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Atmospheric CO2 at Mauna Loa, annual mean

Observed

Annual mean CO2 mole fraction measured at Mauna Loa Observatory, Hawaii, the longest continuous record (from 1959).

Ingestedfrom NOAAfreshJSON export
Current value, United States
427.35ppm
period 2025
Geography
United States (USA)
Observation date
2025
Unit
ppm
Frequency
annual
Ingested
2026-09-07 20:00 UTC
1-year change+2.74worsening+0.65%2024 to 2025from 424.61 to 427.35 ppm
10-year trend+0.64% per yearworsening+6.57%2015 to 2025compound annual growth rate; total +26.34 ppm, from 401.01 to 427.35 ppm
Historical series

Atmospheric CO2 at Mauna Loa, annual mean, United States

Observed
300325350375400425450195919601970198019902000201020202025PPM427.35
67 observations, 1959 to 2025latest point emphasised
Data table (67 rows)
Atmospheric CO2 at Mauna Loa, annual mean, United States: 67 observations from 1959 to 2025, values from 315.98 to 427.35 ppm. Latest 427.35 ppm in 2025. Full data table below.
PeriodValue (ppm)Source revisionIngested at
2025427.352026-08-052026-09-07 20:00 UTC
2024424.612026-08-052026-09-07 20:00 UTC
2023421.082026-08-052026-09-07 20:00 UTC
2022418.532026-08-052026-09-07 20:00 UTC
2021416.412026-08-052026-09-07 20:00 UTC
2020414.212026-08-052026-09-07 20:00 UTC
2019411.652026-08-052026-09-07 20:00 UTC
2018408.722026-08-052026-09-07 20:00 UTC
2017406.762026-08-052026-09-07 20:00 UTC
2016404.412026-08-052026-09-07 20:00 UTC
2015401.012026-08-052026-09-07 20:00 UTC
2014398.812026-08-052026-09-07 20:00 UTC
2013396.742026-08-052026-09-07 20:00 UTC
2012394.062026-08-052026-09-07 20:00 UTC
2011391.852026-08-052026-09-07 20:00 UTC
2010390.12026-08-052026-09-07 20:00 UTC
2009387.642026-08-052026-09-07 20:00 UTC
2008385.832026-08-052026-09-07 20:00 UTC
2007384.022026-08-052026-09-07 20:00 UTC
2006382.092026-08-052026-09-07 20:00 UTC
2005379.982026-08-052026-09-07 20:00 UTC
2004377.72026-08-052026-09-07 20:00 UTC
2003375.982026-08-052026-09-07 20:00 UTC
2002373.452026-08-052026-09-07 20:00 UTC
2001371.322026-08-052026-09-07 20:00 UTC
2000369.712026-08-052026-09-07 20:00 UTC
1999368.542026-08-052026-09-07 20:00 UTC
1998366.842026-08-052026-09-07 20:00 UTC
1997363.882026-08-052026-09-07 20:00 UTC
1996362.742026-08-052026-09-07 20:00 UTC
1995360.972026-08-052026-09-07 20:00 UTC
1994358.962026-08-052026-09-07 20:00 UTC
1993357.212026-08-052026-09-07 20:00 UTC
1992356.542026-08-052026-09-07 20:00 UTC
1991355.72026-08-052026-09-07 20:00 UTC
1990354.452026-08-052026-09-07 20:00 UTC
1989353.22026-08-052026-09-07 20:00 UTC
1988351.692026-08-052026-09-07 20:00 UTC
1987349.312026-08-052026-09-07 20:00 UTC
1986347.612026-08-052026-09-07 20:00 UTC
1985346.352026-08-052026-09-07 20:00 UTC
1984344.872026-08-052026-09-07 20:00 UTC
1983343.152026-08-052026-09-07 20:00 UTC
1982341.482026-08-052026-09-07 20:00 UTC
1981340.122026-08-052026-09-07 20:00 UTC
1980338.762026-08-052026-09-07 20:00 UTC
1979336.842026-08-052026-09-07 20:00 UTC
1978335.412026-08-052026-09-07 20:00 UTC
1977333.842026-08-052026-09-07 20:00 UTC
1976332.032026-08-052026-09-07 20:00 UTC
1975331.132026-08-052026-09-07 20:00 UTC
1974330.192026-08-052026-09-07 20:00 UTC
1973329.682026-08-052026-09-07 20:00 UTC
1972327.462026-08-052026-09-07 20:00 UTC
1971326.322026-08-052026-09-07 20:00 UTC
1970325.682026-08-052026-09-07 20:00 UTC
1969324.622026-08-052026-09-07 20:00 UTC
1968323.052026-08-052026-09-07 20:00 UTC
1967322.182026-08-052026-09-07 20:00 UTC
1966321.372026-08-052026-09-07 20:00 UTC
1965320.042026-08-052026-09-07 20:00 UTC
1964319.622026-08-052026-09-07 20:00 UTC
1963318.992026-08-052026-09-07 20:00 UTC
1962318.452026-08-052026-09-07 20:00 UTC
1961317.642026-08-052026-09-07 20:00 UTC
1960316.912026-08-052026-09-07 20:00 UTC
1959315.982026-08-052026-09-07 20:00 UTC
1 geographies have observations for this metric
NOAA, NOAA NCEI access data service, series gml:co2_annmean_mlo
Definition

What this measures

Annual mean of the monthly mean CO2 mole fraction in dry air (ppm) measured in situ at NOAA's Mauna Loa Observatory on the island of Hawaii, 3,397 m above sea level. Data from March 1958 through April 1974 are Scripps Institution of Oceanography measurements by C. David Keeling; NOAA measurements begin in May 1974. During the Mauna Loa eruption (29 November 2022 to July 2023) measurements were taken at Maunakea Observatories about 21 miles north. This is a single-station record, filed under the United States as the station's country; the global mean is a separate metric.

Direction
lower is better
Geography level
station (United States)
Slug
co2-mauna-loa-annual-mean
Environment & Regeneration

Related metrics

All Environment & Regeneration metrics

Provenance and methodologysource, series, ingestion, revisions
Classification
Observedpublished by the cited source, ingested without transformation
Source organization
NOAA, NOAA NCEI access data service
Series ID
gml:co2_annmean_mlolast fetch: ok
Source links
License and attribution
Approved with attribution
NOAA National Centers for Environmental Information.
Terms of use
Last source update
2026-08-05(source revision label as published by the provider)
Last ingestion
last successful runfresh
Last run
success2026-09-07 20:16 UTC
Parser version
noaa-gml-ncei/1.0.0
Methodology version
1.0
Quality and confidence
Station record, not a national statistic. The most recent year is preliminary pending recalibration of reference gases; NOAA revises it in place and occasionally earlier years. Each revision is stored as a new row labelled with the file creation date. Cite Lan, X., Tans, P. and K.W. Thoning, NOAA Global Monitoring Laboratory (gml.noaa.gov/ccgg/trends/).
Ingestion rejects values outside 250 to 1,000 ppm.
67 periods with values for this geography, 1959 to 2025.
Revisions
Values reported for the latest period (2025) by each source revision ingested. Earlier rows are never deleted; the newest ingested row is shown as current.
Source revisionValue (ppm)Ingested atStatus
2026-08-05427.352026-09-07 20:00 UTCcurrent
No superseded rows for this geography: every period has been ingested once.