Carbon Budget Calculator

A carbon budget is the total amount of CO₂ that can be emitted globally while still keeping warming below a target level (e.g., 1.5°C or 2°C above pre-industrial levels). The IPCC estimates that to have a 66% chance of limiting warming to 1.5°C, the global budget from 2020 onward is approximately 400 billion tonnes of CO₂. Once this budget is exhausted, warming will exceed that threshold.

A carbon footprint is the total amount of greenhouse gases — primarily CO₂ and methane — generated by your actions over a year. This includes energy use at home, transportation, diet, shopping, and more. The average carbon footprint for a person in the United States is about 16 tonnes per year, while the global average is around 4 tonnes per year.

To limit warming to 1.5°C with a 66% probability, global per-person emissions need to fall from today's average (~4 tonnes/year) to near zero by around 2050. For the US average (16 tonnes/year), this requires cutting emissions by roughly 45% by 2030 and reaching net zero before 2050. The exact target depends on your chosen warming limit and probability.

A linear reduction means you cut the same absolute amount of CO₂ each year (e.g., 0.5 tonnes/year). An exponential reduction means you cut the same percentage each year (e.g., 10% of remaining emissions annually). Exponential reductions are often seen as more realistic for economies and businesses, while linear plans are simpler to track personally.

Because climate models have uncertainty ranges, carbon budgets are expressed with a probability of success. A 66% probability means that if global emissions stay within the budget, there is a two-in-three chance that warming will not exceed the target. A higher probability (e.g., 83%) requires a smaller budget — less CO₂ can be emitted — giving more confidence in the outcome.

This calculator divides the global remaining budget equally per person, based on today's world population of approximately 8 billion people. This equal per-capita approach is one of several methods used by researchers; other approaches weight by historical emissions or current GDP. Equal sharing reflects a principle of climate justice — every person has the same right to a stable climate.

Net zero means balancing the amount of greenhouse gases emitted with the amount removed from the atmosphere, so the net addition to the atmosphere is zero. Reaching net zero globally is essential to stop cumulative warming from increasing. The Paris Agreement aims for net zero CO₂ emissions in the second half of this century, with many countries targeting 2050.

Carbon offsets — such as funding reforestation or renewable energy projects — can help compensate for emissions you cannot yet eliminate. However, most climate scientists agree that offsets should complement, not replace, direct emission reductions. Achieving the Paris goals requires deep cuts in actual emissions alongside any offsetting strategies.