Reaction to the conclusion of the United Nations climate change conference in Cancún at the weekend has been almost universally downbeat. "A slap in the face", said Friends of the Earth International. The Guardian's own leader column described it as "Another opportunity lost".
But there's a different way of looking at the deal – on emissions reduction, deforestation, and financial help for developing countries – that 193 nations reached on Saturday. It's to see the very fact of agreement as a crucial advance.
Climate change presents what economists call a "collective action problem". It can be tackled only if everyone acts together: no one country's efforts will be enough. So if governments, businesses and individuals believe that others are not taking action, a rational response is not to do so oneself. It's a version of the prisoner's dilemma – it pays to co-operate, but not if others are not doing so. But of course, if we don't act, we will definitely face catastrophe.
That's what happened after the debacle of the Copenhagen conference last year. Governments and businesses looked at the failure to come to a meaningful agreement and began to withdraw their own commitments. The US, the EU and Australia started rowing back on their pledges. Businesses put clean energy investment plans on hold. Those with a vested interest in not taking action, and the climate sceptics, became emboldened, assiduously spreading further doubt.
Cancún reverses that negative momentum. Now countries have put domestic emissions reduction commitments into a formal UN agreement, further action can be justified. The really convincing political and economic case for investing in low-carbon energy is not just tackling future climate change but generating "green growth" now. It's the jobs and the new clean industries that will be stimulated by a low-carbon world that countries and businesses are eyeing up eagerly. But investing in these requires confidence that others are also cutting emissions – that there will be new low-carbon markets, and that high performance will not be undercut by competition from lower-cost polluters.
After Cancún, the global race to produce clean technologies is back on. Business and investor confidence has a chance of being restored. Europe has justification for moving to its higher 30% emissions reduction target by 2020. The really significant shift is the willingness of emerging economies — China, India, Brazil, South Korea and others – to cut emissions growth, and their refusal to allow the world to be dragged backwards by the dysfunctional domestic politics of the US. The view now is that America will simply have to catch up later when the economic costs of its high-carbon economy become painfully apparent.
Cancún's critics are of course absolutely right to say that what was achieved is not enough. As the agreements themselves insist, all countries' commitments will have to be revisited in the light of a scientific review in three years. But at the same time don't let's miss the significance of what has been done. If the Cancún commitments are fully implemented, global emissions should peak around 2020, and that is the essential first step towards a subsequent decline.
And it isn't correct that Cancún's 2020 targets mean the global temperature will inevitably breach the tolerable 2C threshold. The level at which it will eventually stabilise will be determined as much by what happens after 2020: countries will have to make much greater – and more expensive – efforts, but it is not out of the range of the possible.
Climate change is a frightening phenomenon: it often feels too large and difficult, requiring too much political will, to deal with. For many, fear induces paralysis and feelings of hopelessness. But the world is now beginning to combat global warming. And there is now a chance that this knowledge will encourage further effort. There is no room for complacency; but the real danger is that pessimism becomes self-fulfilling.
So the question about Cancún is not "Did it do enough?" – we knew the answer to that already – but "Does it make further action more or less likely?" On that there's no doubt.
In climate change, fatalism will prove fatal. Optimism that we can combat climate change is therefore not just an essential psychological condition; it's a vital political posture. Cancún gives optimism a boost: it should therefore be a reason not for continuing despair, but for hope and renewed determination to do more.
By Michael Jacobs, a special adviser to Gordon Brown from 2004-10 and a visiting fellow on climate change at the London School of Economics.