|Plumes of methane in Arctic Ocean (Westbrook et al, 2009)|
With its vastly greater global warming potential - up to 100 times more powerful than CO2, over short timescales - a sudden pulse of methane would accelerate human-caused global warming. It could even cause a cascade of other knock-on effects (Amazon deforestation, collapse of the ice-sheets) so creating a runaway greenhouse effect.
It's that sort of a scenario - with 50Gt of methane gushing from a source in the Arctic over 10-20 years - that was recently modeled by economists in Nature. They put a $60 trillion price tag for the global economy from the consequences of ratcheting upwards man-made climate change. A scary monster, made even more real by describing it in the language our leaders understand most - hard cash.
But the Methane Burp is also complete fantasy - at least according to some recent detractors. Many climate scientists believe the methane locked up in frozen soils, or the curious, icy 'methane-hydrates' under the sea-floor, are a real threat - but only as a slow-burn cooker for the globe's climate. As the planet warms, the natural emissions from these sources will increase, they believe. But not at a rate that will be catastrophic. They struggle to see how anything like as large as 50,000 million tonnes of methane can erupt so quickly from Arctic permafrost, or sub-sea methane hydrates. Such sources have been thought to have been stable in the recent geological past.