Introduction to an Atmospheric Radiation Model

Learn the basics of an easy-to-use atmospheric radiation model to gain insight into the detailed mechanism of global warming.

Have you been asked by family and friends about climate change and global warming? As a chemical engineer, you might be expected to have some educated insight. Chemical engineers are uniquely qualified to explain what is happening with our climate and to create and guide technological responses (1). The updated AIChE Climate Change Policy Statement states, “As a professional society, AIChE must be a source of sound information and analysis for its members, for government policymakers, and for the public” (1, 2). To that end, a comprehensive review of climate change, as well as an introduction to atmospheric radiation modeling, was provided in the December 2020 Bonus Issue of CEP, “Thinking About Climate” (3).

The common explanation for global warming is that greenhouse gases (GHGs) — including CO₂, CH₄, N₂O, O₃, halocarbons, and H₂O — trap or capture some of the infrared (IR) energy leaving the Earth’s surface, which leads to increased temperature. GHGs absorb and re-emit some of the energy back toward Earth’s surface, hence warming the surface. It is helpful to focus on the overall energy balance and the radiant energy exiting the top of the atmosphere rather than the energy leaving the surface and working its way through the atmosphere.

Using an atmospheric radiation model is one way to learn more about the mechanism of global warming. It also provides practical experience in the art of using a model to gain insight into a process, as well as a refresher in some aspects of radiation heat transfer. Note that the model highlighted in this article is the one used as an example in the scientific background material for the 2021 Nobel Prize in Physics awarded in part to Dr. Syukuro Manabe “for the physical modelling of Earth’s climate, quantifying variability and reliably predicting global warming” (4). A thorough understanding of the mechanism of radiation provides insight into the role of water vapor, the power of methane, and the saturation effect of CO₂. This article illustrates these effects, as well as how the temperature of the upper atmosphere plays a critical role in global warming...