So near and yet – apparently – so far. All governments now accept the science of man-made climate change. They agree too on the urgency of stemming the rise of carbon dioxide emissions. There is also broad consensus on the means of doing that. The need for equitable emission cuts, an international system of carbon trading and aid transfers from the rich world to developing nations to help them bear the cost of greening their economies is widely understood.
And yet we are told that the deal at the United Nations climate change conference in Copenhagen that would set all this in stone might not actually happen. Some British government officials have suggested that Copenhagen might only produce a "political" agreement, rather than a legally binding replacement for the Kyoto protocol. In other words, warm words rather than action.
That would be a disastrous failure. Copenhagen has long been presented as a crucial moment in the battle against runaway climate change. If it is not seized, it would be severely damaging for the credibility of the UN forum. The danger is that a failure to agree in Copenhagen will result in a deal being repeatedly kicked further down the road, or languishing in a state of permanent stasis like global trade liberalisation negotiations.
The situation is too urgent for such prevarication. Kyoto is due to expire in 2012. The world's governments need to be locked into a replacement long before that date comes. The stakes are also too high. Unless global emissions peak by the end of the next decade, the chances of avoiding catastrophic climate change are virtually extinguished.
So what is holding things up? Developing countries feel that too little money has been pledged in technology transfer payments by the rich world. And they complain of too little evidence of serious intent by industrialised states to take measures to reduce their own emissions.
A particular problem is the fact that a US cap-and-trade bill is still stuck in Congress and looking very unlikely to be law by the end of the year. The failure of the EU to put forward a solid figure for aid transfers to developing nations at its summit last week has also undermined the confidence of some poor states. In short, what is blocking agreement is a lack of faith from developing countries in the willingness of industrialised countries to accept the upfront costs that making a transition to a low-carbon global economy will require.
The only thing likely to restore missing confidence at this late hour is top-level political engagement. Global leaders should commit to attending Copenhagen in person to negotiate a deal. President Lula of Brazil, a nation destined to be one of the most significant economies this century, this week urged such a commitment, saying that he is willing to attend if his counterparts from the US, China and India also do so. This is an overture that needs a response. The US delegation in Copenhagen has indicated that Barack Obama will attend if a deal seems likely. That is not good enough. This conference is simply too important for the leader of the last remaining superpower (and the largest per capita carbon emitter) to be absent.
If world leaders start talking up the likelihood of failure at Copenhagen now, it risks becoming a self-fulfilling prophecy. Now is the time for reinforced signals of commitment from all involved, not retreat.