Projected Global Atmospheric CO2 Levels For 2025 At Mauna Loa Observatory: Between 426 and 427.2 ppm

Following the fastest annual rise in atmospheric carbon dioxide concentration in the Mauna Loa record between 2023 and 2024, the increase between 2024 and 2025 is forecast to remain faster than that required to track IPCC scenarios that limit global warming to 1.5°C. The ongoing CO2 rise is driven by fossil fuel burning and land use change, but the increase this year will be smaller than last year due to a re-strengthening of natural carbon sinks partly linked to a shift from El Niño to emerging La Niña conditions. Despite this, the annual CO2 rise will be too high to be compatible with the IPCC’s 1.5°C scenarios.

We forecast the annual average CO2 concentration at Mauna Loa, Hawaii to be 2.26 ± 0.56 parts per million (ppm) higher in 2025 than in 2024. As a result, we forecast the 2025 annual average CO2 concentration at Mauna Loa to be 426.6 ± 0.6 ppm (Figure 1). This will continue the ongoing rising trend in CO2 seen in the long-term record of measurements from the Mauna Loa observatory in Hawaii that date back to 1958 (also known as the Keeling Curve). The Mauna Loa record is usually a good guide to rise in global average CO2 concentration, which we therefore expect to increase by a similar amount.

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Figure 1. Forecast CO2 concentrations at the Mauna Loa observatory, showing monthly (red curve) and annual (red star) values. The orange band and vertical red line shows the forecast uncertainty ranges. The thin and thick black curves show the observed monthly and annual average concentrations respectively. Blue stars and blue lines show previous forecast annual averages and their uncertainties, with the 2020 value being the updated 2020 forecast issued followed the reduction in global CO2 emissions due to the Covid-19 pandemic. Observed data is from the Scripps Institution of Oceanography, UC San Diego.

The size of the annual CO2 rise has generally been increasing but with substantial variation from year-to-year (Figure 2), with the increase from 2023 to 2024 being the largest on record.

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Figure 2. Annual increments in CO2 concentration at the Mauna Loa observatory from observations (black) and the 2025 forecast (red star). The forecast uncertainty range (red line) is ± 2 standard deviations. The blue line shows statistical reconstructions of past annual CO2 increments using the same method as used in the forecast. Observations are from the Scripps Institution of Oceanography, UC San Diego.

EDIT

https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/long-range/forecasts/co2-forecast