One graph
Carbon dioxide in the air over Mauna Loa, 2005–2025
Notice: The line goes up, up, up. Each dot is one year.
Wonder: What do you wonder? Why might it keep going up? What is in the air we breathe?
Headline: In 2025 the air over Mauna Loa held about 427 parts per million of carbon dioxide — about 47 more than in 2005.
Check it: Did it climb by the same amount every year? Compare 2005→2010 with 2020→2025 using the dots.
Source: NOAA's Global Monitoring Laboratory, annual average CO₂ measured at Mauna Loa Observatory, Hawaii (a record kept since 1958). Freely published data. NOAA Global Monitoring Laboratory — Mauna Loa annual mean CO₂ (retrieved 2026-10-03).
Limits:
- One station on one mountain: a long, careful record, but not a world average (NOAA publishes a global series too).
- Yearly averages hide the seasonal rise and fall within each year.
- NOAA notes the latest year can still change a little after recalibration.
- The 2022 Mauna Loa eruption paused the station; from December 2022 to July 2023 readings came from Maunakea, about 21 miles away.
Start the talk: Ask what they notice before you say anything. Then ask: what would we need to know to say why it rises?