The Swing Continent

When beaten down on the evidence that Anthropogenic Global Warming is real, the last resort of inactionists is always to say “well it doesn’t matter if we do anything…we’re such a tiny part of the problem”.

This of course could be used as an excuse for anything. “Hey I can throw rubbish in the streets, it is not like my bit makes a difference you could notice.” “Why should I pay taxes, my contribution is tiny?” “Oh we shouldn’t commit our soldiers to fight in World War II – it’s not like we make much difference without the Americans. And if they join in they don’t need us.”

On top of this, however, it is untrue, because Australia often has an importance well beyond its size. This is particularly the case for things like the development of solar. As that very rare thing, a rich nation with a lot of sunlight, Australia is in a position to speed solar technologies to a point where they are accessible to most of the rest of the world. On the other hand, as the heaviest emitter per capita amongst large or medium sized nations means that our failure to act is very much noticed by the rest of the world.

All this is old news, but I cam across a striking metaphor for the situation yesterday, which is also quite interesting science.

Sea levels are, on average, rising 3mm a year. But there are variations around this, some of which are understood and some of which are mysterious. For an 18 month period in 2011-2012 they actually dropped by 7mm. No doubt this was seized on by denialists worldwide as evidence that global warming was not happened, although the examples I can remember (eg Andrew Bolt) may have come from earlier such drops.

Now a study at the US National Centre for Atmospheric Research has identified the cause. As many will remember, 2010-2011 were exceptionally wet years. Indeed the wettest two year period in Australia’s history, highlighted by the disastrous floods of early 2011. In 2011 alone the average rainfall was more than 200mm above average.

Lots of places get huge rain events like this now and then – remember the horrific floods in Pakistan than displaced tens of millions of people? But in most places the water pretty quickly heads back to the ocean, so the effect on sea levels is small. Not so Australia. For one thing, we are rather flat so it takes a while for water to drain off. Moreover, if the rain falls in the Lake Eyre catchment area it never reaches the sea at all. Finally (and I didn’t know this part) our soils are such that a lot more rainfall ends up as ground water, rather than running off as on other continents.

Central Australia in 2009 and 2011

Central Australia in 2009 and 2011

Consequently, vast amounts of water stayed in Australia for a long time, either in the Murray Darling Basin, Lake Eyre or under the soil. Enough, in fact, to account for most of the fall in ocean levels, although John Fasullo of the NCAR says South America also played a role. “No other continent has this combination of atmospheric set-up and topography,” Fasullo said. “Only in Australia could the atmosphere carry such heavy tropical rains to such a large area, only to have those rains fail to make their way to the ocean.”

The water that could drain to the sea has mostly done so a while back, and the surface water in the interior has largely evaporated. Some remains trapped underground, but sea levels have been rising even more rapidly than normal to get back close to trend. But you won’t read that on Watt’s Up With That.

In practice I am not sure there is anything Australia can do to ensure we hold onto enough water to slow the rise of the oceans, as romantic as the idea of filling the inland sea might be. However, I regard these observations as highly symbolic of our potential to make a huge difference to slowing all the effects of climate change if we can get our act together to do something about our own emissions.

Update: And here someone has put the science in graphic form.

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About Stephen Luntz

I am a science journalist, specialising in Australian and New Zealand research across all fields of science. My book, Forensics, Fossils and Fruitbats: A Field Guide to Australian Scientists is out now through CSIRO Publishing. I am also a professional returning officer for non-government organisations. I'm very politically active, but generally try to restrict this blog to scientific matters.
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One Response to The Swing Continent

  1. takver says:

    Hi Stephen,
    I came across a video of Kevin Trenbeth in April on this pothole in the global sea level trend. The whole lecture is interesting to listen to.
    http://takvera.blogspot.com.au/2013/04/kevin-trenbeth-on-2011-sea-level-bump.html

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