Much of Australia has again suffered an extremely hot and dry year thanks to climate change. But these conditions could turn around with savage speed, writes Peter Fisher.

Climate change has customarily been viewed as a gradual, creeping process - not entirely human-friendly but unlikely to turn the world into an unruly, totally horrid place. That idea has been shaken by Hurricane Katrina, road-melting European summers, the drought and now cataclysmic wildfires sweeping down from the Victorian Alps. Even so, much of government and corporate thinking remains steeped in the idea that no matter how significant the changes turn out to be there will be enough time - maybe 30 years, maybe 50 or more - for social and economic adjustment.

A similar assumption underlies the rather leisurely search for technological solutions under AP6 (Asia-Pacific Partnership on Clean Development and Climate) signed in Laos in July 2005 and recent emission reduction projects announced by the Federal Government. This has occurred against a backdrop of a United Nations weather agency report that levels of heat-trapping greenhouse gases in the atmosphere hit a record high last year and are likely to keep rising unless emissions are radically cut.

In the circumstances, governments and business would be well advised to take a long, hard look at the growing body of research into the astounding, often unsuspected connections between the regular physical transformations of the planet's weather systems.

Chemical analyses of the tiny bubbles of air in Greenland ice cores establish that the last ice age started to teeter about 14,700 years ago. As it gathered momentum, melt-water poured into the oceans, raising levels by half a metre or more each decade. The sea moved inland like a slow tsunami at a rate of up to 450 metres a year.

But after a hesitant couple of millenniums of warmer conditions, the cold was back with a vengeance, turning western Asia and Europe into ice empires. This event, dubbed the Younger Dryas (after a plant that suddenly reappeared in Scandinavia), returned the planet to cool and dry conditions in the space of a few decades, with the average northern hemisphere temperature plummeting 7 degrees. Just as rapidly, after 1300 years, warm and wet conditions resumed. Another abrupt but lesser cooling which converted the Middle East into a dust bowl began 8200 years ago, but it lasted only a century.

Both events are thought to have been caused by an interruption to the Gulf Stream, or "ocean conveyor", through large volumes of melt-water entering the North Atlantic. (The Younger Dryas probably stemmed from a cataclysmic collapse of an ice dam across Canada's Lake Agassiz.)

In fact, the Earth's geophysical history has so many climate flips that these can be considered normal rather than aberrant. James Hansen of NASA's Goddard Institute for Space Studies says it is our own "relatively static experience of climate that is exceptional". The paleoclimatologist Peter deMenocal warns "that the climate system has much greater things in store for us than we think".

Steven Mithen, in his book After the Ice, has even re-created the climatic maelstroms our forebears must have endured, while Brian Fagan provides a similar historical appraisal in The Long Summer.

Since the cold snap that began 8200 years ago, the world's climate appears to have been remarkably stable. But about AD540 the Earth ran into a cosmic swarm, clouding the sky and leading to prolonged cold (possibly triggering the Dark Ages). It was so sudden that even the scribes abandoned their quills to concentrate on survival.

Another cooling ran from the 14th to the mid-19th century, the biting cold of that period often being portrayed on Christmas cards. New research points the finger at the Gulf Stream, which slowed by 10 per cent during this period.

And the climate between ice ages may not have been so drab as commonly thought. Researchers at the Woods Hole Oceanographic Institute in America reveal in a recent issue of the journal Science that sea levels (linked to the age of coral terraces) rose and fell by as much as 30 metres over intervals of 3000 to 9000 years between 70,000 and 240,000 years ago. A study of a fossilised West Australian coral reef has similarly deduced that the warming that occurred during the middle of the last interglacial period 125,000 years ago caused a catastrophic melting of ice and a rapid sea level rise of 3.5 to 4.5 metres.

A glimpse of the scale and ferocity "climate transit" can assume comes from Philip Allen and Paul Hoffman in a paper in the journal Nature, with their reconstruction of a deglaciation of 635 million years ago when icesheets poured directly into warm seas. They inferred that the ripples in sediments deposited during this period of sea level rise corresponded to giant, long (21- to 30-second) waves "feeling the bottom", 200 to 400 metres below. These waves were estimated to have been produced by winds blowing at speeds of 20 metres a second over the water. On shore, they created huge dust storms, much of the debris layering into the sea.

The course of past climate transitions from cooler periods suggests that they can be extremely rapid - perhaps within a matter of decades rather than a century or centuries. For instance, new research published in Nature has found that the glacial climate in the North Atlantic can swing very quickly, with temperatures rising by 8 to 16 degrees in just a few decades at the end of each ice age.

Such disturbances stem from the elliptical nature of the Earth's orbit and variations in its tilt and spin. Life has long been at the mercy of these happenings, as demonstrated by a horrendous 10,000-year drought in Africa during the Pliocene epoch 2.5 million years ago, which devastated the gorilla population in southern Zaire (later providing a niche for a new breed of chimps) and no doubt brutally affected proto-humans.

Add to these natural cataclysmic events the potential effect of climate forcing from rising carbon dioxide levels, and the outlook becomes much more unpredictable.

James Lovelock, in his book The Revenge of Gaia, posits that the planet has already been pushed over the brink, with rapid rises in temperature of as much as 8 degrees now likely. Hansen, one of the US President's most respected (if not loved) climatologists, doesn't go quite that far. He concludes in an article in Climatic Change on the storing of heat in the oceans that "any increase in global temperature beyond 1 degree could trigger runaway melting of the world's icesheets". Shrinking ice means less sunlight gets reflected and more gets absorbed, exacerbating the problem of warming. "Even 1 degree additional warming may be highly undesirable; 2 to 3 degrees is clearly a different planet," he says.

The first act looks to have played out in the Arctic Circle this northern summer, when large freshwater lakes formed on the Greenland icesheet and then drained away to the depths. Fred Pearce, writing in Britain's The Guardian, records how scientists observed, within hours of the lakes forming, that the vast icesheets rose up, as if floating on water, and slid towards the ocean. The Penn State University glaciologist Richard Alley commented: "We used to think that it would take 10,000 years for melting at the surface of an icesheet to penetrate down to the bottom. Now we know it doesn't take 10,000 years; it takes 10 seconds."

Pearce says: "This highlights why scientists are panicky about the sheer speed and violence with which climate change could take hold. They are realising that their old ideas about gradual change - the smooth lines on graphs showing warming and sea-level rise and gradually shifting weather patterns - are not how the world's climate system works." (New research on the Ross Ice Shelf reveals that collapses over the past 3 million years have taken place very rapidly, with sea levels rising by between 7 and 17 metres.)

The quickening pace of that understanding is proving daunting to climate-change science watchers (but not, it would seem, the politicians).

Hansen stresses the urgency of the policy response. "I think we have a very brief window of opportunity to deal with climate change … no longer than a decade," he said last year.

If he is right we now have nine years at most, and there has been no let-up in emissions growth since then. And the latest UN conference on climate change could not even agree on a timetable for vital decisions on curbing emissions.

Bill McKibbin, reviewing Lovelock's book in The New York Review of Books, says: "Our problem now is that there is no way forward, at least if we're serious about preventing the worst ecological nightmares, that doesn't involve working together politically to make changes deep enough and rapid enough to matter. A carbon tax would be a very good place to start."

Meanwhile, our governments continue to canvass solutions that invoke long lead times - 15 years or more to come fully on stream - which prudence suggests is time we simply don't have. With climate transit looking to be in full swing (in the lead-up to a flip?), extreme extremes in weather patterns due to rising sea levels will force even the most obstinate to take Stern action.

Date: 2014-12-29; view: 819