The term “Phase Down” refers to structured reduction in the use of fossil fuels, while “Phase Out” refers to its complete cessation. Fossil energy is produced by burning fossil fuels – primarily coal, oil, and natural gas – which releases greenhouse gases such as CO2. The combustion of fossil fuels has significantly increased in the wake of industrialization since the mid-19th century and is a major driver of global warming.
Negotiations to reduce the extraction, processing, and consumption of fossil fuels therefore play a crucial role in international climate diplomacy. However, in the annual negotiations under the United Nations Framework Convention on Climate Change, the so-called UNFCCC Process, there has thus far been no binding agreement to end the production or consumption of fossil fuels. The issue played a significant role at the 2021 United Nations Climate Change Conference (COP26) in Glasgow. Initially, some countries called for a commitment to a complete phase out of global coal energy production, but due to resistance from major emerging economies, the final Glasgow Climate Pact eventually included a commitment to a phase down of unabated coal power.
Globally, CO2 emissions have risen persistently and have not yet reached their peak (see graph). To limit global warming to 1.5°C by the end of the century in line with the ambition of the Paris Agreement, however, greenhouse gas emissions would need to reach their peak before 2025 and then rapidly decline by mid-century, according to the Intergovernmental Panel on Climate Change (IPCC).