The Guardian, 17 March 2015:
If we are to have a meaningful debate about climate change, then it is important to get the numbers right (Crunching the numbers on carbon, 10 March). The carbon dioxide allowance produced by the Carbon Tracker Initiative in 2011 was 565bn tonnes, an estimate that was said to provide an 80% chance of staying below 2C. In 2013 however, CTI revised its estimate upwards to 900bn tonnes to take account of the latest report from the Intergovernmental Panel on Climate Change.
For a 66% chance of staying below 2C, the IPCC calculated a total carbon budget of 1tn tonnes, but this is from the start of the industrial revolution and includes other greenhouse gases. As these account for 20% of global warming, the IPCC figure for burnable carbon was actually 800bn tonnes. We have already burnt 550bn tonnes, leaving only 250bn tonnes of carbon. Currently we are producing 36bn tonnes of CO2 a year, which is equivalent to 10bn tonnes of carbon, so we will burn through our carbon allowance by 2040, if emissions stay the same. In fact, they are increasing by 2-3% a year, so we actually have less than 20 years before we enter the territory of irreversible climate change. In this context, China does not plan on reducing its emissions until after 2030.
Dr Robin Russell-Jones
Stoke Poges, Buckinghamshire