Amid all the forecasts and warnings of doom and disaster issued by climate scientists there is the hidden message that all is not yet lost.

Ice sheets are melting and ocean acidity is rising, yet most scientists still believe that global warming can be controlled.

Climate researchers are clear that since the Intergovernmental Panel on Climate Change reported in 2007 the problem of global warming has deepened.

Talk has moved on from looking at probable rises over the next century of 2C or 3C, which would pose problems but be bearable, to increases of 4C or 5C, which would have devastating consequences.

Scientists are under no illusion about the scale of the task, yet most still speak of what can and should be done to prevent temperatures rising.

They believe, as a statement issued at the end of a three-day climate change conference in Copenhagen this week made clear, that most of the tools and technology needed to bring down greenhouse gas emissions are available or at least under development.

Professor Katherine Richardson, of the University of Copenhagen, organised the conference. “I have great faith in humans and their ability to regulate their relationship with this planet that we live on,” she said.

She pointed out that the problems of CFCs destroying the ozone layer, smog and sea pollution caused by dumping had all seemed insurmountable yet had been overcome.

Many of the scientists at the conference cited the recession as an ideal opportunity to turn the global economy green.

With resources at low prices and governments willing to spend huge sums of money to kick-start the economy, they argued that investment in creating a low-carbon economy would reshape society in a way that allowed resources to be managed sustainably and would benefit both rich and poor countries.

But political inaction has frustrated their hopes of getting meaningful measures against climate change, and among the issues that attracted the most debate at the conference was the potential of “unacceptably high” temperatures within the lifetimes of today’s children.

Two years ago it was widely thought that holding temperature increases to a maximum of 2C was achievable if governments made the effort to reduce greenhouse gas emissions by 50 per cent by 2050. It is now recognised that an 80 per cent cut is needed.

With little progress made in the political world at taking the 50 per cent reductions seriously, let alone 80 per cent, there was a growing feeling that preparations needed to be made to cope with temperature rises of 4C or more. Such rises would have severe consequences for human populations, with the brunt being borne by the developing world but with even wealthy countries likely to suffer disastrous changes to the climate. Food production would be an enormous problem because while the human population is forecast to rise to nine billion, agriculture in many regions would collapse.

The combination of droughts, famine and other impacts, including floods, hurricanes and the spread of deadly diseases, would mean that many millions of people would starve or be killed in wars over resources. Numbers of refugees would be in the hundreds of millions, perhaps even billions, putting untold pressures on other regions.

The potential impact of climate disasters outlined in Copenhagen was cited as the reason why politicians, and the public, have to take the issue seriously enough to force through a political deal.

But while painting a bleak picture of the consequences of inaction, researchers were confident that they could see reasons for hope. Professor Diana Liverman, of the University of Oxford, said that while plenty of problems had still to be addressed, progress was being made in tackling climate change.

“It’s clear that corporations and many local governments have gone far beyond international regulations in what they’ve done,” she said.

Al Gore, the former US vice-president, said yesterday he was confident a global deal to avoid environmental catastrophe would be agreed because a “political tipping point” had been reached.

“There is a very impressive consensus now emerging around the world that the solutions to the economic crisis are also the solutions to the climate crisis,” he said.

He said agreement was likely to be reached when 200 nations meet at the international climate summit in Copenhagen in December to try to get agreement on cutting greenhouse gas emissions.

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