The Atmosphere, Climate and
Global Change
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Increase in average surface temperature of
the Earth from 1860 to the present
Increase in carbon dioxide concentrations in
the atmosphere
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What’s happening now in the atmosphere
near the earth’s surface such as Temperature,
pressure, cloudiness, precipitation, winds
-Climate is the average weather
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It shows that average precipitation and
temperature
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Troposphere - bottom layer
-Where weather occurs
-Temperature decrease with elevation
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At the top is tropopause - acts as a lid
-Stratosphere - above the troposphere
-Stratospheric ozone layer just above the
tropopause
-Protects again UV radiation
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Processes generally defined by pressure,
temperature, and water vapor content
-Pressure is force per unit area
-Caused by the weight of overlying
atmospheric gases on those below
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Decreases with altitude
-Low pressure systems usually bring clouds
-High pressure systems usually bring clear
skies
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-Atmosphere moves due to Earth’s rotation
-Differential heating
-Produces global patterns of prevailing
-winds and latitudinal belts of high and low
pressure
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-Under typical conditions Earth’s atmosphere:
-Reflects ~30% of the electromagnetic energy
that comes in from the sun
-absorbs ~25%
-The remaining ~45% gets to the surface
-Radiates back to the atmosphere or into
outer space
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Instrumental Records
-Climate measurements began in 1860s
-Data from pre 19th century is
-Estimates
-Extrapolated (a method or conclusion, especially
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-Interpolated
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one based on statistics)
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-Improved instrumentation
-Historical RecordsGo back a few centuries
-Mostly qualitative
-Books, newspapers, journal articles,
personal journals, ships’ logs, travelers’
diaries, and farmers’ logs
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-Paleoproxy records
-Proxy data- not strictly climatic, but
provides insight into climate
-Tree rings, sediments, ice cores, fossil
pollen, corals, and carbon-14 (14C)
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-Each gas in the atmosphere has its own
absorption spectrum
-Certain gases are especially strong
absorbers in the infrared
-They absorb radiation emitted by the
warmed surfaces of the Earth
-They then re-emit this radiation
-This increases the temperature of the
earth’s surface
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-Water vapor
-Carbon dioxide
-Methane
-Some oxides of nitrogen
-CFCs
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-The atmosphere and its interactions w/ the
ocean and land surfaces experience positive
and negative feedbacks
-Negative feedback
-Warms temps warm air and lead to
increased evaporation
-Evaporation leads to more cloud formation
which reflects more sunlight which could cool
the surface.
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-Positive feedback
-Warms temps warm air and lead to
increased evaporation but instead of clouds
forming remain as water vapor
-Water vapor is a greenhouse gas. The
warmer it gets the more water vapor, and the
process continues
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-19th century
-Scientists began to understand that climate
changed greatly over long periods
-There were times of continental glaciations
-Evidence - debris at the edges of existing
glaciers which looked the same as those
deposited at lower elevations
-Cycles were apparent
-100,000 year cycles divided into 20,000–40,000
year periods
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-Earth is like a wobbling top following an
elliptical orbit around the sun
-Three Cycles
-26,000 year
-Earth Does not keep its poles at a constant
angle in relation to the sun
-Wobble around the pole makes a complete
cycle in 26,000 years
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41,000 yearsThe tilt of wobble also varies
over a period of 41,000 years
-100,000 years
-Elliptical orbit around the sun also changes
-Sometimes it is a more extreme ellipse;
other times it is closer to a circle and this
occurs over 100,000 years.
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-Water has the highest heat capacity of any
compound
-Large amount of heat energy is stored in oceans
-Ocean absorbs dissolved CO2
-As CO2 increases in atmosphere it also
increases in the oceans
-Climate system driven (in part) by ocean
conveyor belt
-A global circulation of ocean waters
-If the conveyor was shut down, major changes
in climate would occur
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-Climate system driven (in part) by ocean
conveyor belt
-A global circulation of ocean waters
-If the conveyor was shut down, major
changes in climate would occur
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-El Niño refers to a specific periodic variation
of Pacific Ocean currents
-Under non-El Niño conditions
-Trade-winds blow west across the tropical
Pacific
-Warm surface water pile up in Western
Pacific
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During El Niño yearsTrade winds weaken
-Western moving current weakens or reverses
-As a result eastern equatorial ocean
unusually warm
-High rates of precipitation and flooding in
Peru
-Changes global atmospheric circulation
-Causes changes in weather in regions that
are far removed from tropical Pacific
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-Two ways to forecast the future:
-Empirical and theoretical
-Empirical approach is to go back to the
geological idea of uniformitarianism
-The past is the key to the future
-Has led to the extensive research on
climates and atmospheric conditions of the
past
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-Computer simulationGeneral Circulation
Models (GCM)
-Based around the atmosphere being divided
into rectangular solids
-Each a few km high and several km N or S
-For each the flux of energy and matter is
calculated to each adjacent cell
-Steady state model - cannot account for
randomness
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-Changes in River Flow
-Melting of glacial ice & reductions in snow
cover
-Rainfall will likely increase, but runoff will be
more rapid than if snow slowly melts
-Reservoirs will overflow - more water will
flow to the ocean
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-Rise in Sea Level Since last ice age, sea level
has risen 1 ft./century
-Global warming could double this
-A major warming could increase sea levels
-Expansion of liquid water as water warms
-Melting of ice sheets on land whose waters
then flow into the ocean
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About half the people on Earth live on or near
the coast - vulnerable to flooding
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-Two types
-Adapt: Learn to live with future global
climatic change
-Mitigate: Work to reduce emissions of
greenhouse gases
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-Energy planning that relies heavily on energy
conservation and efficiency
-Use of alternative energy sources or natural
gas
-Use of mass transit
-Greater economic incentives to energyefficient technology
-Higher fuel-economy
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-Reforestation-Planting more trees
-Increase biospheric sinks for carbon dioxide
-Capture carbon dioxide from power plants
and industrial smokestacks
-Compress the gas and change it to a
mixture of both liquid and gas
-Inject it deep underground
-Have the potential to sequester as much as
1,000 gigatons of carbon
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-A nation or nations agrees to a cap of
carbon emissions
-Then corporations and other entities are
issued emission permits, allowing a certain
quantity of emissions
-These can be traded
-Overall nation does not exceed the cap
-1988: First international meeting to discuss
limiting greenhouse gases held (Toronto,
Canada)
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-1992: Earth Summit in Rio de Janeiro, Brazil.
-General blueprint for reduction of global
emissions suggested
-US thought it would be to costly and no legally
binding limits set
-1997: Legally binding limits discussed in Kyoto,
Japan.
-US eventually agreed to cut emissions to 7%
below 1990 levels (leading scientists recommend
cuts 60-80% below)
-Became a formal treaty in 2006
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COP 21