Indicators of Global Climate Change 2024: annual update of key indicators of the state of the climate system and human influence

The IPCC Sixth Assessment Report (AR6) provided a comprehensive assessment of human influence on key climate indicators based on data available at the time of publication. As preparations for the Seventh Assessment Report (AR7) begin—expected in approximately five years—the rapid pace of climate change underscores the need for timely, evidence-based updates to inform policymaking. To address this gap, the Indicators of Global Climate Change (IGCC) initiative was launched, delivering annual updates on critical climate system indicators and, where possible, quantifying human influence on these changes.

Complementing Existing Climate Assessments

IGCC supplements other annual climate reports, including:

• The BAMS State of the Climate Report (Dunn et al., 2024)
• The WMO State of the Global Climate (WMO, 2025)

A key distinction of IGCC is its focus on process-level estimates of effective radiative forcing and human-attributed climate responses, employing methodologies rigorously assessed in AR6.

Scope and Structure of the Third Annual Update

This update follows the format established in Forster et al. (2024), extending indicators through 2023. It emphasizes metrics related to climate system heating, tracing the pathway from greenhouse gas (GHG) emissions to human-induced warming and the remaining carbon budget for 1.5°C and other policy-relevant thresholds.

Figure 1 provides an overview of the assessed components and their interlinkages, illustrating the causal chain from emissions to physical climate changes and climatic impact drivers. This also serves as a roadmap for the paper’s structure.

Methodological Foundation

The update adheres to methods assessed in:

• IPCC AR6 Working Group I (WGI) (Physical Science Basis; IPCC, 2021a)
• Chapter 2 of WGIII (Dhakal et al., 2022)

It aligns with AR6’s FAIR principles (Findable, Accessible, Interoperable, Reusable) for reproducibility (Pirani et al., 2022; Iturbide et al., 2022). While IPCC reports offer broader scientific assessments, IGCC does not replicate their scope. Instead, it tracks incremental climate system changes and methodological refinements between IPCC cycles, enhancing transparency and consistency.

Report Outline

1. GHG Emissions (Section 2)
2. GHG Concentrations (Section 3)
3. Short-Lived Climate Forcers (SLCFs) (Section 4)
4. Effective Radiative Forcing (Section 5)
5. Earth Energy Imbalance (Section 6)
6. Global Surface Temperature Change (Section 7)
7. Attribution of Temperature Changes (Human vs. Natural Influences; Section 8)
8. Remaining Carbon Budget (Section 9)
9. Climate Extremes (Max Land Surface Temperatures; Section 10)
10. Land Precipitation Trends (New for 2024; Section 11)
11. Global Mean Sea-Level Rise (New for 2024; Section 12)
12. Code & Data Availability (Section 13)
13. Conclusions (Section 14)

Data Accessibility: https://doi.org/10.5281/zenodo.15639576 (Smith et al., 2025a).

Source:

https://essd.copernicus.org/articles/17/2641/2025/essd-17-2641-2025.pdf