Bowen Fan uses theory and numerical model to study planetary climates. He is particularly interested in rocky planets beyond modern Earth (e.g., Mars, Titan, and small exoplanets), where life may exist under novel environments. In a recent study , now in press at Geophysical Research Letters, Bowen showed that the temperature distribution on a rocky planet depends on the greenhouse effect. Humans already knew that “mountaintops are cold” before the modern era. This works for Earth, but was not always the case for Mars . Using global climate simulations, Bowen found the abundance of greenhouse gas in planetary atmospheres impacts the distribution of energy, which impacts atmospheric dynamics and ultimately the temperature distribution. “Mountaintops are cold” only when the greenhouse effect is strong enough. For planets with weak greenhouse effects (e.g., modern Mars), temperature does not change given the same insolation from the star.