Ask Science discusses the science behind climate change—plus how to test it in your own kitchen.
A brief history of climate science
In the 1820s, the French physicist and mathematician Joseph Fourier first noted that the Sun could not be the source of the Earth’s warmth on its own. He realized that the Earth should absorb some of the sun’s rays but then should re-emit them back into space, leaving the Earth cold … far too cold even for life like us. He even went so far as to hypothesize that gases in the Earth’s atmosphere played a role in retaining some of that warmth.
Later in the 1850s, the Irish-born physicist John Tyndall conducted careful experiments to test that hypothesis with different kinds of gases. The most prominent gases in the Earth’s atmosphere, oxygen and nitrogen, turned out to not be all that efficient at trapping heat. However, water vapor (H2O) and carbon dioxide (CO2) were. (It was later shown that methane, another atmospheric gas, also serves as an effective heat trap.) Simply put, CO2 is transparent to the wavelength or type of light emitted by the Sun, enabling sunlight to pass through mostly unimpeded. However, once the Earth absorbs this radiation and re-emits it, the CO2 molecules are opaque to the longer wavelengths of this re-emitted light and thus trap the radiation near the Earth’s surface.
In 1896, the Swedish chemist Svante Arrhenius further linked changing concentrations of CO2 in the atmosphere to warmer vs colder periods in the Earth’s history. He later won the Nobel Prize in Chemistry in 1903 for other work in ionic disassociation.
Reproduce climate change in your own kitchen
Now you can take my (and John Tyndall’s) word for it, or, as promised, you can test this for yourself. The only supplies you will need are two large (~2 liter) bottles each filled about halfway with water, two stoppers, two thermometers, a few Alka Seltzer tablets, and a bright lamp. Depending on what kind of bottles, stoppers, and thermometers you are using, set up your experiment so that you can track the temperature of each bottle with the bottle closed as much as possible to the outside (hence the stoppers).
Place the Alka Seltzer tablets in one of the bottles before closing it up and then shine a bright lamp on both bottles. Leave your set up to sit for about an hour. Upon coming into contact with water, the tablets made from sodium bicarbonate and citric acid create a chain reaction. First, with the help of the water, the sodium bicarbonate forms bicarbonate which itself reacts with hydrogen (supplied by the citric acid) to form water and CO2 gas.
The bottle with the CO2 gas present is more efficient at storing the heat from the lamp. Depending on how far away you place your lamp, how bright your lamp is, and how well stoppered your bottles are, you will see different results, but like in this example experiment based off of materials from the National Oceanic and Atmospheric Administration, temperature differences as high as 9 degrees can be observed in as little as an hour. (And for other fun experiments that can be done with just a little Alka Seltzer, check out the product website.)
In case you still remain unconvinced, the universe has also provided us with a 4.5 billion year old test laboratory where the positive feedback loop of inserting more CO2 gas into the atmosphere has been left to run rampant: it’s called Venus.
Until next time, this is Sabrina Stierwalt with Ask Science’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Ask Science on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at firstname.lastname@example.org.