Transcript Chapter 15

Chapter 15
Air, Weather
& Climate
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Outline
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The Atmosphere and Climate
 Convection Currents
 Greenhouse Effect
Weather
 Winds
 Frontal Systems
 Cyclonic Storms
Climate
 ENSO
 Climate Change
 Kyoto Protocol
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The Atmosphere and Climate
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Atmosphere – the air surrounding the earth which
extends upwards 500km (300 miles)
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Weather - daily temperature and moisture
conditions in a specific place
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Climate - a description of the long-term weather
pattern in a particular area (30+ years)
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Earth’s First Atmosphere
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Composition - Probably H2, He (common in space)
These gases are relatively rare on Earth and were
probably lost to space early in Earth's history due to:
 Earth's gravity was not strong enough to hold
lighter gases
 Earth still did not have a differentiated core (solid
inner/liquid outer core) which created Earth's
magnetic field (magnetosphere = Van Allen Belt)
which deflects solar winds.
Once the core differentiated the heavier gases could
be retained
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Earth’s Second Atmosphere
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Produced by volcanic out gassing.
Gases produced were probably similar to those
created by modern volcanoes (H2O, CO2, SO2,
CO, S2, Cl2, N2, H2) and NH3 (ammonia) and
CH4 (methane)
No free O2 at this time (not part of volcanic gases).
Ocean Formation - As the Earth cooled, H2O
produced by out gassing could exist as liquid in the
Early Achaean, allowing oceans to form.
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The Atmosphere Today
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Atmospheric Aerosols
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AEROSOLS: Aerosols are minute particles or
droplets suspended in the atmosphere which can
affect climate.
 Reflect & scatter sunlight
 Cause chemical reactions in the atmosphere
- ie: ozone depletion
 3 sources of Aerosols
- 1. Volcanic activity (dust, SO2)
- 2. Desert dust
- 3. Anthropogenic (burning forests/fuels)
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Selected Properties of Earth’s Atmosphere
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Layers of the Atmosphere
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“Spheres” are layers
of air
“Pauses” mark
boundaries between
two “spheres”
Due to temperature
variations the air in
the layers do not mix
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Troposphere
Densest layer (nearest
the earth)
• Contains 75-80% of all
gas molecules
• All weather occurs
here
• Convection currents
circulate the air (mix
heat & moisture)
• Highest air pressure
(sea level = 14.7 lbs/in2)
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Stratosphere – “Global Sunscreen”
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Contains majority of
atmospheric ozone
Ozone is produced
when O2 interacts with
UV radiation.
O2 + UV  O3
Ozone blocks UV rays
allowing life to survive
Little mixing of air so
aerosols stay many
years
Commercial jets fly
here – avoid turbulence11
Mesosphere
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Temperatures drop
rapidly in this layer
Coldest temps on
earth -90°C (-130° F)
Least studied due to
its position
(above weather
balloons & aircraft
and below orbiting
spacecraft)
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Thermosphere
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Extremely hot from
suns radiation
Contains highly
ionized (charged) gas
molecules
When solar radiation
hits these ionized
molecules they glow –
“Aurora borealis”
concentrated above
Earth’s magnetic pole
https://vimeo.com/16917950
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Sun’s Energy
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INSOLATION (incoming solar radiation)
 About 25% is reflected by clouds and the
atmosphere.
 Another 25% is absorbed by carbon dioxide, water
vapor, ozone, aerosols and a few other gases.
 About 50% reaches the earth’s surface.
 Insolation is greatest at equator, decreasing
toward higher latitudes (the poles)
 Insolation is short wave radiation (light) which
becomes long-wave (infrared/heat) after
absorption by surface/clouds/gases.
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Energy Balance
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Effects of Albedo (Reflectivity)
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Surfaces that reflect energy have a high albedo.
 Fresh clean snow
80-85%
 Dense clouds
70-90%
 White sand
20-30%
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Surfaces that absorb energy have low albedo.
