The carbon budget refers to the total amount of greenhouse gases that can be emitted into the atmosphere by the end of this century while maintaining global temperature increases below pre-industrial levels. As per the IPCC, the maximum amount of CO₂ that can be absorbed by the atmosphere, calculated from the beginning of 2020, is 400 gigatonnes (Gt) to stay below the 1.5°C threshold. Current annual CO₂ emissions from various sources like fossil fuel burning, industrial processes, and land-use change are estimated to be 42.2 Gt annually. If emissions continue at the current rate, the carbon budget for staying below the 2°C threshold would be used up in approximately 25 years. It’s important to note that the concept of the carbon budget is based on a nearly linear relationship between cumulative emissions and temperature rise, but this doesn’t necessarily mean that the Earth will warm by exactly 1.5°C when the remaining carbon budget for staying below the 1.5°C threshold is exhausted.