The Statistics of Climate Change

Professor Norman Fenton writes about his role co-presenting a forthcoming BBC Four documentary on climate change and the importance of three key statistics. I have the pleasure of being one of three presenters of a documentary called Climate Change by Numbers, to be screened on BBC Four on 2 March 2015. The motivation for the programme was to take a new look at the climate change debate by focusing on three key numbers that all come from the most recent Intergovernmental Panel on Climate Change (IPCC) report. The numbers were: - 0.85 degrees (the amount of warming the planet has undergone since 1880) 95 per cent (the degree of certainty climate scientists have that at least half the warming in the last 50 years is man-made) One trillion tonnes (the cumulative amount of carbon that can be burnt, ever, if the planet is to stay below 'dangerous levels' of climate change) The idea was to get mathematicians/statisticians who had not been involved in the climate change debate to explain in lay terms how and why climate scientists had arrived at these three numbers. The other two presenters were Dr Hannah Fry (UCL) and Professor Sir David Spiegelhalter (Cambridge) and we were each assigned approximately 25 minutes on one of the numbers. My number was 95 per cent. Being neither a climate scientist nor a classical statistician (my research uses Bayesian probability rather than classical statistics to reason about uncertainty) I found the complexity of the climate models and their underlying assumptions to be daunting.