Carbon dioxide in the earth’s atmosphere is at a level that is unprecedented in human experience. University of Dayton professor Bob Brecha explains how we know that we are responsible for the excess CO2.
Carbon dioxide, or CO2 is an important natural part of our atmosphere. Right now, CO2 levels are increasing rapidly. How much of this is part of a natural cycle or is it due to humans? Scientists know how to answer this question.
Since CO2, once in the atmosphere, gets mixed fairly evenly around the globe, measuring the percentage of CO2 in the air at one place on earth gives us a pretty good representation of the state of the atmosphere as a whole. Measurements since the 1950s at Mauna Loa Observatory in Hawaii and elsewhere have confirmed this idea.
What we would really like to know is whether the extra CO2 comes from human activities. Carbon comes in different forms, or isotopes, one of which plants like to use for photosynthesis slightly more than the other. Fossil fuels are the remains of animals and plants that lived millions of years ago. A lump of coal is made up of plants that were buried, compressed and cooked over millions of years. When we dig up and burn these ancient plants, they tell us where the extra CO2 in the atmosphere is coming from.
Measurements of the ratio of carbon isotopes in the atmosphere over time show that increasing amounts of CO2 do come from burning fossil fuels.
I always say that there is no such thing as climate science – there is just science. A nice illustration of this is that these carbon isotope differences show up in our bodies as well. Natural hormones have a certain ratio of carbon isotopes, depending a bit on what’s in our diet – corn-eaters have different amounts than wheat-eaters. Here’s the interesting part. If you decide to start ingesting artificial testosterone, usually made from soy, it will shift the ratio of carbon isotopes in your body just slightly. That means, the World Anti-Doping Agency can use a test for carbon isotope ratios to catch cheating athletes. At least until the science of cheating temporarily outpaces the good-guys’ science.
The science of doping athletes and doping the atmosphere is the same. We all agree that doping athletes is wrong, the question is, where are the sanctions for changing our atmosphere?
Bob Brecha is a professor of physics and renewable and clean energy. He is the coordinator of the Sustainability, Energy and The Environment program at the University of Dayton.
