Carbon Budget Equity

The United States has emitted roughly 400 billion tonnes of CO2 since industrialization. India, with four times the population, has emitted about 50 billion. Both countries sit at the same negotiating table when the world's remaining carbon budget gets divided up.

The carbon budget is a finite, zero-sum quantity: every tonne any country emits reduces what remains for everyone else. This makes budget allocation a distributional question, not just a scientific one. Three competing principles shape climate negotiations. Equal per-capita shares would give every person the same right to emit, favoring populous developing nations. Historical responsibility would subtract past emissions from future allocations, penalizing early industrializers. Ability to pay would allocate cuts based on economic capacity, regardless of historical share.

Frame the arithmetic. The IPCC estimated roughly 500 billion tonnes of remaining CO2 budget from 2020 for a 50% chance of staying below 1.5 degrees C. Current global emissions: about 37 billion tonnes per year. Time remaining at current rates: roughly 13 years.

Apply per-capita logic. Divide 500 billion tonnes by 8 billion people: roughly 62 tonnes per person, lifetime. An average American emits about 14 tonnes per year.

How long would the U.S. per-capita share last at current emission rates?

Expose the tension. At 14 tonnes per year, the per-capita share lasts roughly 4.4 years. For an average Indian (about 2 tonnes per year), it lasts 31 years. Any per-capita framework is mathematically incompatible with current American consumption, which is why the U.S. has historically resisted formula-based allocation.

Most climate agreements use "nationally determined contributions," letting each country set its own target and deferring the distributive conflict.

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