How much carbon can we still emit before hitting critical global warming thresholds?

Nature · Published 3 October 2026 Swipe more like this →

In short: A carbon budget is the finite amount of greenhouse gases humanity can release while keeping global temperature increases within specific limits. By calculating the relationship between emissions and warming, scientists provide a countdown for how much room remains in our atmosphere before we exceed dangerous climate targets.

At its core, a carbon budget translates complex climate science into a tangible limit. Researchers analyze how much warming occurs for every unit of greenhouse gas emitted, allowing them to define the maximum cumulative emissions allowed to stay under a specific temperature goal, such as 1.5°C or 2°C. Because the climate system involves intricate feedbacks—such as how natural carbon sinks react to higher temperatures—these budgets are never absolute. Instead, they are typically presented as probabilities, acknowledging the inherent uncertainty in predicting exactly how the Earth will respond to ongoing atmospheric changes.

The Global Carbon Project assesses this budget annually, synthesizing data on historical emissions with climate modeling to determine the remaining allowance. As of 2025, the analysis indicates that to maintain a 50% chance of limiting warming to 1.5°C, the world has approximately 235 Gigatonnes of CO2 left to emit. At current 2024 emission rates, this budget would be exhausted in just six years. For a less stringent target of 2°C, the remaining allowance is significantly larger, estimated at 1,110 GtCO2, which provides about 27 years of current-level emissions.

Beyond global totals, these concepts are adapted for national policy. In the UK, the Climate Change Committee serves as an independent advisor, crafting pathways toward a Net Zero future by 2050. Their Seventh Carbon Budget, released in February 2025, outlines the necessary trajectory for the UK, including a mandate to reduce emissions by 87% by 2040 relative to 1990 levels. These national frameworks transform abstract global limits into legally binding domestic targets, forcing a structured approach to decarbonization that accounts for industrial capacity and historical responsibility.

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