Climate Literacy for Construction Professionals

About this course.

The greenhouse effect is the natural process by which certain gases in the atmosphere trap heat and keep the planet warm enough to support life. In short: energy arrives from the Sun mostly as visible light, the Earth's surface absorbs it and re-radiates it as invisible heat (infrared radiation), and a small number of gases in the atmosphere absorb some of that outgoing heat and send it back in all directions rather than letting it escape straight to space. Those heat-trapping gases are the greenhouse gases, and the main ones that human activity affects are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Without any greenhouse effect at all, the Earth's average surface temperature would be far below freezing; the effect itself is entirely natural and necessary. The concern is not the greenhouse effect as such, but the way human activity has strengthened it.

It helps to picture the atmosphere as a thin blanket. Most of the air is nitrogen and oxygen, which do not trap heat. The greenhouse gases are present only in small amounts, yet they do the heat-trapping work because of the way their molecules absorb infrared radiation. Add more of them, and the blanket becomes slightly thicker, so a little more heat is retained near the surface before it eventually escapes. That is the essence of the "enhanced" or "human-caused" greenhouse effect: the natural process is amplified because the concentration of these gases has risen.