.
This is a terribly foolish way to live. The anarchist thinker David Graeber writes in Debt: the First 5,000 Years that in response to the blinding obviousness of economic and ecological world buggeration, "the most common reaction - even from those who call themselves 'progressives' - is simply fear. We can no longer imagine an alternative that wouldn't be even worse." Graeber adds: "About the only thing we can imagine is catastrophe."
There is a bitter paradox to this apathetic fatalism that somehow incorporates its own denial. The abstract enormity of climate change and economic meltdown encourages a sort of helpless liberal Calvinism, complete with little rituals of composting orange peel and purchasing sustainable lingerie, as if such devotions might somehow spare us . Which, in a way, they will - if we are lucky enough to live in the cosseted bourgeois west, where you have to be flown out to witness a melting glacier to appreciate the cold reality.
Of course, many millions of people don't need to be told that burning half a trillion tonnes of fossil fuels has had some dodgy consequences for humanity.
At the same time as I'm on a boat watching the Arctic ice-shelf contribute theatrically to rising global sea-levels, hundreds have died in flooding in Pakistan, and over five million have been affected.
There comes a point when you have to make a choice. When a colossal wall of thousand-year-old-ice explodes right in front of you, with a noise like a very large bomb falling very far away, and you feel the chill sting of spray on your face as the ice is eaten away by human greed, you realise that a choice is still possible.
We can choose abject complicity, or we can decide that it's not too late to build a better world. My boots are still wet, so I'm for the latter.