Albedo Weekly

Climate indicators · NOAA Global Monitoring Laboratory

Carbon dioxide (CO₂)

426.1 ppm

September 2026, monthly mean at Mauna Loa. Annual mean 1959: 316.0 ppm. 2025: 427.3 ppm. Rise over the last ten years: 26.3 ppm.

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Monthly mean CO₂ at Mauna Loa Observatory, Hawaii, in parts per million (ppm).

What it measures

The share of carbon dioxide in the air, in molecules per million molecules of dry air, measured continuously on a Hawaiian volcano far from local sources.

Why it matters

CO₂ from burning coal, oil and gas is the main driver of warming. It stays in the atmosphere for centuries, so the curve only bends when emissions fall.

Source and method

NOAA Global Monitoring Laboratory. Monthly means as published. The curve rises and falls each year with plant growth in the northern hemisphere; the annual means remove that cycle.