My Turn: A primer on the carbon footprint
The July 13 Sunday Monitor column on climate change by Ayn Whytemare painted the problem of man-induced global warming with broad strokes.
One aspect that needs refinement is to explain what carbon is and how carbon dioxide effects our global temperatures.
Most of us have seen the term “carbon footprint” in the headlines over the past decade. And, perhaps, you have wondered exactly what that is and how it affects you.
As an earth scientist, I, too, have see the term casually used and decided to study it. The term is somewhat misused, because it is really carbon dioxide that is the concern.
Carbon dioxide is formed when one carbon atom combines with two oxygen atoms to release energy. It is what we exhale with each breath and what is produced by combustion.
Combustion occurs in our cars’ engines and in our heating system and at coal burning power plants. When we turn on a light, prepare a cup of coffee, or charge up our cellphones, we cause more carbon dioxide to be generated and thus increase our footprints.
Now to understand the problem.
In 1958, Charles Keeling began measuring the carbon dioxide content of the atmosphere in an area unaffected by human activity – the top of Mauna Loa in Hawaii.
Since that time, the atmospheric content of carbon dioxide has gone from 315 parts per million to more than 400. Now, parts per million may sound like an inconsequentially small number. However, in the atmosphere, carbon dioxide absorbs heat energy, so the more CO2, the more heat absorption. The sun has warmed the Earth since its birth.
I won’t bore you with energy measurements or physics, except to state that the radiation from the sun comes mostly as light that we can see. This light has a lot of energy per photon and may get reflected back into space by a cloud or the ocean. But some amount will make it to ground and warm it (or hit a leaf and power photosynthesis).
When the sun goes down, the warm ground radiates photons back into space.
These photons, which we cannot see, are infrared. Infra means “below,” so in this use it means “below red” or a photon of less energy than red (which is the lowest energy of what we can see – violet has the most energy).
Carbon dioxide in the atmosphere has the quirky ability to absorb these infrared photons and become warmer (but not absorb visible light photons). In this manner, the atmosphere warms.
How much, you ask?
Berkeley Earth Surface Temperature Project, after using more than 1.3 billion temperature measurements at more than 36,000 weather stations over the past 200 years, has estimated that Earth’s average temperature was very stable until around 1950 and has risen almost 2 degrees Fahrenheit since then.
And, as the amount of CO2 continues to rise, Earth’s average temperature will rise.
Worldwide, mankind continues to burn cubic miles of coal and billions of barrels of petroleum each year in power plants and automobiles, drastically expanding our carbon footprint.
Astronomers have studied Venus for centuries, but only within the past half-century have they been able to determine what gases comprise Venus’s atmosphere.
The primary component is CO2, and astronomers believe it is responsible for Venus’s atmosphere being over 800 degrees Fahrenheit.
Many climatologists are concerned that if Earth’s atmospheric CO2 levels keep rising, our planet may become too hot for mankind. They are also concerned that because CO2 has a very long residence time in the atmosphere, reducing the 400-plus ppm back to pre-industrial levels may take thousands of years.
Please note that what I have stated here are established scientific statements by peer-reviewed scientists, and I invite you to read further about global warming either through searching the internet or books from the library.
(Walter Carlson is a former geologist with the New Hampshire Department of Environmental Services. He lives in Concord)