Naomi Klein acknowledges that the carbon emitted into the atmosphere remains there for hundreds of years. Yet progress around the world continues to be measured in terms of carbon reductions which, however impressive when revealed as efficiency gains, energy-renewables switching or low-carbon developments, make no contribution to reducing its concentration. It can only reduce the rate at which the concentration goes on rising.

Evidence of ice melting in the polar regions indicates that the tipping point beyond which this process can now be reversed has already passed. The Global Commons Institute’s recent carbon budget allocation tool reveals the outcome of any proposal in relation to any budget under consideration. Sadly, there is no escape from coming to terms with the model’s figures on, for instance, sea-level rises, acidification and temperature increase.

Dr Mayer Hillman
Senior fellow emeritus
Policy Studies Institute

Letter published in The Guardian, 11 March 2015