Climate Change

http://www.newscientist.com/article/dn27426-three-in-every-four-extremely-hot-days-linked-to-climate-change.html#.VT--UFyefzI

If climate change was a game, we'd have racked up quite a score. A fresh study suggests that humans are responsible for a hefty number of today's extreme hot days and rainstorms.

Weather extremes, such as a Russian heatwave in 2010 and a drought in Texas in 2011, have been blamed on climate change before – but the attribution of individual events to it is still hotly debated.

So Erich Fischer and Reto Knutti at the Institute for Atmospheric and Climate Science in Zurich, Switzerland, took a bird's-eye view of how human activity is changing the planet. Using 25 different climate models, they calculated how the odds of unusual events – such as a 1-in-100 day temperature high or a 1-in-10,000 day rainfall event – have changed with the rise in global temperatures.

Their results show that global warming of 0.85 °C since the industrial revolution has had a powerful effect. Climate change is now responsible for 75 per cent of our extreme highs in temperature and 18 per cent of extreme rainfall, according to the data. The rarer a particular event, the more likely that warming is the cause, they say.

"A 1-in-10,000 day heat event is something that's only expected to happen every 30 years. But in a global-warming world, it's turned into a 4-in-10,000 day event. Three of those hot days – or 75 per cent – would never have happened if global warming wasn't around," says Fischer.