Why 90% cuts in greenhouse gases?

In 1990 the Intergovernmental Panel on Climate Change said that emissions of greenhouse gases needed to be cut by 60 - 80% to avert further climate change. This was based on the estimation that the planet can absorb around 4 billion tonnes of carbon each year. The mechanisms for this are not understood, but it is presumed to take place mainly through absorption by oceans and forests.

In 1990 6 billion tonnes (of carbon) per year were going into the atmosphere from burning fossil fuels, and 1.5 billion tonnes per year from burning forests. This meant that we needed global cuts of 3.5 gigatonnes out of 7.5 gigatonnes: that is 46%. However, the IPCC increased the figure to 60-80% in recognition that there are many greenhouse gases with multiple causes, many of which are natural (volcanos and natural forest fire cycles) or extremely hard to control. We therefore need to concentrate on those areas that can be most easily controlled- in particular burning fossil fuels.

The main problem is that the estimate is for overall global reductions with no allowance made of existing economic inequalities. If rich countries only achieve cuts at the global level of 60- 80%, poor countries are required to achieve the same percentage reduction even though they had a far lower starting point. This implicitly supports the current inequality in consumption. This is unjust and unacceptable.

The only fair form of reduction would be one that allows everyone an equal share of the 4 billion tonnes in allowable emissions. In a 1990 population of 6 billion people, this would give each person would get a share of only 0.66 tonnes of carbon per person per year. 'Contraction and Convergence' is a widely accepted model that attempts to secure a safe future stable value for rising greenhouse gas concentrations, within a fairer framework. It presents the simple idea of equity for survival. With equity at its centre it calls on 'over- consumers' like the US and the UK to contract - to cut emissions - sharply, while 'under-consumers' like Bangladesh can continue to rise for a while.

Experiment with emissions cuts for yourself with the Contraction and Convergence based numbers game -

www.chooseclimate.org/appv4/

In 1990 each British person emitted 2.74 tonnes carbon, more than four times the equal share. To reduce to an equitable level would require cuts of 76%. However, there are several reasons why this is still too low as a target:

* This figure assumes all emissions are controllable and fails to consider natural emissions;

* The world population is likely to stabilise at 10 billion, giving a per capita limit of only 0.4 tonnes carbon, which would require us to reduce by 85% on 1990 levels;

* It is certain that per capita emissions in the UK in 1990 were far higher than 2.74 tonnes, and that our proportional share of responsibility for the problem was far higher. Fuel consumption by airplanes and shipping are not included in these figures.

* There is no consideration that a substantial part of fuel consumption in the global south is for producing the raw materials and products consumed in the global north. Such relations are currently hidden, but would soon become apparent if a limit was placed on global fuel consumption.

* It is very likely that the capacity of the planet to absorb CO2 may fall below 4 gigatonnes carbon per year. The mechanisms by which carbon is removed are poorly understood. However it is already clear that rapid deforestation, over-fishing, and global warming are having severe effects on the ecological systems that contribute to removing carbon.

Finally, the biggest problem with all these estimates: at best they will only prevent further global warming beyond that already entailed by previous emissions. In other words, although such cuts might stabilise the level of the greenhouse gases in the atmosphere, they fail to reduce the level of greenhouse gases to pre-industrial levels. The technical language talks of "stabilising" emissions, but this does not mean we will have a stable climate; the results of the existing concentrations of greenhouse gases will certainly be disastrous.

All in all, 90% is a far more realistic figure for cuts and anything under 85% leaves permanent inequality in fossil fuel consumption. Please note - due to the 'momentum' of the system, (principally in the slow uptake of carbon and heat by the ocean), decisions about emissions in the next few decades have their greatest impact in 200- 300 years time. Whatever we do we get substantial warming by 2100 due to past emissions. Hang on in there. Any comments or opinions? Write to weathersave@netscapeonline.co.uk