Uhlíkový rozpočet: Kolik ještě zbývá?

The extent of global warming depends primarily on how much more CO₂ humans add to the atmosphere. Limiting warming to well below 2 °C, in line with the Paris Agreement, is becoming increasingly challenging.

The extent of global warming is dictated by a simple, near-linear rule: for every 1,000 Gt CO₂ added to the atmosphere, global temperatures rise by approximately 0.45 °C.¹ Because CO₂ persists for centuries, its warming effect is cumulative. This allows scientists to calculate a “carbon budget” – the maximum amount of CO₂ we can still emit to limit warming to a specific level.

The graph shows the remaining carbon budgets from the start of 2026 to limit global warming to 1.5 °C, 1.7 °C, and 2 °C.² To stay within these limits, the world must eventually reach Net Zero, the point where we stop adding more CO₂ to the atmosphere than we remove. If global emissions continue at 2025 levels, the remaining budget for 1.5 °C will be exhausted by 2030, and the budget for 2 °C will be spent by 2051.

These budgets offer a 50% likelihood of success. For example, if the world emits approximately 1,055 Gt CO₂ from 2026 onwards, there is an even chance that warming stays below 2 °C. If we require a higher degree of certainty, the “allowable” budget becomes even smaller. While CO₂ is the primary driver, these estimates also account for the cooling effects of aerosols and the warming effects of other gases like methane.

What would it take to stay below 1.5 °C, 1.7 °C, and 2.0 °C?

The Minimum Warming Path (1.5 °C)

The budget for 1.5 °C is now extremely tight: only 170 Gt CO₂. To stay within it, the world would need to cut emissions by about 11% (4.6 Gt) every single year, reaching Net Zero by 2034. As global emissions are not expected to drop substantially by 2030, this path is increasingly viewed as unrealistic. While theoretically possible, such scenarios now rely on temperatures “overshooting” 1.5 °C and being brought back down later through large-scale CO₂ removal.

The Net Zero 2050 Path (1.7 °C)

If global emissions begin to drop in 2026 and reach Net Zero by 2050 – as many countries have pledged – emissions would need to decrease by roughly 4% per year. This rate of decline is comparable to the unprecedented drop seen in 2020 during the COVID-19 pandemic. On this trajectory, the world would release just over 500 Gt CO₂, aligning with the 1.7 °C budget. This remains an extremely ambitious goal, especially as many major emitters have set Net Zero targets for 2060 or 2070.

The Plateau and Decline Path (2 °C)

Imagine a scenario where emissions plateau at 2025 levels until 2030, then gradually decrease to Net Zero by 2070. This would require an annual reduction of 2.5%. Under this plan, the world would emit roughly 1,050 Gt CO₂ – significantly more than the previous scenarios, but still within the 2 °C budget. While this path is more in line with current national pledges, it is far from guaranteed; most countries are not yet on track to meet their existing promises (See also: Projections of Warming in 2100).

Footnotes

1. See D.1.1 in IPCC’s AR6 WGI Summary for Policymakers: Intergovernmental Panel on Climate Change. (2021). Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to AR6. DOI: 10.1017/9781009157896.001. ↩

2. We use data from the 2025 Global Carbon Budget: Friedlingstein, P. et al. (in review, 2025). Global Carbon Budget 2025. Earth Syst. Sci. Data Discuss. [preprint]. DOI: 10.5194/essd-2025-659. The authors use averages for the updated estimates of the IPCC AR6 WGI report and the updated revision of those estimates by Forster et al. (2025). ↩