Transcript File - Down the Rabbit Hole

Global Climate Change
Climate Review
Global Circulation
• The solar radiation hitting the Earth is
unequal…WHY?
– Earth is oblate (slightly flattened)
Global Circulation
• Although the loss and gain of radiation is balanced
over the entire climate system, no one part of the
planet’s surface is in equilibrium at a given time.
Spring (sun aims
directly at equator)
To
Polaris
The tilt (23½°
inclination) causes
the seasons
Winter (Northern
Hemisphere tilts away
from sun)
Fall (sun aims
directly at equator)
Summer (Northern
Hemisphere tilts
toward sun)
The Earth is tilted and rotating and revolving
Solar Heating of Earth
Varies with Latitude
• The atmosphere reflects,
scatters and absorbs solar
radiation.
• At high latitudes solar
radiation travels a longer
path through atmosphere.
• Equal amounts of sunlight
are spread over a greater
surface area near the poles
than in the tropics.
• Ice near the poles reflects
much of the energy that
reaches the surface there.
Heat Redistributed
• Heat gained at Equatorial latitudes
• Heat lost at higher latitudes
• Winds and ocean currents redistribute heat
around the Earth
• Oceans do not boil away near the equator or
freeze solid near the poles because heat is
transferred by winds and ocean currents
from equatorial to polar regions.
•
Physical Properties of the Atmosphere:
Density
Warm, low density air
rises
• Cool, high density air
sinks
• Creates circular- moving
loop of air (convection
cell)
Physical Properties of the Atmosphere:
Water Vapor
• Cool air cannot hold
much water vapor, so is
typically dry
• Warm air can hold
more water vapor, so is
typically moist
• Water vapor decreases
the density of air
Physical Properties of the Atmosphere:
Pressure
• A column of cool, dense air causes high pressure at the
surface, which will lead to sinking air
• A column of warm, less dense air causes low pressure at the
surface, which will lead to rising air
Physical Properties of the Atmosphere:
Movement
• Air always moves
from highpressure regions
toward lowpressure regions
• Moving air is
called wind
Atmospheric Circulation
(convection)
• Heated air rises at
equator
Maximum
Sun warming
• Cooler air
descends at poles
The Coriolis Effect
• As Earth rotates,
different latitudes
travel at different
speeds
• The change in
speed with latitude
causes the Coriolis
effect
The Coriolis Effect
• The rotation of the Earth deflects
the path of moving objects.
• As observed from space,
cannonball 1 (shot northward) and
cannonball 2 (shot southward)
move as we might expect; that is,
they travel straight away from the
cannons and fall to Earth.
• Observed from the ground,
however, cannonball 1 veers
slightly east and cannonball 2
veers slightly west of their
intended targets.
• The effect depends on the
observer’s frame of reference.
The Coriolis effect
• The Coriolis effect
– Is a result of Earth’s rotation
– Causes moving objects to follow
curved paths:
• In Northern Hemisphere, curvature is to right
• In Southern Hemisphere, curvature is to left
– Changes with latitude:
• No Coriolis effect at Equator
• Maximum Coriolis effect at poles
Add rotation Add land mass
Unequal heating and cooling of the Earth
Wind Belts of the World
The Total Atmosphere Effect
Global air circulation as described in the six-cell circulation model. Air rises
at the equator and falls at the poles, but instead of one great circuit in each
hemisphere from equator to pole, there are three in each hemisphere.
Ocean Currents
• Surface Currents
– The upper 400 meters of the
ocean (10%).
– Wind-driven currents occur in
the uppermost 100 m or less
• Deep Water Currents
– Thermal Currents (90%)
– Density differences causes by
salinity and temperature
produce very slow flows in
deeper waters.
Upwelling and Downwelling
Vertical movement of water
– Upwelling = movement of deep water to surface
• Hoists cold, nutrient-rich water to surface
• Produces high productivities and abundant marine
life
– Downwelling = movement of surface water
down
• Moves warm, nutrient-depleted surface water down
• Not associated with high productivities or abundant
marine life
El Niño-Southern Oscillation
(ENSO)
• El Niño = warm surface current in
equatorial eastern Pacific that occurs
periodically around Christmastime
• Southern Oscillation = change in
atmospheric pressure over Pacific Ocean
accompanying El Niño
• ENSO describes a combined oceanicatmospheric disturbance
Thermalhaline circulation of the Earth’s
oceans transfers heat from the equator to the
higher latitudes
How does water vapor affect climate?
• Warmer conditions increase the
amount of evaporation, which
then leads to the vast amount of
clouds forming
• Some clouds trap heat (positive
feedback) or they may reflect the
sunlight and cool the air (negative
feedback)