TEN years ago, climate scientists from 60 countries met in Paris, France, and set themselves the task of predicting the world鈥檚 weather years into the future. They dreamed of being able to issue reliable forecasts for an hour, a day, a month, a year, a decade or a century ahead 鈥� all with equal confidence. Now at least part of that dream looks to be on the verge of being fulfilled: viable medium-term forecasts seem within our grasp (see 鈥淐limate change: The next ten years鈥�).
This optimism stems from the better understanding we now have of the role of the oceans. Crudely, short-term weather is determined by the chaotic dynamics of shifting weather systems, while long-term climate is increasingly ruled by the accumulation of human-made greenhouse gases. The medium term, it now appears, is dictated mainly by ocean cycles, and there is growing confidence that these cycles can be predicted years ahead. If so, there could be big benefits. For example, we would have a good idea about rainfall over the next decade in grain-growing regions such as Australia and the American Midwest, or whether Africa should prepare for drought.
Yet there is a political sting in the tail of this good news story. Some medium-term forecasters are predicting that natural oceanic oscillations will push the world towards modest cooling, or at least a cessation of global warming, in the next five years or so. There is a danger that this could take the pressure off politicians to tackle greenhouse gas emissions, and make it harder to convince people of the urgent need for action.
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Earlier this year Robert Watson, former head of the and now chief scientific adviser to the UK鈥檚 environment department, observed: 鈥淟et鈥檚 say there wasn鈥檛 much of a warming for the next 10 years, how will the public and politicians play this out?鈥� It is a good question, especially since 鈥� as 鈥� we could be facing a 4 掳C warming before the century is over. Even the prospect of a cool 2008 has prompted a spate of claims that the whole global warming story is a hoax.
We can expect more of the same. It鈥檚 all nonsense, of course. Even a decade of planetary cooling would not change the long-term prospect of a warmer world. The decade-long oceanic oscillations will come and go, but the carbon dioxide we are putting into the air will stay there for centuries.
It is essential to get this message across. Fluctuations in temperature will be just that 鈥� ripples on a swelling tide of warming. On the timescale of an electoral cycle the world may not be getting hotter, but politicians have a responsibility to take the long view.
Climate Change 鈥� Want to know more about global warming: the science, impacts and political debate? Visit our continually updated special report.
