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Development of Theories

A theory as an explanation supported by evidence with no contradictions. This concept introduces three important theories in Earth Science.

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Discovering the Keeling Curve

Discovering the Keeling Curve

Credit: Laura Guerin
Source: CK-12 Foundation
License: CC BY-NC 3.0

The Keeling Curve was named after Charles David Keeling, who began measuring carbon dioxide on Mauna Loa volcano in 1958. The Keeling Curve shows us the trend in atmospheric CO2 over the past 5.5 decades.

News You Can Use

  • Charles Keeling developed the first instrument that could measure CO2 in atmospheric gas samples.
  • In 1957-1958, Keeling built a CO2 measuring site near the top of Mauna Loa volcano in Hawaii (11,135 feet, 3397 meters).
  • He started collecting samples in 1958. Early on, he discovered summer and winter variations due to plant growth: CO2 is low in summer when plants are using it for photosynthesis and high in winter when plants are dormant.
  • In 1963, Keeling’s research was used to report on a greenhouse effect.
  • Keeling Curve is the set of data that shows the rise in CO2 with time since 1958.
  • NASA now uses satellites to collecte carbon dioxide data. 
  • Credit: AIRS, the Atmospheric Infrared Sounder is a spaceborne instrument
    Source: http://www.flickr.com/photos/atmospheric-infrared-sounder/8787526939/
    License: CC BY-NC 3.0

    Carbon Dioxide in Earth's Mid-Troposphere [Figure2]


Can You Apply It?

With the link below, learn more about the Keeling Curve. Then answer the following questions.

  1. Scientists had a hypothesis that Earth was warming due to fossil fuel burning. What did Charles David Keeling do to test this hypothesis?
  2. Why did Keeling choose the summit of Mauna Loa volcano in Hawaii as his sample location?
  3. Why was Keeling’s CO2 data valuable to scientists?
  4. On May 9, 2013, atmospheric CO2 reached 400 ppm. On November 7, 2013, it is 394 ppm. Why has the value gone down? What will the value do next?

Image Attributions

  1. [1]^ Credit: Laura Guerin; Source: CK-12 Foundation; License: CC BY-NC 3.0
  2. [2]^ Credit: AIRS, the Atmospheric Infrared Sounder is a spaceborne instrument; Source: http://www.flickr.com/photos/atmospheric-infrared-sounder/8787526939/; License: CC BY-NC 3.0

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