From Greenhouse to Green House

The threats of climate change
CO2 emissions and savings


You want to indulge your carbon addiction by jetting off to somewhere sunny ("Hey, man, I just went to Italy and back for less than the cost of a pint") but your conscience is pricking you about all that CO2 spewing out of the back of the plane. Thankfully, someone has been thoughtful enough to provided a 'carbon offset' scheme that allows you to sooth your conscience by paying a few extra pounds towards the cost of planting young trees that will absorb your CO2 emissions as they grow. Wonderful! Now you can relax without that nagging worry any more!

The intention is right but the answer, we believe, is wrong. It is true that trees absorb CO2 as they grow but much more than that is needed to make this kind of carbon sink into an effective answer to CO2 emissions:

bullet To be an effective answer, the CO2 absorbed by the trees must stay locked up for thousands of years. This would mean storing the wood from the mature trees in some way so that it cannot possibly catch fire and it cannot be broken down by bacteria or fungi. There is no human institution on earth and no available technology that can ensure that the CO2 in the mature trees is not released back into the atmosphere on relatively short timescales.
bullet Even if one could guarantee that the carbon in the trees that were planted remained locked up for thousands of years, the scheme would still not, in itself, provide an effective answer to CO2 emissions. Why not? For the scheme to be effective, it would be necessary to ensure that the extra trees produced by the scheme were not offset by loss of trees elsewhere in the world - by logging, by forest fires or by decay.
bullet In a similar vein, George Monbiot points out in his book Heat, "Planting trees, for example, means not planting - or not leaving - something else on the same land. You have no means of knowing what, in twenty years' time, might have stood in their place. If the answer is other trees, then to determine the real carbon uptake caused by your actions, you would have to subtract the carbon that might have been from the carbon that is." (p. 211).
bullet A related point is that, if rainforest is cut down to plant trees or other crops to be burned as a source of renewable energy, we not only lose the biodiversity of the rainforest and its potential to absorb CO2, but we have created an additional source of energy with no guarantee that it will displace any existing source of CO2 emissions.
bullet In Heat, George Monbiot points out that "a tonne of carbon saved today is far more valuable, in terms of preventing climate change, than a tonne of carbon saved in twenty year's time, ..." (p. 211). There seems to be no current scheme that takes account of this in its calculations.
bullet Contrary to widely-accepted botanical wisdom, some research has shown that trees and other plants release methane into the atmosphere as they grow (Nature, 12 January 2006). These methane emissions reduce the benefit derived from the way the plants absorb CO2 as they grow.

For an object lesson in some of the pitfalls in trying to offset CO2 emissions by planting trees see "How Coldplay's green hopes died in the arid soil of India".

None of these points alters the fact that there are often other good reasons for planting trees.

Other schemes

What about carbon-offset schemes that invest in carbon-saving technologies (renewable forms of energy or methods for saving energy)? To be effective, any such scheme:

bullet Should be a source of funding that is additional to what would have been spent anyway, not merely a substitute for existing sources of funds.
bullet Should replace one or more existing sources of energy based on fossil carbon. If it is merely an additional source of energy, it does nothing to reduce global emissions of CO2.

But even if these conditions are met, there are still problems:

  • Any savings in CO2 emissions from such a scheme could easily be nullified by extra emissions from some other source.
  • There is great scope for poor administration and fraud. Here are some examples of the kind of scam that may be used:
    • If a company plans to expand polluting activities by 200% and then scales the plan back to 100%, they can claim carbon credits for the difference.
    • The Sinar Mas pulp and paper company cut down native forest in Indonesia, causing major devastation, and then planted palm oil trees on the wasteland it had created. Perverse as it may seem, they got offset credits for reforesting, despite the fact that it had destroyed an entire forest ecosystem, and installed a monoculture industrial plantation in its place.
    • In China, Stanford professors David Victor and Michael Wara found that a majority of the large hydropower plants and gas burners that went online in recent years have cashed in on the carbon offsets market, making a hefty profit on projects that would have happened anyway (this is the problem of "additionality").
  • To quote George Monbiot again: "At best these schemes merely delay the point at which emissions are saved. At worst, they allow us to believe that we can carry on polluting, just as, before the Reformation, the sale of absolutions encouraged people to believe that they could carry on sinning. I cannot think of a more effective means of postponing the hard choices we need to make now." (p. 212).

In general, carbon offset schemes, in all their forms, are a distraction in the fight against climate change. We need a world-wide system of tradable carbon rations and a "World Carbon Organisation" to administer it.

Notice that tradable carbon rations are very different from carbon offsets. In the first case, there is direct control of emissions of fossil carbon. In the second case, there are numerous opportunities to dodge the real issue which is to stop dumping fossil carbon into the atmosphere.

When the aviation companies say that they are in favour of 'carbon trading', they mean carbon offsets, not carbon rationing. They should not be allowed to dodge their responsibilities in that way.