 Forests
5-10%
 Water (sun overhead)
5%
 Dark soil/Pavement
3%
Absorbed energy causes water to evaporate and
allows for photosynthesis.
Absorbed energy is released as heat.
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Energy and the Greenhouse Effect
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Most insolation reaching the Earth is high energy
light (a.k.a. near infrared) of short wavelength.
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Energy reradiated (reemitted) by earth is heat
(a.k.a. far infrared) of long wavelength.
- Longer wavelengths are absorbed in the
lower atmosphere, trapping heat close to the
earth’s surface.
- GREENHOUSE EFFECT: The atmosphere
transmits sunlight while trapping heat.
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GREENHOUSE EFFECT
Earth’s average temp. today is 58.30F.
Without the greenhouse effect the temp.
would be 330F cooler!!! (250F)
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Contributing Factors to the Greenhouse Effect
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Gases in the atmosphere, especially carbon
dioxide, methane and water vapor, are the
substances that retain heat.
Burning fossil fuels releases carbon dioxide and
particulate aerosols.
Cows, melting permafrost, landfills and
production of fuels releases methane
Increased heat increases evaporation of water
Deforestation destroys carbon sinks (absorbers).
And, MUCH MORE TO COME .....
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Arctic Sea Ice
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Positive feedback loop - poles covered with ice
reflect solar radiation back into space. Now that
ice is melting, open water is absorbing more
heat, which in turn is melting more ice, leading to
more warming.
(there is no balance – only forward momentum)
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Arctic Sea Ice Extent
http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003893/seaIceArea_2011_Wdate.mp4
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WEATHER:
short term physical
conditions of the
atmosphere in a
specific place
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Uneven Heating of the Earth
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Insolation is not equal around the earth.
Much of solar energy absorbed by the Earth is
used to evaporate water.
 When water evaporates it absorbs energy.
(580 calories per gram)
 Energy stored in water vapor is LATENT HEAT.
 When water vapor (gas) cools & condenses
(turns to liquid), heat energy is released.
 Heat and water move from warmer areas near
the equator towards cooler areas at poles. Heat
redistribution prevents extreme temperature
fluctuation.
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Uneven Heating of the Earth
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3 causes of unequal heating:
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1. insolation strikes earth at different angles
2. insolation travels through more/less
atmosphere where it is absorbed
3. effect of albedo on different surfaces
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Earth’s Tilt
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Earth’s tilt causes seasonal variations
Tropics receive more direct insolation than
poles
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Convection Currents
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Releasing latent heat causes air to rise, cool,
and lose more water vapor as precipitation.
Warm air close to equator vs. cold air at poles
also produces pressure differences that cause
weather.
 Air near surface warms and becomes less
dense than the air above it; rises above cool
air creating vertical convection currents.
- Low pressure - air is rising
- High pressure - air is sinking
 Pressure differences cause winds.
Winds move from High to Low
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Circulation Patterns
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4 PROPERTIES OF AIR
1. DENSITY: mass of all molecules in a given volume
less dense air rises, more dense air sinks
2. CAPACITY TO HOLD WATER VAPOR:
warm air holds more water vapor than cold air
SATURATION POINT: the maximum amount of
water vapor air can hold at a given temp.
3. LATENT HEAT RELEASE: Whenever water vapor
condenses, the air becomes warmer and rises
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4 PROPERTIES OF AIR
4. EFFECTS OF CHANGE IN PRESSURE:
ADIABATIC COOLING: the cooling effect of
reduced pressure on air as it rises in the
atmosphere and expands
ADIABATIC HEATING: the heating effect of
increased pressure on air as it sinks toward
the surface of Earth and decreases in volume
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CONVECTION CURRENTS
1. Insolation reaches Earth’s surface
2. Energy is absorbed and the surface warms
3. Surrounding air warms via conduction
4. Warmer air rises carrying heat upward
5. As air rises, it cools and becomes denser
6. This “new” air displaces other air & spreads
7. Cooled air begins to sink
8. Cool/dry air returns to the surface & warms
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Convection Currents
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Weather Happens
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WEATHER – short-term, physical conditions in the
atmosphere (humidity, temperature, air pressure,
wind and precipitation)
 RAIN/PRECIPITATION:
- Air cools as it rises, and water condenses as
air cools.
