John Tyndall and the greenhouse effect

Sophia Bassi, a high school student living in London, passionate about science and journalism, explores the discoveries of John Tyndall and the greenhouse effect.

Physicist John Tyndall’s experiments beginning in 1859 at the Royal Institution (Ri) allowed him to explain the foundations of the greenhouse effect. Tyndall was born in Ireland in 1820 and began working as a surveyor in Ireland and England.

He joined the Ri in 1853 as the Professor of Natural Philosophy, where he held many lectures and conducted important experiments. In addition to proving the greenhouse effect, Tyndall constructed the blue sky apparatus at the Ri, which revealed why the sky is blue during the day and red at sunset. From 1859, he constructed his radiant heat apparatus to test the ability of different gasses to absorb heat. Tyndall discovered that water vapor and carbon dioxide absorb and radiate heat, making them an important part of keeping the Earth warm and announced the culmination of his work at a Discourse at the Ri in 1861, going on to produce a book in the same year publishing his findings.

In order to understand Tyndall’s discovery, it is important to explore what the greenhouse effect actually is. In fact, the greenhouse effect keeps heat in the atmosphere, preventing the Earth from freezing! Energy from the sun passes through the atmosphere and warms the Earth. The Earth then radiates heat back into the atmosphere in the form of infrared radiation. However, instead of going back into space, this heat is absorbed by greenhouse gasses in the atmosphere. Since the heat is trapped in the atmosphere, the Earth’s surface warms up. While this is needed to keep the Earth habitable, too many greenhouse gasses in the atmosphere causes the Earth to warm up too quickly.

Greenhouse gasses include carbon dioxide, methane, water vapor, nitrous oxide and fluorinated gasses. Carbon dioxide is the most significant, and it spends hundreds of years in our atmosphere. Some natural processes on Earth emit carbon dioxide, and these emitters are known as sources. Carbon dioxide is released when volcanoes erupt, when bacteria breaks down organic matter and even by humans during cellular respiration! At the same time, Earth has sinks that remove carbon dioxide from the atmosphere. Plants take in carbon dioxide during photosynthesis, and carbon dioxide is stored in the ocean. The balance between sources and sinks create a natural level of atmospheric carbon dioxide, but human activities have harmfully increased levels. Humans emit carbon dioxide when burning fossil fuels, such as coal and oil, and when burning down trees.

Methane absorbs more heat than carbon dioxide but spends less time in our atmosphere and is less common. There are natural sources and sinks of methane too, and sources include wetland plants decaying and livestock burping methane. However, humans have harmfully released methane through rice cultivation, coal burning and decomposition in landfills. Finally, water vapor is the most present greenhouse gas in our atmosphere, and the amount of water that evaporates depends on how warm the ocean is. This means that, if we cause the Earth to heat up, the amount of water vapor will increase as well.

Due to human activities, the greenhouse gasses in our atmosphere have rapidly risen. Compared to pre industrial times, atmospheric carbon dioxide increased by 30 percent, and methane levels more than doubled. This is causing climate change, whose effects include droughts, rainfall and a disruption of food production. John Tyndall’s experiments on the greenhouse effect showed how the Earth heats up, while also revealing a critical issue that we face today.