My friend and colleague, Professor David Stout, pointed me in the direction of this special report in new scientist (16 August 2007). The article highlights the uncertainties that are involved in some of the non-linear changes in climate and points out that the more we know, the less certain we’re about the directions or the rate at which some of these potentially catastrophic changes in climate may occur.
Climate tipping points loom large – Fred Pearce
SOME climate tipping points may already have been passed, and others may be closer than we thought, it emerged this week. Runaway loss of Arctic sea ice may now be inevitable. Even more worrying, and very likely, is the collapse of the giant Greenland ice sheet. So said Tim Lenton of the University of East Anglia, UK, speaking on Monday at a meeting on complexity in nature, organised by the British Antarctic Survey in Cambridge.
Lenton warned the meeting that global warming might trigger tipping points that could cause runaway warming or catastrophic sea-level rise. The risks are far greater than suggested in the current IPCC report, he says.
Yet climate modellers are in a quandary. As models get better and forecasts more alarming, their confidence in the detail of their predictions is evaporating.
Freeman Dyson: My first heresy says that all the fuss about global warming is grossly exaggerated. Here I am opposing the holy brotherhood of climate model experts and the crowd of deluded citizens who believe the numbers predicted by the computer models. Of course, they say, I have no degree in meteorology and I am therefore not qualified to speak. But I have studied the climate models and I know what they can do. The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world that we live in. The real world is muddy and messy and full of things that we do not yet understand. It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds. That is why the climate model experts end up believing their own models. (
Alun Anderson: Knowing that Arctic climate models are imperfect, it would be reassuring for me, if not for the scientists, to be able to write that scientists keep making grim predictions that just that don’t come true. If that were so, we could follow Dyson’s line that the models aren’t so good and "the fuss is exaggerated". Scarily, the truth is the other way around. The ice is melting faster than the grimmest of the scientist’s predictions, and the predictions keep getting grimmer. Now we are talking about an Arctic free of ice in summer by 2040. That’s a lot of melting given that, in the long, dark winter the ice covers an area greater than that of the entire United States. (
Below is an extract from The Age, with comments from 