WHILE the international community readies itself for gradual global warming over the next century, a growing number of scientists are beginning to worry that climate change might come much sooner - and be much more catastrophic - than previously thought.
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www.sciencefestival.co.ukThey point out that, in the past, climate change has not been gradual. Europe's climate has switched from arctic to tropical in three to five years and, they warn, it can happen again.
Fred Pearce, of the New Scientist, has spent the past two years speaking to climate experts who are studying the possibility of "type 2" climate change - abrupt, catastrophic and irreversible. He will present his findings as part of the Edinburgh International Science Festival today.
The scientists of the Intergovernmental Panel on Climate Change (IPCC), which will present a long-awaited report into the slow but serious effects of global warming tomorrow, have focused on "type 1" predictions based on already observable warming patterns.
But many climate experts say this method of modelling ignores the possibility of "tipping points" at which the climate suddenly spirals out of control.
"The IPCC is a very conservative body. It assumes that global warming will follow an already observable pattern - that it will be a straight line on a graph," Mr Pearce said. "But there are many scientists who are increasingly worried about a sudden and catastrophic acceleration that could happen at any time."
Sudden "type 2" climate change will happen through a series of "positive feedback" cycles, in which each stage of warming sets off another, like cascading dominoes.
Mr Pearce spells out one scenario: the melting of the Arctic Ocean ice increases polar warming, triggering sea-temperature rises that dry out the Amazonian rainforest, leading to forest fires, releasing more carbon, stimulating further warming, reducing snow-cover on permafrost in Siberia, allowing it to melt and release methane, which in turn causes enough warming to release frozen methane hydrates from below the oceans.
Such extreme warming then leads to the melting of at least one of the world's three major icecaps. Hundreds of coastal cities are swallowed by rising sea levels.
Millions of climate refugees are displaced by rising sea levels, failing crops, water shortages and extreme weather.
A team of scientists recently polled colleagues about "type 2" climate change and are preparing to publish the data.
Tim Lenton, an Earth System Scientist at University of East Anglia, said the results were scary: "We found that almost every scientist listed several non-linear changes as real possibilities.
"The fact that scientific experts are even considering this suggests the severity of the issue. We all think we can adapt to smooth change, but step-change is much different."
• Fred Pearce will discuss his book, The Last Generation: How Nature Will Take Her Revenge for Climate Change at Reid Concert Hall today at 6pm.
Orange groves in the Highlands, bananas by the west coast lochs and warm winter cruises. The shape of things to come?
THE year is 2040, and the English are pouring across Hadrian's Wall.
Rising tides in the North Sea have overwhelmed the Thames Barrier and, with the city wiped out, rich Londoners are heading for the hills. Especially the Scottish hills, where the climate is remarkably like that of the Dordogne of a few decades ago.
It wasn't supposed to be like this. Climate change, they said at the start of the 21st century, would be nasty but gradual and fairly predictable. It has turned out to be much more sudden and brutal.
Climate scientists in 2040 stand discredited. Not because they were too alarmist, but because they failed to warn the world of what was to come.
Europe is in a bad way. The south of the continent - Spain, Italy and Greece - is the new Sahara desert. The French vineyards are dead. The first tropical hurricane hit Devon in 2037, obliterating Plymouth.
But climate chaos is global. Refugees fleeing floods and storms, droughts and searing heat have become an unstoppable force. There is guerrilla warfare on the US-Canadian border. The Chinese invaded Siberia after the South China Sea flooded the homes of 70 million people in the world's largest megacity, Shanghai.
Triggered by the catastrophic collapse of the Greenland ice sheet, sea-level rise has proved to be ten times faster than expected. The tides have engulfed Lagos and Bangkok, Sydney and New Orleans.
And there was the unfortunate case of the Sizewell nuclear power station on the English east coast. Dodgy dykes let the sea into the reactor. The rest of Suffolk may have disappeared beneath the waves before the radiation clears.
Wildlife has been on the move, too. There are great white sharks off Blackpool and malarial mosquitoes in the Channel Islands. Polar bears have become extinct as the Arctic ice ran out, but brown bears are marauding US suburbs in search of food.
Killer bees have invaded home counties hives and a family of baby crocodiles released into the Thames took to the warmer waters and started preying on otters.
As crops dry in the fields or are washed away by salty tides, the global economy has been in deepening recession since 2035. The revered economist Nicholas Stern, who forecast just this back in 2006, quietly says "I told you so" from his Highland retreat.
Many blame all this on India. The world's largest economy refused to join an emergency effort, launched by the US in 2020, to ban all burning of coal and oil. But in truth the die was cast before then. The 2020 vision just came too late. Nature is taking her revenge.
Half a century ago, the oceans and soils and rainforests of the world soaked up half of the world's man-made emissions of carbon dioxide. Everyone assumed they would continue this vital task. But in 2040 they are releasing more than they absorb. The Amazon rainforest is engulfed in flames and driving a new surge in global warming. Climate change is accelerating, and is literally unstoppable - whatever humans do.
Ah, but Scotland, independent and basking in its new warm climate, is on to a winner. Winter cruises of the islands are attracting the rich and famous. The country is self-sufficient in vines and wheat and oranges. Sunflowers spread across the Borders. They are even thinking of growing bananas beside the secluded lochs of the west coast.
Downsides? Well, the ski slopes went some times ago, along with a few bird species that found it too hot in the Highlands. But if the new Border guards can keep out the English - and the rest of the world - then Scotland looks increasingly like the last Eden.