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Charles David Keeling (April 20, 1928 – June 20, 2005) [ 1 ][ 2 ] was an American scientist whose recording of carbon dioxide at the Mauna Loa Observatory [ 3 ] confirmed Svante Arrhenius 's proposition (1896) of the possibility of anthropogenic contribution to the greenhouse effect and global warming, by documenting the steadily rising ...
By the middle 1970's, the long-term CO 2 growth rate was sufficiently accurately established to quantify the so-called "air-borne fraction" (sometimes called the "Keeling fraction"), that is, the fraction of the fossil-fuel emissions which remains in the atmosphere. Combining his measurements of the growth rate of carbon dioxide with his own meticulous (and soon officially adopted) methodology ...
Apr 20, 2021 · When Keeling died in 2005, global CO 2 levels had risen to 380 ppm. This year, on April 3, 2021, we surpassed 420 ppm for the first time in recorded history. These measurements were both taken at the Mauna Loa Observatory, Keeling’s legacy. Yet, sixty-three years after its establishment, human-induced climate change is still a topic of ...
- Overview
- Data collection
- Shape of the curve
- Role in the climate debate
Keeling Curve, graph showing seasonal and annual changes in atmospheric carbon dioxide (CO2) concentrations since 1958 at the Mauna Loa Observatory in Hawaii. The graph, which was devised by American climate scientist Charles David Keeling of the Scripps Institution of Oceanography, charts the buildup of CO2 in the atmosphere. It is the longest uni...
Between 1958 and 1964, Keeling managed sampling efforts at Mauna Loa and at the South Pole in order to consider the changes in atmospheric CO2 occurring in the Northern and Southern hemispheres. (Sampling efforts at Mauna Loa were briefly interrupted during the spring of 1964 because of funding problems and in 2022 because of the Mauna Loa eruption. Budget cuts forced the program at the South Pole, which had begun in 1957, to end in 1964.) Since Keeling was interested in building a record of unbiased baseline data, he chose these locations to collect air samples because they were far from substantial CO2 sources such as cities. Atmospheric CO2 concentrations were calculated daily by using instruments that convert infrared absorbance in each sample to CO2 concentrations in parts per million by volume (ppmv), placed at each location, and their values were charted.
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In aggregate, the Keeling Curve shows an annual rise in atmospheric CO2 concentrations. The curve shows that average concentrations have risen from about 316 ppmv of dry air in 1959 to approximately 370 ppmv in 2000 and 416 ppmv in 2021. Average concentrations rose by 1.3 to 1.4 ppmv per year until the mid-1970s, and they were increasing by more than 2 ppmv per year in the 2010s. The year-to-year increase in atmospheric CO2 concentrations is roughly proportional to the amount of CO2 released into the atmosphere by the burning of fossil fuels. Between 1959 and 1982, the rate of CO2 emissions from fossil fuel combustion doubled from approximately 2.5 billion to 5 billion tons of carbon equivalent per year. By 2020 CO2 emissions had risen to nearly 10 billion tons of carbon equivalent per year. This increase in emissions is reflected in the curve by a slight increase in the slope over the period. The shape of the curve has also allowed scientists to conclude that approximately 57 percent of CO2 emissions remain in the atmosphere from year to year.
The curve also captures seasonal changes in atmospheric CO2 concentration. The curve reveals that CO2 concentrations decrease during periods corresponding to the spring and summer months in the Northern Hemisphere. This decline is explained by the rapid leafing of vegetation during the early spring and subsequent plant growth in the summer, when the influence of photosynthesis is greatest. (Photosynthesis removes CO2 from the air and converts it, along with water and other minerals, into oxygen and organic compounds that can be used for plant growth.) When spring arrives in the Northern Hemisphere, the portion of the planet that contains most of the land area and vegetation cover, the increased rate of photosynthesis outpaces the production of CO2, and a decrease in carbon dioxide concentrations can be observed in the curve. As photosynthetic rates slow in the Northern Hemisphere during the autumn and winter months, atmospheric CO2 concentrations rise.
The Keeling Curve serves as a link between modern CO2 concentrations and those of the past. The data in the curve can be compared with the carbon dioxide concentrations of air bubbles trapped in ice cores. Such comparisons reveal that for most of the period between 1000 and 2000 ce, CO2 concentrations fluctuated between about 275 and 290 ppmv. Since about 1900, however, levels have risen steadily, reaching the level of 416 ppmv in 2021. The results of numerous studies reveal the close association between atmospheric CO2 concentrations and near-surface air temperature. Ice core studies also reveal that the timing of ice ages and warm periods parallels the rise and fall of atmospheric CO2.
The recent increase in the concentration of atmospheric CO2, which began in the middle of the 19th century, is troubling to many climatologists, especially those who advocate the notion of global warming. They fear that the continued increase of this compound in the atmosphere will lead to an increase in Earth’s average temperature and greatly modify the climate patterns upon which many species and ecosystems depend.
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- John P. Rafferty
Sep 22, 2023 · Dr. Charles David Keeling’s groundbreaking work in measuring atmospheric CO 2 levels and the creation of the Keeling Curve have been instrumental in advancing our understanding of human-caused climate change. His dedication to scientific inquiry and meticulous measurements laid the foundation for climate science as we know it today.
Apr 30, 2015 · Charles David Keeling’s career in CO 2 monitoring resulted from the combination of his academic background in science and his interest in the outdoors. Applying his Ph.D. in chemistry from Northwestern University (1954) with his love of natural places in the western U.S., Keeling joined the new geochemistry department at the California Institute of Technology in Pasadena, California.
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The first to make long-term measurements of CO₂. Charles David Keeling was the first scientist who committed his entire career to the long-term observation of climate change through the Keeling Curve, which has measured the earth’s CO₂ concentration since 1958. Because of the curve’s precision and simplicity, it sets a precedent for ...
