Essential Question: How is Earth's climate connected to its geological, biological and cultural systems?
ENGAGE
Geo-Caching
We've established that carbon is relatively scarce on Earth and must be recycled for biological purposes. We've also established that there used to be far more carbon dioxide in Earth's early atmosphere and this helped create a more hospitable environment for early life. But where did all that extra carbon dioxide go?
Fortunately for our planet, as our Sun continued to increase its energy output over millions of years, Earth also developed natural methods of sequestering excess atmospheric carbon dioxide, thus helping to moderate the planet's temperature.
Coal Carbon Cache
Plants take up carbon dioxide for photosynthesis and store it in their tissues. When plants are eaten or die and decay, the solid carbon stored in them is returned to the atmosphere as carbon dioxide.
But not all plant material is consumed or decayed over time. Every lump of coal, every drop of oil and every whiff of natural gas is made of the carbon of ancient organisms that did not return their carbon to the atmosphere, but instead sequestered their stores of carbon out of reach, usually underground. Pretty convenient for the changing ancient environment. And very convenient for our much later coal-consuming industrial revolution.
Carbonate Caches
Imagine all the skeletons and shells created by the corals and mollusks and echinoderms and tiny plankton that have lived, thrived and died, settling onto the bottom of the ocean, taking with them their stores of solid, precipitated calcium carbonate - CaCO3.
Every limestone cave, every massive marble column and even the great White Cliffs of Dover, where she sells sea shells, represent stony reservoirs of vast quantities of former atmospheric carbon dioxide that has chemically joined forces with other minerals in the ocean and eventually settled to the bottom, thus removing carbon dioxide from the system--at least for a while.
Ocean Sink
Another enormous source of stored atmospheric carbon dioxide can be found in the waters of our ocean and its associated processes. The serious consequences of ocean acidification notwithstanding, the water in our ocean is capable of storing tremendous quantities of dissolved gases, including carbon dioxide--far more than our gaseous atmosphere can store.
Pesky Positive Feedback
Ironically, as the ocean takes-up more carbon dioxide, it makes the ocean more acidic. Carbon dioxide decreases the ocean's pH by reacting with water, creating carbonic acid. This lower pH further makes it increasingly difficult for marine organisms to extract, or precipitate, the calcium carbonate needed to make their shells.
Apart from the potentially dire consequences of how this may affect the marine food web, chemically speaking, it also means that the more carbon dioxide the ocean absorbs, the less capable the ocean is to chemically sequester the gas as a solid precipitate.
It's another one of those pesky positive feedback loops. We'll learn about more positive feedback loops in subsequent modules about the cryosphere.
Climate Control Issues
So, over millions of years Earth has moved its carbon around using various biological, chemical and geological processes. And as a result, Earth's climate has fluctuated many times over eons from cold to hot to cold, over and again, more or less gradually, as numerous climate variables interacted over the eons.
But, there's much more to Earth's dynamic climate than the amount of carbon dioxide in the atmosphere at any given time. There are many climate variables that interact in complex cycles over long periods of time.
The Sun's increasing energy output, Earth's changing orbital distance, speed of rotation, tilt, plate tectonics, land-to-ocean ratio, volcanoes, wildfires and even meteorites all play roles in the climate dynamics on this little planet.
For the folks conducting actual climate research, it's big math and big science to fit the pieces the puzzle together properly.
Anthropogenic Climate Change
So how is climate change now any different than in the past? What's causing the recent acceleration in the increase of the average temperature on Earth? In a word, industrialization.
The carbon which nature has been sequestering for hundreds of millions of years, humans have been liberating as carbon dioxide and other greenhouse gases, mostly through our industrial technologies and agricultural practices over the past 150 years.
In short, by re-releasing atmospheric gases from nature's carbon caches at rates far exceeding those nature used to create and store them, humans have thrown some of Earth's intricate systems out of balance. Because everything is connected!
EXPLORE
t we've developed a better understanding of the sources and roles of Carbon on our planet and in our lives, let's take a look at how atmospheric carbon dioxide interacts with the Sun's energy in Global Warming: The Physics of the Greenhouse Effect.
And here i
s an excellent TD video of a laboratory demonstration showing how carbon dioxide absorbs infrared energy, Global Warming: Carbon Dioxide and the Greenhouse Effect
This TD
video uses a common experience to demonstrate how the greenhouse effect works--getting into a car on a sunny day. Global Warming and the Greenhouse Effect
Helpful Hint: What do you say to folks who doubt the consensus of climate scientists? Sometimes a picture's worth a thousand words.
EXPLORE SOME MORE...
Check out these two TD resources, a video and an interactive site. Both explore possibilities for compensating for excess carbon that is accumulating in our atmosphere: Capturing Carbon and Capturing Carbon: Where Do We Put It?
Capturing Carbon
Carbon Capture: Where Do We Put It?Helpful Hint: Looking for Good information about who is responsible for carbon output?
Try Good.is/Good Blog (No relation ; )
EXPLAIN
- What is meant by "Earth's Heat Budget"?
- How does carbon dioxide cause global warming?
- Why are carbon dioxide concentrations increasing in our atmosphere?
- What are some ways Earth naturally stores carbon dioxide?
- What are some ways for humans to help store excess carbon dioxide?
EXTEND
- What evidence of climate change exists where you are?
- What scientific and cultural resources can you use to describe local changes?
- Reflect of these resources and evaluate their utility.
- Reflect on the benefits and dilemmas presented by our carbon-based industrialization
