Transcript SNC 2D Climate Change3

Dynamics of Climate Change
Energy Transfer in the Climate System
◊ Earth’s climate is a complex system.
◊ A system is a group of independent parts that work
together to form a single, functioning whole.
◊ An open system is a system in which energy and
matter cross the system’s boundary. (your body)
◊ A closed system allows energy but not matter to
cross the boundary of the system. (The Earth’s
climate system)
◊ As a closed system, Earth must constantly cycle the
matter and energy within it’s boundary.
◊ Interactions among different forms of
matter and energy in Earth’s climate
system create feedback loops.
◊ A Feedback loop is a process in which
part of a system’s output is returned to
the input.
◊ In the Earth’s climate system, many
feedback loops affect the conditions of
the atmosphere, ocean and land.
◊ A positive feedback loop acts to
increase the effects of the interacting
parts.
◊ Example: effect of melting ice,
decreases albedo (reflected light of
surface), which increases warming,
which increases the amount of melting
ice, and so on.
◊ The small initial change in climate can
lead to larger and larger changes.
◊ Negative feedback loops decreases
the interacting parts and help maintain
the system’s equilibrium.
◊ Checks and balances to prevent, slow or
reverse change in a system.
◊ Example: global warming increases rate
of evaporation, increased water in
atmosphere creates clouds, clouds
create more albedo, which produces a
cooling effect.
Types of Energy Transfer
◊ Radiation: transfer of energy as
electromagnetic radiation.
• E.G. Sun to Earth, heat from fire, etc.
◊ Conduction: transfer of energy between 2
objects in direct contact. Moves from an area
of high heat to lower heat.
• E.G. hot plate on stove to frying pan to egg.
◊ Convection: transfer of thermal energy by
highly energized molecules.
• E.G. lava lamp
Energy Transfer in Atmosphere
◊ Land and water gain thermal energy by absorbing
the Sun’s short-wave radiation.
◊ As Earth warms, it emits long-wave radiation to the
atmosphere, which heats the air and contributes to
greenhouse effect.
◊ Conduction heats the air through collisions between
molecules in the ground and in the air.
◊ Convection moves warm air from close to the
ground upward and cool air from higher in the
atmosphere downward.
Convection, Conduction and
Radiation transfer heat in
Earth’s Atmosphere
Energy Transfer in the Oceans
 Uneven heating on Earth creates winds.
 Winds create currents of water that redistribute
thermal energy at the ocean surface.
 Deeper, colder currents also move slowly along
the ocean floor
 Like air masses, large masses of water can move
vertically and horizontally.
 Cold water = dense and sinks, pushing warm
water out of the way
 Salt water = dense and sinks.
 Temperature, salinity, density of water create
continuous, twisting ocean current that mixes ocean
waters.
 Sometimes called the “Great Conveyor Belt”
 This pattern is known as thermohaline circulation.
 Creates a global system of thermal energy
distribution
Global Warming and
Thermohaline Circulation
 Scientists are worried that global warming will affect
the current pattern of circulation.
 Higher temps  increased ice melting increases
fresh water decreases salt content in northern
water
 Higher temps  increased evaporation increased
salt levels in tropics
 Changes in ocean circulation patterns could have a
negative effect on living things (manta ray) in the
ocean by changing patterns of upwelling.
 Upwelling brings nutrients from sea floor to surface
currents.
Energy Transfer
The importance of winds and
ocean currents to global
climate is seen best when
there is a disruption to the
system.
Every few years in the tropics,
there are events called El Nino
and La Nina.
El Nino
Winds blowing west weaken
and might reverse
Warm waters in the western
Pacific move eastward,
preventing cold water from
upwelling
Can trigger changes in
precipitation and
temperature across North
America.
Heavy rains in California can
lead to landslides
La Nina
Stronger than normal winds
push warm Pacific waters
farther west, towards Asia.
Cold, deep-sea waters well
up strongly in the Eastern
Pacific
Colder temperatures to
northwestern North America.
Moisture pushed away from
N.America, parched lands.
Earth’s Energy Budget
Nearly a third of solar energy reaching
Earth is reflected back.
The 70% that is absorbed warms the
ground, water, and air.
The energy budget is a description of the
total energy exchange within a system;
how much energy enters from the Sun
and how much leaves the Earth system.
Percentage of Absorbed and
Reflected Energy
Greenhouse Gases
» The concentration of carbon dioxide in
Earth’s atmosphere increased from 315
parts per million (ppm) to 370ppm.
» 99% of the atmosphere is made up of
nitrogen gas and oxygen gas.
» Neither absorbs infrared radiation or
contributes to greenhouse gases.
» Carbon dioxide and water are the 2 most
abundant greenhouse gases in our
atmosphere.
Water Vapour?
» Responsible for 65-85% of greenhouse
effect
» Water is not added or removed to the
atmosphere in significant amounts by
humans.
» Temperature does control the amount of
water in the atmosphere.
» Higher temperature = more evaporation
CO2 Sources and Sinks
» A sink is a process that removes
greenhouse gases from the
atmosphere.
» Plants are sinks
» Burning of fossil fuels and animal
respiration are the major sources
» Phytoplankton (microorganisms)
can absorb a lot of carbon dioxide
as well.
Methane: greenhouse gas
» Produced in wetlands (bogs and
swamps), rice paddies, termites and
cattle naturally.
» Landfills, processing coal and natural gas
and manure also emit methane.
» Suggestions? Make cows wear
backpacks to capture the methane and
use it as a fuel, feed cows clover and
alfalfa to reduce methane, stop eating
beef.
Methane backpack!
Ozone

Ozone (O3) occurs naturally in the atmosphere
and blocks UV radiation from the Sun.
 Since 1970, there has been a slow decline in
the total ozone and a “hole” appeared over
Antarctic.
 Not actually a hole, just an area where the
ozone is thinning more than other areas around
it.
 Cause: human-made gases that contain
chlorine
Ground-Level Ozone

Smog-forming
pollutant
 Produced when
sunlight reacts with
chemicals and
vehicle exhaust
(hydrocarbons and
nitrogen oxides)
 Can contribute to
global warming.
Halocarbons
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Formed when carbon is mixed with a halogen
(iodine, fluorine, chlorine)
Human-made
Chlorofluorocarbons (CFCs) are best known in
solvents, cleaners and coolants in fridges and
air conditioners.
Absorb infrared radiation so they are
greenhouse gases and also break apart ozone
molecules
Remain in atmosphere for so long and continue
to do damage
Banned in 1987.