Which step(s) of the greenhouse effect are being most affected by the increases in greenhouse gases, leading to an increase in heat? 1. Solar radiation enters the Earth system and is reflected and absorbed. 2. Absorbed energy is released into the atmosphere as heat. 3. Heat is absorbed by the atmosphere. 4. The atmosphere re-releases heat, warming Earth's surface and lower atmosphere. 1 and 2 2, 3 and 4 1, 2, and 3 3 and 4