to those of us who exceed our allowance. Would a carbon credit card tempt you to walk instead? The aim of such a scheme would be to give everyone an incentive to use less carbon. Such an idea already exists within the European Union for large users of energy – power stations, heavy industrial plants and the like. The more greenhouse gases a company puts into the atmosphere, the greater the danger it goes over its allowance and will be forced to buy carbon from companies which manage to …