Carbon budget (emissions planning)

Because greenhouse gases remain in the atmosphere for a very long time (several hundred years in the case of CO2, for example), the key indicator is the cumulative build-up of carbon emissions in the atmosphere over time. This is illustrated by the concept of the carbon budget (also known as the CO2 budget or emissions budget). The carbon budget is the amount of CO2 emissions that human activities have emitted into the atmosphere since the start of the Industrial Revolution, or conversely, the amount that humans can still emit while still having a likelihood of keeping global warming below 2°C; or preferably even below 1.5°C by the Paris Agreement on Climate Action.