Download 15.Globalwarming2

Climate System
• Atmosphere
–
–
–
–
–
Nitrogen
Oxygen
Argon
Carbon dioxide
Other minor gases
N2
O2
Ar
CO2
78%
21%
0.93%
0.035%
0.035%
Greenhouse Gases
• CO2, H20 and methane (CH4):
• Absorb and re-radiate radiation
• Insulates and raises Earth temperature
The influence of Carbon on climate change
ATMOSPHERE
Fossilfuel
burning
(5.3 Gt/yr)
Land-use
change:
deforestation,
agriculture
(1.7 Gt/yr)
Land uptake
By new plant
growth
(1.9 Gt/yr)
Terrestrial biosphere
LAND
Cement production (0.1 Gt/yr)
Fossil
Rock
organic
carbonates
carbon
GEOLOGIC RESERVOIRS
Ocean uptake
by air-sea gas
exchange
(1.9 Gt/yr)
OCEAN
Human activities release
a total of 7.1 Gt of carbon
into the atmosphere each
year.
New plant growth and
air-sea gas exchange
remove 3.8 Gt/yr,…
ATMOSPHERE
Fossilfuel
burning
(5.3 Gt/yr)
Land-use
change:
deforestation,
agriculture
(1.7 Gt/yr)
Land uptake
By new plant
growth
(1.9 Gt/yr)
Terrestrial biosphere
LAND
Cement production (0.1 Gt/yr)
Fossil
Rock
organic
carbonates
carbon
GEOLOGIC RESERVOIRS
Ocean uptake
by air-sea gas
exchange
(1.9 Gt/yr)
OCEAN
…yielding a net
atmospheric
increase of
3.3 Gt/yr.
Climate Change
Understanding Natural Climate
Variability:
Use the geologic record to understand Earth
Climate in the past
(Uniformitarianism)
Milankovitch cycles
Related to variations in:
1. Eccentricity
2. Tilt of axis
3. Precession (wobble)
All of these variables change the earth-sun distance
Is Human-induced
climate change
possible?
Long-term change can be
assessed from ice cores,
which record annual cycles
of ice formation from snow.
Ice Ages
High
Key:
Temperature
CO2
Methane
Thousands of years before present
Relative carbon dioxide and
methane concentrations
Temperature relative to present climate (°C)
Deglaciation
Climate has been
relatively warm and
stable during the last
10,000 years.
Low
CO2 concentration (ppm)
Northern Hemisphere temperature
anomaly (°C)
The 20th-century is clearly
anomalous when compared
with the last millennium.
Temperature
CO2 concentration
Years
Keeling Curve
Temperature
CO2
concentration
Years
CO2 concentration (ppm)
Global temperature anomaly (°C)
A recent warming trend correlates
with the increase in CO2.
Atmospheric CO2 Projections Under 3 Alternate Scenarios….
2000
2020
2040
2060
Year
2080
2100
….and Estimated Average Surface Temperatures for Those Scenarios
Uncertainty envelope due to
lack of knowledge of
climate system
Feedback enhances warming
• Positive Feedback:
– Amplifies changes in the system.
– Temperature increase decreases Earth’s albedo
by reducing snow and ice cover
Evidence for Warming
• Weather is highly variable*
• Glaciers provide long-term trends
1941
2004
Columbia glacier
Greenland
Greenland
Weather Related Hazards
1. Drought
2. Desertification
3. Heat waves
4. Snow and Ice
5. Global Warming
6. El Niño
NMSU Rainfall
14
Cumulative Rainfall (Inches)
12
10
2006
2005
2004
2003
2002
2001
2000
2007
2008
8
6
4
2
0
1
19
37
55
73
91 109 127 145 163 181 199 217 235 253 271 289 307 325 343 361
-2
Days since Jan 1
Transition zones between deserts
and humid areas are fragile
Soil gets eroded by wind and water
Productive land becomes degraded
Main culprits:
Overgrazing
Overplowing
Human activity can stress
the ecosystem
• Grazing
• Cutting trees for charcoal
• Some agriculture
El Niño
• Pacific Ocean is pushed westward by trade winds
• Warm water off Peru is replaced by upwelling of
cold, deep, nutrient-rich water
• Circulation reverses: El Niño
• 6 Year cycle
• Opposite extreme in weather patterns is La Nina
El Niño
Subtropical trade winds weaken
Warm surface water remains in east Pacific
Incessant rain to west coasts
Fisheries suffer (no cold, nutrient-rich upwelling water)
El Niño
Outline
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•
•
•
•
•
Drainage Basins
Discharge
Sediment load
Meandering/Braided rivers
Floodplains
Flooding
SEA
+ 336
+ 398
+ 434
SEA
Runoff from land
Precipitation
over sea
Evaporation
LAND
LAND
+ 434
– 398
Evaporation
Precipitation
+ 107
– 371
Precipitation
Evaporation
+ 107
– 336
Precipitation
Runoff to ocean
+ 436
Excess to land
via precipitation
+ 436
Runoff to
ocean
+ 471
Evaporation
Flux in and flux out over oceans
is almost balanced.
Excess is moved to
land and precipitates.
Precipitation
107
Evaporation
71
Evaporation Precipitation
434
398
The precipitation
runs off into
lakes, streams,
and oceans…
Surface
runoff
Infiltration
Runoff
36
Groundwater
table
Groundwater
flow
…or filters into soil
and rock, where it
moves as groundwater.
Drainage Basin/Watershed
Drainage Basins/Watersheds
• Rio Grande River basin includes:
– Chama
– Puerco
– Pecos (and all of its tributaries)
• It doesn’t include the Gila, because it flows into Colorado
• Continental Divide (in NM) separates:
– Rio Grande drainage
– Colorado River drainage
San Juan
Colorado
Rio Grande
Gila
Rio Grande
Pecos
Rio Grande Watershed
Discharge/Total Flow
•
•
•
•
•
Q=VA
Q is discharge
V is average velocity (m/s)
A is cross-sectional area (m2)
units of Q?
Discharge/Total Flow
Discharge/Total Flow
Stream profile depends on location
Sediment Load and Grain Size
• Streams can be provided with particles of any size
from mud to giant boulders
• Volume and velocity of flow limit size and
amount of sediment that stream can carry
Sediment Load and Grain Size
Alluvial fans have braided streams
Gravel delta at mouth of braided river, Cook Inlet, Alaska
Delta reworked by wave action, Cook Inlet, Alaska