A new theory says that a 30-year cycle in the Atlantic Ocean is the reason why global temperatures are not rising as sharply as before, despite increasing levels of CO2 in the atmosphere.
A team from the University of Washington, led by Prof. Ka-Kit Tung, looked into why rapid warming slowed down in 1999. They found evidence to suggest that a slow-moving current alternates between warming and cooling, and is currently pushing heat into the deep seas. When it switches, global temperatures will likely rise.
The researchers used devices called Argo floats to sample oceans down to 2,000 meters. "The floats have been very revealing to us," Tung told the BBC. "I think the consensus at this point is that below 700 meters in the Atlantic and Southern oceans [they are] storing heat and not the Pacific."
Tung believes this will likely continue for another decade or so, "as global warming itself is melting more ice and ice could flood the North Atlantic. But historically we are in the middle of the cycle." Between 1951 and 2012, global average temperatures rose 0.12 degrees Celsius each decade, according to the Intergovernmental Panel on Climate Change (IPCC); between 1998 and 2012 that rate dropped to 0.05 degrees C per decade.
Read more about this theory at the BBC.