The enthusiasm for carbon offsetting, and the controversy that it has generated, indicate how concerned the public have become about climate change over a very short period. Faced with the realisation that so many of their actions create carbon dioxide emissions, more and more people are choosing to “offset” their flights, their car mileage, even their home heating, by writing a cheque to “buy” an equivalent carbon saving. The cheque goes to any one of a myriad of organisations that promise to neutralise those emissions, some by planting trees which they claim will absorb an equivalent amount of CO2,, others by giving cleaner energy to poor countries.

The enthusiasm is admirable. However, it can be naive. It can be hard to know exactly where the money is going. Does the tree or the wind turbine actually exist? Would it have been created anyway? Will the tree be replaced if it burns down, releasing all the CO2 back into the atmosphere again? It is becoming clear that it is almost impossible to predict how much carbon a tree can sequester: the science is very compli- cated. Renewable energy schemes offer much more promise. But they are also hard to verify. Poor people who are given energy-efficient light-bulbs, for example, one popular way of offsetting, may not be repeat buyers.

Caveat emptor applies in this market as in all others. The Government’s promise to create a code of practice and a quality mark will certainly help to guide consumers towards the most reputable offset schemes.

However, it would be a shame if a quality mark simply encouraged more people to see offsetting as a licence to pollute. David Miliband, the Environment Secretary, was at pains to point out yesterday that offsetting is not the answer to climate change. The first step should be to reduce one’s own carbon emissions in the first place. Offsetting should only be a last resort, not the lazy option.

Nevertheless, the idea that Western citizens could contribute to cleaner energy schemes in developing countries such as China and India is attractive. It is a useful riposte to the common refrain that anything that Britain does to reduce its energy use will be dwarfed by growth in China. By far the most effective of such transfers are going on at a much larger scale, through the EU emissions trading scheme and the carbon credits that it generates. In September the British bank Climate Change Capital announced that it had raised enough money to clean up a vast Chinese chemical company, a process that it says will remove the equivalent of a third of the annual greenhouse gas emissions produced by British households. Not only is this a huge boon to the planet, but the outcome will be relatively easy to verify under the auspices of the UN and the Kyoto Protocol.

It would be nice to think that ordinary investors might eventually be able to contribute to such schemes. As the carbon market matures, and as the big banks begin to get in on the act by investing in carbon credits, it will be important to make sure that middlemen take the smallest possible slice of the world’s goodwill payments.

Offsetting is a very useful way to help people to think about their carbon footprint. Good-quality schemes are vital to reduce the risk of consumers’ enthusiasm turning to disillusion. But offsetting is not the answer to climate change: that can only come when we find permanent ways to use less energy.