Class Notes (834,704)
Canada (508,682)
ENVIRSC 1A03 (130)
Dr (1)
Lecture

Greenhosue effect notes.docx

7 Pages
108 Views
Unlock Document

Department
Environmental Science
Course
ENVIRSC 1A03
Professor
Dr
Semester
Winter

Description
Greenhosue effect  If fossil fuels burn completely, the end products are carbon dioxide and water. Today the carbon dioxide is a waste product, one that goes into the air — adding to global warming; or the oceans — acidifying them; or underground — with as yet unknown consequences.  The global system that regulates the earths temperature is very complex, but many scientists believe that the increase in temperature is caused by an increase of certain gases in the atmosphere that trap energy that would otherwise escape into space. These gases, called greenhouse gases, include carbon dioxide, methane, nitrous oxide, chlorofluorocarbons (CFCs), and the ozone in the lower atmosphere.  There is a natural balance between the energy coming into our atmosphere from the sun and the energy escaping from the earth back into space. A simplified description of this energy balance depicts the energy that comes in as relatively short wavelength UV radiation and the energy that goes out as longer wavelength IR radiation. Much of the high-energy radiant energy from the sun is absorbed in the upper atmosphere, but some of the ultraviolet radiant energy passes through. The lower-energy end of the ultraviolet portion of the light spectrum reaches the earths surface and warms it. As the earth cools down again, it releases energy as infrared radiation figure 1  The greenhouse gases absorb some of the IR energy released as the earth cools. When they re-emit it, some of the energy is sent back toward the earth, rather than out into space. If the greenhouse gases were not there to trap some of this IR energy, the earth would be about 33 C (60 F) colder than it is. The gases are called greenhouse gases because their effect is like the glass panels in a greenhouse. Radiant energy passes through the panels to enter the greenhouse, but the panels slow down the passage of heat energy leaving the greenhouse. On a cold day, more energy comes into the greenhouse than goes out, so the air in the greenhouse is warmed. Even though the actual mechanism is very different, the net effect of the greenhouse gases in the atmosphere is similar: they too tend to trap energy that would otherwise escape, keeping the temperature of the system higher than it would be otherwise.  Increases in the levels of the greenhouse gases trap too much of the escaping energy. It is this situation that scientists believe is causing global warming.  Ways to reduce greenhouse gasses in atmosphere  A second approach is to continue generating carbon dioxide, but to trap it before it is released into the air. One suggestion is to liquefy the C2 produced at fossil fuel power plants and pump the liquid deep into the ocean. It would remain in the ocean water and not return to the surface for a long time. In the interim, scientists would be developing alternatives to fossil fuels.  A third general approach to lowering the carbon dioxide levels in the atmosphere would be to remove the CO a2ter it has been released into the air. Because CO 2ixes throughout the atmosphere, this is generally considered to be too big a task, but at least one suggestion for removing it has been considered seriously: alter the chemistry of the earths oceans such that they will absorb the e2cess CO .  What is Greenhouse effect: The effect produced as greenhouse gases allow incoming solar radiation to pass through the Earth's atmosphere, but prevent most of the outgoing infrared radiation from the surface and lower atmosphere from escaping into outer space. This process occurs naturally and has kept the Earth's temperature about 60 degrees Fahrenheit warmer than it would otherwise be. Current life on Earth could not be sustained without the natural greenhouse effect. The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder. Because of how they warm our world, these gases are referred to as greenhouse gases. The Earth’s atmosphere is all around us. It is the air that we breathe. Greenhouse gases in the atmosphere behave much like the glass panes in a greenhouse. Sunlight enters the Earth's atmosphere, passing through the blanket of greenhouse gases. As it reaches the Earth's surface, land, water, and biosphere absorb the sunlight’s energy. Once absorbed, this energy is sent back into the atmosphere. Some of the energy passes back into space, but much of it remains trapped in the atmosphere by the greenhouse gases, causing our world to heat up.  Greenhouse Gases : Any gas that absorbs infra-red radiation in the atmosphere.  Greenhouse gases include water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), halogenated fluorocarbons (HCFCs) , ozone (O3), perfluorinated carbons (PFCs), and hydrofluorocarbons (HFCs).  In a greenhouse, energy from the sun passes through the glass as rays of light. This energy is absorbed by the plants, soil and other objects in the greenhouse. Much of this absorbed energy is converted to heat, which warms the greenhouse. The glass helps keep the greenhouse warm by trapping this heat.  About 31 percent of the incoming radiation from the sun is reflected directly back to space by the earth's atmosphere and surface (particularly by snow and ice), and another 20 percent is absorbed by the atmosphere. The rest of the incoming radiation is absorbed by the earth's oceans and land, where it is converted into heat, warming the surface of the earth and the air above it. Particular gases in the atmosphere act like the glass of a greenhouse, preventing the heat from escaping.  These greenhouse gases absorb heat and radiate some of it back to the earth's surface, causing surface temperatures to be higher than they would otherwise be. The most important naturally occurring greenhouse gas is water vapour and it is the largest contributor to the natural greenhouse effect. However, other gases, although they occur in much smaller quantities, also play a substantial and growing role in the greenhouse effect. These include carbon dioxide, methane, and nitrous oxide.  Without this natural greenhouse effect, the earth would be much colder than it is now - about 33 degrees Celsius colder - making the average temperature on the planet a freezing -18 degrees Celsius rather than the balmy 15 degrees Celsius it is. The warmth of our climate is crucial because on earth and in the atmosphere, water can exist in all three of its phases - frozen as snow or ice, liquid as water, and gaseous as water vapour. The cycling of water from one phase to another is critical to sustaining life since it is this cycling of water through the land-ocean-atmosphere system that replenishes the water available to life on earth. The water cycle is also an important part of what drives our weather and the climate system generally.  Interesting facts:  They claim it would violate the 2nd Law of Thermodynamics, which basically states that energy must flow from where there is more to where there is less. The reason for this apparent violation is that the existence of greenhouse gases in the COLDER layers of the atmosphere make the surface WARMER, which would suggest energy flow from colder to warmer, which would seem to violate the 2nd Law. But the greenhouse effect is kind of like adding a lid to cover a pot of water on the stove...even though the lid is colder than the water, its presence actually makes the water warmer. It's the TOTAL (net) flow of energy which must be from warmer to colder, which is indeed the case in both the greenhouse effect, and adding a lid to the pot of water on the stove.  What is the greenhouse effect? There are two meanings o
More Less

Related notes for ENVIRSC 1A03

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit