Wallace Broecker advocated millions of “carbon scrubbers” – giant artificial trees to pull CO2 from the air. Dr Broecker told the Hay literary festival in Powys: “We’ve got an extremely serious problem. It’s a race against time and we are just sort of crawling along at a slow pace.” He said some 20 million of the scrubbing devices would be required to capture all the CO2 currently produced in the US.

But he told the festival: “Okay, you say that’s enormous, but we make 55 million cars a year, so if we really wanted to we could. Over 30 or 40 years we could easily make that number.” After addressing the festival, Dr Broecker told the BBC News website that 60 million of the devices would be needed worldwide at an estimated cost of $600bn a year.

The towers would be about 50ft high and 8ft in diameter, and use a special type of plastic to absorb the CO2. The gas would then be either liquefied under pressure and pumped underground or turned into a mineral. Dr Broecker said the most likely location for the towers would be desert areas of the planet.

However, he admitted that such a project faced an uphill struggle.

“If I were a betting man I would bet against it because I don’t know if we have the political will to do it,” he said. “But looking at countries like Germany and here in the UK the will is developing.”

He said the challenge was to get rapidly developing countries such China, India and Brazil behind the idea.