Transcript Climate Change

Climate Change and Earth
Mommy, what were glaciers like?
13
Goals
• The Earth’s unique atmosphere?
• How does what we know about natural climate
change relate to what humans can do?
13
The Terrestrial Planets
World
Atmos.
Compsn.
Surface
Pressure
Ave Surface
Temp.
Winds,
Weather
Clouds,
Hazes
Mercury
He, Na, O
10-14 bar
Day: 800F
Night: -280F
none
none
Venus
96% CO2
3.5% N2
90 bars
880F
Slow winds,
acid rain
Sulfuric acid
clouds
Earth
77% N2
21% O2
H2O
1 bar
60F
Winds,
hurricanes,
rain, snow
H2O clouds,
pollution
Moon
He, Na, Ar
10-14 bar
Day:260F
Night: -280F
none
none
Mars
95% CO2
2.7% N2
0.007bar
-60F
Winds, dust
storm
H2O and
CO2 clouds,
dust
13
Why is Earth so Different?
1.
•
•
•
Why do we have oceans of water?
Why do we have so little carbon dioxide?
Why do we have so much O2 and N2?
Why do we have a UV-absorbing
stratosphere?
13
Concept Test
•
The Earth retained so much outgassed water relative to
Venus and Mars because:
a.
b.
c.
d.
e.
The Earth is closer to the Sun than Mars and so was kept warmer,
whereas Venus was too hot.
The Earth is farther from the Sun than Venus and so didn’t lose
water due to thermal escape, but Mars was too cold and it all
froze.
Both Venus and Mars lost their water due to evaporation and then
UV-dissociation (while much of Mars’ water also froze).
The Earth simply outgassed much more water than the other two.
None of the above.
13
I like Rain
1.
2.
3.
4.
Temperature just right.
Water vapor could rain.
Liquid oceans didn’t completely evaporate.
CO2 could dissolve in oceans.
– 60x CO2 dissolved in oceans as atmosphere.
– 170,000x CO2 in carbonate rocks as atmosphere.
13
N and O
• Nitrogen is the third most common
product of outgassing.
• Water in oceans.
• Carbon dioxide in oceans/rocks.
• Oxygen is from life.
– Galileo spacecraft performed experiment
to see if there was life on Earth.
• Life produces oxygen: O and O2.
• Oxygen produces ozone O3.
• Ozone absorbs UV-rays, not present on mars or Venus.
13
Goldilocks Planet
• Delicate balance: Earth
is just right.
– No oceans without
greenhouse gasses.
– Without oceans too many
greenhouse gasses.
– Without oceans no life.
– Without life, no ozone.
– No ozone, no life.
• How does Earth
maintain this balance?
13
Carbon Cycle
Tectonics are crucial!
13
Nature’s Thermostat
• Carbon Cycle has negative feedback.
• Increasing temperatures lead to feedback that
decreases temperatures, etc.
• Positive and negative feedbacks have nothing to
do with desirability of outcome.
13
Too Cool
Less Rain
Less CO2
dissolves from
oceans.
More CO2
builds up in
atmosphere
Increased
greenhouse
Heats Up.
13
Too Warm
More Rain
More CO2
dissolves from
oceans.
Less CO2
builds up in
atmosphere
Decreased
greenhouse
Cool Down.
13
Ice Ages and Cycles
13
Concept Test
•
Under what circumstances is thermal escape
likely to be important?
a.
b.
c.
d.
e.
Light gases on big planets far from the Sun
Heavy gases on big planets far from the Sun
Light gases on small planets near the Sun
Light gases on small planets far from the Sun
Equally well on any kind of gas from any kind of
planet
13
Cycles
13
Human Input
• Affecting CO2
cycle.
• Moving C from
ground to air at
increased rate.
• No increase in rate
of C from air to
ground.
13
Mars Today
13
Positive Feedback
•
•
•
•
Fossil Fuels – Increase CO2 to atmosphere.
Deforestation – decrease CO2 from atmosphere
Increase CO2 – Increase greenhouse effect
Increase temp – Melting glaciers, ice sheets, polar
caps
• Less ice – lower planetary albedo
• Lower albedo – Earth absorbs more light
• More absorption – Increasing surface
temperatures.
13
Homework #18
•
•
•
Due Friday 14-Nov:
Read Hansen and other web articles.
Do: Email me a single question about global
warming of the form “But, I heard that ….”
13