A year can be cooler than its predecessor and still rank among the hottest ever measured. In its January 14, 2026 analysis, NASA reported that global surface temperature in 2025 was 1.19 degrees Celsius above its 1951–1980 reference average. The year was cooler than 2024, the record holder, but remained close to 2023.
NASA described 2023 and 2025 as effectively tied within the study's uncertainty. The agency identifies 2024 as the hottest year in its temperature record, which begins in 1880. That result is easy to misunderstand if an annual decline is interpreted as evidence that the longer warming trend has ended.
The reported number is a temperature anomaly: a difference from an explicitly chosen reference average. NASA uses 1951–1980 as its baseline. A 1.19-degree anomaly does not describe Earth's absolute average temperature, nor is it necessarily interchangeable with a figure measured from a different historical reference period.
The analysis draws on measurements from more than 25,000 land weather stations, ships and ocean buoys, and Antarctic research stations. Scientists account for uneven station coverage and other factors that can bias a simple comparison, including local urban heat effects.
Independent groups can rank close years slightly differently because they process observations and missing coverage differently. NASA noted that NOAA, Berkeley Earth, the Hadley Centre and Europe's Copernicus service also placed 2025 as the third warmest year in their analyses. Their methods differ, but all show the broader warming pattern.
Short-term variations can arise from ocean conditions and natural climate variability. A record-setting year does not require the next year to be even hotter. To understand the long-term signal, researchers examine multiple years and decades instead of selecting one change between neighboring dates.
Three questions strengthen a climate headline: Which dataset is being used? What baseline defines the anomaly? And does the claim describe one year or a sustained trend? Those distinctions can prevent technically correct numbers from becoming misleading arguments.
Reporting note: This is an original Civora explanation of NASA's publicly released analysis, not a new climate measurement.
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