Saturday, September 19, 2009

Sceptics seize on climate cooling model

Research suggesting that global temperatures may fall is being used by deniers and sceptics to dismiss the entire canon of climate science

The sun shines high above a cluster of palms. Photograph: Andy Newman/AFP/Getty Images

Professor Latif's model suggested that the long-term warming trend could be masked - perhaps for as long as 10 or 20 years - by a temporary cooling. Photograph: Andy Newman/AFP/Getty Images

Could it be true that global temperatures will fall before they rise? That's the thrust of a presentation at last week's World Climate conference. Mojib Latif of Kiel University in Germany suggested that cooling caused by natural factors could suppress global temperatures for several years, after which they will start to rise again.

His presentation, first reported by the eagle-eyed Fred Pearce in the New Scientist, has been seized upon by sceptics and deniers all over the blogosphere. It was picked up this morning by the BBC's Today programme, which invited my old friend Philip Stott (who spends his time championing such dubious productions as The Great Global Warming Swindle and Michael Crichton's State of Fear) to raise questions about the global warming thesis.

Professor Latif suggested that the long-term warming trend could be masked - perhaps for as long as 10 or 20 years - by a temporary cooling caused by natural fluctuations in currents and temperatures called the North Atlantic oscillation. "Thereafter," he told the Today programme, "temperatures will pick up again and continue to warm."

Could Latif be right? Who knows? As far as I can tell, his paper has not yet been published, so other scientists haven't had the opportunity to see how strong it is. Vicky Pope of the Met Office suggested this morning that his model might not be as accurate as hers, as it measures only sea-surface temperatures, while the Met Office also takes temperatures below the surface into account.

We know that the world's climate system is a noisy one, in which natural variations of all kinds jostle constantly with the man-made warming signal. No one ever proposed that the global warming trend would be a smooth one, in which temperatures move up a notch every year. What we have seen so far are minor fluctuations weaving around a solid long-term trend. Nor does anyone claim that climate models are perfect. They need to be constantly refined and updated as new information comes to light. But in seeking to predict the future, you have only two options: wild guesswork, supported by a feeling in your bones, or models incorporating all the data scientists can lay their hands on. Those who reject modelling altogether must propose a better means of prediction. Seaweed, entrails and crystal balls don't qualify.

But Latif's presentation is being used by the deniers to dismiss the entire canon of climate science. They choose to overlook the inconvenient fact that he is also a climate scientist, who believes that the warming trend caused by human actions will bounce back as the oscillation moves into another phase.

People demand certainty, but the future resists it. All we can do is to make use of the best available information. And this tells us that we must act.