2 (h.c.b.) The Greenhouse Effect
Recall that gases in Earth’s atmosphere hold in heat from the sun, keeping the atmosphere at a comfortable temperature for living things. The process by which gases in Earth’s atmosphere trap this energy is called the greenhouse effect. Notice that sunlight does not heat the air in the greenhouse directly. Instead, sunlight first heats the soil, benches, and pots. Then infrared radiation from these surfaces heats the air in the greenhouse. The greenhouse effect in Earth’s atmosphere is similar in some ways.
Gases in the atmosphere that trap energy are called greenhouse gases. Carbon dioxide, water vapor, and methane are some of the greenhouse gases. Many scientists have hypothesized that human activities that add greenhouse gases to the atmosphere may be warming Earth’s atmosphere.
Changing Levels of Carbon Dioxide
Scientists think that an increase in carbon dioxide is a major factor in global warming. For example, the burning of wood, coal, oil, and natural gas adds carbon dioxide to the air. During the last 100 years, these activities have increased greatly in many different countries. The carbon dioxide in Venus’s atmosphere traps heat so well that Venus has the hottest surface of any planet. At 460°C, its average surface temperature is hot enough to melt lead. This trapping of heat by the atmosphere is called the greenhouse effect.