- Cooling occurs because pressure decreases
as air rises.
- CONDENSATION NUCLEI
(tiny particles/aerosols) must also be present
to have precipitation.
Water vapor collects/condenses on them!
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Weather Happens
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WIND:
- Movement of large air masses
- Air moves from areas of high pressure to
areas of low pressure
- Winds are deflected by the Coriolis effec
HUMIDITY:
- The amount of water vapor in the air
- Relative humidity, expressed as a percent,
measures the current absolute humidity
relative to the maximum for that temperature.
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CORIOLIS EFFECT
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Surface air flows do not move straight north and
south, but are deflected due to the CORIOLIS
EFFECT.
The curving pattern results from the rotation of
earth in an eastward direction as winds move
above it.
Winds are deflected
because earth’s rotation
at the equator is faster
than its rotation at the poles.
Therefore – air at the
equator is moving faster
than air at higher latitudes
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Winds and currents move clockwise in the
Northern Hemisphere and counterclockwise in
the Southern Hemisphere.
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JET STREAMS
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JET STREAMS hurricane force winds
at the top of the
troposphere which
follow an undulating
path
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RAIN SHADOW EFFECT
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Warm moist air rises, adiabatically cools and
precipitation forms on windward side of mountain.
Dry, desert-like conditions are found on the leeward
side of the mountain.
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Ocean Currents
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Ocean currents are affected by several factors:
 Temperature, salinity, continents, Coriolis effect,
gravity, & surface winds
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Ocean currents strongly influence the climate
conditions on adjacent land.
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As surface water moves, deep water wells up to
replace it. Upwelling brings huge amounts of
nutrients from the ocean bottom which supports
large amounts of producers which in turn support
large populations of fish. Most upwelling occurs
on the west coasts of continents
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Ocean Currents
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Temperature: warm water rises, cold water sinks
as water warms, it expands. (tropical water is
actually a few inches higher than subtropical water)
Gravity: the force of gravity allows the tropical water
to flow to higher latitudes
Salinity: salty water is denser and sinks
Coriolis Effect: like the air masses, water is also
defected due to the rotation of the earth.
Continents: create barriers that shape currents
Surface Winds: create water movement on the
surface of oceans called GYRES.
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OCEAN CURRENTS & GYRES
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GYRES: circular surface currents that move
between continents
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THERMOHALINE CIRCULATION
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Ocean circulation is also driven by differences in
water density due to temperature and salinity of the
water – referred to as the Global Conveyer Belt
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CHANGES TO THE THC
Lake Agassiz – 11,000 years ago, an ice
dam broke and the lake drained into the N.
Atlantic. Stopping the THC and created a
mini-ice age in Europe.
Vast melting of Greenland ice sheets
could have similar
effects.
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Seasonal Winds and Monsoons
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Monsoon - seasonal reversal of wind patterns
caused by differential heating and cooling rates of
oceans and continents
 Most prevalent in subtropical and tropical areas.
 Tilt of Earth’s axis changes location where the
Sun is most intense over the course of the year.
Places where the Sun shines most directly have
evaporation and convection currents which bring
thunderstorms.
 Seasonal rains support tropical forests and fill
great rivers such as the Ganges and Amazon.
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Summer Monsoons in India
Summer cycle:
(Monsoon season)
Winds from the ocean
carry warm, moist air
causing rain on land
Winter cycle:
Winds come from the
land are dry and cool,
rains occur over the
oceans
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Frontal Weather
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COLD FRONT - boundary formed when cooler air
displaces warmer air
 Cold air is more dense and pushes warm air up.
- Creates strong, short-lived storms
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Frontal Weather
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WARM FRONT - boundary formed when warm air
displaces cooler air
 Warm air is less dense and slides over cool air,
creating a long wedge-shaped band of clouds
and precipitation.
