How immediate is the threat from climate change? Scientists report that the devastating floods that hit north-eastern Australia last year were worsened by abnormally high ocean temperatures – and global warming was very likely a contributing factor.
Those floods followed extremely heavy rainfall in the state of Queensland in December 2010 and January 2011. Dozens of towns were inundated, including the state capital of Brisbane, and 36 people were killed. Property damage was in the billions.
'Extreme weather event'
In December 2010, the Pacific Ocean was experiencing a strong La Niña phenomenon: that's a cyclical weather pattern that typically brings rain to eastern Australia. But researchers say that wouldn't be enough to account for the 400mm (15.7in) of rain that fell on Queensland within just a few days. They calculate that at least a quarter of that was the result of record ocean surface temperatures.
Warmer water means more humidity, and that contributes to excess rainfall. Add in the effects of a cyclone that hit on Christmas Eve, and you've got what Dr Jason Evans, from the Climate Change Research Centre at the University of New South Wales, termed “an extreme weather event".
Of course, it's hard to prove that any particular natural disaster is directly caused by global warming. Weather has a lot of moving parts and, as in the Queensland floods, there are always many variables.
But as Professor Matthew England, also of the Climate Change Research Centre at UNSW, put it: “While the La Niña event played a big role in this record ocean warmth, so too did the long-term warming trend over the past 50 years.”
Read more: The Australia-based Climate Action Centre gathers articles and documents about the influence of climate change on extreme weather.