Some will remember rationing during and after the Second World War. We had ration books to buy limited amounts of food, clothes and petrol and we were close to it again in 1973 during the oil crisis. It may well be a key feature of future attempts to limit climate change.

Various schemes have already been introduced to try to cut emissions and so reverse the warming trend because there is more talk than action about reducing the amount of CO2.

The European Emission Trading Scheme began in 2005 and is taking time to get going. All 25 countries must take part and each is allocated a limit of CO2 it can emit from heavy industry and power stations. The governments then divide out the national total amongst the various industries.

If they exceed their figure then they have to buy the extra tonnes from other industries or countries that have a surplus and produce less CO2. The aim is to encourage industries to invest in energy efficiency and CO2 saving technologies otherwise they become uncompetitive.

The first allocations were over generous and it was too easy to meet the targets with the result that the cost of each tonne was very low and the impact was minimal. The next round of trading is expected to be more challenging. Similar problems have arisen outside Europe with the system organised through the 1997 Kyoto agreement and fraud is not unknown.

It will take decades before the world community is prepared to accept the Contract and Convergence' plan put forward by Bradfordian Aubrey Meyer. His Global Commons Institute suggests countries agree their emissions total, and then gradually reduce them over time.

The poorer countries with an allowance to spare would sell it to the countries who could not meet their target and this would help to raise their standard of living while making the rich countries more efficient. It's a useful theory but it will be very difficult to implement.

Because the amount of CO2 in the air is still rising, despite the above efforts, the UK Government is funding a two-year research project to consider how a personal carbon allowance' might be introduced sometime in the future.

We would all have an electronic swipe card with an annual allowance of carbon credits and we would have to use it when we bought two main commodities, car fuel and electricity. If we had a big car and left house lights burning we might run out of carbons' and would need to buy more.

However if we have some over at the end of the year we can sell them and benefit from not having a car, or using it less and always switching off the lights. It would also move money from the rich to the poor and would be no more complicated than having a supermarket loyalty card.

The polluter paying is as it should be.