Please read & share this important post. Climate science is not at all simple, not at all settled & many parameters are subject to measurement errors that make deducing future from current measurements a nonsense.
A ‘global average temperature’ is just another climate science nonsense.
Key limitations of global average surface temperature (GMST/GST):
•Not a true physical “temperature of the Earth”: Temperature is an intensive thermodynamic property (not additive like mass or energy). Averaging it across vastly different systems (land, ocean, atmosphere, varying heat capacities, non-equilibrium conditions) lacks strict physical meaning. Critics argue it is statistically useful but thermodynamically imprecise or even “meaningless” as a single global value.18
•No single accurate absolute value: Estimates of the global mean absolute temperature (around 14–15°C) have uncertainties of ~±0.5°C or more. Datasets focus on anomalies (changes relative to a baseline) because these are far more reliable (±0.05°C in recent decades) than absolutes. You cannot reliably add anomalies to absolutes for precise yearly figures.20
•Spatially and temporally incomplete sampling: Measurements come from unevenly distributed stations, ships, and buoys. Polar regions, oceans, deserts, and early records (pre-1950) have large gaps. Interpolation and reanalysis fill these but introduce assumptions (e.g., about Arctic amplification). Historical coverage is poor, raising uncertainties.23
•Not simultaneous or uniform timing: Readings occur at different local times and follow varying schedules. Daily means often use max/min or hourly data, but historical time-of-observation biases require adjustments. No instantaneous global snapshot exists.4
•Adjustments and homogenization needed: Data require corrections for station moves, instrument changes (e.g., buckets to engine intakes), urbanization, and other non-climatic factors. While necessary and tested, these introduce “structural uncertainty”—different groups’ methods can differ by >0.1°C on long-term trends.6
•Uncertainty grows backward in time: Recent annual anomaly uncertainty is low (~±0.03–0.05°C), but it rises to ~±0.1–0.15°C or more by the late 19th century due to sparse data and biases. Structural disagreements between datasets persist.2
•Regional and seasonal variations ignored: The global average smooths out stronger warming on land, in the Arctic, or in certain seasons. Many regions already exceed 1.5°C locally even if the global figure has not.
•Practical vs. philosophical utility: It serves as a robust index for tracking long-term trends and comparing to climate models, with independent datasets agreeing on warming direction and rough magnitude. However, it is a constructed statistical composite, not a direct physical measurement, and debates continue over its precision for policy thresholds (e.g., 1.5°C).
Overall, GMST is a practical tool for detecting multi-decadal change despite these limitations, but it should not be treated as a highly precise, literal “Earth temperature” reading. Uncertainties are openly quantified in scientific products.