EarthLabs > Climate and the Carbon Cycle: Unit Overview > Lab 3: Carbon in the Atmosphere > 3B: CO2 - My Life's Story

Carbon In the Atmosphere

Part B: CO2My Life's Story

The carbon cycle has changed over Earth's history

Imagine if fossils didn't exist. How would we know that dinosaurs, woolly mammoths and other long-extinct creatures once roamed the Earth and swam in our oceans. Like fossils, carbon dioxide has left its own set of "clues" about past atmospheres and climates in ice cores a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere. from Antarctica.

Take several minutes to examine the graph pictured above and then answer the Checking In questions below. The carbon dioxide data (blue lines) and temperature data (red lines) are taken from ice cores drilled in Vostok Station Antarctica. The peaks of carbon dioxide indicate interglacialwarm period within a glacial age periods and the troughs represent ice ages any geological period in which long-term cooling takes place and ice sheets and glaciers exist. (also called glacial ages).

Checking In

Answer the following questions based on the graph above:
  1. Which of the following best describes the temperature pattern?
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  2. Which of the following best describes the CO2 pattern?
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  3. From 600,000 years ago to 100,000 years ago, what was the highest concentration of carbon dioxide(ppm)
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  4. The carbon cycle can change on vastly different time scales. CO2 data from the Vostok ice cores provides evidence for the carbon cycle fluctuating between ice ages on a time scale of approximately ______?
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  5. How much of a global temperature change occurred as ice ages gradually changed to interglacial periods and back again?
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Discuss

The ice core CO2 and temperature data you just explored raises some interesting, more complex questions. Read the questions below and be prepared to discuss them after watching the movie below. Take notes, pausing and replaying as needed. NOTE: Your teacher may decide to assign each group specific questions to take notes on.
  • How are ice ages and interglacial periods related to carbon dioxide and temperature? Why are ice cores critical to revealing this relationship?
  • What causes ice ages to come and go?
  • Does ice core data measured at Vostok reflect historic temperatures and concentrations of atm CO2on a regional scale or a global scale. What is the evidence? Why is knowing the spatial scale important?
  • How were changes in CO2 and temperature related to each other as Earth swung back and forth between ice ages and interglacial periods? For example, which came first- a rise in temperature or a rise in CO2?
  • Were there any feedbacks operating as temperature and concentrations of CO2 changed? If so, how did they operate and at what time scale?


To help you answer these important questions, focus on the following topics as you watch the video:
  • Temperature data from ice cores from Vostok and Epica in Anarctica and ice volume changes from ocean sediment cores.layers of ocean sediments that contain shells and fossils of marine organisms that died long ago, dust and other materials; varieties and concentration of certain fossil microorganisms record past changes in ocean temperature and composition; collected by scientists to reconstruct past paleoclimates
  • Milaknovitch cycles and ice ages
  • The relationship between changes in temperature, CO2, water vapor (H2O) evaporated from ocean.
  • NOTE: If the video does not load, you can watch it at this link: Mother Nature's History Book from the Pacific Institute for Climate Solutions

    Ice cores come from every place in the world where ice accumulates over time. Ice cores from the Antarctic and Greenland ice sheets are the most famous. The longest records of atmospheric CO2 in ice cores collected by scientists extends back to 800,000 years. Molecules of CO2and other gases in the atmosphere diffuse into the top layer of snow and are trapped there in ice bubbles. As new layers of snow and ice accumulate over time, a record of concentrations of atmospheric CO2 and other gases form over time revealing clues about past climates. Watch this video Ice Core Secrets Could Reveal Answers to Global Warming - Science Nation - YouTube and other videos at The National Ice Core Laboratory

    Stop and Think

    1: Describe the relationship between carbon dioxide, temperature and ice ages.


    A slow acting geologic carbon cycle is key to reducing the concentration of atm CO2 over very long time scales (hundred thousands of years to millions of years).


    As Earth swung between ice ages and interglacial periods over the past 800,000 years, the concentration of atm CO2 rose and fell with these swings. A slow-acting geological carbon cycle is responsible for reducing the concentration of atm CO2as Earth swung from interglacial periods to ice ages. Atmospheric chemistry, rain, and rock weathering worked in concert to slowly remove CO2 from the atmosphere over long time scales of hundreds of thousands of years. Watch and listen to Harvard University professor Dr. Daniel Schrag explain to high school students why the processes of Earth's geological carbon cycle is critical to the stability of Earth's climate over long time scales. As you watch the video, take notes on the following:



    NOTE: If the video does not load, you can watch it at HHMI: The Geological Carbon Cycle

    Here are the key concepts of the geological carbon cycle:

    • volcanos release CO2 to the atmosphere. NOTE: The amounts are very small but even amounts of CO2build up over thousands and thousands of years;
    • CO2combines with H2O in the air to form carbonic acid (H2CO3);
    • carbonic acid reacts with silicate minerals in rocks (rock weathering);
    • rock weathering releases calcium, bicarbonate, and other ions that are transported to the oceans by rivers;
    • the ions produced are used by shell-building marine organisms to build their calcium carbonate (CaCO3) shells. These organisms die, many of them sinking to the bottom sediments of the ocean. Their CaCO3 shells become part of the sediments.;
    • Over millions and millions of years, the sea floor is recycled by plate tectonics, carbonate sediments are subducted and carbon dioxide is released through volcanoes on land and at mid-ocean ridges. All of these processes combine to complete the geological carbon cycle.

    Checking In

    1: Explain how the geological carbon cycle is critical to the stability of Earth's climate over very long timescales.
    By drawing down CO2from the atmosphere, the geological carbon cycle can cool the planet by reducing the greenhouse effect. The geological carbon cycle happens on very slow times scales so would not have an impact on today's fossil fuels CO2emissions which operate on very fast time scales.

    2: Explain how the Biosphere and Geopshere work together in the geological carbon cycle to create a long term carbon sink of millions of years.

    Rock weathering (Geosphere) produces bicarbonate ions which are washed down by rivers in the ocean. Shell-building marine organisms (Biosphere), such as planktonic coccolithophores, clams, corals, and oysters use these bicarbonate ions (HCO3-) to make their calcium carbonate (CaCO3) shells. Many of these shells eventually sink to the seafloor and become part of deep sea sediments for millions and millions of years.

    Optional extensions

    Want to learn more about ice cores, sediment cores, Milankovitch cycles, and changes in CO2over Earth's history? Check out these resources:


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