Carbon Budget

The term has two common meanings. Globally, it is the cumulative amount of carbon dioxide that can still be emitted while keeping warming below a given level with a stated probability, as assessed by the IPCC and updated by research such as the Global Carbon Budget. Nationally, it can be a legal limit on total emissions over a multi-year period, as in framework laws that set successive five-year budgets.

Why it matters in the room

The global budget explains why the timing of cuts matters as much as end dates. National budgets turn a long-term target into checkable steps, and are one of the clearest signs that a target has been given legal force.