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Cyclonic Storms
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When rising air is laden with water vapor, latent
heat energy released by condensation intensifies
convection currents and draws up more warm air
and water vapor. (___________ feedback)
 HURRICANES (Atlantic)
 (Form off W Coast of Africa)
 TYPHOONS (Western Pacific)
 CYCLONES (Indian Ocean)
These storms are usually very large and generate
high winds. Cause severe wind and flood damage
Winds are highest in the center
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Hurricane Classification
Hurricane Katrina – Category 5
Hurricane Matthew – Category 4
Hurricane Sandy – Category 3
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Cyclonic Storms
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TORNADOES - swirling funnel clouds
 Rotation not generated by Coriolis forces
 Generated by a “supercell”
frontal systems where strong
dry cold fronts collide with
warm humid air
 Common in midwest
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Tornado Intensity
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Studying Climate
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CLIMATE - a description of the long-term weather
pattern in a particular area (30+ years)
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ICE CORES - collected from glaciers reveal light
and dark bands caused by annual snow
accumulation on a glacier
 Gas bubbles can be analyzed for atmospheric
composition.
 Ash and sulfur deposits correlate with volcanic
eruptions.
 Vostok ice core gives us a record back 420,000
years. (from Antarctica – 3,100m in length)
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Ice core from
Greenland is 3,000
meters and records
climate date for
250,000 years.
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Climate
Data show that:
 Abrupt climatic change has catastrophic effect on
living things as organisms are unable to adjust
before conditions exceed their tolerance limits.
Species may become extinct.
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There is a close
correlation between
carbon dioxide
concentration and
temperature of the
atmosphere.
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CAUSES OF CLIMATE CHANGE
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Sunspot & Solar magnetic cycles
Cycle of shift in angle of moon alters tides and
currents.
VOLCANIC ERUPTIONS – dust and sulfur can
cool planet suddenly.
MILANKOVITCH CYCLES - periodic shifts in
Earth’s orbit and tilt which change distribution
and intensity of sunlight
- Ice cores show drastic changes may have
occurred over short periods of time (years to
decades).
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Milankovitch Cycles
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ENSO - El Nino Southern Oscillation
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Large area of warm surface water in the Pacific
Ocean moves back and forth between Indonesia
and South America.
 La Nina: Most years, this warm water is held in
western Pacific by steady equatorial trade winds.
 Surface waters driven westward by trade winds
are replaced by upwelling of cold, nutrient rich
waters off west coast of South America.
Nutrients supply food for fisheries.
 El Nino: Every 2-7 years the Indonesian low
collapses and the mass of warm surface water
surges back east.
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El Nino/Southern Oscillation
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During an El Nino year, the northern jet stream
pulls moist air from the Pacific over the U.S.
- Intense storms and heavy rains from
California to the Midwest
- ENSO events are becoming stronger and
more irregular due to global warming.
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During other years La Nina - hot, dry weather is
often present.
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CYCLES AFFECT OCEAN PRODUCTIVITY
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El Nino/Southern Oscillation
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THESE CYCLES HAVE MANY EFFECTS:
1. Decrease in upwelling off the SA coast
 Reduction in productivity in the oceans
 Reduction in commercial fisheries
2. Cooler & wetter conditions in Southern USA
 Replenish water in SW USA
3. Warmer conditions in northern US & Canada
4. Drier weather in Africa and SE Asia
 Reduces hurricanes in N Atlantic
5. Disease frequency changes
 Wet – increase of mosquitoes
 Dry – decrease in safe water sources
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PACIFIC DECADAL OSCILLATION (PDO) a
very large area of warm water moving back and
forth across the North Pacific every 30 years.
Affects fishing harvest on NA west coast.
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Evidence of Climate Change is Overwhelming
“As best as can be determined, the world is now
warmer than it has been at any point in the last two
millennia, and, if current trends continue, by the end
of the century it will likely be hotter than at any point
in the last two million years.”
