Time Narrows for Global Carbon Emission Reductions: A Six-Year Window

In an urgent call to action, new research has revealed that the world has a narrow six-year window to achieve net zero carbon emissions to prevent temperatures from rising above 1.5°C. This startling information comes from a recent report, providing a critical update on the global carbon budget.

According to World Economic Forum, the world is currently emitting carbon dioxide at a rate of 40 gigatonnes per year. As of the start of 2023, calculations indicate that to maintain a 50% chance of limiting global warming to 1.5°C, only 250 gigatonnes of CO2 can be emitted. This effectively sets a six-year deadline for reaching net zero emissions, with the possibility of the timeframe being even shorter, potentially closer to five years. This estimate aligns with an assessment from 50 leading climate scientists published in June and updates key figures previously reported by the Intergovernmental Panel on Climate Change (IPCC) in August 2021.

The concept of a “carbon budget” refers to the amount of CO2 that can still be emitted while keeping global warming under a specified limit. Since the industrial revolution, there has been a linear relationship between the increase in global mean surface temperature and total CO2 emissions. It is noted that warming will cease when net zero CO2 emissions are achieved, highlighting the critical nature of net zero targets adopted by numerous countries, cities, and companies.

This report revises the remaining carbon budget down from the IPCC’s reported 500 gigatonnes from the start of 2020. This revision accounts for 120 gigatonnes of CO2 emissions over the past three years and methodological improvements in budget adjustments. The research also accounts for non-CO2 pollutants and greenhouse gases contributing to climate change, with adjustments made for projected warming from these sources. Despite aerosols like sulphates providing a cooling effect, future reductions in aerosol emissions are anticipated, regardless of fossil fuel usage, due to stricter air quality legislation and cleaner combustion methods. This expected decrease in air pollution is projected to contribute more to warming than previously assessed, reducing the 1.5°C budget by an additional 110 gigatonnes.

The methodology updates also include considerations for thawing permafrost, which was not included in earlier estimates. While there are uncertainties in various aspects of the carbon budget estimate, the 50/50 likelihood of limiting warming to 1.5°C with a remaining budget of 250 gigatonnes of CO2 remains a sobering statistic. A more cautious estimate provides a two-in-three chance of staying under 1.5°C with just 60 gigatonnes remaining, equating to one-and-a-half years of current emissions.

Despite the daunting outlook, the report emphasizes the continued necessity of dramatic greenhouse gas emission reductions. While limiting warming to 1.5°C appears less likely, the report provides a revised budget for a 2°C limit, reducing it from the IPCC’s 2021 estimate of 1,350 gigatonnes to 1,220 gigatonnes, or 30 years of current emissions. If existing national climate policies are fully implemented, it may still be possible to keep warming below 2°C.

Emphasizing the importance of continued efforts, the report concludes that effective action on emissions can limit peak warming to 1.6°C or 1.7°C, with the possibility of reducing temperatures back below 1.5°C over the long term.