Keeling Curve

Last updated
Atmospheric carbon dioxide (CO2) concentrations from 1958 to 2023 Mauna Loa CO2 monthly mean concentration.svg
Atmospheric carbon dioxide (CO2) concentrations from 1958 to 2023

The Keeling Curve is a graph of the annual variation and overall accumulation of carbon dioxide in the Earth's atmosphere based on continuous measurements taken at the Mauna Loa Observatory on the island of Hawaii from 1958 to the present day. The curve is named for the scientist Charles David Keeling, who started the monitoring program and supervised it until his death in 2005.

Contents

Keeling's measurements showed the first significant evidence of rapidly increasing carbon dioxide (CO2) levels in the atmosphere. [1] According to Naomi Oreskes, Professor of History of Science at Harvard University, the Keeling curve is one of the most important scientific works of the 20th century. [2] Many scientists credit the Keeling curve with first bringing the world's attention to the current increase of CO2 in the atmosphere. [3]

Background

Prior to the 1950s, measurements of atmospheric CO2 concentrations had been taken on an ad hoc basis at a variety of locations. In 1938, engineer and amateur meteorologist Guy Stewart Callendar compared datasets of atmospheric CO2 from Kew in 1898–1901, which averaged 274 parts per million by volume (ppmv), [4] and from the eastern United States in 1936–1938, which averaged 310 ppmv, and concluded that CO2 concentrations were rising due to anthropogenic emissions. [5] However, Callendar's findings were not widely accepted by the scientific community due to the patchy nature of the measurements. [6] [7]

Charles David Keeling, of the Scripps Institution of Oceanography at UC San Diego, was the first person to make frequent regular measurements of atmospheric CO2 concentrations in Antarctica, and on Mauna Loa, Hawaii from March 1958 onwards. [8] Keeling had previously tested and employed measurement techniques at locations including Big Sur near Monterey, rain forests of the Olympic Peninsula in Washington state, and high mountain forests in Arizona. [1] He observed strong diurnal behavior of CO2, with excess CO2 at night due to respiration by plants and soils, and afternoon values representative of the "free atmosphere" over the Northern hemisphere. [1]

Mauna Loa measurements

The Mauna Loa Observatory Mauna Loa Observatory from air.jpg
The Mauna Loa Observatory

In 1957–1958, the International Geophysical Year, Keeling obtained funding from the Weather Bureau to install infrared gas analyzers at remote locations, including the South Pole and on the volcano of Mauna Loa on the island of Hawaii. Mauna Loa was chosen as a long-term monitoring site due to its remote location far from continents and its lack of vegetation. Keeling and his collaborators measured the incoming ocean breeze above the thermal inversion layer to minimize local contamination from volcanic vents. [8] The data was normalized to remove any influence from local contamination. Due to funding cuts in the mid-1960s, Keeling was forced to abandon continuous monitoring efforts at the South Pole, but he scraped together enough money to maintain operations at the Mauna Loa Observatory, which have continued to the present day. [9]

External videos
Nuvola apps kaboodle.svg Scripps Institution of Oceanography at UC San Diego, The Keeling Curve Animation, Scripps Institution of Oceanography at UC San Diego
Nuvola apps kaboodle.svg Ralph Keeling, "The (Ralph) Keeling Curve", Scripps Institution of Oceanography at UC San Diego
Nuvola apps kaboodle.svg John Barnes, Mauna Loa Observatory I Exploratorium, Exploratorium
Nuvola apps kaboodle.svg Charles David Keeling, "The Keeling Curve Turns 50"
Nuvola apps kaboodle.svg Charles David Keeling, 2005 "Tyler Prize Laureate Lecture", Scripps Institution of Oceanography at UC San Diego

Keeling's Tellus article of 1960 presented the first monthly CO2 records from Mauna Loa and Antarctica (1957 to 1960), finding a "distinct seasonal cycle...and possibly, a worldwide rise in CO2 from year to year." [10] [9] : 41–42  By the 1970s, it was well established that the increase of atmospheric carbon dioxide was ongoing and due to anthropogenic emissions. [11] [12]

Carbon dioxide measurements at the Mauna Loa Observatory in Hawaii are made with a type of infrared spectrophotometer, now known as a nondispersive infrared sensor, that is calibrated using World Meteorological Organization standards. [13] This type of instrument, originally called a capnograph, was first invented by John Tyndall in 1864, and recorded by pen traces on a strip chart recorder. [14] Currently, several laser-based sensors are being added to run concurrently with the infrared spectrophotometer at the Scripps Institute of Oceanography, while NOAA measurements at Mauna Loa still use the nondispersive infrared sensor.

