The Great Game

This article looks at the level of climate change that governments say that they are willing to accept and compares it to the level of CO2 that they are trying to reach. There is a big gap between the two. Big like an melting ice sheet.

This isn’t easy to follow, but please bear with me, as you cannot understand the world’s most important issue without grappling with some numbers. The average global temperature is affected by the concentration of greenhouse gases in the atmosphere. This concentration is usually expressed as “carbon dioxide equivalent”. It is not an exact science – you cannot say that a certain concentration of gases will lead to a precise increase in temperature – but scientists discuss the relationship in terms of probability. A paper published last year by the climatologist Malte Meinshausen suggests that if greenhouse gases reach a concentration of 550 parts per million, carbon dioxide equivalent, there is a 63-99% chance (with an average value of 82%) that global warming will exceed two degrees(5). At 475 parts the average likelihood is 64%. Only if concentrations are stabilised at 400 parts or below is there a low chance (an average of 28%) that temperatures will rise by over two degrees.

The IPCC’s draft report contains similar figures. A concentration of 510 parts per million (ppm) gives us a 33% chance of preventing more than two degrees of warming(6). A concentration of 590ppm gives us a 10% chance(7). You begin to understand the scale of the challenge when you discover that the current level of greenhouse gases in the atmosphere (using the IPCC’s formula) is 459ppm(8). We have already exceeded the safe level. To give ourselves a high chance of preventing dangerous climate change, we will need a programme so drastic that greenhouse gases in the atmosphere end up below the current concentrations. The sooner this happens, the greater the chance of preventing two degrees of warming.

But no government has set itself this task. The European Union and the Swedish government have established the world’s most stringent target. It is 550ppm, which gives us a near certainty of an extra 2°C. The British government makes use of a clever conjuring trick. Its target is also “550 parts per million”, but 550 parts of carbon dioxide alone. When you include the other greenhouse gases, this translates into 666ppm carbon dioxide equivalent (a fitting figure)(9). According to the Stern Report, at 650ppm there is a 60 – 95% chance of 3°C of warming(10). The government’s target, in other words, commits us to a very dangerous level of climate change.

To quote Mike Dunbar, "Time to get into the business of adaptation"

# posted by Jacob @ 5/01/2007 01:51:00 p.m.