American Geophysical Union
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Global Warming is Happening
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Global Surface Temperature, 1884--‐2012
http://svs.gsfc.nasa.gov/vis/a000000/a004000/a004030/2012_GISSTEMP_update_withdates.mp4
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In 2007, the Intergovernmental Panel on Climate
Change (IPCC) released its fourth report.
 Represents a consensus by more than 90% of
all scientists working on climate change
 Gives a probability value of 90% that the
warming we are now seeing is anthropogenic
 Bush administration praised the report but said it
opposes mandatory cuts in greenhouse gas
emissions because they are too costly.
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Carbon Dioxide Concentrations on Mauna Loa
Mauna Loa observatory was created in 1957 to obtain
air chemistry data.
CO2 levels have increased from 315ppm in 1958 to
383ppm in 2006 – a .5% increase per year.
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Rate of Global Warming
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Change in temperature is happening quickly!
Best predictions of temperature increase are from
1.8 to 4.0°C (3.2 to 7.8°F) by 2100 depending on
population growth, energy conservation, etc.
In contrast, there has been a 5oC rise since the
middle of the last ice age (about 20,000 years ago).
Ice core samples can tell scientists the relative
abundance of gases in the atmosphere
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Effects of Global Warming
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Most people will experience more extreme weather
including droughts, floods, heat waves and
hurricanes. These extremes have increased globally
in the last decade.
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Sea levels are projected to rise 17-57 cm (7 to 23 in).
If Greenland’s ice melts it will raise sea level 20 ft.
 Most of Florida, Manhattan, Hong Kong, Tokyo,
Mumbai, and other large cities would be flooded
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Coral bleaching worldwide, loss of biodiversity
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Sources of Greenhouse Gases
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Carbon Dioxide
- increased 31% since pre-industrial times
- fossil-fuel burning, cement production, burning
forests,
- 30 billion tons of CO2 released annually
 8 billion tons of carbon
 3 billion absorbed by terrestrial plants
 2 billion absorbed by oceans
 Atmospheric levels increasing steadily
could reach 500ppm by 2100.
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Sources of Greenhouse Gases
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Methane –
- Increased 151% since pre-industrial times
- Accumulating 2x faster than CO2
- Absorbs 23x more infrared than CO2 .
- Released by animals (cows/termites), rice
paddies, coal mines, landfills, swamps,
melting permafrost, pipeline leaks
- (methane is produced when decomposition
takes place w/o oxygen present)
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Sources of Greenhouse Gases
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Chlorofluorocarbons (CFC’s) a.k.a “Freon”
- Absorb large amounts of infrared heat
- Used in refrigerants, air conditioners, as a
propellant in aerosol cans
- Banned in US 1978 due to Ozone depletion
- the manufacture of CFC’s has been phased
out under the Montreal Protocol, and they
are being replaced with other products such
as hydrofluorocarbons (HFCs)
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Sources of Greenhouse Gases
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Nitrous Oxide
- emitted by agricultural fertilizer, industrial
activities (synthetic fabric production),
combustion of fossil fuels & solid waste,
burning organic material
- N2O is a natural gas – part of Nitrogen cycle
- Global warming impact of 1 pound of N2O is
almost 300x that of 1 pound of CO2 .
Sulfur Hexafluoride
- 23,000 times that of CO2
- electrical insulator, production of magnesium.
a filler for cushioning
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Types of Greenhouse Gases
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Contributing Activities
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Country Contribution to Greenhouse Gases
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U.S. has less than
5% of world’s
population but
produces 28% of
carbon dioxide.
China, with 1.3
billion people, is
second.
Japan and Europe
produce half as
much carbon
dioxide per person
as the U.S.
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Evidence of Climate Change is Overwhelming
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Ave. global temperature climbed 0.6°C (1°F) in last
century.
 15 of the 16 warmest years on record have
occurred during the 21st century.
 Poles are warming fastest (4°C, 7°F over past 50
years). Permafrost is melting in Alaska and
Canada
Arctic Sea ice is half as thick as it was 30 years
ago, and the ocean area covered by ice has
decreased by 1 million sq. km. in 30 yr.
