The Global Climate System and The Greenhouse Effect SNCD0 – Climate Change

Components of our Climate System Earth’s climate system is composed of four major parts that interact with one another Atmosphere Air Hydrosphere Water Lithosphere Land Living Organisms

Atmosphere The atmosphere is a layer of gases surrounding the planet These gases reach more than 100 km above Earth’s surface After this height the gases are very diffuse, and eventually there are no gases at all (more than 600 km) Atmospheric Layers Troposphere Stratosphere Mesosphere Thermosphere Exosphere

Atmospheric Contents The atmosphere contains several gases ~78% nitrogen ~21% oxygen ~1% is made of several gases: argon, carbon dioxide, water, ozone (O3), helium, hydrogen, methane, etc... The proportions of gases are slightly different at different altitudes

Ozone Layer In the stratosphere, there is a high ozone content This ozone is very efficient at absorbing UV radiation The ozone layer protects us from UV light UV light can cause cancer and can damage living organisms Our ozone layer has sustained damage and is now much thinner than it was a century ago Areas over the Arctic and the Antarctic have very thin ozone layers This damage has been shown to be from the use of chlorofluorocarbons

Ozone Layer The blue regions show areas where the ozone layer is thin

Chlorofluorocarbons CFCs are carbon based molecules containing fluorine and chlorine bonded to the carbon CFCs have been used for several things in the past; Refrigerant Dry-cleaning solution In Spray cans In air-conditioners

Chlorofluorocarbons The free chlorine atoms react with ozone CFCs break down when reacted with UV light 𝐶𝐹𝐶𝑙 3(𝑔) The free chlorine atoms react with ozone 𝐶𝑙 (𝑔) + 𝑂 3(𝑔) → 𝐶𝑙𝑂 (𝑔) + 𝑂 2(𝑔) 𝐶𝑙𝑂 (𝑔) + 𝑂 3(𝑔) → 𝐶𝑙 (𝑔) + 𝑂 2(𝑔) The chlorine atoms get recreated and are able to go and react with more ozone! Because of this, small quantities of CFCs can continually destroy large portions of the ozone layer, and take decades to leave the atmosphere UV → 𝐶𝐹𝐶𝑙 2(𝑔) + 𝐶𝑙 (𝑔) Very Reactive!!

Montreal Protocol In 1987, governments around the world agreed to halt all use and production of CFCs for several uses Certain CFCs are still used, but significantly less The ozone layer should rebuild itself over time It is estimated to take another 50 years to get back to normal

Hydrosphere Includes all water on Earth Lakes, Oceans, water vapour, and ice Water absorbs sunlight and heats up the air around it It takes longer to heat up and cool down than land This allows it to keep the temperature of surrounding areas moderate Also adds to the precipitation in surrounding areas

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Ice Ice is very reflective 2% of the Earths water is frozen This is part of the reason why the poles are so cold 2% of the Earths water is frozen Increasing the temperature of the Earth causes more ice to melt Which worsens the problem of global warming

Lithosphere The Earth’s crust Includes solid rock, soil, and minerals On land and below oceans Land formations have a large effect on temperature Altitude As altitude increases, the air pressure and temperature drops

Mountain Effect As warm, humid air rises up it cools The cool air forms clouds, and eventually precipitation This leaves cool, dry air moving overtop of the mountain This is the reason why the prairies are so dry

Living Things Living things excrete gases into the atmosphere and change its composition Carbon dioxide, methane, oxygen Carbon dioxide and methane are “heat sinks” This means they are really good at absorbing light and trapping it in the atmosphere as heat They contribute greatly to the “greenhouse effect”

Greenhouse Effect Gases in the atmosphere absorb light from the sun They can also absorb light that is reflected from the surface of the Earth This light is absorbed, heating up the air It can be re-emitted by the gases in the atmosphere and spread throughout the atmosphere This effectively traps heat in the atmosphere for a long period before it is lost to space as infrared radiation

Greenhouse Gases Carbon dioxide ~ 0.0385% of the atmosphere Causes ~25% of the natural greenhouse effect on Earth Carbon dioxide is released into the atmosphere naturally Cellular respiration Forest fires Decomposition of previously living organisms Carbon dioxide is also released through human activities Combustion of fossil fuels and garbage

Carbon Sinks There are several things that trap carbon Carbon sinks And thus remove carbon dioxide from the atmosphere They are called carbon sinks Carbon sinks Plants – photosynthesis Living organisms – mainly composed of carbon Marine life – Shells Rocks and sediment Losing carbon sinks increases the amount of CO2 in the atmosphere

Water Vapour Water vapour accounts for ~ 66% of the greenhouse effect on Earth The amount of water vapour in the atmosphere depends on the temperature of the air Ranges from trace amounts (less than 0.1%) to 4% of air Warm air holds more water vapour than cold air This generates a feedback loop A process where the result influences the original process

Water Vapour Feedback Loop Warm air holds more water Water vapour retains heat, and heats up the air This is a positive feedback loop, where the result of the process increases the effect

Methane Methane (CH4) is about 23 times better at retaining heat than carbon dioxide But there is very little in the atmosphere The concentration of methane has steadily increased since the industrial age Pre-industry = 0.7 ppm (0.7 molecules in every million air particles) Modern day = 1.785 ppm (~ 1.8 molecule in every million air particles) It has more than doubled! Methane is produced in plant decomposition and through animal digestion

Ozone and Nitrous Oxide Ozone O3 Found in the stratosphere mainly Can be formed in the troposphere when car emissions react with UV light producing smog (ozone one part of smog) Nitrous Oxide N2O Almost 300 times as effective as carbon dioxide at retaining heat Very little in the atmosphere Produced by bacteria in soil and water and also in combustion Pre-industry = 270 ppb Modern-day = 321 ppb

How do Gases trap Infrared Radiation? When molecules absorb light it causes the atoms to vibrate back and forth Thus heating them up The more atoms, the more energy can be absorbed Vibration Videos N N N N O

Homework Climate System pg 335 #1 – 7 Greenhouse Effect pg 342 #1 – 7