A simple equation for the surface temperature of a planet based on the radiation it receives from the Sun, the planet’s albedo, and the greenhouse effect can be used to model the effect of increased carbon emissions on Earth’s global average surface temperature (GAST), giving results similar to those from currently used more complex climate models.

In previous articles in this journal, we reported on student use of a simple expression derived from the Stefan–Boltzmann law for estimating planetary temperatures and modified to include the effects of both albedo and the greenhouse effect.1–3 Focusing on the greenhouse effect in Earth’s atmosphere provides a simple model for estimating increases in Earth’s GAST as a result of carbon dioxide emissions that gives results similar to current more complex climate models.

The estimated average surface temperature of a planet in an orbit of radius r (measured in astronomical units—AU) based only on...
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