Constraints on long term warming in a climate mitigation scenario

Abstract

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.

Context for interpreting equilibrium climate sensitivity and transient climate response from the CMIP6 Earth system models

“…In addition, there are different time scales of response in the system, with some feedbacks and responses acting on the subcentury time scale and others operating on the multicentury time scale, with the nonlinear relationship between ECS and TCR indicative of those different time scales of response (41,44,45). The linear fit of ECS versus TCR in the CMIP6 models has a similar R 2 value of 0.61 compared to 0.60 in CMIP5 ( Fig.…”

The Multi-hub Academic Conference: Global, Inclusive, Culturally Diverse, Creative, Sustainable

“…The global situation will almost certainly get steadily worse in coming decades, as global mean surface temperature gradually rises (IPCC, 2018). Even if global net zero is reached, global mean surface temperature will continue to rise, possibly for decades (Sanderson, 2020). Positive feedbacks could push planetary climate across a threshold toward a "hothouse Earth," in which human survival is unlikely (Steffen et al, 2018).…”