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The real risk with climate change is feedback effects as key thresholds are passed

What would it take to get the lead countries in the world to take climate change seriously? The 4th report of the UN International Panel on Climate Change produced by 1,250 of the world’s top scientists and approved by 194 governments, has just been published with the irrefutable argument that diverting funding from fossil fuels to renewable energy and cutting energy waste would reduce expected annual economic growth rates of 1.3%-3% by a minuscule 0.06%.

Given the imminent risk of cataclysmic climate upheaval within the next 20 years, you might think such a deal couldn’t be resisted, but that of course is without reckoning with the political lobbying power of the oil, gas and coal industries. But there is another argument which ought to give governments pause enough even to override the selfish pleading of the vested interests putting profits before human survival. And that is the very real risk of dramatic feedbacks.

Conventional thinking about global warming predicts that rising CO2 emissions will produce a steady rise in atmospheric concentrations. But past history of the planet indicates that that is not the pattern at all. One obvious concern is that deforestation in the Amazon, which has hitherto absorbed and stored vast quantities of greenhouse gases, will turn the world’s greatest rainforest into a desert by 2050, which is expected then to increase the rate of global warming by a massive 50%.

Another example is the release of methane (21 times more potent as a greenhouse gas than CO2) frozen in the Siberian permafrost. But climatic lurches don’t need big releases of greenhouse gases. The oceans are an equally important planetary thermostat. The basic circulation system – the thermohaline circulation – can be turned off with potentially big impacts on climate by changes in ice formation in the far north Atlantic.

There are a string of similar hair-trigger climate systems across the planet that are ripe for change. In the Pacific Ocean a warmer world could create a near-permanent El Nino, with dried-out rainforests across the tropics. Some scientists warn that the ozone layer could still spring big surprises. Then there is hydroxyl, a highly reactive and short-lived oxygen gas that reacts with common pollutants and could cause near-permanent smogs. And abrupt change could happen to sea levels too.

The Greenland ice cap, which has survived the 10,000 years since the last ice age virtually unaltered, now looks close to a threshold that triggers total meltdown. It is calculated that warming of less than 3 degrees, likely in that part of the Arctic within a couple of decades, could start a runaway melting that will eventually raise seal levels worldwide by 20-25 feet. The message of all these examples is that when the world is near any of these tipping points, a small push can have a huge effect. Any takers, Cameron or Paterson?

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