Flanked by former US vice president Al Gore and other distinguished environmentalists, Sir Richard called for scientists to come up with a way to extract greenhouse gases from the atmosphere.
Describing the challenge as the largest prize ever offered, Sir Richard compared it to the competition for a person to devise a method of estimating longitude accurately. It was 60 years before Yorkshire clock maker John Harrison came up with an accurate method and received his prize from King George III.
Sir Richard said: "The earth cannot wait 60 years. We need everybody capable of discovering an answer to put their minds to it today."
He said he had been influenced by James Lovelock, the inventor of Gaia Theory, which suggests that the world may already have crossed a "tipping point".
"My wife Joan is a down-to-earth, practical Glaswegian," he said.
"When I told her that Lovelock believed we may already be doomed, she responded by saying 'There are a lot of brilliant minds out there. Surely one of them would be able to come up with a solution'."
He said that most people's experience of the idea of a "planet under threat" came from science fiction stories in which a superhero steps in to save the day.
He said: "Today we have a threat. Still we have to convince many people that the threat is urgent and real and there is no superhero. We have only our own ingenuity and we have no hope of a meaningful solution unless we find a way to work together."
He added: "Necessity is the mother of invention."Reuse content