An observer of Keeling Curve data queried last week why there’s such a spread in atmospheric CO2 measurements this year. In response, Scripps CO2 Program Director Ralph Keeling offered the following:

“It’s true the Mauna Loa Observatory (MLO) record typically has considerable day-to-day variability in the first half of the calendar year.  It’s also true that this type of variability (or ‘spread’) was a lot more pronounced in 2024 than 2023.

While we have not studied this issue in detail, a few points can be made.

Since late 2022, we have had the benefit of a second record from Maunakea and the comparison shows the two records have almost the exact same variability day to day.  This makes it clear that the variability is almost entirely connected with large-scale weather patterns.

On some days, the air is more from the west.  On other days it is more from the east.  The air from the west may contain excess CO2 due to fossil-fuel emission in Eurasia, for example.  These large-scale weather changes are impacting the air at both MLO and Maunakea almost identically.

The amount of spread varies quite a bit from year to year. These changes are probably mostly caused by differences in the weather patterns from year to year.

While 2024 was a lot more variable than 2023, it wasn’t so remarkably different from 2021 and 2022. The increase in variability from 2023 to 2024 was as much caused by low variability in 2023 as by high variability in 2024.”

Photo: Erik Jepsen/UC San Diego