Atmospheric carbon dioxide may set another annual record.
NOAA's monitoring shows 2026 concentrations above the comparable months of 2025.
Bad outcome probability
NOAA's globally averaged marine-surface annual mean CO2 concentration for 2026 will exceed its 2025 annual mean.
Climate records can make the future look inevitable, but each number comes from physical measurements made over decades. The upward trend in atmospheric carbon dioxide is one of the most persistent signals in environmental monitoring.
NOAA's global marine-surface series reports a June 2026 mean of about 427.62 parts per million against 425.90 in June 2025. Year-on-year increases at the same point in the seasonal cycle strongly suggest that the complete annual 2026 global mean will exceed 2025's. Our 99% judgment is an editorial assessment of that prospective annual measure, not a promise about the exact concentration.
An annual average is not a single daily reading, nor does a higher concentration prove every region emitted more carbon this year. CO2 reflects accumulated additions and removals globally. Continued increases nevertheless deepen the long-term climate burden.
What this could mean.
- Why this could be bad
- Higher atmospheric CO2 increases long-lived warming pressure even when annual emissions growth varies.
- Possible repercussions
Future heat and rainfall extremes could become more likely over the long run.
Climate adaptation and emissions reductions may require greater investment.
Ocean uptake and ecosystem responses will remain important scientific uncertainties.
The assessment.
- What we are forecasting
- NOAA's globally averaged marine-surface annual mean CO2 concentration for 2026 will exceed its 2025 annual mean.
- Time horizon
- Calendar 2026, using NOAA's final global annual marine-surface CO2 series.
- Editorial confidence in the evidence: 99%
- NOAA's published June 2026 global mean was 427.62 ppm versus 425.90 ppm in June 2025, consistent with the long-running upward trend.
- What could change the outcome
- Year-end data revision, changes in uptake by ocean and land systems or unusual seasonal anomalies could slightly change reported means.
The evidence.
- Global monthly mean carbon dioxide ↗NOAA Global Monitoring Laboratory · 2026-09
- Global atmospheric CO2 data ↗NOAA Global Monitoring Laboratory · 2026-10