SCIENCE LITERACY WORKING WITH DATA
The U.S. Energy Information Administration (EIA) was established by law to be an independent and impartial energy authority. It provides statistical and analytical information on energy issues, including pollution and climate change, to support public understanding and policy making. The EIA’s data on carbon dioxide (CO2) emissions and atmospheric concentrations are shown in the following graph.
Interpretation
Question 24.16
Describe in one or two sentences how atmospheric concentrations of carbon dioxide have changed since about 1750.
Atmospheric carbon dioxide concentrations were pretty constant between 1750 and 1800, then began rising slowly. The rate of increase became much greater beginning around 1950.
Question 24.17
How have anthropogenic (human-caused) emissions of carbon dioxide changed since about 1860? Why do you think that there are no data on anthropogenic emissions before 1860?
Anthropogenic emissions of carbon dioxide have been increasing rapidly since around 1860. There would have been little human emission of carbons before then (this is before the Industrial Revolution), hence the lack of data.
Question 24.18
What relationship do you see between anthropogenic emissions of carbon dioxide and atmospheric concentrations of carbon dioxide?
Atmospheric concentrations of carbon dioxide only began increasing rapidly once humans were releasing a lot of carbon dioxide, which suggests (but does not prove) causality.
Advance Your Thinking
Question 24.19
How would you predict that the two lines on this graph will change if new, more stringent emission targets are set and countries start meeting their goals? Explain your reasoning.
If countries start meeting more stringent emission targets then the emissions line should start to fall as soon as emissions fall but the line showing atmospheric CO2 concentration would not fall immediately but would level off (assuming there are not new sources of CO2 emissions) since CO2 has a long residence time in the atmosphere. But in time the atmospheric line would level off and even fall if technologies or projects like reforestation were used to remove CO2 from the atmosphere.
Question 24.20
About 75% of anthropogenic emissions of carbon dioxide are created during the burning of fossil fuels, and about one-third of this is from vehicle emissions. Suppose we started using electric cars. Identify the circumstances under which this might or might not lead to decreased atmospheric carbon dioxide.
Possible answer: If we began to run our cars using electricity generated from wind, solar or other non-carbon sources, this could decrease the anthropogenic emissions that are caused by fossil fuel burning. Even biofuels, which are carbon based, represent carbon recently removed from the atmosphere and do not contribute to a net increase as long as there are not significant amounts of fossil fuels used in their production. However, if the electricity is generated by a source that adds carbon to the atmosphere (i.e. burning coal, oil or natural gas), then atmospheric carbon dioxide levels might not decrease.