Greenhouse Effect UNIT 7 STANDARDS: NCES 2.2.1, 2.2.2, LESSON 4

Greenhouse Effect You may have heard of the greenhouse effect in the news. This has to do with the balance of the gases in the atmosphere. A greenhouse is a building with a glass roof and glass walls that trap the heat from the sun. The heat comes in, but it can’t escape due to the thermal properties of the glass and the heat capacity of the air. This keeps the inside of the greenhouse warm enough to grow certain kinds of plants and vegetables during cooler months.

Earth as a Greenhouse In many ways the earth acts like a greenhouse. The gases in the atmosphere are like the glass building, trapping the sun’s heat near the surface of the earth. The greenhouse effect helps keep earth at a temperature that is warm enough for plants, animals, and people to live.

Increase Carbon dioxide Several greenhouse gases, including ozone are carbon dioxide, act like a glass building trapping the heat. With too little of these gases, the earth would get cold. For example, the Year Without a Summer in 1816 or the beginning of the Little Ice Age. With too much of these gases, the earth would get hot.Year Without a Summer Little Ice Age.

Burning Fossil Fuels When we burn coal, oil and natural gases, we are releasing more carbon dioxide into the air, and we are changing the balance of gases. The more carbon dioxide there is in the air, the more heat the atmosphere traps, and the warmer the earth stays.

Formation of Coal How does coal, for instance, happen to have carbon dioxide in it that is released when coal is burned? That question has to do with how coal was made in the earth millions of years ago. During the Triassic and Cretaceous periods (200 million years ago) there were larger plants than there are now. These first flowering plants grew to enormous size due to the warm global temps, the extremely high concentrations of carbon dioxide in the air for the previous 4.3 billion years of volcanic activity, and the abundance of more free water due to the higher temperature.

Formation of Coal Much of the land was still swampy. This means the ground was soft and wet. As the plants died, they fell into then swampy land and were covered with layers of sediment. Bacteria couldn’t make the plants decay underwater, and the plants were slowly covered with layers of more mud and sediment. After thousands of years, layers of sedimentary rock began to form over the dead plants, and slowly the water was squeezed out. The plants hardened into the hard, dark material, which we call coal.

Stored energy still There But the energy from the sun, which plants store for making food, was never released from the coal because the plants never decayed. Coal still has the energy stored in it. When coal is burned, (mixed with oxygen), the energy is released. Gases and other materials are released into the air. We call these gases pollutants. When the air is filled with pollutants, we say that there is air pollution.

Greenhouse Gases = Acid Rain Some of these gas pollutants combine with water vapor and rain to form acid. The gas molecules are combined with water vapor in the atmosphere to produce weak acids in the atmosphere. The acid falls with the rain and can damage buildings and plants. Then we have a problem with acid rain. In fact trees in some parts of the world are dying because of acid rain.

And yes our cars Car exhaust is also full of gases that change our atmosphere. As we drive more cars, build more factories, and create more pollutants, we are creating problems for ourselves. We have to keep our air clean so we can breathe it and so the plants can grow without harm.

Carbon Footprint The total set of greenhouse gas emissions produced by an organism, product, or industry. Calculating a total carbon footprint is impossible based on research on each producer and the simple fact that carbon dioxide is produced in nature.

“Carbon Credit” A permit (sold by the EPA) to allow the production and release of one tonne of greenhouse gases. Remember breathing release carbon dioxide. Sold globally to help offset the increase in greenhouse gases. Question: What happens when only a few countries follow the idea of carbon credits and choose to continue to develop without paying any money for the right to release carbon (yes even breathing)? Why are Cows BadWhy are Cows Bad