Why is Earth the only planet in the solar system known to have a life? The main reason is Earth’s atmosphere. The atmosphere is a mixture of gases that surrounds the planet. We also call it air. The gases in the air include nitrogen, oxygen, and carbon dioxide. Along with water vapor, air allows life to survive. Without it, Earth would be a harsh, barren world.
Gases in the atmosphere surround Earth like a blanket. They keep the temperature in a range that can support life. The gases keep out some of the sun’s scorching heat during the day. At night, they hold the heat close to the surface, so it doesn’t radiate out into space
To extend the growing season, many farmers use greenhouses. A greenhouse traps heat so that days that might be too cool for a growing plant can be made to be just right. Similar to but not exactly like a greenhouse, the greenhouse gasses in our atmosphere absorb energy that is emitted by the Earth and then radiates the energy back to the Earth at a different wavelength- thus keeping the Earth at a habitable temperature.
The Greenhouse Effect :
The role of greenhouse gases—(gases that absorb and emit heat)—in the atmosphere is very important in balancing Earth’s temperature. Greenhouse gases warm the atmosphere by absorbing and re-emitting heat. Some of the heat that radiates out from the ground is absorbed and re-emitted by greenhouse gases in the troposphere. Like a blanket on a sleeping person, greenhouse gases act as insulation for the planet. The warming of the atmosphere because of insulation by greenhouse gases is called the greenhouse effect (see Figure below). Greenhouse gases are the component of the atmosphere that moderate Earth’s temperatures.
Greenhouse Gases :
Greenhouse gases include carbon dioxide (CO2), water vapor (H2O), methane (CH4), ozone (O3), nitrous oxides (NO and NO2), and chlorofluorocarbons (CFCs). All are a normal part of the atmosphere except CFCs. The table on the next page shows how each greenhouse gas naturally enters the atmosphere Different greenhouse gases have different abilities to trap heat. For example, one methane molecule traps 23 times as much heat as one CO2 molecule. One CFC-12 molecule (a type of CFC) traps 10,600
times as much heat as one CO2. Still, CO2 is a very important greenhouse gas because it is much more abundant in the atmosphere and has increased by over 40% since the industrial revolution. Human Activity and Greenhouse Gas Levels Human activity has significantly raised the levels of many greenhouse gases in the atmosphere. Methane levels are about 250% higher as a result of human activity.
Carbon dioxide has increased by more than 35%. CFCs have only recently existed. What do you think happens as atmospheric greenhouse gas levels increase? More greenhouse gases trap more heat and warm the atmosphere. The increase or decrease of greenhouse gases in the atmosphere affects climate and weather the world over. For additional help check out this PowerPoint review, Atmospheric Energy and Global Temperatures, it looks at the movement of energy through the atmosphere