Global warming is dominated by the near-linear relationship between the global average temperature increase and cumulative CO₂ emissions. This relationship helps define a ‘carbon budget’, with uncertainties relating to the climate system and society through non-CO₂ emission pathways.
The carbon budget has been an extremely powerful concept to quickly and succinctly explain the climate challenge, such as making comparisons with our current emissions to illustrate the urgency of short-term mitigation. Whilst seemingly simple, the concept also has
many layers of complexity, such as the incorporation of uncertainty, the role of non-CO₂emissions, and continual updates due to scientific
improvements and our continued emissions.
The carbon budget concept will remain a useful communication tool, but some of its shortcomings may be exposed as the remaining carbon budget for 1.5°C will soon be exhausted.