What has actually changed?
Three published records show two different quantities: temperature is a response of the climate system, while CO₂ is one of its most important drivers. Different reference periods are clearly identified.
Annual temperature anomaly
An anomaly shows the difference from a defined reference period. It is not an absolute temperature.
Temperatures from weather stations and sea-surface measurements are combined spatially. Copernicus ERA5 also combines observations with a consistent weather model.
Weather, ocean cycles, volcanoes and other short-term influences affect individual years. The development over decades is what matters for the climate trend.
Show measurements and method
The global HadCRUT5 series was rebased from its published 1961–1990 reference to the 1850–1900 mean. The published 95% uncertainty interval is shifted by the same amount.
| Year | Score | Uncertainty |
|---|
CO₂ in the atmosphere
Concentration is expressed as a fraction of dry air in parts per million: 400 ppm equals 0.04 percent.
NOAA calculates the global annual mean from its cooperative network of atmospheric monitoring stations. The latest value may be revised slightly during quality control.
The fact that temperature and CO₂ rise together is not by itself a complete demonstration of causation. Physical effects, carbon sources and attribution studies follow in the next steps.
Show CO₂ measurements
| Year | CO₂ | Uncertainty |
|---|
Warming is visible in several independent datasets
The measurements initially answer only whether temperature and greenhouse gas concentration have changed. The next section tests why Earth is warming by examining natural and human influences.
Data and responsible institutions
Global temperature · 1850–2025 · annual anomaly and 95% interval
European land temperature · 1950–2025 · 1991–2020 reference
Atmospheric CO₂ · 1979–2025 · ppm and uncertainty
Context for multiple datasets, reference periods and methods