Leading article: The outlook for our climate is dark – but hope remains

We have become used to stark warnings from scientists of what lies in store if we fail to curb our carbon emissions. But, even so, the statement that emerged from the international scientific conference on global warming this week in Copenhagen was sobering in its bluntness. The summit, attended by some 2,000 leading scientists, stated: "The climate system is already moving beyond the patterns of natural variability within which our society and economy have developed and thrived. Rapid, sustained and effective mitigation based on global and regional actions is required to avoid dangerous climate change."

The urgency of the warning and the demand for political action are inspired by the most recent data on the progress of global warming which suggest our climate is heating up faster than many scientists expected only two years ago. Research papers were presented to the conference which showed a range of potentially catastrophic consequences if we adopt a "business as usual" approach. The melting of Arctic sea ice could cause global sea levels to rise by more than a metre by the end of the century. The disappearance of the Amazon rainforest is a possibility if the world warms by 3C over the next 100 years. Under such conditions, billions of people, particularly in the poorer parts of the world, would be forced to move across existing national borders in order to survive.

Lord Stern, the author of a seminal report for our Treasury on global warming, summed up the likely effect on human societies: "Extended conflict, social disruption, war essentially, over much of the world, for many decades." Those are the stakes. And they could not be higher.

Some have suggested that, with people concerned about losing their jobs, now is not the time to ask them for sacrifices for the sake of the climate; that the recession trumps the environment. This is misguided. On the contrary, the environment ought to be at the centre of attempts to pull us out of this slump. Unemployed labour should be put to work on schemes that help conserve household energy. And if governments invest in renewable energy schemes while resources are relatively cheap, they can use this downturn to lay the foundations for future green growth.

But in the longer term, the role of governments will be facilitating green growth, rather than directing it. By taxing carbon-intensive industries at a level that reflects the true cost of their emissions to the environment upon which we all depend, national leaders will provide a powerful incentive for the global private sector to conserve energy and also to develop clean alternatives to fossil fuels. This is the theory behind the European Union's Emissions Trading Scheme and the US cap-and-trade system outlined in Barack Obama's recent budget.

The economic crisis also provides a golden opportunity for political leaders to convince the public about the need to put environmental protection at the centre of policy-making. It is now widely acknowledged that the manner in which some of our societies in the West relied on cheap debt for growth was unsustainable. There is an obvious parallel in the manner in which we have relied on fossil fuels to power our economies.

And just as the world needs global co-operation to fend off a prolonged economic slump, we need international partnership to meet the threat of climate change. Every nation is suffering because of the economic crisis. They stand equally exposed to the threat of runaway climate change, as Lord Stern warns.

So curbing emission has to be part of a global partnership. That is why December's international meeting in Copenhagen to agree on a successor to the Kyoto protocol is of such critical importance. Despite the evident frustrations of scientists on display this week, the signs of success for a new global agreement on curbing emissions have never been more promising. This is mainly due to the willingness of President Obama to throw his support behind an international deal, ending the obstructive stance of his predecessor in the White House. The world's largest and still richest economy has signalled that it is prepared to accept binding cuts to its emissions. That opens the door for the world's fast-developing but still poor nations, such as China, India and Brazil, to sign up to a deal. It cuts through the knot of suspicion and antagonism that has constricted negotiations for so long.

We must hope that in this apparently dark hour, the light of co-operation is set to break through and that the global climate can indeed be pulled back from the brink.