Mauna Loa Record

Definition

The Mauna Loa Record (or Mauna Loa Carbon Dioxide Record) is the longest continuous record of atmospheric concentrations. The level of CO₂ in the Earth’s atmosphere is one of the primary determinants of global temperature, and higher levels of CO₂ correspond with warmer global temperatures. The CO₂ data collected at the Mauna Loa Observatory in Hawaii since 1958 has been called the most important geophysical record on Earth.

Significance for Climate Change

In the 1950s, continuous monitoring of CO₂ levels represented a break from the conventional view that occasional measurements in selected places would provide enough data. Despite this, scientists at the Mauna Loa Observatory, founded by the U.S. Weather Bureau, decided to maintain continuous records of the CO₂ levels at its location. The observatory is located at an elevation of 3,353 meters on the island of Hawaii, and its CO₂ measurements have been supported by the Weather Bureau and the National Oceanic and Atmospheric Administration (NOAA) ever since. Within only a few years of the project’s founding, an annual increase in atmospheric CO₂ concentration was measured.

In 1974, NOAA installed a new CO₂ analyzer that operated parallel to the original analyzer installed by the Scripps Institution of Oceanography. The Scripps analyzer was replaced with a newer model in 2006. The two-analyzer system provides redundancy to ensure the quality of the Mauna Loa Record and the integrity of the global CO₂ measurement network. In the 1960s and 1970s, Scripps added several measurement stations ranging from the Arctic to Antarctica. However, these stations collect flask samples that are analyzed in a lab rather than collecting on-the-spot data via an analyzer, as the Mauna Loa Observatory does.

Despite the project’s importance, it has faced numerous budget and staff cuts over its existence, as well as questions of whether it constituted basic research or routine monitoring. Even today, such long-term studies are rare and often poorly supported. Despite the obstacles it has faced, the Mauna Loa project has continued, producing large amounts of valuable data that have led to several breakthroughs in climate science.

A simple graph of the Mauna Loa Record data (called the Keeling Curve after Scripps scientist Charles Keeling, who cofounded the project) shows a steady increase of 2 parts per million (0.53 percent) per year in atmospheric CO₂ since the observatory began collecting data in 1958. According to NOAA’s Earth System Research Lab, 63 percent of global warming due to greenhouse gases is due to CO₂. The record has provided crucial evidence that human activity has changed and is changing the composition of the atmosphere. Climate scientists have used the Mauna Loa data to model the state of the Earth’s future climate, affecting political actions such as the drafting of the Kyoto Protocol, a multinational agreement to limit carbon emissions.

The Mauna Loa data also demonstrated for the first time the annual fluctuation in atmospheric CO₂ attributable to biological activity. CO₂ levels reach their maximum in May and their minimum in October. Both of these averages, however, have increased every year since the project began. While the curve is small, it indicates an exponential increase rather than a linear one—the average CO₂ level increases by slightly more each year than the previous year. Atmospheric CO₂ has increased by more than 35 percent over amounts recorded before the Industrial Revolution, and over 6 percent between 1990 and 2009. Comparison with ice-core records suggests that current CO₂ concentrations are unprecedented in the past 650,000 years.

In 1983, Keeling and other scientists began addressing how El Niño weather events affected atmospheric temperature and CO₂ concentration, using the data from Mauna Loa. They were able to identify approximately ten-year fluctuations in temperature correlated with CO₂ fluctuations, leading to a better understanding of long-term global temperature variance.

Skeptics have put forth critiques of the Mauna Loa data, citing the Mauna Loa Observatory’s location on an active volcano and increasing traffic near the observatory. However, the project has attempted to minimize contamination through careful sampling and by normalizing to negate local contamination. Atmospheric CO₂ samples from other stations worldwide corroborate the Mauna Loa data, and the Mauna Loa Record continues to form a base data set for crucial research into climate change.

Bibliography

Field, Christopher B., and Michael R. Raupach, eds. The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World. Washington, D.C.: Island Press, 2004.

"How Do We Know Mauna Loa Carbon Dioxide Measurements Don't Include Volcanic Gas?" NASA, 10 May 2023, science.nasa.gov/earth/natural-disasters/volcanoes/how-do-we-know-mauna-loa-carbon-dioxide-measurements-dont-include-volcanic-gases/. Accessed 21 Dec. 2024.

Keeling, Charles D. “Rewards and Penalties of Monitoring the Earth.” Annual Review of Energy and the Environment 23 (November 1998): 25-82.

Keeling, C. D., et al. “Atmospheric CO₂ and CO₂ exchange with the Terrestrial Biosphere and Oceans, from 1978 to 2000: Observations and Carbon Cycle Implications.” In A History of Atmospheric CO2 and Its Effects on Plants, Animals, and Ecosystems, edited by J. R. Ehleringer, T. E. Cerling, and M. D. Dearing. New York: Springer Verlag, 2005.