No hiding place?
Jan 7th 2010
From The Economist print edition
The betting is that 2010 will be the hottest year on record. But understanding how the planet’s temperature changes is still a challenge to science
IT MAY seem implausible at the moment, as northern Europe, Asia and parts of America shiver in the snow, but 2010 may well turn out as the hottest year on record. Those who doubt that greenhouse gases are quite the problem they have been cracked up to be by most of the world’s climatologists have taken comfort from the fact that the Hadley Centre, part of Britain’s Meteorological Office, reckons the warmest year since records began was 1998 (see chart 1). Twelve years without a new record would, the sceptics reckon, be rather a large lull in what is supposed to be a rising trend. Computer modelling by the Met Office, though, gives odds-on chances of the lull being broken.
The fact that no record high happened in the 2000s does not mean that there was no warming over the decade—trends at scales coarser than the annual continued to point upwards, and other authorities suggest there have been record years during the period. Nor was the length of time without an annual record exceptional. Models simulating centuries of warming normally have the occasional decade in which no rise in surface temperatures is observed. This is because heat can be stored in other parts of the system, such as the oceans, for a time, and thus not show up on meteorologists’ thermometers.
Indeed, one reason for thinking that the coming year will be hotter than all known previous ones is that the tropical Pacific is currently dumping heat. This phenomenon, by which heat that has been stored up in the sea over the previous few years is released into the atmosphere, is known as El Niño. A strong Niño contributed to the record temperatures in 1998. In 2007 and 2008 the opposite phenomenon, a cooling Niña, was happening. That goes some way to explaining why those years were chilly by the standards of the 2000s.
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And on top of El Niño, there is the sun. The sun’s brightness fluctuates over an 11-year cycle. Though the fluctuation is not vast, it is enough to make a difference from peak to trough. In 2009 the sun was at the bottom of its cycle. Unless it is behaving particularly strangely, it should, over the next 12 months, begin to brighten.
more:
http://www.economist.com/sciencetechnology/displayStory.cfm?story_id=15211377