Wednesday, September 23, 2009

350 ppm – what does that mean?

There has been some news coverage recently on the 350 ppm target promoted, amongst others, by the organization Whilst “350” is a very catchy phrase to use for public campaigning and lobbying, I started wondering the other day what it actually means.

Firstly, 350 ppm refers to 350 parts per million of CO2 in our atmosphere. This figure was arrived at by Dr. James Hansen, a NASA scientist who has researched climate change for longer than anyone else. According to Hansen, 350 ppm is the maximum concentration of CO2 in our atmosphere that we can allow in order to avoid global temperature to rise beyond 2 degrees Celsius. 2 degrees Celsius, on the other hand, is by many regarded as “the tipping point” beyond which the biosphere reverses a number of its natural cycles, causing what is called “runaway climate change”. This includes melting polar ice caps and thus replacing large, white, reflective surfaces with dark, heat absorbing ocean water. It includes acidification of the oceans, die-off of corals and algae and consequently a significant reduction in the oceans’ ability to absorb CO2. It includes the melting of the permafrost soils in the Russian tundra, causing them to release vast amounts of additional CO2.

350 ppm is also a significant number, because it indicates a need for a net reduction in atmospheric CO2, as we have actually already passed this point – our atmosphere currently holds around 385 ppm of CO2 – and this is without considering the time delay in carbon emissions reaching the atmosphere (which stay there for about 200 years). This means that, in effect, we have to reduce the amount of carbon in our atmosphere, rather than continuing to add to it at all.

But HOW do we reduce the amount of carbon in the atmosphere? – The answer is, simply put, that we have to keep our carbon emissions below our planet’s natural ability to absorb carbon. This would mean that, on an annual basis, our home planet would gradually reabsorb carbon from the atmosphere and thus reduce the ppm – ideally, until we reach 350 ppm.

Currently, the planets’ ability to absorb carbon is estimated around 4 billion tons / year. Our current carbon emissions lie around 7 billion tons / year. Already, this means that in order to achieve a net reduction in atmospheric CO2, we’d have to reduce our carbon emissions by about 50%. That’s half as much driving your car, half as many light bulbs, hot showers, pieces of toast and cooked meals (for most of us) – and in fact probably eating only half as much food in general, if we take into account the carbon emissions produced by our food industry.

To make matters worse, our planets’ ability to absorb carbon is being reduced on an ongoing basis due to the ongoing reduction in forest cover and disturbance of ecosystems. Based on a paper published by the Met Office, the total capacity of the biosphere to absorb carbon will, by 2030, have reduced from the current 4 billion tons / year to about 2.7 billion tons. At the same time, world population is likely to increase to an estimated 8.2 billion in 2030.

By dividing the total carbon sink (2.7 billion tons) by the number of people, we find that to achieve stabilization the weight of carbon emissions per person on the planet should be no greater than 0.33 tons per year – this means around a 90% reduction for most rich countries. In order to achieve not only equilibrium, but a net reduction in atmospheric carbon over current levels, the reduction rate would be even higher.

Trying to translate those 90% percent into actual lifestyle changes we are required to make leaves me puzzled as to how that is achievable. One answer is provided by George Monbiot in his book “Heat”. The good news is that – if we force ourselves to count on the best possible outcomes – such a reduction seems, in fact, achievable. However, for those of us who think that they can continue with business as usual, Monbiots’ suggestions are - sobering, to say the least.

Whether achievable or not – I believe we can’t but try our best. We are living only one of many possible lifestyles, and I certainly don’t think it is the best option. What we create for our future is up to us – all we need to do is take this information to be a guide for our design.

“Our imagination is a preview of life’s coming attractions”
Albert Einstein

No comments:

Resilience Education For Individuals and Enterprises
[Home] [About us] [Education] [Consultancy] [Design] [Photography]