The Atmosphere

1.         From space, the atmosphere looks like a thin blue blanket covering the Earth.

2.         This is what makes life on the planet possible.

3.         The blue color is caused when sunlight is scattered as it passes through the atmosphere.

4.         The atmosphere is a thin layer of gases surrounding the planet. It is composed of:

            a.         Nitrogen - 78%

            b.         Oxygen - 21%

            c.         Carbon dioxide, water vapor, and others - 1%

5.         The atmosphere makes life possible by

            a.         Providing the oxygen we breathe and the carbon dioxide plants need for photosynthesis.

            b.         Moderating the temperature. On the moon the temperature ranges from 120^oC during the day to -170^oC at night.

            c.         Absorbing harmful radiation from space. Of the solar energy reaching the Earth:

                        i.         30% is reflected by clouds and the planet’s surface

                        ii.        51% is absorbed by the surface

                        iii.       19% is absorbed by the atmosphere

The Ozone Shield

1.         The stratosphere is the layer of the atmosphere which contains ozone.

2.         Ozone is formed by the chemical reactions when UV light or lightning strikes oxygen molecules

                                    O₂ + UV ➝ O + O

                                    O + O₂ ➝ O₃

3.         The ozone layer absorbs about 99% of the harmful UV radiation coming from the sun

Effects of UV Radiation

1.         Exposure to UV radiation causes

            a.         Skin cancer

            b.         Cataracts

            c.         Damage to plants which means less food and oxygen for the planet

            d.         Legumes are especially sensitive so the nitrogen cycle suffers

            e.         Damage to algae in the ocean which form the basis of many food chains

2.         In Canada, there are over 82,000 new cases every year and the rate is increasing.

3.         As the ozone layer continues to be depleted, skin cancer rates will increase.

Ozone Depletion

1.         Naturally, ozone is made and destroyed at about the same rate so the ozone layer remains balanced.

2.         Human activity and the use of chemicals has increased the rate of destruction

3.         In the late 1970s a hole was found in the ozone layer and now holes appear over Antarctica and the Canadian arctic every (Canadian) fall. The is about the size of North America.

4.         The major problem chemical is CFC (chlorofluorocarbons) which are used in:

            a.         foam insulation

            b.         cleaners

            c.         air conditioners

            d.         refrigeration

            e.         propellants in aerosol cans

5.         Effect on the Ozone Layer

                        CFC + UV ➝ CFC + Cl

                        Cl + O₃ ➝ ClO + O₂

                        ClO + O ➝ Cl + O₂ 

6.         The Cl made here can then react with more O₃ in a chain reaction and can stay in the atmosphere for 100 years.

7.         One Cl atom can destroy 100,000 O₃ molecules

8.         Eventually, the Cl atoms fall back into the lower atmosphere where they are washed out by the rain.

The Montreal Protocol

1.         In 1987 an international agreement was signed to phase out the use of CFC by between 1996 and 2030 depending on the chemical.

2.         Several additions have been made since then and all countries in the UN have now signed the agreement. It could be the most widely supported international agreement.

3.         Replacement chemicals are being developed to replace CFC.

4.         Levels of CFC and other ozone-destroying chemicals have leveled off or decreased.

Greenhouse Effect & Global Warming

1.         Solar energy from the sun enters the atmosphere and is absorbed by Earth.

2.         The energy is converted to heat.

3.         Certain gases in the atmosphere absorb and trap the heat which keeps the planet warm.

4.         This is called the greenhouse effect.

5.         The major greenhouse gases are: water vapor, carbon dioxide, methane, CFC, and nitrogen oxide.

            a.         These gases cause the greenhouse effect.

            b.         The gases act like insulation.

            c.         Remember that the greenhouse effect is a good thing

6.         If the amounts of these gases changes, the temperature of the planet will also change.

7.         It doesn’t take a large temperature difference to make a big difference in the climate. During the last ice age, the average global temperature was 3-5^oC cooler than it is today. At that time the carbon dioxide concentration was about 60% lower than it is today.

8.         Some greenhouse gases are caused by human activity

            a.         Carbon dioxide

                        i.         makes up 55% of greenhouse gases.

                        ii.        has increased 25% in last 200 years; 10% since 1958; now increasing 0.4% per year.

                        iii.       release is mostly from fossil fuel consumption and deforestation.

            b.         Methane

                        i.         makes up 15% of greenhouse gases.

                        ii.        is bad because methane traps more heat than carbon dioxide.

                        iii.       has doubled in the last 200 years.

                        iv.       release is mostly from the decomposing of garbage and manure, fermenting rice paddies, and leaking natural gas pipes.

            c.         CFC

                        i.         makes up 25% of greenhouse gases.

                        ii.        absorb 10,000x as much heat as carbon dioxide

                        iii.       is especially harmful because it also destroys ozone

                        iv.       is still being released from old vehicles and appliances even though the Montreal protocol has controlled their production.

                        v.         release is from refrigerants, cleaners, aerosol cans, foam, solvents, some styrofoam.

            d.         Nitrogen oxides

                        i.         make up 6% of greenhouse gases.

                        ii.        are released mainly source is the burning of coal and wood.

9.         Global warming is the slow increase in the average global temperature.

10.       It is happening because human activity is adding too much of the greenhouse gases to the atmosphere.

Results of global warming

1.         Flooding

            a.         Polar ice sheets and glaciers will melt.

            b.         The water flows into the ocean causing sea level to rise and massive flooding.

            c.         Sea level could rise by 1 m by 2100. If it rises 30 cm most of coastal North America would be flooded.

            d.         If it rose 1 m, 7 out of the 10 largest cities in the world would be flooded.

            e.         Most islands in the world would be underwater.

            f.         Saltwater would rise and contaminate drinking water.

2.         Climate change could

            a.         change ocean currents which move heat from the tropics to the north and south.

            b.         change weather patterns so species cannot adapt and farmers cannot predict when to plant or harvest crops.

                        i.         Massive food shortages would result.

            c.         cause more droughts and heat waves and longer, hotter summers

            d.         Warm the ocean. As the ocean gets warmer it releases CO₂, making things even worse.

            e.         cause more forest fires which means increased CO₂ production and fewer trees to absorb CO₂.