Global temperature departures

Absolute temperature is not comparable across the globe. A departure is this month minus the long-term average for that place and calendar month, so +2°C over Siberia and +2°C over the tropical Pacific both mean unusually warm for that location.

GISTEMP blends GHCN-M land air temperature with ERSST sea-surface temperature (same family of inputs as NOAA Climate at a Glance). Native anomalies are vs 1951–1980; this map subtracts each cell’s 1901–2000 monthly mean so the zero is the 20th-century average. The global number is an area-weighted mean (cos(latitude)), because 2° boxes shrink toward the poles.

This is not NOAAGlobalTemp’s 5°×5° product. The field is interpolated from 2° cell centers so it is continuous rather than blocky.