 Polar bears are dying
Droughts are more frequent and widespread
Cyclonic storms more common and severe.
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Evidence of Climate Change is Overwhelming
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Antarctic ice shelves are disappearing.
 Penguins declined 50% in last 50 yrs.
Greenland’s ice is melting
Glaciers are melting all over the world.
(Glacier Nat’l Park, Mt Kilimanjaro, Himalayas)
Sea level has risen 6 to 8 inches in last century.
Oceans have been absorbing some of the extra
CO2 but that is acidifying the ocean and damaging
coral and shellfish.
Growing seasons are lengthening in Northern
hemisphere. Some animals are breeding earlier or
extending their range. Others are disappearing.
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Global Warming will be Expensive
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At present, reducing greenhouse gas emissions
would cost 1% of world GDP according to Stern
report. (IPCC report says less than that.)
If we delay, it could cost as much as 20% of world
GDP.
Energy production will need to be 80% decarbonized by 2050 to stabilize climate.
 Ethical issue - Poor will suffer the most; perhaps
200 million people will become refugees of flood
and drought.
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Steps For Combating Climate Change
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Emissions trading
 markets already exist
Technology sharing
Reducing deforestation
Helping poorer countries adapt to climate change
 Tropical areas will not change as much as
middle and high latitudes.
 If all ice on Greenland and Antarctica melt,
1/3 of Earth’s population will be displaced.
- South Pacific island nation of Tuvalu already
abandoned due to climate change
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Combating Climate Change
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Insurance companies have $2 trillion in insured
properties along U.S. coastlines at risk from
flooding or severe storms.
Infectious diseases will increase as insects that
spread them are able to move to places where
they could not live before.
 West Nile, malaria, and dengue fever, Zika have
appeared in North America.
Melting of permafrost may release stores of
methane hydrate. Uncertainty about whether that
would increase warming or cooling.
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International Climate Negotiations
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Kyoto Protocol (1997)
 160 nations agreed to roll back carbon dioxide,
methane, and nitrous oxide emissions about 5%
below 1990 levels by 2012.
- Sets different limits for different countries,
depending on prior output
 Developing countries exempted
(China & India to allow development)
 126 countries have ratified the Protocol.
U.S. took a leading role in the 1990s, but Bush
declined to honor U.S. commitments. Said it
would be too costly and was unfair.
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International Climate Negotiations
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PARIS AGREEMENT –
Drafted Dec. 2015 – Goes into effect Nov 2016
4 main objectives
 1. Holding the increase in global average temperature to
well below 2 °C & to pursue efforts to limit the temperature
increase to 1.5 °C above pre-industrial levels
 2. Increase the ability to adapt to adverse impacts of
climate change and low greenhouse gas emissions
development
 3. Make finance flows consistent with a pathway towards
low greenhouse gas emissions and climate-resilient
development.
 4. Countries aim to reach “global peaking of greenhouse
gas emissions” as soon as possible
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Regulating Emissions
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2007, the CEOs of 10 of the largest business
conglomerates in the U.S. called for legislation to
reduce greenhouse gases – working with
Environmental Defense Fund, and other groups.
A single national standard would be better for
business than a patchwork of state and local
rules.
Companies engaged in international business
will have to modify their products anyway to
compete abroad.
EPA told to uphold the Clean Air Act and
regulate greenhouse emissions.
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Controlling Greenhouse Emissions
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Reducing carbon dioxide levels
 Renewable energy sources
- Increase fuel economy
- Switch to efficient lighting and appliances
- Wind turbines, Solar
- Biofuels, Nuclear
- Planting vegetation/trees
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Carbon Management
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IDEAS TO COMBAT CO2
Build “trees” in which calcium hydroxide solution
would absorb carbon dioxide
Fertilize the oceans with iron to permit
phytoplankton growth, which would take up
carbon dioxide
Sequestration into rock layers or deep ocean
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