Initial Publication Date: July 7, 2011

Carbon In the Atmosphere

Part B: CO₂—My 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:

Which of the following best describes the temperature pattern?
temperature is mostly cold, with a few periods of warm

temperature fluctuates between periods of warm and cold without any detectable pattern

temperature is mostly warm, with a few periods of cold

temperature fluctuates between periods of warm and cold in fairly regular cycles
Which of the following best describes the CO₂ pattern?
Ice ages are correlated with lower amounts of CO₂

Ice ages are correlated with higher amounts of CO₂

Higher levels of CO₂ are correlated with higher temperatures

Higher levels of CO₂ are correlated with lower temperatures
From 600,000 years ago to 100,000 years ago, what was the highest concentration of carbon dioxide(ppm)
180 ppm

260 ppm

300 ppm

380 ppm
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 ______?
years

decades

hundreds of years

thousands of years

hundred thousand years
How much of a global temperature change occurred as ice ages gradually changed to interglacial periods and back again?
25 degrees F

-10 degrees F

10 degrees F

50 degrees F

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

Milankovitch cycles and ice ages

The relationship between changes in temperature, CO_2, 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

Show me more about ice cores

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 and other videos at The National Ice Core Laboratory

Stop and Think

2: 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).

×

The Long Term Geological Carbon Cycle
Provenance: Dr. Lingling, WuUniversity of Waterloo
Reuse: If you wish to use this item outside this site in ways that exceed fair use (see http://fairuse.stanford.edu/) you must seek permission from its creator.

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

Show me the key concepts of 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.

Show me the answer

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.

Show me the answer

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:

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
- Sediment Yields Climate Record For Past Half-million Years -- ScienceDaily
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
- Paleoclimate: A History of Change
- Use the Earthviewer interactive to explore the science of Earth's deep history. Challenge yourself to find the time in Earth's history where atm CO₂concentrations were the highest. NOTE: You can use this interactive on-line or on one of Earthviewer's free APPs.
Watch a video on a huge "burp of CO₂" that occurred 55 million years ago in Science Bulletins: PETM - Unearthing Ancient Climate Change on 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
- http://icestories.exploratorium.edu/dispatches/big-ideas/ice-and-sediment-cores/ 'Ice Stories: Dispatches from Polar Scientists: Ice and Sediment Cores' new
Read new research on Of Orbits and Ice Ages
Explore this interactive on the Milankovitch cycles.
- Milankovitch Cycles and Glacial and Interglacial Periods
Watch in a must-see AGU video, scientist Dr. Richard Alley explains The Biggest Control Knob: Carbon Dioxide in Earth's Climate History