6.2 & 6.3 Influences on Climate Global warming 6.2 & 6.3 Influences on Climate

The greenhouse effect

The greenhouse effect The greenhouse effect is a natural process that warms the Earth’s surface. When the sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. The absorbed energy warms the atmosphere and the surface of the Earth. This process maintains the Earth’s temperature at around 33◦C warmer than it would otherwise be, allowing life on Earth to exist. Without the greenhouse effect, the average temperature on Earth would be -18 ◦C

How does a greenhouse work? Short wavelengths from the sun have a lot of energy They are strong enough to pass through glass Once the suns radiation touches an object the short wavelength changes into a large wavelength The large wave length has less energy and cannot pass back through the glass hence keeping the greenhouse warm

Greenhouse gases in our atmosphere act like glass in the greenhouse

The greenhouse effect and the Enhanced greenhouse effect

The enhanced greenhouse effect The enhanced greenhouse effect is human induced Increased amount of greenhouse gases are released into our atmosphere from burning fossil fuels Hence more heat is being trapped in our atmosphere, warming the Earth at a faster rate

Gases in our atmosphere Nitrogen (N2) followed by oxygen (O2) are the most abundant gases in our atmosphere  They are not greenhouse gases and do not trap the suns radiation. Greenhouse gases include: carbon dioxide (CO2) water vapour (H2O) methane (CH4) nitrous oxide (N2O) ozone (O3) chlorofluorocarbons (CFCs) Greenhouse gases trap the suns heat and keep the earth warm. They do not allow the sun’s radiation (long wavelengths) to escape into space

Carbon dioxide (CO2) Human activities are altering the carbon cycle—both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests, to remove CO2 from the atmosphere. Carbon dioxide is constantly being exchanged among the atmosphere, ocean, and land surface as it is both produced and absorbed by many microorganisms, plants, and animals. However, emissions and removal of CO2 by these natural processes tend to balance. Since the Industrial Revolution began around 1750, human activities have contributed substantially to climate change by adding more CO2 and other heat-trapping gases to the atmosphere.

Main Sources of CO2 emissions Many industrial processes emit CO2 through fossil fuel combustion. Several processes also produce CO2 emissions through chemical reactions that do not involve combustion, for example, the production and consumption of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals Electricity is a significant source of energy and is used to power homes, business, and industry. The combustion of fossil fuels to generate electricity is the largest single source of CO2 emissions The combustion of fossil fuels such as gasoline and diesel to transport people and goods is the second largest source of CO2 emissions

Methane (CH4) Methane traps 20 times more heat than CO2 one tonne of methane emitted to the atmosphere (for example from livestock) is equivalent to 34 tonnes of carbon dioxide emissions Formed from the break down of organic matter Found in stomachs of cows and sheep, rice paddies, garbage tips and coal mines. Permafrost formed near the poles of the Earth. Methane bubbles trapped. The Arctic stores billions of tonnes of methane and are melting, releasing this methane!!!

Nitrous oxide (N2O) Nitrous oxide is capable of trapping 300 times more heat than CO2 One tonne of nitrous oxide is equivalent to 298 tonnes of carbon dioxide. Produced in car exhausts, industrial processes, burning forests and the use of fertilisers. Nitrous oxide has an atmospheric lifetime of 110 years. The process that removes nitrous oxide from the atmosphere also depletes ozone. So nitrous oxide is not only a greenhouse gas, but also an ozone destroyer.

summary Carbon Dioxide Methane Nitrous Oxide Most abundant greenhouse gas in the earths atmosphere Carbon Dioxide Traps 20 times more heat than CO2 1 tonne of CH4 = 34 tonnes of CO2 Methane Traps 300 times more heat than CO2 1 tonne of N2O = 298 tonnes of CO2 Nitrous Oxide

Ozone (O3) Ozone (O3) occurs naturally in the atmosphere, mostly in the stratosphere. It is vitally important to life on Earth because it absorbs ultraviolet (UV) radiation emitted by the sun. Too much exposure to UV radiation is a cause of skin cancer and eye disease

Ozone depleting substances – CFC’s and halogens Ozone depleting substances are those substances which thin out the ozone layer: used in refrigerators air-conditioners fire extinguishers in dry cleaning as solvents for cleaning electronic equipment agricultural fumigants

Depletion of Ozone Layer The suns UV radiation breaks the chlorine bond in the CFC molecule Chlorine reacts with oxygen from the ozone molecules The chlorine atom than detaches from the oxygen to find more ozone to react with Each radical can decompose many thousands of molecules of ozone.

Hole in the Ozone layer

Variables - recap Independent Variable The factor you change in your set up Dependent Variable The factor you are measuring Controlled Variable The factors you keep the same

The greenhouse effect practical Aim: To investigate the greenhouse effect Materials: 2 thermometers, 3 microscope slides, sticky tape, 3 triangular pieces of cardboard block of wood, lamp Method: Create a hole in one end of the cardboard and pass a thermometer through it Use the three microscope slides to make a greenhouse (do not use too much sticky-tape) Place the greenhouse outside in a sunny area or under a lamp Place the second thermometer next to the greenhouse Record the temperature inside the greenhouse and outside every 2 minutes for 14 minutes

The greenhouse effect practical Results: Time (minutes) Temperature (C°) Greenhouse Air   2    4 6 8 10 12 14 Record your results into your table Draw a line graph to represent your results

The greenhouse effect practical Discussion: Identify the controls, independent and dependant variables in the experiment. Compare the temperature patterns inside and outside the greenhouse. Identify what the glass slides represent in this greenhouse model. Compare the greenhouse effect and the enhanced greenhouse effect. What are the gases that contribute to greenhouse gases? Discuss the effects of an increased amount of greenhouse gases. Suggest the effects of an absence of greenhouse gases in our atmosphere. What part of the experiment represented this? Conclusion: Refer back to your aim