1. Loading the Weather Dice Attribution of extreme weather events to climate change Friederike Otto, Neil Massey, Richard Jones, Richard Washington & Myles Allen School of Geography and the Environment & Department of Physics, University of Oxford & The Met Office Supported by Microsoft Research and EQUIP

2. Not all extreme events should be blamed on anthropogenic climate change A flood that happened – and one that did not Pall et al, 2011 and Kay et al, 2011 100% increase in risk 40% decrease in risk

3. Performing simulations using distributed computing: weatherathome.net

4. Not everyone thinks this is a good idea "Funding will no longer go to those who are most at risk from climate-impacts and with low adaptive capacity, but will go to those who are lucky enough to live in regions of the world where weather extremes happen to be most attributable by climate models to human agency. These regions tend to be in mid-to-high latitudes, with lots of good weather data and well calibrated models. So, goodbye Africa.” Mike Hulme, quoted in The Guardian

5. Consider a region with poor weather data and poorly-calibrated models: the Congo basin

6. Very poor weather data

7. But high potential predictability in a large AMIP- style ensemble: and reliable against ERA-interim

8. Changing risks of drought conditions in the Congo

9. Conclusions: the prospects for attribution of harm to human influence on climate Allegations of harm are entering negotiations, with no agreed procedure for assessing evidence. Attribution bridges seasonal/decadal information gap. IPCC regional assessments are not the answer. IPCC can play a role in standardising terminology. US/UK modelling groups are laying the groundwork for regular attribution assessments: –UKMO/NOAA/SSEE Workshop in Oxford, 12-14 September, 2012, sponsored by FCO & Risk Prediction Initiative Disaster-prone nations must be fully involved – not penalised by trend towards quantitative attribution.