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Evolution of the Atmosphere
Review of last lecture
• The modern climatology (meteorology) was born in the
1940s (a very young science!), but has been growing
very fast! Now we have a global observational network
with many satellites, ships, radars and surface
stations, as well as very comprehensive prediction
models running on the world’s fastest supercomputers.
• The current status of weather and climate predictions:
(1) weather prediction good to 10 days, (2) tropical
cyclone prediction good in track but not in intensity,
(3) climate prediction good to two seasons, (4) climate
change projections have a 3-fold difference in
magnitude.
• The main reasons of the difficulties in weather and
climate predictions: (1) Teleconnection problem, (2)
Feedback problem, and (3) Subgrid-scale problem.
Some basic concepts
• Units of measurement
• Scientific notation
Standard units of measurement
SI (System International)
Quantity
Length
Mass
Time
Temperature
Density
Speed
Force
Pressure
Energy
Power
Name
meter
kilogram
second
Kelvin
kilogram
per cubic meter
meter per
second
newton
pascal
joule
watt
Units
m
kg
s
K
kg/m3
Symbol
m
kg
s
K
kg/m3
m/s
m/s
m.kg/s2
N/m2
N.m
J/s
N
Pa
J
W
Scientific Notation
nano
micro
milli
centi
deci
deka
hecto
kilo
mega
giga
…
yotta
one-billionth
one-millionth
one-thousandth
one-hundredth
one-tenth
ten
one hundred
one thousand
one million
one billion
10-9
10-6
10-3
10-2
10-1
101
102
103
106
109
1024
0.000000001
0.000001
0.001
0.01
0.1
10
100
1000
1000000
1000000000
The Universe
Hubble (2012) view –
each light speck is a
galaxy – some of these
are as old as 13.2
billion years – the
Universe is estimated
to contain 200 billion
galaxies.
• The Universe is made up of voids and filaments, that can be broken
down into superclusters, clusters, galaxy groups, galaxies, and
subsequently into stars and their constituents (e.g. our Solar System).
Our Milky Way galaxy
Our solar system is in the Orion arm, and we are about 25,000
light years (2.5 X 1017 miles) from the very center of the Galaxy.
Life cycle of the Sun and Earth
The earth will be inhabitable
for another 0.5 billion years,
if we protect it well enough.
After another 1 billion years,
all oceans and rivers will
have completely disappeared.
The mean global temperature
will reach 160 F.
Formation of the Earth
• 4.6 billion years ago, as part of the birth of the solar system
Earth’s first Atmosphere
• Topic of much debate
• Probably H and He, no oxygen
• No oceans
• No magnetic field to deflect
solar winds and cosmic rays
Differentiation of the Earth
• Cooled enough to form
crust, heavily populated
with volcanoes
• Formation of magnetic
field that deflects the
solar wind and cosmic
rays
• Increasing volcano
activity, releasing gases
into atmosphere
Earth’s Second Atmosphere
• Around 4 - 3.8 billion years ago
• Composition similar to gases
released from volcanoes (CO2,
water vapor, nitrogen)
• Large concentration of gases in
the atmosphere (100 times of
today’s)
• Greenhouse effect keeps the
earth from freezing
Earth Begins to Cool
• Water condenses to form
oceans
• Carbon Dioxide dissolves
into oceans eventually
forming carbonates
• Nitrogen becomes major
component of the
atmosphere
Life and oxygen
• Around 3.5 billion years ago
cyanobateria were known to be
carrying out photosynthesis
CO2 + H2O + sunlight = organic
compounds + O2
• Eukaryotes capable of respiration
emerge around 2.5 billion years ago.
Photosynthesis becomes more
efficient
• Increased oxygen concentration,
around 1% of atmosphere, produced
the ozone layer
• Life emerges outside of the oceans.
Formation of terrestrial plants lead
to atmospheric saturation of oxygen
Earth’s third atmosphere (current)
• Reached around 400
million years ago
• Consisting of gases,
water droplets
(clouds/precipitation)
and aerosols
Formation of the continents and
ocean basins
• 225 million years ago from Pangaea (the super continent)
Permanent gases and variable gases
• Residence time: The amount of
time a gas is in the atmosphere
• The permanent gases: gases
having long residence times
(N2=42,000,000 y, O2=5,000 y),
99.999% of total atmosphere
mass
• The variable gases: Gases
generally having shorter
residence times (H2O=10 days,
CO2=150 y).
Importance of the Variable Gases
• CO2 and water vapor are the
major greenhouse gases
• Water can exist in all three
phases (vapor, liquid, ice) on
Earth. The released latent heat
during phase changes of water
drives global atmospheric
circulation and many weather
systems (e.g. hurricanes).
• O3 protects us against harmful
ultraviolet radiation
Montreal Protocol
to ban freon
Earth’s climate history
Temperature variation during the past 2.4
billion years - The ice ages
• An ice age is a long interval of time (106 to 107 of years) when
global temperatures are relatively cold and large areas of the Earth
are covered by continental ice sheets and alpine glaciers.
• At least 5 ice ages have occurred throughout Earth’s history.
Currently, we are living in an ice age!
• Typically develop slowly, but end more abruptly.
Variations within an ice age:
– Abrupt climate change and tipping point
Some examples of tipping points
Variations within an ice age:
The 100,000-year glacial cycle
Possible causes:
•Change in atmospheric composition (e.g. CO2, CH4)
•Change in earth’s orbit (e.g. Milankovitch cycles)
•Motion of tectonic plates
•Change in solar output
The little ice age (1350AD-1850AD)
Evolution of the atmosphere
– The standard units of measurements (SI)
– Earth’s three atmospheres:
1st: 4.6 billion years ago, H, He
Transition: formation of magnetic field, volcano activities
2nd: 4 billion years ago, CO2, H2O, N2
Transition: emergence of life, formation of ocean
3rd: 400 million years ago, O2
Important event: formation of seven continents
– What is the residence time? What is the difference between
the permanent and variable gases? Name 3 of each. What are
the most and second most abundant gases?
– Given that variable gases are so rare, why are they considered
at all? How are CO2 and O3 changing?
– Earth’s climate history: ice ages (at least 5 have occurred so far.
We’re in an ice age!), 100,000-year cycle, little ice age (1350-1850AD)
Works cited
• http://ase.tufts.edu/cosmos/view_picture.asp?id=850
• http://www.waterconservation.co.za/2010/10/26/theres
-never-been-a-better-time-to-start-harvestingrainwater/