Results and interpretation

The measurements collected at Mauna Loa Observatory show a steady increase in mean atmospheric CO2 concentration from 313 parts per million by volume (ppmv) in March 1958 to 406 ppmv in November 2018, [15] with a current increase of 2.48 ± 0.26 (mean ± 2 std dev) ppmv CO2 per year. [16] This increase in atmospheric CO2 is due to the combustion of fossil fuels, and has been accelerating in recent years. Since CO2 is a greenhouse gas, this has significant implications for global warming. Measurements of CO2 concentration in ancient air bubbles trapped in polar ice cores show that mean atmospheric CO2 concentration was between 275 and 285 ppmv during the Holocene epoch (9,000 BCE onwards), but started rising sharply at the beginning of the nineteenth century. [17]

The Keeling Curve also shows a cyclic variation of about 6 ppmv each year corresponding to the seasonal change in uptake of CO2 by the world's land vegetation. Most of this vegetation is in the Northern hemisphere where most of the land is located. From a maximum in May, the level decreases during the northern spring and summer as new plant growth takes CO2 out of the atmosphere through photosynthesis. After reaching a minimum in September, the level rises again in the northern fall and winter as plants and leaves die off and decay, releasing CO2 back into the atmosphere. [10] [12]

Legacy

Global monitoring

Due in part to the significance of Keeling's findings, [9] NOAA began monitoring CO2 levels worldwide in the 1970s. [18] Today, atmospheric CO2 levels are monitored at about 100 sites around the globe through the Global Greenhouse Gas Reference Network. [19] Measurements at many other isolated sites have confirmed the long-term trend shown by the Keeling Curve, [20] although no sites have as long a record as Mauna Loa. [21]

Ralph Keeling

Since Charles David Keeling's death in 2005, responsibility and oversight of the project was transferred to Keeling's son, Ralph Keeling. On the fiftieth anniversary of the beginning of the project, the younger Keeling wrote an article in Science magazine describing his father's life and work, along with how the project has grown and evolved over time. [22] Along with more precise measurement materials and funds for the project of monitoring of the Earth's CO2 levels, Keeling wrote about his pride for his father's work and how he has continued it in his memory.

Recognition

In 2015, the Keeling Curve was designated a National Historic Chemical Landmark by the American Chemical Society. [23] Commemorative plaques were installed at Mauna Loa Observatory and at the Scripps Institution of Oceanography at the University of California, San Diego.

Passing 400 ppm in 2013

On May 9, 2013, the daily mean concentration of CO2 in the atmosphere measured at Mauna Loa surpassed 400 parts per million (ppmv). [24] Estimates of CO2 during previous geologic eras suggest that CO2 has not reached this level since the mid-Pliocene, 2 to 4 million years ago. [25] This level of carbon dioxide, causing climate change, suggests a continued worsening in natural and ecological disasters, which increasingly threatens human and animal habitats on Earth, if greenhouse gas emissions are not significantly reduced.

See also

Related Research Articles

<span class="mw-page-title-main">Greenhouse effect</span> Atmospheric phenomenon causing planetary warming

The greenhouse effect occurs when greenhouse gases in a planet's atmosphere insulate the planet from losing heat to space, raising its surface temperature. Surface heating can happen from an internal heat source as in the case of Jupiter, or from its host star as in the case of the Earth. In the case of Earth, the Sun emits shortwave radiation (sunlight) that passes through greenhouse gases to heat the Earth's surface. In response, the Earth's surface emits longwave radiation that is mostly absorbed by greenhouse gases. The absorption of longwave radiation prevents it from reaching space, reducing the rate at which the Earth can cool off.

<span class="mw-page-title-main">Global warming potential</span> Potential heat absorbed by a greenhouse gas

Global warming potential (GWP) is an index to measure how much infrared thermal radiation a greenhouse gas would absorb over a given time frame after it has been added to the atmosphere. The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide, which is taken as a reference gas. Therefore, the GWP has a value of 1 for CO2. For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered.

<span class="mw-page-title-main">Svante Arrhenius</span> Swedish scientist (1859–1927)

Svante August Arrhenius was a Swedish scientist. Originally a physicist, but often referred to as a chemist, Arrhenius was one of the founders of the science of physical chemistry. In 1903, he received the Nobel Prize in Chemistry, becoming the first Swedish Nobel laureate. In 1905, he became the director of the Nobel Institute, where he remained until his death.

