Download What is the Atmosphere?

Chapter 15 Study Guide
Case Study: When Wedges do more than Silver Bullets
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Each year new reports of heat waves, droughts, declining water supplies, unpredictable
weather, and HIGH crop prices
Artic sea ice reflects the sun’s energy and helps neutralize global climate
But the artic sea ice has declined by HALF in summer
Increasing concentrations of greenhouse gases in our atmosphere are retaining (keeping)
more of the sun’s energy in the atmosphere
The past 30 years have been the hottest in the past 1,300 years.
Even a little bit of climate warming allows new crop pests and weeds to survive winters
o also dries the soil so much that farmers have to irrigate crops more than usual
o if farmers aren’t able to irrigate the crops they abandon the farm
Parts in the western U.S rely on mountain snowmelt for water
Climate change worries politicians and voters, yet we still have a hard time figuring out
ways to stop it
If we don’t reduce our output of CO2 emissions in the following years we will
PERMANENTLY LOSE ICE CAPS AND PERMAFROST
o This will cause rapid change
o Our temperature will increase by 5-7 degrees Celsius
o Sea levels will rise by 1 meter
Our carbon emissions are triggering climate change
o These changes will be very costly, human and economic terms
Politicians are looking for a Silver Bullet (technology that will fix the problem all at
once)
o Nuclear fusion
o Space based solar energy
o A giant mirror to reflect sunlight away from earth
 But these cannot be created yet
 Immediate action is required in avoid the further melting of the polar ice
caps
Wedge Analysis: the breaking down of a large problem into smaller, bite- sized pieces
o By adding up the problems we can see the total magnitude of their effects and
decide if it’s worth trying to move forward
Three Possible Solutions:
o “Business as Usual”- follows the current pattern of constantly increasing CO2
output
 Triple CO2 and temp increase of 9 degrees Fahrenheit by 2100
 Lead to a sea level rise of 0.5-1 m
o “Stabilization Scenario”- prevent further increase of CO2 emissions
 Only doubles CO2 in the atmosphere
 Temp increase of 2-3 degrees Celsius
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 Sea levels rise 29-50 cm
o The third option: declining CO2 emissions could result in new energy sources and
better land management
 Need to reduce annual carbon emissions by 7 BILLION TONS per year
within 50 years
 Increase fuel economy in our cars
 Cut driving from average miles from 10,000 to 5,000 per year
 Better appliances in homes
 Increase efficiency in our coal power plants
 Reduce reliance on cars
 Use public transportation
Cleaner power sources will also reduce asthma and other respiratory illnesses, saving
health care costs and improving the quality of life
This review talks about the composition and behavior of our atmosphere and the
factor that make it change over time
15.1 Review: What is the Atmosphere?
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The atmosphere is layered with the more massive molecules near the ground surface
Weather: short-lived and local patterns of temperature and moisture that result from this
circulation
Climate: long-term patterns of temperature and precipitation
Earth’s earliest atmosphere consisted of light weight hydrogen and helium
o Over billions of years that hydrogen and helium diffused into space
o Volcanic emissions added carbon, nitrogen, oxygen, sulfur, and other elements
o All the oxygen was introduced by photosynthesis, and blue green bacteria
Clean dry air is mostly nitrogen and oxygen
o Water vapor concentrations vary from 0-4%
 This depends on the air temp and the amount of moisture
Aerosols- minute particles and liquid droplets
o Atmospheric aerosols are important in capturing, distributing, or reflecting energy
o These are also in the air
Atmosphere has four distinct zones – These four zones contrast temperature, this
results in differences in absorption of the sun’s energy
o 1st layer: immediately adjacent to the earth’s surface- TROPSHPERE
 Air is in constant motion because it is redistributing heat and moisture
around the globe
 The air absorbs energy from the sun warmed earth’s surface and from the
moisture evaporating from the oceans
 Warmed air circulates in great vertical and horizontal convection currents.
