The UN IPCC climate committee never ceases to stress how urgent it is for us to reduce the output of greenhouse gases. Scientists at the ETH in Zurich and the specialist research bodies associated with it have agreed for their part what values would be tolerable globally for energy requirements and CO2 emissions: in the medium and long term, use has to be reduced to 2000 watt per head and CO2 emissions to 1 ton of CO2 per head per year. With all consumed goods and services included, the average Swiss citizen uses three times more, in other words a continuous consumption of 6500 watt.