The president`s promise to renegotiate the international climate agreement has always been a smokescreen, the oil industry has a red phone at the Home Office, and will Trump bring food trucks to Old Faithful? In this regard, we do not intend to address these gaps. On the contrary, we want to study the sensitivity of our results to alternative mitigation cost functions. To do this, we keep the initial socio-economic setting of our DICE model unchanged and implement the three reduction functions we have recalibrated with a process model for SSP sensitivity analysis (see above). In addition, we control uncertainty in our calibration process. To do this, we use the variance of the parameters estimate and the estimated optimal value to deduce normal distributions for each parameter and each SSP. Each of these distributions is scanned for 1000 sets of parameters, or 1000 alternative mitigation cost functions. The specific objectives and measures set by each country11 to contribute to the fight against climate change are entirely autonomous. The reason for this bottom-up approach is that universal participation is more likely to be achieved than by a top-down approach, with centrally defined objectives. The implementation of universal participation in a new agreement has become a priority above all other points of view, with the intention of addressing gaps in ambition12 through the establishment of a mechanism for periodic review and upward revision of contributions. Here, we expand the analysis of uncertainty with respect to SCT values, as shown in Figure 1. To this end, we use an estimated ECS probability distribution from a series of GCM simulations (see Figure 3 (A) in Roe and Baker26 and Complementary Figure 9).
From 30 November to 11 December 2015, France hosted representatives from 196 countries at the end of the Un Climate Change Conference (UN), one of the largest and most ambitious global meetings ever held. The goal was nothing less than a binding and universal agreement to limit greenhouse gas emissions to levels that would prevent global temperatures from rising more than 2oC above the lower temperature levels set before the start of the industrial revolution. The first NDC is expected to be presented on or before the date the parties ratify the agreement.14 Most parties have already submitted their INDC, which will become their national contribution (CNN) in 2020. Due to differences of opinion between the parties, the agreement does not provide for the parties to revise their current INDCs upwards before 2020, meaning that the INDCs currently presented by the parties will be the ones they are expected to implement from 2020. The resulting distribution of economically optimal temperatures in 2100 inherits the properties of the distribution of the probabilities of the ECS. As the main text shows, higher ECS values imply a higher temperature target because of the limited room for manoeuvre to achieve lower temperatures with climate policy.