Introduction

The report evaluates progress towards the Paris Agreement’s goals using a Bayesian probabilistic modelling approach to project future carbon dioxide (CO₂) emissions and global temperature rise. It integrates post-2015 data through to 2024, providing an updated view of how economic and policy developments have influenced climate change trajectories since the agreement’s adoption.

Carbon Emissions, NDCs, And Probabilistic Forecasts Since 2015

Between 2015 and 2024, global carbon intensity decreased by 25%—an annual rate of 3.1%—outperforming projections but still below the 31% target of the initial nationally determined contributions (NDC-1s). Total CO₂ emissions, however, rose by 5.6% as global GDP expanded by 41%, offsetting gains in efficiency.

China achieved a 37% fall in carbon intensity, meeting its target, but emissions grew 18% due to rapid growth. The United States cut emissions by 10% against a 15% goal, while Germany surpassed expectations with a 28% reduction against a 9% target. Germany’s 2024 carbon intensity was the lowest among major economies, with China’s three times higher and the US 50% higher. This demonstrates scope for large emitters to reduce intensity through policies adopted in lower-emission countries.

Implications For Projections Of Future Carbon Emissions

Updated projections indicate annual CO₂ emissions will fall by 64% by 2100, compared with only a 10% reduction projected in 2015. Uncertainty has narrowed by 75%, with the 2100 range now 7–25 Gt CO₂. Global net zero emissions remain unlikely this century under current trends. The most probable peak year for emissions is 2024, though they could continue rising until 2045.

Implications For Climate ChangeDespite notable progress in carbon intensity, the expected rise in average global temperature by 2100 decreased only marginally—from 2.6 °C (2015 data) to 2.4 °C (2024 data)—reflecting that much future warming is already committed. The probability of staying below 2 °C remains at 17%. The likelihood of catastrophic warming over 3 °C has dropped substantially from 26% to 9%, with overall uncertainty reduced by 36%.

Probability Of Countries Meeting Their NDCs

The likelihood of meeting NDC-1 targets has improved modestly. Germany (97%), Japan (50%), and France (36%) are likely to meet their goals, while China’s probability has increased to 26%. The United States remains low at 1%. Under more ambitious second-round NDC-2 targets, probabilities drop: China (8%), USA (0%), Germany (22%), India (0%), Japan (0%), Russia (61%), and the UK (21%).

If all nations meet their NDC-1s and sustain reductions beyond 2030 (“Continued” scenario), the projected rise is 2.1 °C, with a 34% chance of staying below 2 °C. Under NDC-2s, if countries continue cutting emissions post-2030, warming could fall to 2.0 °C, with a 53% probability of remaining under 2 °C.

Additional Efforts Needed To Stay Under 2 °C

To achieve an 80% likelihood of limiting warming below 2 °C, global cumulative emissions must be capped at 845 Gt CO₂ by 2100, requiring a 4.2% annual decline—nearly double the current rate. To meet a 66% probability target, a 2.2% annual decline is needed. Additional reductions over NDC-1 levels must increase by 13% for China, 14% for the USA, 36% for Germany, 19% for India, and 6% for Japan.

Discussion

The nine years following the Paris Agreement show faster improvements in carbon intensity than in the preceding decades, but economic growth has outweighed these gains. Although the chance of extreme warming has declined, meeting global temperature goals requires accelerated emissions cuts, particularly in high-intensity economies. Stronger, sustained global cooperation is necessary to achieve meaningful decarbonisation and climate stabilisation.

Methods

The analysis uses annual data from 1960–2024 for 157 countries covering over 99% of the global population. It applies Bayesian hierarchical models to project population, GDP per capita, and carbon intensity, combined to estimate CO₂ emissions. The Transient Climate Response to Cumulative CO₂ Emissions (TCRE) from the IPCC Sixth Assessment Report quantifies the relationship between cumulative emissions and temperature change. Markov Chain Monte Carlo sampling generates probabilistic forecasts for emissions and temperature outcomes. Data sources include the UN World Population Prospects (2024), the Maddison Project and IMF World Economic Outlook (2024) for GDP, and the Global Carbon Budget (2024) for emissions. Temperature data are from the HadCRUT5 dataset.