 Contains 75 percent of the total mass of the atmosphere
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Within the troposphere temperatures drop rapidly with increasing distance
from the earth reaching about -76 degrees Fahrenheit (at this point air is
no longer warmer than its surroundings, and it ceases to rise)
 The boundary where mixing ends is called the tropopause
Convection Currents- these occur when warm, low-density air rises above the cooler
denser layer
o Ex. A pot of simmering water on the stove.
 Water heated the at the bottom of the pot rises up above the cooler
layers at the top creating convection circulation patterns
Convection constantly redistributes heat and moisture around the globe
The depth of the troposphere ranges from about 11 miles over the equator where heating
and convection are intense to about 5 miles over the poles where the air is cold and dense
Equator- heating and convection are intense
Poles- air is cold and dense
Stratospheric ozone- important for blocking ultraviolet solar energy
2nd layer- extends from the troposphere up to 31 miles: STRATOSPHERE
o More dilute than the troposphere, but has similar composition – except has almost
no water vapor and nearly 1,000 times more ozone
o Stratosphere is relatively calm, b/c warm layers lie above cold layers
o So little mixing that when one-quarter is reflected by the clouds and atmospheric
gases
o Above the stratosphere the temp diminishes again in the mesosphere (middle
layer)
 This region is made up of highly ionized (electrically charged) gases
heated by a steady flow of high energy solar and cosmic radiation
o The thermosphere (heated layer) begins at about 80km
 In thermosphere intense pulses of high energy radiation causes electrically
charged particles (ions) to glow.
 This is called the aurora borealis & australis (northern and
southern lights)
o Ozone serves a very important function in the stratosphere
OZONE IS A POLLUTANT NEAR THE EARTH’S SURFACE
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Ozone absorbs certain wavelengths of ultra violet solar radiation (UVB Rays)
This energy warms the upper stratosphere so temp increases with elevation
Stratospheric UV ABSORPTION also protects life on the earth’s surface
o This is important because UV RADIATION causes damage to living tissues, crop
failure, etc.
o Air pollutants deplete stratospheric ozone, especially over the Antarctica
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This has allowed increased amounts of UV radiation to reach the earth’s
surface
No specific boundary marks the end of the atmosphere
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o Density of gas molecules decrease w/ distance from Earth until it becomes
undistinguishable from the near- vacuum of interstellar space
Absorbed solar energy warms our world
Our sun gives out a lot of energy, but the energy is not evenly distributed around the
globe
Insolation- Incoming solar radiation is much stronger near the equator than at high
latitudes
Of the solar energy that reaches the outer atmosphere about one quarter is absorbed by
carbon dioxide, water vapor, methane, ozone and other gases.
o This energy absorption warms the atmosphere
o The rest is absorbed by the Earth’s surface and water
Surfaces that reflect energy have a HIGH ALBEDO
o Many of these surfaces appear bright to us because they reflect light as well as
other forms of radiative energy
Surfaces that absorb energy have a LOW ALBEDO
o These appear darker
 Ex. Black soil, pavement, and open water
Of the 100%of incoming solar energy
o atmospheric gases and clouds reflect about 25
o and the surface reflects about 5
o gases and clouds absorb 25%
o and earth’s surface absorbs the remaining 45
Absorbed energy heats absorbing surfaces (asphalt parking), evaporates water, or
provides the energy for photosynthesis in plants
Thermodynamics: second law- absorbed energy is gradually reemitted as lower quality
heat energy
Water is extremely good at absorbing and storing energy
For billions of years the artic has been mostly white which reflected much of the energy
to hit the surface
Now because it is melting it is causing the open water to capture and store the energy
making it hotter
Positive feedback loop- melting leads to further melting with huge consequences
Atmosphere selectively absorbs longer wave lengths
A lot of the energy is intense, high- energy light or near-infrared wavelengths which pass
relatively easily through the atmosphere to the earth’s surface
Energy which is re-released from the earths warmed surface (terrestrial energy) is lower
