Statement of Resource Person, Myles Allen 4) 5) 6) 7) 24 October 2018 IPCC Special Report on a global warming of 1.5°C, with particular responsibility for the assessment of the level of human-induced warming to date and its rate of increase.7 A central issue that the Commission may need to consider is the distinction between two approaches to framing the event attribution problem: assessing how human influence on climate may have affected the magnitude of an event or of the harm caused by an event, assuming that event occurs; versus how human influence may have affected the probability of an event of a given magnitude occurring. In 2012, we demonstrated that the same event could be characterised as “mostly natural” and “mostly anthropogenic” depending on which framing was used, highlighting the importance of clarity of approach to the attribution problem.8 This distinction is of particular importance in assessing contributions to the impacts of tropical storms, typhoons and hurricanes, where any change in event-probability remains unclear, but human-induced warming has a well-understood impact on potential intensity and extreme rainfall.9 I have contributed to publications assessing the attribution of changes in large-scale temperatures, sea level and extreme event risk to individual greenhouse gas emissions arising from individual countries10 or products sold by major corporations.11 Having led and co-authored papers on the cumulative impact of carbon dioxide emissions on climate,12 I have argued for a mandatory link between carbon sequestration and fossil fuel extraction as a mechanism for both incentivising the development of carbon dioxide capture and disposal technologies, and a means of imposing the costs and risks associated with carbon dioxide disposal on present-day fossil fuel producers and consumers.13 I agree to be a resource person for the petitioners, following a Skype call with Attorney Hasminah Paudac. 7 K. Haustein, M. R. Allen, P. M. Forster, F. E. L. Otto, D. M. Mitchell, H. D. Matthews, and D. J. Frame, “A real-time Global Warming Index,” Sci. Rep., vol. 7, no. 1, 2017. 8 F. E. L. Otto, N. Massey, G. J. van Oldenborgh, R. G. Jones, and M. R. Allen, “Reconciling two approaches to attribution of the 2010 Russian heat wave,” Geophys. Res. Lett., vol. 39, L04702, 2012. 9 G. J. van Oldenborgh et al, “Attribution of extreme rainfall from Hurricane Harvey, August 2017”, Environ. Res. Lett. 12 124009, 2017. 10 F. E. L. Otto, R. B. Skeie, J. S. Fuglestvedt, T. Berntsen, and M. R. Allen, “Assigning historic responsibility for extreme weather events,” Nat. Clim. Chang., vol. 7, no. 11, pp. 757–759, 2017. 11 B. Ekwurzel, J. Boneham, M. W. Dalton, R. Heede, R. J. Mera, M. R. Allen, and P. C. Frumhoff, “The rise in global atmospheric CO2, surface temperature, and sea level from emissions traced to major carbon producers,” Clim. Change, vol. 144, no. 4, pp. 579–590, 2017. 12 M. R. Allen, D. J. Frame, C. Huntingford, C. D. Jones, J. A. Lowe, M. Meinshausen, and N. Meinshausen, “Warming caused by cumulative carbon emissions towards the trillionth tonne,” Nature, vol. 458, no. 7242, pp. 1163–1166, 2009. 13 M. R. Allen, D. J. Frame, and C. F. Mason, “The case for mandatory sequestration,” Nat. Geosci., vol. 2, no. 12, pp. 813–814, 2009. 2