Mauna Loa Observatory (MLO) is an

atmospheric An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere ...

baseline station on

Mauna Loa Mauna Loa (, ; ) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. Mauna Loa is Earth's largest active volcano by both mass and volume. It was historically considered to be the largest ...

on the island of Hawaiʻi, located in the

US state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

Mauna Loa CO2 monthly mean concentration

History

MLO was founded on June 28, 1956, as part of the US Weather Bureau. It was established on the northern flank of Mauna Loa at after 1951–1954 efforts were unable to maintain a summit observatory at . MLO was developed specifically to monitor solar, atmospheric, and meteorological parameters in the free atmosphere. The establishment of a solar constant, routine weather observations, the determination of ozone, and monitoring atmospheric circulation were early priorities. Continuous

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

measurements began in March of 1958 directed by Charles David Keeling from the

Scripps Institute of Oceanography Scripps Institution of Oceanography (SIO) is the center for oceanography and Earth science at the University of California, San Diego. Its main campus is located in La Jolla, California, La Jolla, with additional facilities in Point Loma, San Die ...

. The data set, referred to as the Keeling Curve, is the foundational study in the composition and behavior of greenhouse gases in the atmosphere. Other early research at the observatory included measurements of cosmic radiation, the atmosphere of Mars, atomic fallout, snow crystals, the solar corona, meteors, cosmic rays, and radio transmission. The

International Geophysical Year The International Geophysical Year (IGY; ), also referred to as the third International Polar Year, was an international scientific project that lasted from 1 July 1957 to 31 December 1958. It marked the end of a long period during the Cold War w ...

enabled many of the early projects at the observatory to secure support and funding.

The observatory

MLO has been part of the

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with Weather forecasting, forecasting weather, monitoring oceanic and atmospheric conditions, Hydrography, charting the seas, ...

(NOAA) Global Monitoring Laboratory (GML)'s Baseline Observatory network since 1972. The observatory's location, far from continental sources of emissions and above the marine inversion layer, makes it an ideal site for atmospheric monitoring. The absence of continental weather patterns, lack of vegetation, and a predictable diurnal wind pattern provide routine access to clean, well-mixed air from the free troposphere. The observatory's reading of a historic high in its daily recording of

carbon dioxide emission Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...

s—400

parts per million In science and engineering, the parts-per notation is a set of pseudo-units to describe the small values of miscellaneous dimensionless quantity, dimensionless quantities, e.g. mole fraction or mass fraction (chemistry), mass fraction. Since t ...

, in 2015—was referenced by

Pope Francis Pope Francis (born Jorge Mario Bergoglio; 17 December 1936 – 21 April 2025) was head of the Catholic Church and sovereign of the Vatican City State from 13 March 2013 until Death and funeral of Pope Francis, his death in 2025. He was the fi ...

in his apostolic exhortation on the

climate crisis ''Climate crisis'' is a term that is used to describe global warming and climate change and their effects. This term and the term ''climate emergency'' have been used to emphasize the threat of global warming to Earth's natural environment an ...

, '' Laudate Deum''.

Cooperative research

In addition to NOAA-GML projects, the observatory campus remains host to projects from partner institutions, governmental organizations, and universities from around the world. The Mauna Loa Solar Observatory and

National Science Foundation The U.S. National Science Foundation (NSF) is an Independent agencies of the United States government#Examples of independent agencies, independent agency of the Federal government of the United States, United States federal government that su ...

's Global Oscillations Network Group station share this site. The observatory site is also a temporary home to a

cosmic microwave background The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...

observatory called Yuan-Tseh Lee Array.

Site access

The observatory is located at the end of the Mauna Loa Observatory Access Road. Gated access to the observatory is managed by NOAA. The northern trailhead to the summit of Mauna Loa is located below the observatory site and is managed by Hawaiʻi Volcanoes National Park. It passes through State of Hawaii conservation land managed by the Hawaii Department of Land and Natural Resources. The access road was obstructed by lava flow from the 2022 eruption of Mauna Loa. , deposits continue to block vehicular access to the observatory. Utility lines that powered the facility were also damaged, further impeding operation. Temporary solar power has been established, which allows the observatory to operate at approximately 33 percent of its full capacity. This is as renovations are underway to upgrade the facility with new power distribution infrastructure.

References

External links

NOAA Mauna Loa Observatory
official website
Global Monitoring Division, Boulder, CO, USA

Worldwide Carbon Dioxide concentrations - in real time
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Observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysics, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Th ...