Global warming's impact on the environment is not necessarily a drawn-out affair. Recent evidence shows that dramatic changes or 'climatic flips' could happen virtually overnight.
The once-green land of Ireland turned into a frozen wilderness. Harp seals swimming among ice-floes off the coast of France. Polar bears prowling the streets of Amsterdam. These are the images conjured up by the latest research into global warming.
Yes, you read that correctly: global warming - the rise in the world's average temperature caused by the trapping of the sun's heat by pollution in the atmosphere.
If you are baffled by that, then prepare to be shocked. For the same research is now suggesting that such dramatic changes in the climate of northern Europe could take place in as few as 10 years.
Again, this figure is not a misprint: no zero has gone missing. Scientists have recently uncovered compelling evidence that global warming can have a devastating impact on timescales far shorter than anyone believed possible. Not centuries, not even decades, but years, in what are being called "climatic flips". One leading expert has recently gone on record to warn that some north Atlantic countries could find themselves plunged into Arctic conditions over the space of just 10 years.
Risk of sudden upheaval
In geological terms, that is as fast as the blink of an eye. But even in human terms, such a rate of climatic change is incredibly - and quite probably intolerably - rapid. It is far from clear whether any economy or agricultural system could cope with such sudden upheaval.
Yet evidence is now mounting that such "climatic flips" not only can happen, but have happened in the past. It is evidence that adds new urgency to the global warming debate, which has lost much of its momentum in recent years. It also highlights the frightening complexity of the task facing scientists trying to predict the earth's response to human activity.
Arguments about climatic change typically focus on how increasing levels of so-called greenhouse gases - principally carbon dioxide from burning fossil fuels - in the earth's atmosphere trap ever more of the sun's heat.
Huge efforts have been put into predicting the likely global temperature rise caused by the extra greenhouse gases, and current best estimates point to a rise of 1.5 degrees Celsius or so over the next century.
But while scientists warn that even so apparently small a rise in temperature could cause upheaval in everything from agricultural practices to the spread of disease, the rate of change hardly seems terrifying. Surely we can cope and have coped with events that change over several generations?
Such arguments are buttressed by another, apparently compelling, argument against rapid climate change. The earth's oceans have colossal thermal inertia, and would surely iron out any sudden upheaval: weight for weight, it takes ten times more energy to heat water than it does solid iron.
Small wonder, then, that scientists were unsurprised when they failed to find any signs of rapid climatic changes when they first studied ancient ocean sediments, the isotope levels of which retain a record of past temperatures.
The end of the lee Age: a puzzling discovery
But this apparently comforting confluence of theory and data is now known to contain two huge loopholes. The first reared its head in the early 1980s, when a joint U.S.-European team of scientists working in Greenland made a puzzling discovery. They had extracted an ice-core from a site in the southern part of the country, and had measured isotope levels in the gas trapped at different depths in an attempt to gauge the temperature in the region over thousands of years.
Because the ice builds up relatively rapidly, the ice-core was expected to give the researchers the most fine-detailed picture yet of temperature changes in the region. …