Transcript Slide 1

CLIMATE
An Abrupt Climate Change Scenario and Its Implications for United States National
Security (Pentagon Report, 2003). Global warming “should be elevated beyond a
scientific debate to a US national security concern... future wars will be fought over the
issue of survival rather than religion, ideology or national honour.”
Understanding climate matters...
CLIMATE
I. Large Scale Determinants
A. Solar Radiation
1. Average Radiation Budget
- Solar Constant = 2 calories/cm2/min
- 50% is reflected, absorbed, reradiated (Most
ultraviolet light is reflected/absorbed) by the
atmosphere
- on average, 1 cal/cm2/min strikes earth.
(but this varies dramatically, as we will see…)
- 50% is reflected, absorbed, reradiated (Most ultraviolet light is reflected/absorbed)
YAY
OZONE!
Greenhouse effect
ABSORBANCE
CO2 fills ‘window’ in H2O
absorbance
A. Solar Radiation
1. Average Radiation Budget
2. Local Radiation Budget – Angle of incidence (latitude and season)
1) Goes through more atmosphere
2) Less energystrikes/unit area
(since it is spread over more
area)
3) More is reflected off surface; a
lower percentage of what
strikes/unit area is absorbed
A. Solar Radiation
1. Average Radiation Budget
2. Local Radiation Budget – Angle of incidence (latitude and season)
HIGH ENERGY
LOW ENERGY
B. Effects on Atmospheric Circulation
LOW ENERGY
HIGH ENERGY
LOW ENERGY
LOW ENERGY
As air rises:
- decrease pressure
- increase volume
- decrease energy/unit volume
- decrease temperature
As air rises:
- decrease pressure
- increase volume
- decrease energy/unit volume
- decrease temperature
Decrease temp, increase
tendancy of water vapor to
condense
“Adiabatic cooling”
As air rises:
- decrease pressure
- increase volume
- decrease energy/unit volume
- decrease temperature
“Adiabatic cooling”
Decrease temp, increase
tendancy of water vapor to
condense
PV = nRT
As dry cold air falls:
- increase pressure
- decrease volume
- increase energy/unit volume
- increase temperature
“Adiabatic warming”
As dry cold air falls:
- increase pressure
- decrease volume
- increase energy/unit volume
- increase temperature
“Adiabatic warming”
30oN
Increase temp of this dry air,
evaporate water off surface
30oS
HOT, DRY, DESERTS
30oN
TROPICAL RAINS
at solar equator
HOT, DRY, DESERTS
30oS
30 N
30 S
Latitude of solar equator drive seasonal rainy seasons in tropics
Latitude of
solar
equator
Three cycles in each
hemisphere:
Hadley
temperate (Ferrel),
polar
Transfer of energy from equator to poles
(“Why are global warming’s greatest effects at the poles,
not in raising the temperature of the tropics?)
C. The Coriolis Effect
- Pattern of air movement along the surface of
the earth…
C. The Coriolis Effect
- Pattern of air movement along the surface
of the earth…
- conservation of momentum east
- speed relative to Earth changes
(treadmill analogy)
C. The Coriolis Effect
D. Effects on Ocean Circulation
E. Long-Term Effects
1. ENSO (El Nino Southern Oscillation)
E. Long-Term Effects
1. ENSO (El Nino Southern Oscillation)
E. Long-Term Effects
1. ENSO (El Nino Southern Oscillation)
E. Long-Term Effects
2. Younger Dryas
- Dramatic cooling of northern Europe 11,000-13,000 years
ago, correlating with the melting of the Laurentian Ice Sheet in
North America.
- Fresh water formed a lens on surface; deflecting Gulf Stream
to the east at a much lower latitude, starving Europe of the
heat transferred by the Gulf Stream.
F. Difficulties in Modeling Global Climate
1. Positive Feedback Loops
F. Difficulties in Modeling Global Climate
1. Positive Feedback Loops
F. Difficulties in Modeling Global Climate
1. Negative Feedback Loops
II. Determinants of Local Climate
A. Topography
1. mountains
Merriam’s Life Zones in the southwestern U.S.
II. Determinants of Local Climate
A. Topography
1. mountains
2. valleys
Valleys - Day
II. Determinants of Local Climate
A. Topography
1. mountains
2. valleys
Valleys - Night
II. Determinants of Local Climate
A. Topography
1. mountains
2. valleys
3. slope face
B. Water Bodies - act as heat sink/source as temp
changes more slowly than air
SPRING to SUMMER
Land warms more rapidly than water body; heat transfers
to cold water...increase in temp is buffered
B. Water Bodies - act as heat sink/source as temp
changes more slowly than air
FALL to WINTER
Land cools more rapidly than water body; heat transfers to
cold land...decrease in temp is buffered
B. Water Bodies - act as heat sink/source as temp
changes more slowly than air
CONTINENTAL CLIMATE
Continental climate
MARITIME CLIMATE
Maritime climate
focus on temp (red) and NOTE scales differ!!
B. Water Bodies
- also a source of moisture
B. Water Bodies
- also a source of moisture
Maritime climate
B. Water Bodies
also a source of moisture
Continental climate (max 100)
focus on precip (blue)
Maritime climate (max 160)
B. Water Bodies
-also a source of moisture
- depends on onshore vs. offshore winds/currents
Vancouver, 49N
Boston, 42 N
Note differences
in scale
C. Additive Effects - Atacama Desert
D. Seasonality in Temperate Lakes