intensity, longer wavelength radiation in the far- infrared part of the spectrum
CO2 and water vapor absorb much of the long wave-length energy and re-release it in the
lower atmosphere
This long wave terrestrial energy provides most of the heat on the lower atmosphere
The retention of long wave terrestrial energy in the atmosphere is called the Greenhouse
effect b/c the atmosphere transmits sunlight while trapping heat inside
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Greenhouse effect is necessary for life
o But too strong of a greenhouse effect can affect the environment and alter it in a
way we are not used to
Greenhouse gases- general term for trace gases that are especially effective at capturing
the long wave-length energy
Water vapor is the most abundant greenhouse gas
Carbon dioxide is the most abundant and long lasting human caused greenhouse gas
followed by methane
Evaporated water stores energy, and wind redistributes it
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Near the equator the sun shines straight overhead and solar heating (and water
evaporation) is most intense
Mid latitudes sun is less intense
At the poles the sun rarely shines as intense and heat absorption by the ground and water
is very low
Solar energy absorbed by the ground eventually reradiates as long wave infrared energy
or heat
o This energy warms the lowest layers of the air
Warmer air expands and becomes less dense than the cooler air above it and begins to
rise
Convection cells- rising warm air produces vertical convection currents
Convection is more vigorous near the equator at higher latitudes
Hadley Cells- equatorial convection cells (one north and one south of the equator)
Ferrell Cells/ Polar Cells- mid-latitude and polar cells
o These have less intense heating and less vigorous circulation than the Hadley cells
Where air rises in convection currents, air pressure at the surface is low
Where is air is sinking or subsiding air pressure is high
Incoming solar energy is also used to evaporate water
Latent heat- water vapor adds up to huge amounts of stored energy
Atmospheric circulation carries a great deal of heat and moisture from warm humid
places to colder drier places.
The redistribution of heat and water around the globe is essential to life on earth
15.2 Regional Patterns of Weather
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Precipitation happens when moisture cools and condenses
The troposphere is heated when there is contact with the warmed earth’s surfaces
Convection cells: these result when warm air rises
Atmospheric circulation redistributes heat and moisture
Weather: temperature, wind, and precipitation that change over days or weeks
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Weather patterns :happen b/c of uneven solar heating on the earth’s surface, together with
spinning of the earth
Water condenses as air cools, and air cools as it rises
o Any time air is rising, snow, rain, etc. may form
Cooling occurs b/c of changes in temperature with altitude
Air cools as it rises
o Pressure decreases
Air warms as it sinks
o Pressure increases
Air rises in convection currents where solar heating is intense
o Ex. The equator
o Air rises when two air masses collide & must rise over each other
o Air also rises when it encounters mountains
If air is moist, condensation and rainfall are likely to occur as the air is lifted
Colliding air masses get a lot of precipitation
As air warms the moisture tends to evaporate
o Ex. Warm areas usually do not get a lot of rain b/c of high pressure
High pressure/dry conditions occur where convection currents are sinking
Condensation nuclei: tiny particles of smoke, dust, sea salts, spores, and volcanic ash
o These particles form a surface on which water molecules can begin to collect
 Without them even super cooled vapor they would still remain in a
gaseous form
The Coriolis Effect explains why winds seem to curve
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Northern Hemisphere winds bend clockwise
o Ocean waves bend clockwise in northern hemisphere
Southern Hemisphere bend counter clockwise
o Ocean waves bend counter clockwise in southern hemisphere
Coriolis Effect: curvature of the winds
o Ex. Merry go round and throwing a ball from the middle
o Predicts wind patterns and currents
o Produces cyclonic winds/ wind movements controlled by the earth’s spin
 These winds spiral clockwise in high pressure in northern hemisphere
 Counter clockwise in southern hemisphere
Top of troposphere are JET STREAMS – hurricane- force winds that circulate the earth
o Jet streams affect weather patterns
