: Here you will find clear descriptions of what you just saw, how they know what they said they knew, why they know it to be trustworthy information. Finally we will ask the question, "So what!" and explore why the information is important.
In this 2001 clip from “Variability of Northern Forests and Forestry--The Disturbing Influence of Climate,” Ecologist Dr. Mike Apps uses a flow chart to discuss sources and sinks of the global carbon cycle. When Dr. Apps refers to “carbon” during this clip, he means more specifically, the amount of carbon found in carbon dioxide1. His image uses arrows to show the amount of carbon released, carbon taken up, and carbon remaining in the atmosphere. There is an error on the slide, which Dr. Apps verbally corrects. The correct statement is that the amount of carbon emitted by fossil fuels is equal to burning all of Canada’s forests once a year or all of British Columbia’s forests twice a year. Since 2001, CO2 emissions from fossil fuel burning have continued to rise and, as of 2013, around 8.6 gigtons of carbon are now released per year.
1What percent of carbon dioxide is carbon? If you add up the atomic weight of carbon (12) and the atomic weight of oxygen as (16 x 2 ) you get 44, so the ratio of CO2 to C is 44/12 or 3.67. In other words 10 gigatons C = 36.7 gigatons CO2. In general, atmospheric scientists use gigatons of carbon when they talk about emissions, whereas the media and others often use gigatons of CO2--which gives a much higher number. In this clip, Dr. Apps is referring to gigatons of carbon.
Amounts of carbon dioxide being released or taken up by different processes can be determined by using chemical equations and confirmed using field tests where CO2 concentrations are measured for a given area of forest or a specific industrial release. Dr. Apps is careful to differentiate between numbers that are well known and numbers that have a high degree of uncertainty. For example, he mentions that there is a great deal of uncertainty surrounding carbon dioxide uptake by the oceans, as shown in the accompanying graph. This uncertainty relates to the fact that the ability of a liquid to dissolve a gas and hold it in solution relates to water temperature, as well as water chemistry--both of which may change in future oceans.
Dr. Apps compares data from multiple soueces and is careful to differentiate between fact and opinion. In science, it is critical to be clear when you are stating something you have drawn from data, such as "6 gigta tons of carbon is equivalent to burning all of Canada's forests once a year," and when you are stating something that is your opinion, "It is my opinion that we need to do something here and here."
For example, another scientist may find Dr. App's data (the facts) to be accurate, but disagree that it would be difficult to increase the ocean as a carbon sink (the opinion).
In this clip, Dr. Apps depicts that fossil fuel burning is adding more carbon dioxide to the atmosphere than is being taken out of the atmosphere through oceans and other carbon sinks, like forests. Scientific studies link the amount of carbon dioxide in the atmosphere with increases in global average temperature. Even a 3 degree Celsius increase in global temperature could lead to changes in our current Earth systems, impacting human society ecologically, socially, and economically. Studies such as Dr. App’s can help society to better understand the causes and preventions of a carbon dioxide increase so that decisions can be made about potential action.
Reflect on the clip using these questions. Then, record your thoughts in a science journal or discuss them with a friend.
Materials: Notebook, paper, and pencil or dedicated computer file where you can keep your work.
Using the following science journal template (a 7 part process) answer one of the questions that follow:
The complete PowerPoint from this presentation is available on the AGCI website.
"Forest Carbon." Natural Resources Canada: Climate Change: July 10, 2013. http://cfs.nrcan.gc.ca/pages/36