In summer last year the British Chancellor, Gordon Brown, asked me to examine the economics of climate change, basing the analysis on sound science and the latest economic literature.

The Stern Review of the Economics of Climate Change, which reported yesterday to the British Prime Minister and Chancellor, accepts the overwhelming scientific evidence that climate change is a man-made, global threat to the sustainability of life on earth. But our research indicates that it is still possible to avoid the worst risks and impacts of climate change at an affordable cost, if well-designed and co-ordinated action at a national and global level is taken forward as a matter of urgency.

The annual flow of carbon dioxide and other greenhouse gases that warm Earth’s atmosphere has accelerated ever since coal, then oil and gas too, began to fuel the industrial revolution which has brought better lives to so many. The billions of tons of carbon dioxide and other greenhouse gases still accumulating in the earth’s fragile, protective atmosphere have already raised concentrations to around 430ppm (parts per million) of carbon dioxide equivalent (CO2e), compared to 280ppm before the industrial revolution.

Human activities are pouring 45 billion tonnes of greenhouse gases (in CO2e) into the atmosphere a year, and rising. Earth’s intricate eco-systems currently absorb around half, but the rest is retained in the atmosphere, pushing the accumulated stock of gases higher every year.

Our research indicates that global efforts should concentrate on limiting the ultimate level of greenhouse gases in the atmosphere to between 450-550ppm. This is achievable, economically feasible, and will significantly reduce the risk of extreme temperature changes. Such a goal requires us to reduce the annual flow of emissions by at least 25 per cent from today’s levels by 2050, and to keep cutting until emissions eventually fall to a level at least 80 per cent lower than now, which would allow stabilisation.

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