8.4 Components of Earth’s Climate System
The Atmosphere
We have looked at the different layers of the atmosphere. Now we are going to focus on the stratosphere because of the protective gas found there, ozone (O3). Ozone prevents most of the harmful energy that comes from the sun from reaching Earth.
There is more naturally occurring ozone gas in the stratosphere than in the rest of the atmosphere. In the stratosphere, ozone absorbs high-energy ultraviolet (UV) radiation from the Sun. If all UV radiation were to reach the Earth’s surface, it would cause damage to plants and cause cancers in animals (including humans).
In the 1970s, scientists found the first “hole” (thinning of the ozone) that was forming over Antarctica. In the 1990s, a similar “hole” started to form over the Arctic. Scientists have found that this ozone depletion is caused by human-made compounds called chlorofluorocarbons (CFCs), a type of halocarbon. These CFCs were found for many years in pressurized spray cans, refrigerators, and air conditioners. Because CFCs are very stable and last for a long time, CFCs gradually travel up to the stratosphere.
In 1987, governments around the world started to take major action against ozone depletion and agreed to stop the production and use of CFCs. Today, there are still other halocarbons being used. GOOD NEWS: As a result of the action taken by governments, the ozone layer is beginning to recover. Scientists predict, however, that it could take at least 50 more years for the ozone layer to return to its original thickness.
Having ozone in the stratosphere is a good thing. However, ozone found in the troposphere is not. In the troposphere, ozone has a toxic and corrosive effect. This occurs by UV from the Sun combining with exhaust from cars to produce toxic chemicals and ozone gas at ground level. In other words, this creates smog. This type of smog is referred to as photochemical smog and can be harmful to human health, damages buildings, and affects plants and other animals. Unfortunately, the ozone being released in to the troposphere does not move up into the stratosphere and offers not UV protection.
Programs such as Drive Clean have been introduced to help combat this problem, but there is still a ways to go to solve the problem.
The Hydrosphere
The hydrosphere includes liquid water, water vapour, and ice. All of the Earth’s water, both fresh and salt, forms what is called the hydrosphere. Only 2.5% of the hydrosphere contains fresh water, (not necessarily clean but at least not salty). The water is moved in and out of the atmosphere by the water cycle. The water cycle is an important part of the climate system. Water vapour enters the atmosphere by sublimation, evaporation and transpiration and leaves the atmosphere in some from of precipitation (rain, snow etc.).
The importance of clean fresh water cannot be overstated. It is essential to our survival. There are concerns about maintaining water supply. Measurements of annual rainfall indicate that the water supplies are decreasing in some parts of the world and as ground water is being used up, water will be more difficult to find. As the world’s population increases so will the demand for fresh water. In Canada’s Prairie Provinces, scientists are finding increased concentrations of minerals in the underground water in some cases are making the water undrinkable. As humans pollute the water with more harmful substances, it can eventually affect the safety of the drinking water of an entire region.
(Source: Adam-Carr, C., et al. (2010). Science Perspectives 10. Toronto: Nelson Education Ltd.)
The Lithosphere
The lithosphere is the Earth’s crust. It includes all the solid rock, soil, and minerals on land and extends under the oceans as well.
The lithosphere is a climate zone in that as air moves (clouds are blown upward) over mountains, the clouds lose their moisture as rainfall on the windward side. The leeward side of the mountain receives little rain. This process is called the rain shadow effect.
Windward sideLeeward side
(Source: Adam-Carr, C., et al. (2010). Science Perspectives 10. Toronto: Nelson Education Ltd.)
Also, as altitude increases, atmospheric pressure decreases because there is less air above pushing down. This means that as the air from lower altitudes rises to high altitudes, it expands and cools down. Therefore, at high altitudes, air is cooler than at low altitudes.
Living Things
All organisms are part of the climate system. Through photosynthesis and cellular respiration, plants and animals can change the relative amounts of gases in the atmosphere.
In photosynthesis, plants take carbon dioxide and release oxygen. In cellular respiration, plants and animals take in oxygen and release carbon dioxide. Some animals, such as cows and sheep, produce methane gas as they digest their food. Other organisms such as termites, and bacteria that live in wetlands and shallow bodies of water, also produce methane.
Certain gases, such as carbon dioxide and methane, absorb infrared radiation emitted by Earth. Therefore, if the amount of carbon dioxide or methane in the atmosphere changes, it affects how much radiation the atmosphere can aborb. This of course contributes to the Greenhouse Effect.
Questions: page 335, #1-7