Mitigation in the Context of the Paris Agreement

Key characteristics of scenarios in line with limiting warming to below 1.5°C in 2100 with 50% probability have been identified in the post-AR5 literature: (1) no scenarios are available which peak global greenhouse gas emissions later than 2020 and comprehensive emission reductions thus need to occur over the 2015-2025 time period; (2) global net zero CO2 emissions are achieved around mid-century, 10 to 20 years earlier than in scenarios that limit warming to below 2°C with a 66% probability, and CO2 reductions beyond global net zero are achieved afterwards to peak and decline global temperatures. This requires CO2 to be removed actively from the atmosphere; (3) additional emission reductions coming mainly from CO2 compared to 2°C scenarios with 66% probability, while also non-CO2 greenhouse gas need to be reduced but not beyond what is already assumed for 2°C. Furthermore, (4) energy supply is rapidly and profoundly decarbonized over the next two decades, and (5) energy efficiency is key resulting in lower demand in hard-to-decarbonize sectors, like industry, buildings, and transportation.