RESEARCH
Environment: Six agencies confirm 2024 as hottest year on record, but split on whether the 1.5°C Paris threshold was crossed
2024 was unambiguously the warmest year in the global temperature record — confirmed by every major climate monitoring agency. But the specific claim that 2024 was the first calendar year to exceed 1.5°C above the 1850–1900 pre-industrial baseline is not uniformly confirmed. Copernicus, WMO, and Berkeley Earth report anomalies of 1.55–1.62°C and explicitly call it the first year above 1.5°C. NASA GISS and NOAA, using different methodologies, report 1.46–1.47°C — just below the threshold. The Delta Engine returned INDETERMINATE (deltaFinal 0.313), correctly surfacing a real and consequential methodological disagreement between the world's top climate agencies.
Findings
- Copernicus (ERA5 reanalysis) measured 2024 at 1.60°C above pre-industrial; Berkeley Earth at 1.62°C; WMO's consolidated multi-dataset estimate at 1.55°C — all above the 1.5°C Paris threshold. NASA GISS measured 1.47°C and NOAA measured 1.46°C, both just below.
- The Delta Engine measured a prominence spread of 0.313 across six sources: Copernicus (96) and WMO (91) headline the 1.5°C milestone explicitly; NASA (72) and NOAA (70) confirm the warmest year on record but do not assert the threshold was crossed.
- The divergence is methodological, not political. ERA5 reanalysis provides broader spatial coverage of data-sparse polar regions, where warming is fastest. NASA and NOAA rely more heavily on direct station observations, which underrepresent the rapidly warming Arctic — systematically pulling their anomaly estimates lower.
- For climate risk professionals: citing "2024 crossed 1.5°C" in a regulatory filing or risk model requires specifying which agency and methodology. UVRN's INDETERMINATE result is the correct answer — it prevents false precision on a claim that the scientific record itself does not resolve uniformly.
Delta Engine result
↔ Divergence Detected — Δ 0.313 (threshold 0.05)
- Copernicus/ERA5 T5 96
- WMO T5 91
- Carbon Brief T0 88
- Berkeley Earth T4 85
- NASA GISS T5 72
- NOAA T5 70
Evidence quality
avg 81.7 · min 25 · max 95 · spread 70