The Sound of Climate
Sixty-seven years of Mauna Loa CO₂ measurements turned into one continuous sound. As the curve climbs, the pitch climbs with it — a perfect fifth from the start to today. Press play, then close your eyes.
Four moments on the way up.
- 1958
Keeling starts measuring.
March 1958. Charles David Keeling installs an infrared CO₂ analyser at Mauna Loa Observatory, 3,400 m above sea level. First reading: 313 ppm. Nobody yet sees what is coming.
- 1988
350 ppm crossed.
By 1988 the atmosphere passes 350 ppm — the threshold later named by climate scientist James Hansen as the upper safe limit. The same year, Hansen testifies before the U.S. Congress on global warming.
- 2013
400 ppm reached.
May 2013. For the first time in human history — and likely in three million years — Mauna Loa records a daily mean above 400 ppm. The annual mean follows shortly after.
- 2025
Today.
The 2025 annual mean sits near 427 ppm and is still climbing by about 2.5 ppm per year. That acceleration is what the drone in the soundtrack carries — getting heavier as we approach now.