Goal: To understand the climate of the earth.

1
Goal To understand the climate of the earth.

• Objectives
• To understand the Greenhouse effect.
• To compare Greenhouse effect vs the climate.
• To learn about Carbon cycle.
• To explore Global warming
• To examine the possible Solutions if any

2
Which of the following most accurately describes
the greenhouse effect?

• A) Another term for global warming.
• B) The process by which heat is trapped.
• C) Reflection of sunlight by the atmosphere.
• D) Sunlight which is reflected off of the earth
  reflected by the atmosphere.
• E) Sunlight being absorbed by the atmosphere.
• F) Sunlight is absorbed by the earth. Earth
  emits IR light which is absorbed by the
  atmosphere then re-emitted in the IR.
• G) Sunlight is absorbed by the earth. Earth
  emits IR light which is reflected by the
  atmosphere.
• H) all of the above
• I) None of the above

3
The greenhouse effect

• The greenhouse effect starts with the sun.
• Some of the suns light gets reflected by our
  atmosphere. However, that actually COOLS the
  planet, and is therefore a separate topic.
• 20 of the suns light gets absorbed by the
  atmosphere, 30 is reflected by the surface out
  to space, and 50 goes elsewhere, but where?
• A) absorbed by the earth
• B) trapped by the earth
• C) trapped by the atmosphere
• D) none of the above

4
Greenhouse effect, part 2

• What does the earth do with this energy?
• The earth emits this energy like a blackbody.
• Since the earth is 288 K on average, it emits in
  the infrared.

5
Greenhouse Effect part 3

• Most of the IR energy emitted by the earth
  (80-90) is absorbed by the atmosphere.
• The absorbers are gasses called Greenhouse
  gasses.
• These are gasses that absorb infrared heat, but
  most let optical light pass through.
• Note it is NOT trapped, and it is not
  reflected.
• What is the largest contributing greenhouse gas?
• A) Carbon Dioxide
• B) Nitrogen
• C) Oxygen
• D) Water Vapor

6
Greenhouse effect part 4

• Finally, the atmosphere emits its own energy.
  Half of this goes up, and half goes down.
• The half going up mostly escapes to space.
• The half going down is absorbed by the earth.
• So, while most scientists oversimplify this
  picture by calling the atmosphere a blanket,
  really it is a heat lamp.

7
http//earthobservatory.nasa.gov/Features/EnergyBa
lance/printall.php
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Summer of Greenhouse effect

• So, the Greenhouse effect acts as a heat lamp
  which is powered by the earth thus heating the
  earth.
• The greenhouse effect warms the earth by 60 F.
• Is the greenhouse effect a good thing or bad
  thing?
• A) good
• B) bad

9
Greenhouse Effect implications

• Without the greenhouse effect, the earth would be
  FROZEN! So, in moderation, the greenhouse effect
  is a good thing.
• However, over long time spans (thousands of
  years), levels of greenhouse gasses such as
  Carbon Dioxide change.
• This changes the climate!

10
CO2 over past 200,000 years vs climate

• As you can see, the climate and the CO2 levels
  are almost and exact match.
• Please note the low points every 26,000 years,
  which represents the ice ages.
• Please see how the temperature levels were
  dropping slowly over the last 10k years.

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Geologic Carbon Dioxide levels
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Why does the earths temperature rise and fall?

• There is usually an energy balance.
• The energy absorbed energy emitted.
• Totally energy stays the same.
• HOWEVER, if more energy is absorbed for some
  reason, then there is no longer in balance.
• So, the earth gains energy!
• This means the earth gets warmer.
• As the earth gets warmer, it emits more energy.
• At some point the energy absorbed energy
  emitted, and there is a new balance.
• So, gt greenhouse effect higher temperature (if
  everything else remains equal).

13
What changes the Carbon Dioxide levels?

• What part of the Carbon Cycle absorbs (net) the
  most Carbon Dioxide per year?
• A) plants
• B) animals
• C) atmosphere
• D) ocean

14
Carbon Cycle diagram courtesy of wikipedia
15

• Ledley et all 1999
• Oops, CO2 levels are rising FAST!
• 2 ppm per year!

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How do we know?
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What are the possible results?

• Melting of Ice caps!
• Greenland and Antarctica could add 40 m to the
  ocean levels!
• That would flood most cities in the world!
• Indianapolis elevation 240 m
• Warming of global temperatures by up to 5C (9 F)
  over next 50-100 years
• More severe weather.
• Shift in climate zones, and shifts in climate.

18
Uncertainties

• None of the models agree on the specifics.
• There is a lot of uncertainty on how clouds play
  a role in the equation.
• Also, other chemicals BLOCK sunlight, this
  dampers the temperature increases in the short
  term.
• However, they all show increased temperatures
  worldwide.

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Temporary relief!

• It seems that the Antarctic ice mass is
  INCREASING at least on the east side
• This could keep ocean levels steady for the next
  few decades but it is not currently well
  understood
• When will this trend reverse?

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Possible Effects?

• It is uncertain how species will react. Some
  will probably not survive.
• Most probably will though, although it will
  change ours lives greatly as we basically have to
  move all our cities inland as ocean levels rise.
• Also, the change in climates will move all of the
  best places to farm.
• This will hurt India and China.
• Also, this will drop the sustainable human
  potential population from 8 billion down to
  possibly 2 billion.

21
http//www.printableworldmap.org/
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Solutions?

• Move cities inland evacuate Florida and
  Louisiana.
• Move farmlands to the areas that will be the new
  farm zones.
• Develop new farming technologies to increase crop
  yields or be able to grow crops using less water.
• Switch to energy sources that dont produce
  greenhouse gasses (such as solar and wind), or
  ones that only put back what they take out such
  as biomass and ethanol.
• No matter what we do, it will take a good amount
  of effort, time, and lots and lots of

23
How much land do you think it would take to power
the entire US by wind and solar power?
                                                                                                                
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Why dont we?

• Cost would be in the tens of trillions of
  dollars!
• Would require a complete change of our system
  including to electric/fuel cell powered cars and
  hydrogen powered jets.
• Tradition

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Structure of the Earths atmosphere
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Conclusion

• The greenhouse effect is the atmosphere absorbing
  the infrared energy the earth emits, then
  reemitting it back.
• The greenhouse effect is useful, in moderation.
• The magnitude of greenhouse effect changes with
  time naturally although not as quickly as we
  have changed it.
• This could cause problems for us if we care about
  things such as coastal cities and being able to
  keep our farms where they are.
• If we are okay with moving our cities and farms,
  then there is not much of a problem.