Game

The Data Explorer

Read the real numbers, year by year, then test your eye for the trend.

Play

Read the record

Slide through the years from 1880 to 2025 and read the real numbers: carbon dioxide measured at Mauna Loa in Hawaii, and the world’s average temperature. Then switch to Higher or Lower and test your eye for the trend.

The Explorer is our own code. It plots NOAA’s yearly Mauna Loa averages and NASA’s yearly GISTEMP figures exactly as published: NOAA Global Monitoring Laboratory: Mauna Loa CO2 annual mean data (text file) NASA GISS: GISTEMP v4 global annual mean data (CSV file)

What the lines show

The Keeling Curve, devised by Charles David Keeling of the Scripps Institution of Oceanography, charts carbon dioxide at Mauna Loa since 1958. Encyclopaedia Britannica: Keeling Curve
“Parts per million” means the number of carbon dioxide molecules in every million molecules of dry air. NASA: Carbon dioxide (vital sign)
NOAA’s yearly averages for Mauna Loa run from 315.98 ppm in 1959 to 427.35 ppm in 2025. NOAA Global Monitoring Laboratory: Mauna Loa CO2 annual mean data (text file)
NASA’s analysis uses more than 25,000 weather stations, plus ship and buoy readings of sea temperature and Antarctic research stations. NASA: Global temperature (vital sign)
In NASA’s GISTEMP data, 2024 stands 1.28 °C above the 1951–1980 average, the highest yearly value since 1880. NASA GISS: GISTEMP v4 global annual mean data (CSV file)
In 2025 the global surface temperature was 1.19 °C above the 1951–1980 average, slightly cooler than 2024. NASA: Global temperature (vital sign)