Transcript CO2 concentrations are more than 200 times greater

4.4: CLIMATE CHANGE
NEED TO KNOW:
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Carbon dioxide and water vapour are the most significant greenhouse gases.
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Other gases including methane and nitrogen oxides have less impact.
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The impact of a gas depends on its ability to absorb long wave radiation as well as in its
concentration in the atmosphere.
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The warmed Earth emits longer wavelength radiation (heat).
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Longer waved radiation is absorbed by greenhouse gases that retain the heat in the
atmosphere.
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Global temperatures and climate patterns are influenced by concentrations of greenhouse
gases.
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There is a correlation between rising atmospheric concentrations of CO2 since the start of the
industrial revolution 200 years ago and average global temperatures.
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Recent increases in atmospheric CO2 are largely due to increases in the combustion of
fossilized organic matter.
WHAT WE ARE CONCENTRATING ON
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Many factors are thought to contribute to global temperature changes
over time.
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Volcanic activity
Position of the continents
Oscillation in ocean currents
But we are focusing on: the influence of changes in the composition of the
atmosphere, notably the presence of greenhouse gases.
Visible light from sun
passes through glass
in greenhouse
Visible light is absorbed by
surface (ground)
• GHG’s have the ability to absorb and radiate IR
(heat).
• They keep the atmosphere near Earth’s surface
warm by absorbing heat from the warmed surface
and redirecting it in all directions.
Glass is semi-transparent
to infrared radiation
• Objects inside radiate their heat
into the greenhouse.
• Light is re-radiated as heat
(infrared)
Trapped IR waves (heat
waves) – warm up
greenhouse
• Glass prevents warm air
from rising through
convection to dissipate
heat.
• Results in the
temperature inside the
greenhouse being
warmer than outside.
Different gases, different impacts
Influence due to:
• Ability to absorb long-wave radiation (heat)
• Concentration of gas in atmosphere
Methane:
• Warming Potential: High
• Duration: Short – 12 yrs
• Increase: 150% since 1750
• Concentration: 1700 p.p.b.
Methane can be broken
down into other
molecules, whereas
carbon dioxide is not
very reactive.
Nitrous Oxide:
• Warming Potential: Great
• Duration: Long– 114 yrs
• Concentration: 320 p.p.b.
Carbon Dioxide:
• Warming Potential: Good
• Duration: Long– 50-200 yrs
• Increase: 40% since 1750
• Concentration: 400 p.p.m.
Water Vapor:
• Warming Potential: Fair
• Duration: 9 days
• Concentration: variable
WARMED EARTH EMITS LONGER WAVELENGTH
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Only a small amount of sunlight is converted into infrared to warm up the
surface.
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The ability of a surface to reflect light is called its albedo.
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Light colored objects, such as ice and snow, have a high albedo so very little light is
absorbed.
Dark colored objects, such as dark rocks and black sand, have a low albedo so more
light is absorbed. This light is converted to heat.
Low Albedo Effect
High absorption, less
reflective surfaces warmer atmosphere
High Albedo Effect
Low absorption is
due to reflective
surfaces – cooler
atmosphere
HOW GREENHOUSE GASES HEAT THE ATMOSPHERE
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If Earth had no atmosphere, the heat from low albedo objects would
radiate back into space, causing our night time temperatures to plunge.
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The greenhouse gases absorb and retain the IR coming from the surface,
and re-radiate the heat in ANY direction.
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Shorter days during winter and at a different angle. Not as long for the sun
to warm up the Earths surface.
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Certain gases also prevent harmful rays, like UV rays, from reaching the
Earths surface. Preventing temperatures from reaching extremely high
temperatures, like the moon (+120°C)
Effect of angle of the
sun?
Types and amounts of
gases in atmosphere?
GLOBAL CLIMATE CHANGE IN AFFECTED BY GREENHOUSE GASES
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Climate: the patterns of temperatures and precipitation
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Weather can change from hour to hours, but climate does not change typically.
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Earths’ temperature from thousand or millions of years ago can be inferred
from proxies.
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Thermometers have only been around for a few hundred years.
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15,000 years ago, it was very cold, and Earth was undergoing a glaciation (ice
age).
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Proxy data: tree rings, coral reef growth, and the presence of fossils of tempsensitive organisms, to estimate climate back then.
Due to atmosphere
being opaque to
more harmful, high
energy waves 
protective barrier
Prevents
overwarming
IR is absorbed by
atmosphere 
leads to warming
THE INDUSTRIAL REVOLUTION
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Since the 1800s, humans have produced increasing quantities of carbon
dioxide from factories, transport and other processes using fossil fuels.
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Diet also has an impact. Why do you think this?
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Give me an example. =)
Since we eat a lot of meat, the raising of cattle has increased.
What do cattle produce?  Methane with the aid of microorganisms.
The problem?
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We do not see a sign of slowing the industrial revolution.
Industrial Revolution
Muscle power  fuel
(fossilized organic matter)
power
Concentrations of GHGs naturally low 
prevents too much warming
CO2 emissions: Human transport,
deforestation, heating homes, high meat
diet, purchasing high mileage goods
Methane emissions: Cattle
Nitrous oxide emissions: catalytic
converters in cars, fertilizers, industrial
processes
Releases GHGs into atmosphere
CO2 increased 35%
THREAT TO CORAL REEFS
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Water temperature:
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Water acidity: increased CO2 in the atm, lead to increased CO2 dissolved in
the ocean, lowering the pH.
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Leading to the death of coral polyps and algae, when they die the reefs are not built up
anymore.
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Depth of the water:
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This causes a “bleaching” of the coral and the organisms that live there are
forced to find shelter elsewhere. This causes an interruption in the food
chain.
Threats to Coral Reefs
Death of coral = bleaching
Sensitive to:
• Water temperature
• Water acidity
• Depth of water
ARE HUMANS CAUSING CLIMATE CHANGE?
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Distinguish between politically
controversial and scientifically
controversial.
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P. 212 for more examples.
HOMEWORK
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Study Guide Questions 4.4
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Challenge yourself p. 207
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Light is divided into wavelengths. The colour of incoming light is determined by it's
wavelength, or the frequency of the wave. Shorter wavelengths (higher frequency)
contain more power than longer wavelengths (lower frequency) and are considered
"bluer."
Why bluer? Well, from longest wavelength to the shortest, colours are: Infrared> Red >
Orange > Yellow > Green > Blue > Purple > UV
So, you can see how a blue wavelength is shorter than a red wavelength... and thus, it
contains more power.
Now, greenhouse gasses, especially CO2 reflect longer wavelength radiation, and let
higher wavelength radiation pass. This means, that the majority of the Infrared light that
intercepts a CO2 molecule, will be scattered or reflected.
Sunlight is a mix of wavelengths, most are within the red > blue spectrum (with little UV
and IR radiation). Sunlight is allowed to pass through the greenhouse layer, and be
absorbed by the surface of the Earth.
Since all objects emit radiation (and the wavelength of this radiation is determined by the
temperature of the emitting body) the earth's surface emits radiation too. However, since
the earth is MUCH cooler than the sun, the earth mainly produces IR radiation. This, of
course, travels outwards to space, yet is reflected back towards the earth by the
greenhouse layer.
Therefore, incoming radiation is allowed to pass, yet outgoing radiation is reflected and
captured... More CO2, more reflection, higher temperatures for everyone.