The effect of carbon dioxide on the atmosphere has been studied experimentally since 1856, when Eunice Foote compared the air temperatures in two flasks, one filled with “carbonic acid gas” (as it was then termed) when they were warmed by sunlight.

In recent years a number of similar “greenhouse gas demonstrations” have been described on YouTube.  These demonstrations usually involve the warming of two flasks by an infrared heat lamp after introducing carbon dioxide into one of these flasks, for example by using a substance containing sodium bicarbonate. The presence of CO2 causes that flask to warm noticeably more than the control flask, due to the absorption of infrared radiation by the CO2 molecules.

During 2019 a small group of Canberra citizens with affiliations to 350 Canberra and the Australian Association for Environmental Education (AAEE) sought to reproduce these experiments. We attempted to eliminate potential causes of bias due to factors such as chemical reactions occurring in the active flask, and asymmetry in the positioning of the infrared lamp.     A description of the apparatus used, and the experimental conditions, is given here.

A sample result from a public demonstration run during Science Week, on 10 August 2019, is given here.

A brief and simplified discussion of the molecular physics, explaining why  CO2 is a greenhouse gas, is given here.

 

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