Deep mitigation of CO2 and non-CO2 greenhouse gases toward 1.5 °C and 2 °C futures

Stabilizing climate change well below 2 °C and towards 1.5 °C requires comprehensive mitigation of all greenhouse gases (GHG), including both CO₂ and non-CO₂ GHG emissions. Here we incorporate the latest global non-CO₂ emissions and mitigation data into a state-of-the-art integrated assessment model GCAM and examine 90 mitigation scenarios pairing different levels of CO₂ and non-CO₂ GHG abatement pathways. We estimate that when non-CO₂ mitigation contributions are not fully implemented, the timing of net-zero CO₂ must occur about two decades earlier. Conversely, comprehensive GHG abatement that fully integrates non-CO₂ mitigation measures in addition to a net-zero CO₂ commitment can help achieve 1.5 °C stabilization. While decarbonization-driven fuel switching mainly reduces non-CO₂ emissions from fuel extraction and end use, targeted non-CO₂ mitigation measures can significantly reduce fluorinated gas emissions from industrial processes and cooling sectors. Our integrated modeling provides direct insights in how system-wide all GHG mitigation can affect the timing of net-zero CO₂ for 1.5 °C and 2 °C climate change scenarios.