<span class="mw-page-title-main">Satellite temperature measurement</span> Measurements of atmospheric, land surface or sea temperature by satellites.

Satellite temperature measurements are inferences of the temperature of the atmosphere at various altitudes as well as sea and land surface temperatures obtained from radiometric measurements by satellites. These measurements can be used to locate weather fronts, monitor the El Niño-Southern Oscillation, determine the strength of tropical cyclones, study urban heat islands and monitor the global climate. Wildfires, volcanos, and industrial hot spots can also be found via thermal imaging from weather satellites.

<span class="mw-page-title-main">Atmospheric chemistry</span> Branch of atmospheric science in which the chemistry of the atmosphere is studied

Atmospheric chemistry is a branch of atmospheric science that studies the chemistry of the Earth's atmosphere and that of other planets. This multidisciplinary approach of research draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and volcanology, climatology and other disciplines to understand both natural and human-induced changes in atmospheric composition. Key areas of research include the behavior of trace gasses, the formation of pollutants, and the role of aerosols and greenhouse gasses. Through a combination of observations, laboratory experiments, and computer modeling, atmospheric chemists investigate the causes and consequences of atmospheric changes.

Trace gases are gases that are present in small amounts within an environment such as a planet's atmosphere. Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make up 99.934% of its atmosphere.

<span class="mw-page-title-main">Mauna Loa Observatory</span> Atmospheric research station on island of Hawaii

The Mauna Loa Observatory (MLO) is an atmospheric baseline station on Mauna Loa, on the island of Hawaii, located in the U.S. state of Hawaii.

<span class="mw-page-title-main">Charles David Keeling</span> American scientist (1928-2005)

Charles David Keeling was an American scientist whose recording of carbon dioxide at the Mauna Loa Observatory confirmed Svante Arrhenius's proposition (1896) of the possibility of anthropogenic contribution to the greenhouse effect and global warming, by documenting the steadily rising carbon dioxide levels. The Keeling Curve measures the progressive buildup of carbon dioxide, a greenhouse gas, in the atmosphere.

<span class="mw-page-title-main">Roger Revelle</span> American scientist (1909–1991)

Roger Randall Dougan Revelle was a scientist and scholar who was instrumental in the formative years of the University of California, San Diego and was among the early scientists to study anthropogenic global warming, as well as the movement of Earth's tectonic plates. UC San Diego's first college is named Revelle College in his honor.

<span class="mw-page-title-main">Guy Stewart Callendar</span>

Guy Stewart Callendar was an English steam engineer and inventor. His main contribution to human knowledge was developing the theory that linked rising carbon dioxide concentrations in the atmosphere to global temperature. In 1938, he was the first to show that the land temperature of Earth had risen over the previous 50 years. This theory, earlier proposed by Svante Arrhenius, has been called the Callendar effect. Callendar thought this warming would be beneficial, delaying a "return of the deadly glaciers."

<span class="mw-page-title-main">Atmospheric infrared sounder</span> Science instrument on NASAs Aqua satellite

The atmospheric infrared sounder (AIRS) is one of six instruments flying on board NASA's Aqua satellite, launched on May 4, 2002. The instrument is designed to support climate research and improve weather forecasting.

<span class="mw-page-title-main">Carbon dioxide in Earth's atmosphere</span> Atmospheric constituent and greenhouse gas

In Earth's atmosphere, carbon dioxide is a trace gas that plays an integral part in the greenhouse effect, carbon cycle, photosynthesis and oceanic carbon cycle. It is one of three main greenhouse gases in the atmosphere of Earth. The concentration of carbon dioxide in the atmosphere reached 427 ppm (0.04%) in 2024. This is an increase of 50% since the start of the Industrial Revolution, up from 280 ppm during the 10,000 years prior to the mid-18th century. The increase is due to human activity.

<span class="mw-page-title-main">Greenhouse gas</span> Gas in an atmosphere with certain absorption characteristics

Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases is that they absorb the wavelengths of radiation that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).

<span class="mw-page-title-main">Atmospheric methane</span> Methane in Earths atmosphere

Atmospheric methane is the methane present in Earth's atmosphere. The concentration of atmospheric methane is increasing due to methane emissions, and is causing climate change. Methane is one of the most potent greenhouse gases. Methane's radiative forcing (RF) of climate is direct, and it is the second largest contributor to human-caused climate forcing in the historical period. Methane is a major source of water vapour in the stratosphere through oxidation; and water vapour adds about 15% to methane's radiative forcing effect. The global warming potential (GWP) for methane is about 84 in terms of its impact over a 20-year timeframe, and 28 in terms of its impact over a 100-year timeframe.

