A group of atmospheric scientists from three research institutions in the United States and Europe formally filed a request for reanalysis of this year's global temperature data on Monday, contending that a divergence between satellite measurements and surface station records makes the current record claim statistically uncertain and that the contribution of this year's El Niño event to the anomaly may have been underestimated.
The researchers' central argument concerns a dataset disagreement. The University of Alabama at Huntsville's lower-troposphere satellite dataset shows a temperature anomaly approximately 0.18 degrees Celsius smaller than the surface station records being used by NASA, NOAA, and the UK Met Office to support the record claim. At that margin, the scientists argued, the year would remain unusually warm but would not constitute a new record by a statistically unambiguous margin.
The group has also submitted formal requests to NOAA and the Met Office for a detailed breakdown of how the El Niño contribution to this year's temperature anomaly has been quantified and attributed. "Our concern is that if El Niño accounts for a larger share of the anomaly than is currently being attributed to it, the characterisation of this year's warming needs to change," said one of the researchers involved in the request. "We are not disputing long-term warming. We are asking for precision about individual years."
NOAA and the Met Office pushed back on the satellite comparison in responses issued before the formal request was filed. Both agencies noted that the University of Alabama dataset measures the lower troposphere rather than the Earth's surface, and that satellite instruments carry calibration uncertainties stemming from orbital drift and sensor degradation over time. A NOAA spokesperson described the agency's surface station methodology as "the internationally agreed standard for surface temperature assessment" but did not directly address the 0.18-degree divergence.
Two of the scientists involved in the reanalysis request had published a similar challenge to the 2023 temperature record on comparable methodological grounds. That analysis was contested by several climate research institutions but was not formally refuted in peer review.
The reanalysis request was filed four days before the opening of an international climate summit at which the temperature record was expected to feature prominently in discussions. The researchers filing the request noted the timing explicitly, arguing that the credibility of climate science depended on precision in how individual years are characterised, and that contested claims could be exploited by critics of the scientific consensus on long-term warming.
No government or research institution had formally announced plans to conduct a reanalysis by the time of publication.