The story
From carbon + budget; widely used in climate science (e.g., IPCC) for the cumulative amount of CO₂ compatible with a given warming limit.
Etymology from Wiktionary, CC BY-SA 4.0.
carbon budget
Today it means: The maximum cumulative amount of anthropogenic carbon dioxide emissions compatible with a given global-warming target (e.g., 1.5 °C), for a stated probability and from a stated baseline date. Full definition →