Mitigating climate disruption in time: A self-consistent approach for avoiding both near-term and long-term global warming

Significance

This study clarifies the need for comprehensive CO ₂ and non-CO ₂ mitigation approaches to address both near-term and long-term warming. Non-CO ₂ greenhouse gases (GHGs) are responsible for nearly half of all climate forcing from GHG. However, the importance of non-CO ₂ pollutants, in particular short-lived climate pollutants, in climate mitigation has been underrepresented. When historical emissions are partitioned into fossil fuel (FF)- and non-FF-related sources, we find that nearly half of the positive forcing from FF and land-use change sources of CO ₂ emissions has been masked by coemission of cooling aerosols. Pairing decarbonization with mitigation measures targeting non-CO ₂ pollutants is essential for limiting not only the near-term (next 25 y) warming but also the 2100 warming below 2 °C.

Abstract

The ongoing and projected impacts from human-induced climate change highlight the need for mitigation approaches to limit warming in both the near term (<2050) and the long term (>2050). We clarify the role of non-CO ₂ greenhouse gases and aerosols in the context of near-term and long-term climate mitigation, as well as the net effect of decarbonization strategies targeting fossil fuel (FF) phaseout by 2050. Relying on Intergovernmental Panel on Climate Change radiative forcing, we show that the net historical (2019 to 1750) radiative forcing effect of CO ₂ and non-CO ₂ climate forcers emitted by FF sources plus the CO ₂ emitted by land-use changes is comparable to the net from non-CO ₂ climate forcers emitted by non-FF sources. We find that mitigation measures that target only decarbonization are essential for strong long-term cooling but can result in weak near-term warming (due to unmasking the cooling effect of coemitted aerosols) and lead to temperatures exceeding 2 °C before 2050. In contrast, pairing decarbonization with additional mitigation measures targeting short-lived climate pollutants and N ₂O, slows the rate of warming a decade or two earlier than decarbonization alone and avoids the 2 °C threshold altogether. These non-CO ₂ targeted measures when combined with decarbonization can provide net cooling by 2030 and reduce the rate of warming from 2030 to 2050 by about 50%, roughly half of which comes from methane, significantly larger than decarbonization alone over this time frame. Our analysis demonstrates the need for a comprehensive CO ₂ and targeted non-CO ₂ mitigation approach to address both the near-term and long-term impacts of climate disruption.