Each year human activity contributes some 25+bn tonnes of CO2 and other active greenhouse gases directly into the atmosphere, each person in the developed world has a typical carbon footprint between 10 to 20 tonnes.
							CO2 has increased in the atmosphere from 280 parts per million (ppm) pre-industrial revolution to around 370ppm in 2007. If present trends continue levels are predicted to exceed 700ppm which could lead to further global warming, damage to fragile eco-systems, and more frequent severe weather events, and a major impact on the world economy, quantified in the Stern Report. The challenge is to stabilise and then reduce CO2 levels to prevent the most damaging aspects of climate change at around 500 ppm, against a background of rapid global population and economic growth