ABSTRACT
The fourth Assessment of the Inter-governmental Panel on Climate Change (IPCC) produced in 2007 went further than the previous report in stating that there is a 90 per cent probability that humans are implicated in forcing climate change. Since then, there has been a discernible increase in the level of anxiety regarding climate change and one of the reasons is the wider awareness of the signifi cance of so-called ‘tipping points’. The key tipping point indicator for climate change is the concentration of atmospheric carbon dioxide. At present concentrations of CO2 are about 383 ppm and increasing at 2-3 ppm per year and rising. The tipping point would be when the concentration of carbon dioxide reaches 450 parts per million (ppm), accompanied by a 2°C rise in average temperature. There is general scientifi c agreement that this concentration would signal a steep change in the rate of global warming and associated climate change. Mutually reinforcing feedback systems will gather momentum, leading rapidly to a situation which is irreversible – in other words, runaway global warming driven largely by the heat trapped in the atmosphere. It could mean that there is less than 15 years in which to halt the rise in CO2 levels.
