Why are the world's governments bothering? Why are they jetting to Cancun next week to discuss what to do now about global warming? The vogue has passed. The fad has faded. Global warming is yesterday's apocalypse. Didn't somebody leak an email that showed it was all made up? Doesn't it sometimes snow in the winter? Didn't Al Gore get fat, or molest a masseur, or something?

Alas, the biosphere doesn't read Vogue. Nobody thought to tell it that global warming is so 2007. All it knows is three facts. 2010 is globally the hottest year since records began. 2010 is the year humanity's emissions of planet-warming gases reached its highest level ever. And exactly as the climate scientists predicted, we are seeing a rapid increase in catastrophic weather events, from the choking of Moscow by gigantic unprecedented forest fires to the drowning of one quarter of Pakistan.

Before the Great Crash of 2008, the people who warned about the injection of huge destabilizing risk into our financial system seemed like arcane, anal bores. Now we all sit in the rubble and wish we had listened. The great ecological crash will be worse, because nature doesn't do bailouts.

And that's just one effect of the way we are altering the chemical composition of the atmosphere. Perhaps the most startling news story of the year passed almost unnoticed. Plant plankton are tiny creatures that live in the oceans and carry out a job you and I depend on to stay alive. They produce half the world's oxygen, and suck up planet-warming carbon dioxide. Yet this year, one of the world's most distinguished scientific journals, Nature, revealed that 40 percent of them have been killed by the warming of the oceans since 1950. Professor Boris Worm, who co-authored the study, said in shock: "I've been trying to think of a biological change that's bigger than this and I can't think of one." That has been the result of less than one degree of warming. Now we are on course for at least three degrees this century. What will happen?

The scientific debate is not between deniers and those who can prove that releasing massive amounts of warming gases will make the world warmer. Every major scientific academy in the world, and all the peer-reviewed literature, says global warming denialism is a pseudo-science, on a par with Intelligent Design, homeopathy, or the claim that HIV doesn't cause AIDS. One email from one lousy scientist among tens of thousands doesn't dent that. No: the debate is between the scientists who say the damage we are doing is a disaster, and the scientists who say it is catastrophe.

Yet the world's governments are gathering in Cancun with no momentum and very little pressure from their own populations to stop the ecological vandalism. The Copenhagen conference last year collapsed after the most powerful people in the world turned up to flush their own scientists' advice down a very clean Danish toilet. These leaders are sometimes described as "doing nothing about global warming." No doubt that form of words will fill the reporting from Cancun too. But it's false. They're not "doing nothing" -- they are allowing their countries' emissions of climate-trashing gases to massively increase. That's not failure to act. It's deciding to act in an incredibly destructive way.

The collapse of Copenhagen has not shocked people into action; it has numbed them into passivity. Last year, we were talking -- in theory, at least -- about the legally binding cap on the world's carbon emissions, because the world's scientists say this is the only thing that can preserve the climate that has created and sustained human civilization. What are we talking about this year? What's on the table at Cancun, other than sand?

Almost nothing. They will talk about how to help the world's poor "adapt" to the fact we are drying out much of their land and drowning the rest. But everybody is backing off from one of the few concrete agreements at Copenhagen: to give the worst-affected countries $100 billion from 2020. Privately, they say this isn't the time -- they can come back for it, presumably, when they are on rafts. Oh, and they will talk about how to preserve the rainforests. But a Greenpeace report has just revealed that the last big deal to save the rainforests -- with Indonesia -- was a scam. The country is in fact planning to demolish most of its rainforest to plant commercial crops, and claim it had been "saved."

Karl Rove -- who was George W. Bush's chief spin-doctor -- boasted this year: "Climate is gone." He meant it is off the political agenda, but in time, this statement will be more true and more cursed than he realizes.

It's in this context that a new, deeply pessimistic framework for understanding the earth's ecology -- and our place in it -- has emerged. Many of us know, in outline, the warm, fuzzy Gaia hypothesis, first outlined by James Lovelock. It claims that the Planet Earth functions, in effect, as a single living organism called Gaia. It regulates its own temperature and chemistry to create a comfortable steady state that can sustain life. So coral reefs produced cloud-seeding chemicals which then protect them from ultraviolet radiation. Rainforests transpire water vapour so generate their own rainfall. This process expands outwards. Life protects life.

Now there is a radically different theory that is gaining adherents, ominously named the Medea hypothesis. The paleontologist Professor Peter Ward is an expert in the great extinctions that have happened in the earth's past, and he believes there is a common thread between them. With the exception of the meteor strike that happened 65 million years ago, every extinction was caused by living creatures becoming incredibly successful -- and then destroying their own habitats. So, for example, 2.3 billion years ago, plant life spread incredibly rapidly, and as it went it inhaled huge amounts of heat-trapping carbon dioxide from the atmosphere. This then caused a rapid plunge in temperature that froze the planet and triggered a mass extinction.

Ward believes nature isn't a nurturing mother like Gaia. No: it is Medea, the figure from Greek mythology who murdered her own children. In this theory, life doesn't preserve itself. It serially destroys itself. It is a looping doomsday machine. This theory adds a postscript to Darwin's theory of the survival of the fittest. There is survival of the fittest, until the fittest trash their own habitat, and do not survive at all.

But the plants 2.3 billion years ago weren't smart enough to figure out what they were doing. We are. We can see that if we release enough warming gases we will trigger an irreversible change in the climate and make our own survival much harder. Ward argues that it is not inevitable we will destroy ourselves - because human beings are the first and only species that can consciously develop a Gaian approach. Just as Richard Dawkins famously said we are the first species to be able to rebel against our selfish genes and choose to be kind, we are the first species that can rebel against the Medean rhythm of life. We can choose to preserve the habitat on which we depend. We can choose life.

Yet at Cancun, the real question will be carefully ignored by delegates keen to preserve big business as usual. Long after our own little stories are forgotten, the choice we make now will still be visible -- in the composition of the atmosphere, the swelling of the seas, and the crack and creak of the great Antarctic ice. Do we want to be Gaia, or Medea?

Johann Hari is a writer for the Independent. To read more of his articles, click here or here. You can email him at j.hari [at] independent.co.uk

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