September third-hottest globally on record: climate monitor

Dataset

The Copernicus ERA5 dataset, managed by the European Centre for Medium-Range Weather Forecasts (ECMWF), provides hourly climate data since 1940, with a focus on atmospheric, land-surface, and sea-state parameters, as cited in Hersbach et al. (2023).

The 10-year centred average temperature anomaly has risen from -0.7°C to +0.43°C since 1940, reflecting a steady increase driven by human-induced greenhouse gas emissions, as noted in the IPCC's 2023 Synthesis Report.

Reference

The 1991-2020 period serves as the standard reference for calculating anomalies, chosen for its alignment with recent climate norms, per the Copernicus Climate Change Service methodology.

Global surface temperatures reached 1.1°C above pre-industrial levels (1850-1900) by 2011-2020, with 2024 being the warmest year on record at 1.35°C above that baseline, according to NOAA Climate.gov (2025).

Recent wildfires in California, intensified by record heat in September 2025, highlight the real-world impact of these temperature anomalies, as AP reported on October 7, 2025.

Climate impacts

Advances in Climate Change Research, published by Elsevier, emphasises the socioeconomic implications of rising temperatures, urging policy responses to mitigate climate impacts.

The ERA5T initial release data, available within three months of real-time, ensures timely updates (like the September 2025 figures), enhancing climate monitoring capabilities, per ECMWF documentation.