Development of Educational Apparatus to Demonstrate the Global Warming in Consideration of Radiative Energy Balance

Abstract

　　　A novel apparatus simulating the global warming mechanism and attendant variations in the global mean temperature was developed. The apparatus was designed so that the surface temperature of a model Earth was determined solely by a suitably simulated radiative energy balance. In simple experiments using acrylic plates as a layer of greenhouse gases, the steady state temperature was found to decrease with increasing plate thickness beyond 1 mm. However, this demonstration didn’t provide an accurate simulation because the energy loss and heat capacity were affected by the thickness and the pressure effect of the gas layer couldn’t be simulated. An improved system was devised, incorporating supplies of gaseous CO₂ and N₂, and experiments were carried out using both high and low CO₂ concentrations. The resulting temperature increases based on the greenhouse effect were 0.7 and 0.3 °C, respectively. These data showed that the extent of warming varied with the CO₂ concentration, although the concentration was artificially high and the atmosphere in the model was not homogeneous. Various improvements, such as the use of a more powerful cooling system and the addition of a metered gas supply unit, allowed the apparatus to more accurately demonstrate temperature changes corresponding to gas composition.