One cannot look at a single storm, flood, or drought and say conclusively, “climate change caused that.” But what researchers are attempting to do lately is climate change risk assessment—figuring out how much more likely severe events may become as our world continues to warm up. Two new studies in Nature today try to do just that with heavy rains and flooding, saying definitively that warm temperatures make these events more likely.
More-localized weather extremes have been harder to attribute to climate change until now. “Climate models have improved a lot since ten years ago, when we basically couldn’t say anything about rainfall,” says Gabriele Hegerl, a climate researcher at the University of Edinburgh, UK. [Nature]
Hegerl and climate researcher Francis Zwiers were authors on study number one, a broad-based look at how much humans are contributing to intense precipitation events in the Northern Hemisphere. The simple physics of it makes sense: warmer air can hold more water. To show a link, however, the researchers pulled together a half-century of rainfall records, which they compared to the results of eight different climate models.
Richard Allan, a climate scientist at the University of Reading in England who was not part of the study, called the method employed by Zwiers “very rigorous.” He added, “There’s already been quite a bit of evidence showing that there has been an intensification of rainfall” events across the globe. But until now “there had not been a study that formally identified this human effect on precipitation extremes,” Zwiers said. “This paper provides specific scientific evidence that this is indeed the case.” [Washington Post]
The flooding created by enormous downpours near Brisbane in eastern Australia shows no signs of abating, and that region is now bracing for things to go from bad to worse.
Heavy rains pounded Brisbane’s region, called Queensland, in December. And things really started to get bad yesterday, when flooding caused by the constant rain sent a wall of water—evocatively being called an “inland tsunami”—crashing through the nearby town of Toowoomba. Brisbane, which is Australia’s third-largest city at about two million people, in next in the crosshairs.
Normally it is protected from periodic flooding of the Brisbane river by the Wivenhoe dam, 80 kilometres [50 miles] away. But Wivenhoe is already 81 per cent over capacity after last month’s heavy rains saturated Queensland. To save Brisbane from flooding, officials began releasing water from Wivenhoe last month. But because of the inland tsunami now hurtling towards the city, officials have increased the amount of water released from 140 million tonnes yesterday to 344 million tonnes today. [New Scientist]
But there’s only so much they can do. As of this morning, the Christian Science Monitor reports at least 30 deaths and 78 missing, with the number expected to grow as flooding threatens Brisbane.
[Brisbane] Mayor Campbell Newman warned 6,500 homes, businesses and other properties were likely to be flooded by Thursday. “Today is very significant, tomorrow is bad, and Thursday is going to be devastating for the residents and businesses affected,” he said. [BBC News]
The city of New Orleans’ defenses are certainly better than they were five years ago, when Hurricane Katrina breached the levees and flooded the city. With the five-year anniversary of that disaster upon us, however, the question that hangs in the air is: Would those refurbished barriers stand up to another Katrina, or something worse?
In the last five years, the federal government has invested about $15 billion to revamp the New Orleans levee system.
This time, tougher foundation material like a mixture of construction clay and cement, is being used in the soil to hold structural sections of wall designed as an inverted T instead of their previous I-shape. The new design is considered stronger, allowing steel pillars to bracket each end into the ground. Total completion is expected in June 2011. [Christian Science Monitor]