Ahead of COP21 in Paris, countries have tabled their emissions reductions pledges in the form of Intended Nationally Determined Contributions (INDCs). New Oxfam-commissioned research, carried out by Climate Analytics, uses modelling to assess the impact of aggregate INDC ambition. It estimates that 3°C of warming, compared with 2°C of warming, could mean that developing countries are faced with an additional $600bn per year in economic losses by 2050, and see their adaptation finance needs raised by almost $300bn per year by the same date. The technical specifications and calibration of the models used are explained in this paper.