The Real Global Warming Scenario -- That No One Wants to Talk About

I've been working heavily on local community and regional planning & organization -- I'll give updates here as I consolidate some info. For now, remember to look past the glitz and glare of the financial crisis and keep an eye to the wider threats:

A key factor in how well we deal with a warmer world is how much time we have to adapt. When, and if, we get this hot depends not only on how much greenhouse gas we pump into the atmosphere and how quickly, but how sensitive the world's climate is to these gases. It also depends whether "tipping points" are reached, in which climate feedback mechanisms rapidly speed warming. According to models, we could cook the planet by 4 °C by 2100. Some scientists fear that we may get there as soon as 2050.

If this happens, the ramifications for life on Earth are so terrifying that many scientists contacted for this article preferred not to contemplate them, saying only that we should concentrate on reducing emissions to a level where such a rise is known only in nightmares.

"Climatologists tend to fall into two camps: there are the cautious ones who say we need to cut emissions and won't even think about high global temperatures; and there are the ones who tell us to run for the hills because we're all doomed," says Peter Cox, who studies the dynamics of climate systems at the University of Exeter, UK. "I prefer a middle ground. We have to accept that changes are inevitable and start to adapt now."

Bearing in mind that a generation alive today might experience the scary side of these climate predictions, let us head bravely into this hotter world and consider whether and how we could survive it with most of our population intact. What might this future hold?

The last time the world experienced temperature rises of this magnitude was 55 million years ago, after the so-called Palaeocene-Eocene Thermal Maximum event. Then, the culprits were clathrates - large areas of frozen, chemically caged methane - which were released from the deep ocean in explosive belches that filled the atmosphere with around 5 gigatonnes of carbon. The already warm planet rocketed by 5 or 6 °C, tropical forests sprang up in ice-free polar regions, and the oceans turned so acidic from dissolved carbon dioxide that there was a vast die-off of sea life. Sea levels rose to 100 metres higher than today's and desert stretched from southern Africa into Europe.

While the exact changes would depend on how quickly the temperature rose and how much polar ice melted, we can expect similar scenarios to unfold this time around. The first problem would be that many of the places where people live and grow food would no longer be suitable for either. Rising sea levels - from thermal expansion of the oceans, melting glaciers and storm surges - would drown today's coastal regions in up to 2 metres of water initially, and possibly much more if the Greenland ice sheet and parts of Antarctica were to melt. "It's hard to see west Antarctica's ice sheets surviving the century, meaning a sea-level rise of at least 1 or 2 metres," says climatologist James Hansen, who heads NASA's Goddard Institute for Space Studies in New York. "CO2 concentrations of 550 parts per million [compared with about 385 ppm now] would be disastrous," he adds, "certainly leading to an ice-free planet, with sea level about 80 metres higher... and the trip getting there would be horrendous."

Half of the world's surface lies in the tropics, between 30° and -30° latitude, and these areas are particularly vulnerable to climate change. India, Bangladesh and Pakistan, for example, will feel the force of a shorter but fiercer Asian monsoon, which will probably cause even more devastating floods than the area suffers now. Yet because the land will be hotter, this water will evaporate faster, leaving drought across Asia. Bangladesh stands to lose a third of its land area - including its main bread basket.

The African monsoon, although less well understood, is expected to become more intense, possibly leading to a greening of the semi-arid Sahel region, which stretches across the continent south of the Sahara desert. Other models, however, predict a worsening of drought all over Africa. A lack of fresh water will be felt elsewhere in the world, too, with warmer temperatures reducing soil moisture across China, the south-west US, Central America, most of South America and Australia. All of the world's major deserts are predicted to expand, with the Sahara reaching right into central Europe.

Glacial retreat will dry Europe's rivers from the Danube to the Rhine, with similar effects in mountainous regions including the Peruvian Andes, and the Himalayan and Karakoram ranges, which as result will no longer supply water to Afghanistan, Pakistan, China, Bhutan, India and Vietnam.

Along with the exhaustion of aquifers, all this will lead to two latitudinal dry belts where human habitation will be impossible, say Syukuro Manabe of Tokyo University, Japan, and his colleagues. One will stretch across Central America, southern Europe and north Africa, south Asia and Japan; while the other will cover Madagascar, southern Africa, the Pacific Islands, and most of Australia and Chile (Climatic Change, vol 64, p 59).