Warm and cold ocean currents strongly influence climate conditions on land
Surface ocean currents result from wind pushing on the ocean surface
When surface water moves, deep water rises up to replace it = deeper ocean currents
Differences in ocean density also drive ocean currents
o Depends of temp and saltiness of the water
Gyres: huge cycling currents
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o They carry water north & south redistributing heat from low altitudes to high
altitudes
Ocean Conveyer system: water cools and evaporates, becomes less dense and salty and
plunges downward creating a strong deep southward current
Quantitative Reasoning
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Currents can shift abruptly
Seasonal Rain Supports Millions of People
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Large parts of the world, especially near the tropics, get a lot of rain
o Rain helps maintain ecosystems and human communities
When rains don’t come it causes
o Crop failure
o Famine (starvation)
Monsoons: regular seasonal rains
Where ever sun shines a lot evaporation and convection of currents are very strong
Reason for tropical and subtropical regions to have seasonal rain and dry seasons is b/c in
that region intense solar heating and evaporation shifts through the year
As earth orbits the sun, b/c of tilt of axis causes seasons
As year shifts from summer to winter:
o Solar heating weakens
o Rainy season ends
o Little rain may fall
Frontal systems occur where warm and cold air meet
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Front: boundary between two air masses of different temperature and density
Cold Front: when cooler air pushes away warmer air
o cold, dense air of a cold front tends to hug the ground and push under the lighter,
warmer air as it advances
o as the warm air is forced upward, it cools, and its water vapor condenses to
become ice crystals/ water droplets
o air masses near ground move slower b/c of friction and turbulence near the
ground surface
 when this happens upper layers of the moving mass move ahead of the
lower layers
Cold fronts generate strong convection currents as they push the warmer air upwards
o Violent winds and thunderstorms are a result
o Weather after cold front is nice and clear
Warm Front: the advancing air mass is warmer than its surrounding air
o b/c warm air is less dense than cool air the advancing warm front will slide up
over cooler air masses
o warm front and cold front different b/c
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gradual lifting and cooling in a warm front lacks the violent updrafts and
convection currents that come with a cold front
Warm front can have many layers of clouds at diff heights
o Highest layer is called wispy cirrus clouds- made up of icy crystals
Cyclonic storms can cause extensive damage
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Latent heat intensifies circulation thus producing swirling winds that capture more
moisture and latent heat energy
These storms swirl in a direction dictated by the Coriolis effect
o Called Cyclonic Storms
Hurricanes: very powerful storms filled with winds and rain
Tornadoes: Swirling funnel clouds that form over land
o Also considered cyclonic storms
o Tornadoes generated by giant “supercell” frontal systems where strong, dry-air
fronts collide with warm, humid air
The bigger the temp difference the bigger/powerful the storm
As warm air rises rapidly over dense cold air intense vertical convection currents
generate as it rises
o This releases latent heat and speeds up within the supercell
o If these penetrate the stratosphere and collide with jet streams it creates even
stronger convection currents
15.3 Natural Climate Variability
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Milankovitch cycles : periodic shifts in the earth’s orbit and tilt
o Changes the distribution and intensity of sunlight reaching the earth’s surface
How climatologists find evidence
o Tree rings:
 The widths let them count back to find dry or wet seasons
o Remains of plants or pollen:
 Found in lake beds or marine mud
o Ice cores:
 KEY sources of data b/c they provide long climate records
Scientists sometimes use snow bubbles:
o Snow falls to ground with bubbles
o Bubbles can determine the atmosphere and how the weather was at the time the
snow fell
o Can also detect ash layers and spikes in sulfate concentrations that record volcanic
eruptions
o MOST IMPORTANTLY we can look at isotope of oxygen
Because of the snow fall and other ways climatologists use to see the weather, we can
now see that CO2 concentrations have varied
