Atmospheric co2 forecasts 2026

The 2025 annual mean atmospheric CO₂ concentration at Mauna Loa was 427.35 ppm Verified Answer #1. To reach a threshold of 429.50 ppm in 2026, the annual mean must increase by at least 2.15 ppm over the 2025 level Verified Answer #1.

Historical Trends

Over the decade spanning 2016 to 2025, the average annual increase in the Mauna Loa CO₂ mean was 2.63 ppm per year Verified Answer #1. The annual increase met or exceeded the 2.15 ppm threshold in eight of those ten years Verified Answer #1. The only years during this period that did not meet this rate of increase were 2018 and 2022 Verified Answer #1.

2026 Projections

In February 2026, the UK Met Office projected that the annual CO₂ increase at Mauna Loa would be 2.37 ± 0.55 ppm Verified Answer #1. This projection suggests a point estimate of 429.72 ppm for the 2026 annual mean Verified Answer #1.

Influencing Factors

Several climate factors are expected to influence the rate of CO₂ accumulation throughout 2026 Verified Answer #1.

• Preliminary data from early 2026 showed year-over-year growth of approximately 1.48 to 1.54 ppm Verified Answer #1.
• This lower growth rate was attributed to a moderate La Niña in late 2025 and early 2026, which temporarily enhanced terrestrial carbon sinks Verified Answer #1.
• April 2026 multi-model forecasts project the onset of a strong El Niño for the winter of 2026-2027 Verified Answer #1.
• El Niño events typically accelerate atmospheric CO₂ accumulation by causing tropical droughts that weaken terrestrial carbon sinks Verified Answer #1.
• The second half of 2026 will be compared against a lower baseline from the La Niña-depressed period of late 2025 Verified Answer #1.