Updated at 12:42 pm
This week we celebrate the 50th Anniversary of a landmark mission that took humans to the surface of the moon. It was a triumph of perseverance, technology, and pride for the National Aeronautics and Space Administration (NASA). As a former scientist at NASA, I am always excited for the successes of the agency because it is so important for our nation and the world. Many people contributed to the early successes of NASA. The movie Hidden Figures recently told the story of three women that struggled to be acknowledged for their contributions to the U.S. Space program. Other scientific fields have "hidden figures" too. By show of hands, how many of you have heard of Eunice Foote? I am guessing that not too many hands are raised as you peer at your screen. Her pioneering experiments over 150 years ago laid the foundation for what we know about how our climate works and why it is changing. July 17th is the 200th anniversary of her birthday, and I wanted to amplify her contributions.
What exactly did Eunice Foote do? In 1856, this American scientist published something interesting about water vapor and carbon dioxide. She explored how both gases interact with solar radiation (heat). While there are nuances (see this link), her contributions are generally acknowledged. I will circle back to why that is important momentarily, but a little atmospheric science lesson is warranted. In my introductory weather and climate classes at the University of Georgia, the students learn that certain gases are selective absorbers of electromagnetic radiation. According to a NASA website:
Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays (see graphic below)...When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven, you are using electromagnetic energy. You depend on this energy every hour of every day. Without it, the world you know could not exist.
The Sun emits electromagnetic radiation to Earth in the form of ultraviolet (UV), visible, and infrared (heat) energy. The Earth also emits infrared energy back to the atmosphere. Your body is emitting infrared energy right now.
With that context, I can appropriately explain selective absorption. Most people are familiar with the ozone layer in the stratosphere. It protects us from harmful UV radiation from the Sun. It can do this because ozone is a selective absorber of UV radiation. In other words, the visible light and infrared energy pass through the stratosphere, but UV radiation is absorbed. Foote's experiments revealed that carbon dioxide and water vapor affect sunlight. Her experiments, according to the Royal Society, were three years prior to John Tyndall who is cited as the person that advanced these fundamental processes associated with the greenhouse effect. Most scholars believe Tyndall was unaware of Foote's work so they both deserve their place in history.
Colorado State University professor Scott Denning often says, "we survive every night (on Earth) because of the greenhouse effect" so we know that it exists. Our atmosphere contains water vapor, carbon dioxide, methane, and other greenhouse gases that selectively absorb heat energy and then re-emit it. From this explanation, you should discern that our atmosphere does not really behave exactly like a greenhouse, but it is a good analogy for science literacy. Without greenhouse gases, it would be a bit cold for us to live on Earth. In fact, the average temperature would on Earth would be 0 degrees F rather than 59 degrees F. However, excessive concentrations cause too much warming.
In 2018, the University of California Santa Barbara held a symposium in celebration of Eunice Foote's contribution to climate science. The National Oceanic and Atmospheric Administration (NOAA) also released a story this week celebrating the anniversary of Foote's untold contributions. NOAA Public Affairs Office Theo Stein told me in a message:
Her work was described in a column in the September 1856 issue of Scientific American, titled “Scientific Ladies--Experiments with Condensed Gases.” Despite her remarkable insight into the influence that higher carbon dioxide levels in the past would have had on Earth’s temperature, Foote went pretty much unnoticed by modern climate science until recently....We think she deserves a little attention.
I agree too.
