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Saturday, August 3, 2013

Climate and Weather

This year’s weather has been completely crazy in Germany. March was the fourth coldest in recorded history, suddenly bringing large amounts of snow after a rather mild winter, a cold that stayed with us longer than usual. Spring then saw enormous flooding of the south and east, larger than the already huge century flood of 2002. And now we barely managed to not set a record high temperature in recorded history last weekend, but July will be one of the top ten hottest in recorded history.

A recurring question I hear in media is, well, is this because of climate change?

That question has no good answer. Climate is not weather, weather is not climate. They influence each other, but they are not the same. Weather is a highly chaotic system. Difficult to predict, and minor changes in any of the plenty factors involved can have large effects. Climate change loads the dice, so to speak, for stronger weather extremes. But it’s impossible for any single weather extreme to say if this was “because of climate change.”

Think of a die that is loaded to have a higher chance of getting a six. If you roll it once and you get a six — was this specific six because of the loading? It would have been completely possible for a fair die to roll a six at that point, too. The loading made it more likely, but whether a single roll of a six was “because of the loading” is impossible to say. But if you roll a hundred times and a third of the rolls are sixes, that distribution is very likely because of the loading. It still could have been pure random chance, but with each roll of a six more often than in about one sixth of the cases, the likelyhood for it to be pure random chance decreases.

The same applies to climate change. Was the cold March because of climate change? Possibly, but it could have happened without climate change, too. Was the flooding because of climate change? Possibly, but it could have happened without climate change, too. Is the current heat wave because of … you get the drift. Just like for Hurricane Sandy, the Australian Heat Wave, the Siberian Heat Wave, or any of the other recent climate extremes. Each individual incident could have been “because of climate change,” but probability being what it is, we can’t know for sure.

But when the UN reports that “[t]he world experienced ‘unprecedented high-impact climate extremes’ between 2001 and 2010 and more national temperature records were broken during that period than in any other decade,” that indicates that the weather dice are loaded differently than before, and that is quite likely because of climate change.

And all signs currently point to us getting more of that in the future.

… yay.

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