10.1 Setting the scene

The world faces an “existential threat” in climate change – as acknowledged by judges in both the UK and the US.2 The Intergovernmental Panel on Climate Change (IPCC) reports show that: to stabilise at 2ºC over pre-industrial levels (taking 1850 as the baseline) by 2100 there must be no more than a concentration of 450 parts per million (ppm) of CO2; for 1.5ºC, the new target set by IPCC in 2018, the concentration must be no more than 430 ppm. The world is currently at about 415 ppm mean concentration, rising about 2.9 ppm annually, with a slight reduction in increase in 2020 due to the effect of coronavirus. The maths shows that we shall hit 430 ppm in five to six years’ time and 450 ppm in about 13 years’ time. This is confirmed by the figures in the 2018 IPCC SR-1.5 report quoted by Greta Thunberg in her Montreal speech of 27 September 2019: