Post on 28-Mar-2015
The Global Climate System and The
Greenhouse Effect
SNCD0 – Climate Change
Components of our Climate SystemEarth’s climate system is composed of four major
parts that interact with one anotherAtmosphere
AirHydrosphere
WaterLithosphere
LandLiving Organisms
AtmosphereThe atmosphere is a layer of gases
surrounding the planetThese gases reach more than 100 km above
Earth’s surfaceAfter this height the gases are very diffuse,
and eventually there are no gases at all (more than 600 km)
Atmospheric LayersTroposphereStratosphereMesosphereThermosphereExosphere
Atmospheric ContentsThe 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 LayerIn the stratosphere, there is a high ozone content
This ozone is very efficient at absorbing UV radiationThe ozone layer protects us from UV lightUV 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 agoAreas over the Arctic and the Antarctic have very thin
ozone layers
This damage has been shown to be from the use of chlorofluorocarbons
Ozone LayerThe blue regions show areas where the ozone layer is
thin
ChlorofluorocarbonsCFCs are carbon based molecules containing fluorine
and chlorine bonded to the carbon
CFCs have been used for several things in the past;RefrigerantDry-cleaning solutionIn Spray cansIn air-conditioners
C F
Cl
Cl
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ChlorofluorocarbonsCFCs break down when reacted with UV light
The free chlorine atoms react with ozone
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 →𝐶𝐹𝐶𝑙2(𝑔)+𝐶𝑙(𝑔)
Very Reactive!!
Montreal ProtocolIn 1987, governments around the world agreed to
halt all use and production of CFCs for several usesCertain CFCs are still used, but significantly less
The ozone layer should rebuild itself over timeIt is estimated to take another 50 years to get back to
normal
HydrosphereIncludes all water on Earth
Lakes, Oceans, water vapour, and ice
Water absorbs sunlight and heats up the air around itIt takes longer to heat up and cool down than landThis allows it to keep the temperature of surrounding
areas moderateAlso adds to the precipitation in surrounding areas
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IceIce is very reflective
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 meltWhich worsens the problem of global warming
LithosphereThe Earth’s crust
Includes solid rock, soil, and mineralsOn land and below oceans
Land formations have a large effect on temperature
AltitudeAs altitude increases, the air pressure and temperature
drops
Mountain EffectAs 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 ThingsLiving things excrete gases into the atmosphere and
change its compositionCarbon 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 heatThey contribute greatly to the “greenhouse effect”
Greenhouse EffectGases in the atmosphere absorb light from the sun
They can also absorb light that is reflected from the surface of the EarthThis light is absorbed, heating up the airIt 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 GasesCarbon dioxide
~ 0.0385% of the atmosphereCauses ~25% of the natural greenhouse effect on Earth
Carbon dioxide is released into the atmosphere naturallyCellular respirationForest firesDecomposition of previously living organisms
Carbon dioxide is also released through human activitiesCombustion of fossil fuels and garbage
Carbon SinksThere are several things that trap carbon
And thus remove carbon dioxide from the atmosphereThey are called carbon sinks
Carbon sinksPlants – photosynthesisLiving organisms – mainly composed of carbonMarine life – Shells Rocks and sediment
Losing carbon sinks increases the amount of CO2 in the atmosphere
Water VapourWater vapour accounts for ~ 66% of the greenhouse
effect on Earth
The amount of water vapour in the atmosphere depends on the temperature of the airRanges from trace amounts (less than 0.1%) to 4% of air
Warm air holds more water vapour than cold air
This generates a feedback loopA 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
MethaneMethane (CH4) is about 23 times better at retaining
heat than carbon dioxideBut there is very little in the atmosphere
The concentration of methane has steadily increased since the industrial agePre-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 OxideOzone O3
Found in the stratosphere mainlyCan be formed in the troposphere when car emissions
react with UV light producing smog (ozone one part of smog)
Nitrous Oxide N2OAlmost 300 times as effective as carbon dioxide at
retaining heatVery little in the atmosphereProduced by bacteria in soil and water and also in
combustionPre-industry = 270 ppbModern-day = 321 ppb
How do Gases trap Infrared Radiation?When molecules absorb light it causes the atoms to
vibrate back and forthThus heating them up
The more atoms, the more energy can be absorbed
Vibration Videos
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Homework
Climate System pg 335 #1 – 7
Greenhouse Effect pg 342 #1 – 7