Global warming is a fact, no one disputes that these days. The question now is just how serious is it? The answer from Mark Lynas’s book Six degrees: Our Future on a Hotter Planet (Fourth Estate, 2007) is that it could not be more serious. Furthermore, it is all happening much faster than most people think.
Lynas is a science writer in the UK who trawled through numerous scientific papers that rarely get popular attention to get a sense of how various rises in temperature would affect life on earth. He found there was a growing body of research from the past (paleoclimatology) which made current trends even more worrying and that overall science has underestimated the severity of the problem. Certainly the ICCP reports do not adequately indicate the real level of overall threat.
Six degrees is the outside ICCP temperature forecast and seemingly a long way off, but according to Lynas, as bad as a 6C rise would be, it would just be the start of much worse. Indeed, the most shocking conclusion of the book is the growing realisation that if we cannot keep temperature rises to below 2C, it is probably all over for human civilisation.
The basic problem is that each rise in temperature will likely unleash new bio-chemical processes that radically increase greenhouse gases. At 3C carbon cycle feedback means that hotter soils and rotting vegetation give off more carbon dioxide. At 4C the vast area of Siberian permafrost gives off greatly increased amounts of methane as it melts. At 5C the oceans give up hydratic methane, causing a massive irreversible shift in global climate.
These are all probabilities, not certainties, but the science has become more reliable and more worrisome as it improves.
So basically, the reasoning goes like this:
Currently, atmospheric carbon dioxide levels are about 380 ppm (parts per million). Once they hit about 400 ppm, average global temperature will rise 2C. To keep rises at this level global emissions must peak by 2015 and then start to decline to 90 per cent by 2050.
If carbon dioxide levels reach 450 ppm and peak at 2030, causing a temperature rise of 3, positive feedback factors start to kick in. This means that natural systems which had previously not played a role in climate suddenly do, and that change is dramatic. At 3C methane trapped in Siberian tundra is released.
And here’s the rub: once we cross over 3C and this threshold is reached, an unstoppable process of climate change sets in. It seems we cannot stabilise temperature rises at 3C due to ongoing feedback.
At 4C, with global emissions peaking in 2050 and carbon dioxide at 550 ppm, methane hydrate locked in the oceans is released.
At 5C, with carbon dioxide levels reaching 650 ppm, most mega-fauna (like humans) on earth will be unable to exist.
So we either keep temperature rises to less than 2C or it is goodnight nurse for civilisation, maybe even humanity. In other words, we have to sort out this mess and get on top of emissions within the next eight years or so. We have to lower emissions so that by 2050 they have fallen by 90 per cent globally, or about 400 ppm.
Discuss in our Forums
See what other readers are saying about this article!
Click here to read & post comments.
37 posts so far.