Carbon In the Atmosphere
Part B: CO2My Life's Story
The carbon cycle has changed over Earth's historyImagine 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).
DiscussThe 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:
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 In1: Explain how the geological carbon cycle is critical to the stability of Earth's climate over very long timescales.
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.
Want to learn more about ice cores, sediment cores, Milankovitch cycles, and changes in CO2over Earth's history? Check out these resources:
- Research the latest research! New research on the carbon cycle, climate and the environment is on-going. You can use ScienceDaily and Phys.org to find recent research on the carbon cycle and paleoclimate by using combinations of the following tags: carbon cycle, sediment cores, greenhouse gases, CO2, paleoclimate, PETM Here are two examples
- New understanding to past global warming events: Hyperthermal events may be triggered by warming -- ScienceDaily
- Explore changes in CO2and temperature in Earth's history using two great interactive resources from HHMI's BioInteractive
- Watch a video on a huge "burp of CO2" that occurred 55 million years ago in Science Bulletins: PETM - Unearthing Ancient Climate Change - YouTube
- Learn more about ice cores:
- National Ice Core Laboratory.
- Use this interactive applet on Ice Core Research and Analysis. Scroll down the page until you see "Ice Core Analysis" and click on Run Applet.
- Learn about sediment cores and climate:
- Earthlabs Climate Detective module. You can access this module from the menu on the left side of this page.
- Paleoclimatology: A Record from the Deep
- Ice Stories: Dispatches from Polar Scientists: Ice and Sediment Cores
- Read new research on Of Orbits and Ice Ages
- Explore these two interactives on the Milankovitch cycles. (NOTE: Flash is needed}
- Watch in a must-see AGU video, scientist Dr. Richard Alley explains The Biggest Control Knob: Carbon Dioxide in Earth's Climate History