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In cold years water molecules with lighter oxygen atoms evaporate more easily than
water atoms with heavier isotopes
o Bu looking at this climatologists can see temps from over time and see the temp
changes against CO2 concentrations
There is a strong correlation between atmospheric temps and CO2 concentrations
Now we know that CO2 concentrations have varied between 180-330ppm (parts per
million)
Ice core data also shows that the climate now is warmer than it has ever been since the
beginning of civilizations
El Nino is an ocean-atmosphere cycle
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Oscillations: periodic shifts
There are oscillations in ocean currents and atmospheric circulation over the years and
decades
EL NINO SOUTHERN OSCILLATION: the weakened upwelling currents and warming
water led to the disappearance of fish
Sometimes between el nino events the water (coastal) becomes so cold that and these are
called la nina
o These two are called el nino southern oscillation
The core of the ENSO system is a huge pool of warm surface water in the pacific that
sloshes back and forth between Indonesia and south America
Trade winds also help drive ocean currents in the pacific
Upwelling currents along the coast of south America draw the cold nutrient rich water
from deep in the ocean
o Supports the school of fish
Every 3-5 years convection currents weaken
the pool of warm surface water goes back east across the pacific toward Peru and Cali
el nino affects us because it brings heavy rains from Cali
o la nina brings extreme dry HOT weather
ENSO related droughts are predicted to strengthen and intensify b/c pool of water is
expanding
15.4 Anthropogenic Climate Change
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Anthropogenic: Human caused global climate change
o most important environmental issue
CO2 concentrations have increased by 0.5% each year
Every may CO2 levels drop slightly as plant growth captures the CO2 in photosynthesis
During northern winter levels rise again as plants release the CO2
CO2 levels are rising by more than 2ppm per year
The IPCC accesses data for policymakers
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Intergovernmental Panel on climate Change : brought together scientists and
government representatives from 130 countries to see the evidence of effects of climate
change
Fourth Assessment Report (AR4): published in 2007 by the work of 2,500 scientists
o Newer ar5 published in 2013-2014 paves the way for newer work to be done in
favor of climate control
o 90% probability that the recent climate changes have been from human activities
Increases in carbon emissions have exceeded too much
o Artic ice is shrinking
o If this continues there will be a 3-6 foot increase of ocean water which will flood
coastal cities
H2O is a gas that is especially good at holding heat/ energy in the atmosphere
o Blocking and absorbing these long wave lengths
CO2 can stay decades in the atmosphere and is very good at capturing long- wave
lengths
CO2 doubled in the last 40 years
CO2 produces 76.6 % of human caused climate impacts
o 1st most important gas in atmosphere
Methane is the 2nd most abundant gas in the atmosphere
o 14% of greenhouse output
o Absorbs 23 times more energy as CO2
o Produced when plant matter decays in oxygen-free condition, also from natural
gas wells
 At the bottom of wetlands
Nitrogen oxide: 3rd most important greenhouse gas
o Accounts for 8% of greenhouse gases in atmosphere
o Produced from agricultural processes, plant decays, vehicle emissions
o Important because it is really good at capturing heat
Burning fossil fuels is or most abundant source of greenhouse gas
Fossil fuels produce 50% of greenhouse gases
o Deforestation and agriculture 30%
o And industry produces 20%
Positive Feedbacks Accelerate Change
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Melting of polar ice will increase energy absorption
o b/c water has lower albedo than ice
Peat: soggy, semi decayed plant matter accumulated over thousands of years
o As peat dries it releases CO2 and CH4
o Release of these two can cause the same as CO2 ever burned
Increased ocean evaporation could make the snowfall at high latitudes even worse
o It would also restore some of some of the high albedo surfaces
How do we know recent climate change is caused by humans??
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We are doing an uncontrolled experiment
o We keep adding more greenhouse gases to the air without knowing the
consequences
o We also do not have another earth to use after we destroy this one