---
id: data-sources/noaa-gml-co2-trends
about:
  label: NOAA GML Trends in CO2
  description: >-
    NOAA Global Monitoring Laboratory's record of atmospheric carbon dioxide at
    Mauna Loa Observatory since 1974, as daily, weekly, monthly and annual
    means, with a global mean series.
  tags:
    - carbon dioxide
    - greenhouse gases
    - Mauna Loa
    - time series
datasource:
  coverage: 'Mauna Loa Observatory, Hawaii; also globally averaged marine surface series'
  cadence: weekly means from May 1974; the last several months are preliminary
  access: 'open download, no key'
  format: 'CSV, text, JSON'
  homepage: 'https://gml.noaa.gov/ccgg/trends/'
  cost: 'free, US public domain; NOAA asks for a citation'
open:
  source: unknown
  data: open
  api: unknown
  participation: unknown
  licence: US public domain
domains:
  - climate
provenance:
  origin: agent
  sources:
    - title: 'NOAA GML, Trends in CO2'
      url: 'https://gml.noaa.gov/ccgg/trends/'
    - title: Mauna Loa weekly mean CO2 (co2_weekly_mlo.csv)
      url: 'https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_weekly_mlo.csv'
  created: '2026-10-17'
  reviewed: '2026-10-17'
  reviewed_by: 'Claude, from the sources listed'
  status: draft
---
The Global Monitoring Laboratory of the US National Oceanic and Atmospheric Administration publishes the carbon dioxide record from its Mauna Loa Observatory as flat files: weekly means from May 1974, with monthly and annual means, daily values and a globally averaged series beside them. Each file carries its own header on use and contact. The data are freely available; NOAA asks that publications cite the data providers, and the trends page gives the citation form.

The weekly file notes two things a model should know. Values for the last several months are preliminary and still under quality control. And measurements at Mauna Loa were suspended from 29 November 2022, after the volcano erupted, until July 2023; observations from December 2022 to 4 July 2023 come from a site at the Maunakea Observatories about 21 miles north.

The [Vitals](/vitals/) page here reads the weekly file.