Abstract. Cumulative emissions budgets and net-zero emission target dates are often used to frame climate negotiations (Frameet al., 2014; Millar et al., 2016; Van Vuuren et al., 2016; Rogelj et al., 2015b; Matthews et al., 2012). However, their utilityfor near-term policy decisions is confounded by an uncertainties in future negative emissions capacity (Fuss et al., 2014; Smith et al., 2016; Larkin et al., 2018; Anderson and Peters, 2016) and in long term Earth System response to climate forcers(Rugenstein et al., 2019; Knutti et al., 2017; Armour, 2017) which may impact the utility of an indefinite carbon budget if peak temperatures occur significantly after net zero emissions are achieved, the likelihood of which in a simple model is conditionalon prior assumptions about the long term dynamics of the Earth System. Here we illustrate that the risks associated with nearterm positive emissions can be framed using a definite cumulative emissions budget with a 2040 time horizon, allowing thenecessity and scope for negative emissions deployment later in the century to be better informed by observed warming overcoming decades.
Supplementary material to "Constraints on long term warming in a climate mitigation scenario"
