Nerang River Catchment

2011: A Year Of Weather Extremes

By many accounts 2011 has been a year of weather extremes and some commentators have used certain events to highlight the risks associated with climate change. While there is increasing evidence of unusual global weather events, should we just assume that every disaster is a sign of things to come? I find, given my job title, that people do ask me about these associations, so it is perhaps time to put some thought to this and at least give my perspective on the issue.

For me, two particular series of events have stood out in 2011, the very extensive flooding in my home country of Australia and the recent upsurge in tornado activity in the USA.

There are also plenty of other events in recent times – for example, “Snowmaggedon” in the US North East in January 2010, the Australian bushfires of 2009 and the intense heat wave of the same period and going back a bit further the European  heat wave of 2003 during which all-time record temperatures were reached in many cities. Although Australia has a long history of bushfires, much of that part of Southern Australia also broke all-time temperature records in the days prior to the fires.

As the world warms the convective processes in the atmosphere could be expected to increase simply because of the additional energy into the system. Similarly, global precipitation (rain, snow, ice) should increase as the hydrological cycle speeds up given the overall higher level of moisture held in the atmosphere. Estimating global precipitation is a relatively new field of science, but there is some evidence that precipitation levels may be increasing. The US National Climate Data Centre said early this year that 2010 equaled the hottest on record – less noticed was their calculation that global rainfall levels were the highest since at least 1900. 

 Returning to the events of 2011, it is perhaps too easy to assume that this is climate change on show. In fact it probably isn’t.

Australian floods: Why were we so surprised? | Coffs Outlook

The following article written by Germain Greer and published in the U.K. Guardian puts things much more clearly into perspective!

Meteorologists warned Australians six months ago to prepare for a soaking. And nobody did a thing …

‘The problem is rain’ … Clinging to railings on a flooded street, residents in Toowoomba are caught in floods that have devastated Australia’s north-east. Photograph: AP

What’s going on in Australia is rain. British people might think that they’re rain experts. Truth is that they hardly know what rain is. The kind of cold angel sweat that wets British windscreens isn’t proper rain. For weeks now rain has been drumming in my ears, leaping off my corrugated steel roof, frothing through the rocks, spouting off the trees, and running, running, running past my house and down into the gully, into the little creek, into the bigger creek, and on to the Nerang river and out to sea at Southport. We’ve had more than 350mm in the last four days. My creek is running so high and so fast that I can’t get out and my workforce can’t get in. I can’t even go for a walk under the dripping trees, because I’ll come back festooned with leeches. In these conditions you can end up with a leech in your eye, and there’s no one here to help get it out.

The rain comes in pulses. When the noise abates, momentarily, I can see Mount Hobwee through veils of wet mist, and then I hear the advancing roar of the next pulse, and everything shuts down again. Behind my house a white cataract is charging down the gully through the rocks. When I’m in bed I can feel the thudding of its raw power through my bones.

So, yeah, as Australians say, the problem is rain. The ground is swollen with months of it. The new downpours have nowhere to go but sideways, across the vast floodplains of this ancient continent. We all learned the poem at school, about how ours is “a sunburnt country . . . of droughts and flooding rains”. Groggy TV presenters who have been on extended shifts, talking floods for endless hours, will repeat the mantra, so hard is it wired into the heads of Australian kids. And yet we still don’t get it. After 10 years of drought, we are having the inevitable flooding rains. The pattern is repeated regularly and yet Australians are still taken by surprise.

The meteorologists will tell you that the current deluge is a product of La Niña. At fairly regular intervals, atmospheric pressure on the western side of the Pacific falls; the trade winds blow from the cooler east side towards the trough, pushing warm surface water westwards towards the bordering land masses. As the water-laden air is driven over the land it cools and drops its load. In June last year the bureau of meteorology issued a warning that La Niña was about “to dump buckets” on Australia. In 1989-90 La Niña brought flooding to New South Wales and Victoria, in 1998 to New South Wales and Queensland. Dr Andrew Watkins, manager of the bureau’s climate prediction services, told the assembled media: “Computer model forecasts show a significant likelihood of a La Niña in 2010.” In Brisbane the benchmark was the flood of 1974; most Queenslanders are unaware that the worst flood in Brisbane’s history happened in 1893. Six months ago the meteorologists thought it was worthwhile to warn people to “get ready for a wet, late winter and a soaked spring and summer”. So what did the people do? Nothing. They said, “She’ll be right, mate”. She wasn’t.

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