2 DEGREES OF WARMING
At this level, expected within 40 years, the hot European summer of 2003 will be the annual norm. Anything that could be called a heatwave thereafter will be of Saharan intensity. Even in average years, people will die of heat stress.
"The first symptoms," says Lynas, "may be minor. A person will feel slightly nauseous, dizzy and irritable. It needn't be an emergency: an hour or so lying down in a cooler area, sipping water, will cure it. But in Paris, August 2003, there were no cooler areas, especially for elderly people.
"Once body temperature reaches 41C (104F) its thermoregulatory system begins to break down. Sweating ceases and breathing becomes shallow and rapid. The pulse quickens, and the victim may lapse into a coma. Unless drastic measures are taken to reduce the body's core temperature, the brain is starved of oxygen and vital organs begin to fail. Death will be only minutes away unless the emergency services can quickly get the victim into intensive care.
"These emergency services failed to save more than 10,000 French in the summer of 2003. Mortuaries ran out of space as hundreds of dead bodies were brought in each night." Across Europe as a whole, the heatwave is believed to have cost between 22,000 and 35,000 lives. Agriculture, too, was devastated. Farmers lost $12 billion worth of crops, and Portugal alone suffered $12 billion of forest-fire damage. The flows of the River Po in Italy, Rhine in Germany and Loire in France all shrank to historic lows. Barges ran aground, and there was not enough water for irrigation and hydroelectricity. Melt rates in the Alps, where some glaciers lost 10% of their mass, were not just a record - they doubled the previous record of 1998. According to the Hadley centre, more than half the European summers by 2040 will be hotter than this. Extreme summers will take a much heavier toll of human life, with body counts likely to reach hundreds of thousands. Crops will bake in the fields, and forests will die off and burn. Even so, the short-term effects may not be the worst:
PLANTS START RELEASING CO2
"From the beech forests of northern Europe to the evergreen oaks of the Mediterranean, plant growth across the whole landmass in 2003 slowed and then stopped. Instead of absorbing carbon dioxide, the stressed plants began to emit it. Around half a billion tonnes of carbon was added to the atmosphere from European plants, equivalent to a twelfth of global emissions from fossil fuels. This is a positive feedback of critical importance, because it suggests that, as temperatures rise, carbon emissions from forests and soils will also rise. If these land-based emissions are sustained over long periods, global warming could spiral out of control."
In the two-degree world, nobody will think of taking Mediterranean holidays. "The movement of people from northern Europe to the Mediterranean is likely to reverse, switching eventually into a mass scramble as Saharan heatwaves sweep across the Med." People everywhere will think twice about moving to the coast. When temperatures were last between 1 and 2C higher than they are now, 125,000 years ago, sea levels were five or six metres higher too. All this "lost" water is in the polar ice that is now melting. Forecasters predict that the "tipping point" for Greenland won't arrive until average temperatures have risen by 2.7C. The snag is that Greenland is warming much faster than the rest of the world - 2.2 times the global average. "Divide one figure by the other," says Lynas, "and the result should ring alarm bells across the world. Greenland will tip into irreversible melt once global temperatures rise past a mere 1.2C." The ensuing sea-level ?rise will be far more than the half-metre that ?the IPCC has predicted for the end of the century. Scientists point out that sea levels at the end of the last ice age shot up by a metre every 20 years for four centuries, and that Greenland's ice, in the words of one glaciologist, is now "thinning like mad and flowing much faster ?than [it] ought to". Its biggest outflow glacier, Jakobshavn Isbrae, has thinned by 15 metres every year since 1997, and its speed of flow has doubled. "At this rate," says Lynas, "the whole Greenland ice sheet would vanish within 140 years. Miami would disappear, as would most of Manhattan. Central London would be flooded. Bangkok, Bombay and Shanghai would lose most of their area. In all, half of humanity would have to move to higher ground."
WATER SHORTAGE AND FAMINE
Not only coastal communities will suffer. As mountains lose their glaciers, so people will lose their water supplies. The entire Indian subcontinent will be fighting for survival. "As the glaciers disappear from all but the highest peaks, their runoff will cease to power the massive rivers that deliver vital freshwater to hundreds of millions. Water shortages and famine will be the result, destabilising the entire region. And this time the epicentre of the disaster won't be India, Nepal or Bangladesh, but nuclear-armed Pakistan."
Everywhere, ecosystems will unravel as species either migrate or fall out of synch with each other. By the time global temperatures reach two degrees of warming in 2050, more than a third of all living species will face extinction.
Chance of avoiding two degrees of global warming: 93%, but only if emissions of greenhouse gases are reduced by 60% over the next 10 years.