Soon after the Queensland floods of 2010/11,
skeptics were quick to rush out and deny there could be any connection to global warming.
At the time, I thought "That's odd. I'm sure I read that record sea temperatures - which, call me crazy, but just
might have some connection with global warming - was one of the key reasons that led to the weather bureau giving a specific warning to the Queensland government in late 2010 that it was looking like a very high probability of big summer floods."
But there were some voices
making a cautious connection between global warming possibly being responsible for making hot La Nina water temperatures even worse than they would otherwise be:
Professor Matthew England, co-director of University of New South
Wales Climate Change Research Centre, is reluctant to explicitly
apportion any of the flood crisis to climate change. But he stressed
that “to exclude climate change would be premature”.
Earlier this week, he told Reuters
news agency: “I think people will end up concluding that at least some
of the intensity of the monsoon in Queensland can be attributed to
climate change. The waters off Australia are the warmest ever measured
and those waters provide moisture to the atmosphere for the Queensland
and northern Australia monsoon.”
Professor England explained to me the waters to the north of
Australia have warmed by about 0.5C over the last 50 years. Those waters
are currently about 1.5C warmer than average, he said, so it’s likely
that about a third of this warming is due to long-term ocean temperature
increases, the remainder due to the normal La Nina cycle.
(For anyone doubting the extent of the floods that came, and the high sea temperatures around Northern Australia that preceded it, you should have a look through
the slides the BOM used at the flood enquiry earlier this year.)
And now, we have the first paper that does some detailed analysis. The bottom line,
as reported in the Sydney Morning Herald is this estimate:
A Sydney researcher, Jason Evans, ran a series of climate models and
found above average sea surface temperatures throughout December 2010
increased the amount of rainfall across the state by 25 per cent on
average....
Between December 23 and 28 many places experienced up to 400
millimetres of rain in a few days. "That [means] 100 millimetres of rain
was attributable to sea surface temperatures," said Dr Evans, a future
fellow at the University of NSW's Climate Change Research Centre.
While the flooding occurred during one of the strongest
La Nina events on record it was insufficient to produce the extreme
rainfall recorded, he said.
The effect of the high sea surface temperatures coupled
with the impact of a La Nina, both of which are associated with above
average rainfall over eastern Australia, plus tropical cyclone Tasha,
combined to create an extreme weather event, he said.
The resulting floods stretched across 1.3 million square
kilometres all the way to Brisbane, caused billions of dollars in damage
and killed 35 people.
Now, the study does not actually look at what caused the high temperatures, and as such you can't really call it an attribution study relating specifically to the role of AGW. (I suppose it's like the first half an attribution study - first look at whether warmer waters did contribute to increased flooding, then look at how the water got warmer.) Still, surely it's reasonable to strongly suspect, seeing the gradual rise in the relevant sea surface temperatures over the last 30 years, that AGW might just have something to do with it. From the
university press release:
And this:
Sea-surface temperatures off northern Australia in the Indian Ocean,
Arafura Sea and Coral Sea were unusually warm at the time, in places as
much as 2 degrees C, the study notes: analysing 30 years of historic
measurements, the study identified a general warming trend there of at
least 0.2 degrees C per decade.
“If the observed warming trend in the sea-surface temperatures
continues, this result suggests that future La Niña events are more
likely to produce extreme precipitation and flooding than is present in
the historical record,” says Dr Jason Evans, of the UNSW Climate Change Research Centre. Dr Evans led the study, to be published in the journal Geophysical Research Letters, with a French co-author, Dr Irène Boyer-Souchet.
A
few posts back, I noted that some studies indicate a substantial warming of nearly 3 degrees in parts of the Pacific by the end of the Century.
Here's the thing: if sea temperature rises that are already being observed can make floods substantially worse, what's the situation going to be like in 50 - 100 years with another 2 - 3 degree increase?
And what's the best the
climate "fake skeptic" world can come up with in response to this? Well, seeing the study doesn't look at what caused the high temperature water:
"abnormally high ocean temperatures" may have simply been natural
variability at work. But according to England, climate change "could not
be excluded". Similarly, therefore, we cannot exclude the possibility
that the Flying Spaghetti Monster was behind it, sneakily raising sea
temperatures with his noodly appendage…
It's a really pathetic and lame attempt to turn around (what I would say) is an overly cautious choice of words into an attempted bit of logical ridicule.
As for those who argue for adaptation to climate change as opposed to seeking serious reduction to greenhouse gases: tell me how well you think Queensland can adapt to a potential increased severity (and frequency?) of floods affecting a million or so square kilometres?
My hunch formed during 2010 - 2011 that increased intensity of floods was soon going to be recognised as one of the most serious aspects of AGW is still probably right, I reckon.
