Two climate change sceptics, who believe the dangers of global warming are overstated, have put their money where their mouth is and bet $10,000 that the planet will cool over the next decade.
The Russian solar physicists Galina Mashnich and Vladimir Bashkirtsev have agreed the wager with a British climate expert, James Annan.
The pair, based in Irkutsk, at the Institute of Solar-Terrestrial Physics, believe that global temperatures are driven more by changes in the sun's activity than by the emission of greenhouse gases. They say the Earth warms and cools in response to changes in the number and size of sunspots. Most mainstream scientists dismiss the idea, but as the sun is expected to enter a less active phase over the next few decades the Russian duo are confident they will see a drop in global temperatures.
Dr Annan, who works on the Japanese Earth Simulator supercomputer, in Yokohama, said: "There isn't much money in climate science and I'm still looking for that gold watch at retirement. A pay-off would be a nice top-up to my pension."
To decide who wins the bet, the scientists have agreed to compare the average global surface temperature recorded by a US climate centre between 1998 and 2003, with temperatures they will record between 2012 and 2017.
If the temperature drops Dr Annan will stump up the $10,000 (now equivalent to about £5,800) in 2018. If the Earth continues to warm, the money will go the other way.
The bet is the latest in an increasingly popular field of scientific wagers, and comes after a string of climate change sceptics have refused challenges to back their controversial ideas with cash.
Dr Annan first challenged Richard Lindzen, a meteorologist at the Massachusetts Institute of Technology who is dubious about the extent of human activity influencing the climate. Professor Lindzen had been willing to bet that global temperatures would drop over the next 20 years.
No bet was agreed on that; Dr Annan said Prof Lindzen wanted odds of 50-1 against falling temperatures, so would win $10,000 if the Earth cooled but pay out only £200 if it warmed. Seven other prominent climate change sceptics also failed to agree betting terms.
In May, during BBC Radio 4's Today programme, the environmental activist and Guardian columnist George Monbiot challenged Myron Ebell, a climate sceptic at the Competitive Enterprise Institute, in Washington DC, to a £5,000 bet. Mr Ebell declined, saying he had four children to put through university and did not want to take risks.
Most climate change sceptics dispute the findings of the Intergovernmental Panel on Climate Change which suggest that human activity will drive global temperatures up by between 1.4C and 5.8C by the end of the century.
Others, such as the Danish economist Bjorn Lomborg, argue that, although global warming is real, there is little we can do to prevent it and that we would be better off trying to adapt to living in an altered climate.
Dr Annan said bets like the one he made with the Russian sceptics are one way to confront the ideas. He also suggests setting up a financial-style futures market to allow those with critical stakes in the outcome of climate change to gamble on predictions and hedge against future risk.
"Betting on sea level rise would have a very real relevance to Pacific islanders," he said. "By betting on rapid sea-level rise, they would either be able to stay in their homes at the cost of losing the bet if sea level rise was slow, or would win the bet and have money to pay for sea defences or relocation if sea level rise was rapid."
Similar agricultural commodity markets already allow farmers to hedge against bad weather that ruins harvests.
