Were they linked to global warming? Two news outlets offer different answers
Update: After reading this post, some readers might conclude that I think we should wait to take action to reduce our vulnerability to climate change. Nothing is further from the truth. I believe we have enough knowledge right now to justify reducing carbon emissions, and taking action to adapt to climatic disruptions — which are obviously occurring, right now.
Have a look at the ABC News evening news broadcast above, and the network’s more in-depth article here. It’s extraordinary these days for American television news to cover climate change in any way, as the recent analysis by Robert Brulle of Drexel University has shown. So it’s heartening to see at least one network news division wake up again to what still is a huge story.
That said,, the broadcast unequivocally tied the flooding in Australia, as well as in Brazil and Sri Lanka, to global warming. And in its headline on the web, ABC also made no bones about it:”Raging Waters in Australia and Brazil Product of Global Warming.” That’s as strong a cause and effect statement as you could make.
Reuters wouldn’t go quite so far, as this dispatch carried by MSNBC on the web shows:
SINGAPORE — Climate change has likely intensified the monsoon rains that have triggered record floods in Australia’s Queensland state, scientists said on Wednesday, with several months of heavy rain and storms still to come.
But while scientists say a warmer world is predicted to lead to more intense droughts and floods, it wasn’t yet possible to say if climate change would trigger stronger La Niña and El Niño weather patterns that can cause weather chaos across the globe.
Which story is more accurate?
The evidence for a link between a warming globe and extreme rainfall events like we’ve been seeing is supported by the last IPCC report, which stated:
The frequency of heavy precipitation events has increased over most land areas, consistent with warming and observed increases of atmospheric water vapour.
Those words, “consistent with,” are key. Scientists have used the same words in interviews with me, saying that extreme rainfall events are “consistent with” a revved up hydrological cycle in a warming world.
But “consistent with” is is not dispositive. So to what degree does the evidence justify going as far as ABC’s statement of cause and effect?
The severity of the Brisbane floods played a significant part in the case ABC made for their being caused by global warming. Yet it doesn’t seem that they explored whether there was something about this event that has broken significantly with the past history of flooding in the region.
My colleague here at the University of Colorado, Roger Pielke, Jr., has examined this issue, and in this post he produced the following graph examining the incidence of floods in the Brisbane area going back to 1841:
It’s obvious that this flood is by no means unprecedented. Flooding in 1974 was even worse, and moderate to major flooding was far more common prior to 1900.
In fact, 1893 saw at least three floods, with two of them peaking at more than 30 feet above flood stage (9.51 meters for the first, and 9.24 meters for the second, with another flood in between at 3.29 meters).
The article at right from the Feb. 21, 1893 edition of the Brisbane Courier tells the story of receding waters from one of the two larger floods. Click on it, and a larger version will open in a new window. (It’s from “Trove”, a marvelous resource of digitized materials such as newspapers, music, pictures, and video from the National Library of Australia).
Based on the history of flooding in the Brisbane area, Anthony Watts concluded that ABC’s story was “ridiculous,” and Richard Somerville, a scientific source in ABC’s story, needed a “swift kick in the butt style reality-check” [sic].
Other climate change contrarians are going even further, claiming that “warmists” are actually to blame for the floods. Their logic: Because the Queensland government was worried about drought due to global warming, it allowed the Wivenhoe dam upstream of Brisbane to get “dangerously full,” as one commentator put it at the Telegraph in the U.K.
According to the Austrailian, part of the devastation wrought by the flooding in Brisbane was in fact caused by “sudden releases this week of massive volumes of water from Wivenhoe Dam.” The dam was built after the 1974 flood to provide drinking water and to mitigate flooding during heavy rains.
Did operation of the dam actually contribute to the flooding? Or conversely, was the flooding actually less intense because of the dam, and perhaps others that have been constructed in the watershed since the period of frequent and intense flooding in the 1800s?
If you want to know just how unusual this flood was in the historical context, these questions merit investigation. As far as I can tell, neither ABC nor Reuters examined this issue.
The massive 1974 flood provides another clue that can help us arrive at the best way of characterizing a possible link to global warming. It occurred during a particularly strong La Niña episode — similar to the strong La Niña we’re experiencing right now.
Here’s what the Australian Bureau of Meteorology says about the impacts of La Niña on the country:
La Niña periods are generally associated with above normal winter, spring and summer rainfall, particularly over eastern and northern Australia.The current event has contributed to 2010 being Australia’s third wettest year on record, and Queensland having its wettest December on record.
Based on the cool conditions in the central equatorial Pacific Ocean associated with La Niña, this was the bureau’s precipitation forecast for January to March 2011, published on Dec. 17:
Brisbane is located near the 70% label. And so it’s obvious that heavier than normal precipitation was expected, thanks to the strong La Niña now underway.
But that does not rule out a role for global warming. Far from it.
Purely from a logical perspective, it is entirely possible that warming has conspired with a strong La Niña to make the rains in Australia even more intense than they would have been.
And that is precisely the case made in the Reuters story:
“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,” said Matthew England of the Climate Change Research Center at the University of New South Wales in Sydney.
“The waters off Australia are the warmest ever measured and those waters provide moisture to the atmosphere for the Queensland and northern Australia monsoon,” he told Reuters.
And this from David Jones, head of climate monitoring and prediction at the Australia Bureau of Meteorology:
“The first thing we can say with La Niña and El Niño is it [sic] is now happening in a hotter world,” he told Reuters, adding that meant more evaporation from land and oceans, more moisture in the atmosphere and stronger weather patterns.
“So the El Niño droughts would be expected to be exacerbated and also La Niña floods because rainfall would be exacerbated,” he said, though adding it would be some years before any climate change impact on both phenomena might become clear.
And that last caveat is key, I think. Scientists can’t say for sure yet whether climate change has been making those La Niña floods more severe.
Of course the flooding in Australia is not happening in a vacuum. There is also catastrophic flooding in Brazil and Sri Lanka. And along the U.S. Northeast Coast, records were recently set for snowfall.
Moreover, in April of last year, 11 inches of rain fell in Rio de Janiero in 24 hours, the heaviest rainfall event in 48 years. (Meanwhile, to the north, parts of Amazonia experienced the worst drought in 40 years.)
After having experienced its second driest April since 1901 (behind 2007), Germany was hit by its wettest August since the same year.
Of course there was the astonishingly massive flooding in Pakistan last summer. And a host of other unusual rainfall events around the world during 2010 as well, as documented by the National Oceanic and Atmospheric Administration a few days ago.
And last but not least, 2010 was the wettest year globally on record, by NOAA’s accounting.
It seems obvious to me as a science journalist that there’s something happening here, and while it may not yet be exactly clear (apologies to Buffalo Springfield), both ABC News and Reuters were right to pursue this story aggressively. I only wish other news outlets, particularly national television news, would follow their lead.
But in my opinion, ABC went too far in declaring cause and effect, whereas the Reuters story was more accurate, thanks to the caveats and greater scientific nuance.
Oh, one other thing: ABC spelled Richard Somerville’s name incorrectly. (It’s one ‘m’ guys, not two.)