[link to www.newscientist.com
] If 2013 breaks heat record, how will deniers respond?
With an El Niño on the way, 2013 could be the warmest year on record. But the climate-denial machine will keep on churning
IT HAS been another "normal" global-warming summer in the northern hemisphere. The US sweltered in the hottest July on record, following the hottest spring on record. More than 60 per cent of the contiguous US is suffering from drought, as are parts of eastern Europe and India. In the Arctic, sea ice cover is at a record low and the Greenland ice sheet shows what the US National Snow and Ice Data Center calls "extraordinary high melting". Global land temperatures for May and June were the hottest since records began in the 19th century
Meanwhile, El Niño conditions are forecast to develop in the tropical Pacific Ocean, warming up ocean surface temperatures. Some observers have predicted that this will lead to record-breaking global temperatures next year.
If El Niño does arrive and temperature records are broken, there will inevitably be much discussion of the causes of the warming. So now is a good time to sort signal from noise in the global temperature records...
In fact, predictions by the US National Oceanic and Atmospheric Administration suggest that El Niño conditions are likely to arrive any time now. These two factors, combined with the ongoing warming trend, make it likely that a global temperature record will be set next year - unless a major volcano erupts.
Perhaps a record year will silence those unscientific voices who claim that global warming has come to an end. But the denial industry has already come up with a plan B: to claim that global warming is completely down to El Niño. To expose the fallacy of that, we just need to look again at where the heat comes from: below or above...
So if global warming of the past decades was due to El Niño or another mechanism involving heat from the ocean, the ocean would have lost heat. But the heat content has gone up, not down. And it is well understood why: because we created a radiation imbalance by adding greenhouse gases to our atmosphere.
The signal of global warming caused by humans is very clear, despite attempts by certain parties to drown it out with a lot of noise.
Stefan Rahmstorf heads the Earth System Analysis department at the Potsdam Institute for Climate Impact Research in Germany. He is coauthor of The Climate Crisis (Cambridge University Press, 2009)