The UnAustralian

Thursday, February 27, 2003
Global Warming Emission Scenarios: Part 1

Recent, the various IPCC reports into global warming have been attacked for having unrealistic emission scenarios. Therefore, I've decided to do a series of posts detailing what they are, and why they are important.

In order to forecast future human induced climate change, you have to know how humanity will alter the world. Obviously, this is impossible, so we have to do the next the best thing, take a guess. However, predicted what will happen in the future is a fools guess, so the best thing that one can really do, is to take several guesses, and hope that reality will fit somewhere in-between them.

The IPCC has taken four possible scenarios (they are further divided up, but will we ignore that for the time being) called A1, A2, B1, and B2. Each scenario describes a possible future. As we hope that reality will fall in-between these scenarios, we must make sure that we are not describing average values, but rather outliers.

The A1 scenario is quite a nice place. There has been lots of international trade, and the third world is rapidly catching up with the first world. The worlds population has risen to 10 billion, and then dropped to 7 billion by 2100, as low birth rates spread all around the global. The service and information economy is huge, and inequality between nations has been considerable reduced. Per capita incomes are very high, but the amount of energy used to generate it is relatively low. The amount of CO2 and other greenhouse gases produced varies quite significantly in different versions of this scenario, depending on the degree of replacement of coal and oil as energy sources. Think Japan or South Korea's 20th century development.

The A2 scenario is also high growth, however, in this development really spread to the third world. The world is highly polarised, between the first world (who's economy is roughly similar to the A1's global economy) and the third world (who rely on large amounts of coal and oil to sustain themselves. The worlds population has skyrocketed to 15 billion, with of the extra people living in the third world. Per capita incomes of 1st world people people have increased by a moderate amount, meanwhile the third world has grown quite slowly. Large amounts of energy are generate to create this wealth, and the amounts of hydrocarbons used is very high.

The B1 scenario is similar to A1, but with more of an emphasis on sustainability, and less on high growth rates. The population is the same as the A1 scenario. The growth rates aren't quite as high, and there is a significantly higher gap between the first and third world. However energy usage is quite low.

The last scenario, B2 is similar to B1 but with more of an emphasis on ecology matters. The population isn't as high (10 billion by 2100), growth rates are moderate, but there is a large difference between the developing and industrialised worlds.
| 10:49 PM