<span class="mw-page-title-main">Greenhouse gas monitoring</span> Measurement of greenhouse gas emissions and levels

Greenhouse gas monitoring is the direct measurement of greenhouse gas emissions and levels. There are several different methods of measuring carbon dioxide concentrations in the atmosphere, including infrared analyzing and manometry. Methane and nitrous oxide are measured by other instruments. Greenhouse gases are measured from space such as by the Orbiting Carbon Observatory and networks of ground stations such as the Integrated Carbon Observation System.

<span class="mw-page-title-main">Atmospheric carbon cycle</span> Transformation of atmospheric carbon between various forms

The atmospheric carbon cycle accounts for the exchange of gaseous carbon compounds, primarily carbon dioxide, between Earth's atmosphere, the oceans, and the terrestrial biosphere. It is one of the faster components of the planet's overall carbon cycle, supporting the exchange of more than 200 billion tons of carbon in and out of the atmosphere throughout the course of each year. Atmospheric concentrations of CO2 remain stable over longer timescales only when there exists a balance between these two flows. Methane, Carbon monoxide (CO), and other human-made compounds are present in smaller concentrations and are also part of the atmospheric carbon cycle.

Ralph Franklin Keeling is a professor at Scripps Institution of Oceanography. He is the Principal Investigator for the Atmospheric Oxygen Research Group at Scripps and is the director of the Scripps CO2 Program, the measurement program behind the Keeling curve, which was started by his father Charles David Keeling in 1958. Ralph Keeling has developed precise instruments and techniques for the measurement of atmospheric oxygen and anthropogenic CO2 in the ocean, and for the analysis of land and ocean carbon sinks.

<span class="mw-page-title-main">Dr. Neil Trivett Global Atmosphere Watch Observatory</span> Observatory

The Dr. Neil Trivett Global Atmosphere Watch Observatory is an atmospheric baseline station operated by Environment and Climate Change Canada located about 6 km (3.7 mi) south south-west of Alert, Nunavut, on the north-eastern tip of Ellesmere Island, about 800 km (500 mi) south of the geographic North Pole.

<span class="mw-page-title-main">Space-based measurements of carbon dioxide</span> Used to help answer questions about Earths carbon cycle

Space-based measurements of carbon dioxide are used to help answer questions about Earth's carbon cycle. There are a variety of active and planned instruments for measuring carbon dioxide in Earth's atmosphere from space. The first satellite mission designed to measure CO2 was the Interferometric Monitor for Greenhouse Gases (IMG) on board the ADEOS I satellite in 1996. This mission lasted less than a year. Since then, additional space-based measurements have begun, including those from two high-precision satellites. Different instrument designs may reflect different primary missions.

Lisa Welp is a biogeochemist who utilizes stable isotopes to understand how water and carbon dioxide are exchanged between the land and atmosphere. She is a professor at Purdue University in the department of Earth, Atmosphere, and Planetary Sciences.

References

  1. 1 2 3 "The Early Keeling Curve | Scripps CO2 Program". scrippsco2.ucsd.edu. Retrieved 2018-11-24.
  2. ↑ Naomi Oreskes (23 January 2017). Climate Disruption (video). Awesome Documentaries TV. Archived from the original on 2021-12-12. Retrieved 27 August 2017.
  3. ↑ Nisbet, Euan (2007). "Cinderella science" (PDF). Nature. 450 (7171): 789–790. doi: 10.1038/450789a . PMID   18063983.
  4. ↑ Brown, Horace Tabberer; Escombe, F. (1905). "On the variations in the amount of carbon dioxide in the air of Kew during the years 1898-1901". Proc. R. Soc. Lond. B. 76 (507): 118–121. Bibcode:1905RSPSB..76..118B. doi:10.1098/rspb.1905.0004. ISSN   0950-1193. S2CID   97664092.
  5. ↑ Callendar, Guy Stewart (1938). "The artificial production of carbon dioxide and its influence on temperature" (PDF). Quarterly Journal of the Royal Meteorological Society. 64 (275): 223–240. Bibcode:1938QJRMS..64..223C. doi:10.1002/qj.49706427503. Archived from the original (PDF) on 2020-11-12. Retrieved 2018-11-24.
  6. ↑ Fleming, James Rodger (1998). Historical Perspectives on Climate Change. Oxford: Oxford University Press. ISBN   978-0195078701.
  7. ↑ "The Carbon Dioxide Greenhouse Effect". history.aip.org. Retrieved 2018-11-24.
  8. 1 2 Harris, Daniel C. (2010). "Charles David Keeling and the Story of Atmospheric CO2 Measurements". Analytical Chemistry. 82 (19): 7865–7870. doi:10.1021/ac1001492. ISSN   0003-2700. PMID   20536268.
  9. 1 2 3 Keeling, Charles D. (1998). "Rewards and Penalties of Monitoring the Earth". Annual Review of Energy and the Environment . 23: 25–82. CiteSeerX   10.1.1.173.2051 . doi: 10.1146/annurev.energy.23.1.25 .
  10. 1 2 Keeling, Charles D. (1960). "The concentration and isotopic abundances of carbon dioxide in the atmosphere" (PDF). Tellus. 12 (2): 200–203. Bibcode:1960Tell...12..200K. doi: 10.3402/tellusa.v12i2.9366 .
  11. ↑ Pales, Jack C.; Keeling, Charles David (1965). "The Concentration of Atmospheric Carbon Dioxide in Hawaii". Journal of Geophysical Research. 70 (24): 6053–6076. Bibcode:1965JGR....70.6053P. doi:10.1029/JZ070i024p06053.
  12. 1 2 Keeling, Charles D.; Bacastow, Robert B.; Bainbridge, Arnold E.; Ekdahl Jr., Carl A.; Guenther, Peter R.; Waterman, Lee S.; Chin, John F. S. (1976). "Atmospheric carbon dioxide variations at Mauna Loa Observatory, Hawaii". Tellus. 28 (6): 538–551. Bibcode:1976Tell...28..538K. doi: 10.3402/tellusa.v28i6.11322 . ISSN   0040-2826.
  13. ↑ Tans, Pieter; Thoning, Kirk (March 2018). "How we measure background CO2 levels on Mauna Loa" (PDF).
  14. ↑ "Sampling the Air". The New York Times . December 22, 2010.
  15. ↑ "Recent Monthly Average Mauna Loa CO2". Earth System Research Laboratory. Retrieved 9 May 2016.
  16. ↑ Rasmussen, Carl Edward. "Atmospheric Carbon Dioxide Growth Rate".
  17. ↑ Neftel, A.; Moor, E.; Oeschger, H.; Stauffer, B. (1985). "Evidence from polar ice cores for the increase in atmospheric CO2 in the past two centuries". Nature. 315 (6014): 45–47. Bibcode:1985Natur.315...45N. doi:10.1038/315045a0. S2CID   4321970.
  18. ↑ Keeling, Charles D. (1978). "The Influence of Mauna Loa Observatory on the Development of Atmospheric CO2 Research". In Mauna Loa Observatory: A 20th Anniversary Report. (National Oceanic and Atmospheric Administration Special Report, September 1978), edited by John Miller, pp. 36–54. Boulder, CO: NOAA Environmental Research Laboratories.
  19. ↑ NOAA, Earth System Laboratory, US Department of Commerce Research. "ESRL Global Monitoring Division - Global Greenhouse Gas Reference Network". www.esrl.noaa.gov. Retrieved 2018-11-25.
  20. ↑ Global Stations CO2 Concentration Trends. Scripps CO2 Program.
  21. ↑ Keeling, Charles D.; Whorf, T. P. (2004). "Atmospheric CO2 from Continuous Air Samples at Mauna Loa Observatory, Hawaii, U.S.A." Archived from the original on 2016-03-03. Retrieved 2007-10-17.
  22. ↑ Keeling, Ralph F. (2008). "Recording Earth's Vital Signs". Science. 319 (5871): 1771–1772. doi:10.1126/science.1156761. ISSN   0036-8075. PMID   18369129. S2CID   206512305.
  23. ↑ "Keeling Curve - American Chemical Society". American Chemical Society. Retrieved 2018-11-25.
  24. ↑ Showstack, Randy (2013). "Carbon dioxide tops 400 ppm at Mauna Loa, Hawaii". Eos, Transactions American Geophysical Union. 94 (21): 192. Bibcode:2013EOSTr..94Q.192S. doi: 10.1002/2013eo210004 . ISSN   0096-3941.
  25. ↑ Montaigne, Fen. "Son of Climate Science Pioneer Ponders A Sobering Milestone". Yale Environment 360. Yale School of Forestry & Environmental Studies. Archived from the original on 8 June 2013. Retrieved 14 May 2013.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.