Transcript Introduction - Weather Underground

MET 12 Global Climate Change - Lecture 9
Climate Models and the Future
Shaun Tanner
San Jose State University
Outline




Current status
Scenarios
Global Models
Future Predictions
1
2
3
4
CO2, Methane, Nitrous Oxide
5
Climate Change and humans
 Anthropogenic increases in
– greenhouse-gas concentrations
– sulfate aerosols due to anthropogenic
emissions
 Emission scenarios have been developed
 Changes in solar irradiance and volcanic
aerosols
– Unpredictable and difficult to model
7
Q: How do we predict what the
future climate will be like?
A: We use global models of the
earth system
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Sequence of Steps
1. Estimate future GHGs concentration
2. Using future GHG levels, calculate
what future climate (e.g. temp, precip)
will be like.
3. Assess the uncertainty of the
predictions
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Global Climate Modeling
1. Carbon cycle model
2. Global Climate Model
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Figure 4.6 Main floor of the Earth Simulator Center in Yokohama, Japan
Figure 4.7 Elements of a global climate model
Figure 4.8 Genealogy of atmosphere GCMs
Figure 4.9 Examples of grid box systems
Figure 4.10 GCMs characterize fluxes into and out of a grid box during a time step
Calculation of Future CO2
Concentrations
CO2 Emissions -How
much is going into
atmosphere
Carbon Cycle Model –
Simulates atmosphere-biosphere
and atmosphere-ocean interactions
CO2 Concentration How much remains in
atmosphere
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Carbon Cycle Models
 Atmosphere/ocean and atmosphere/biosphere
interactions not well understood
 Model calculations contain uncertainty; the
largest uncertainty:
– Future uptake of carbon by the biosphere
– Future uptake of carbon by the oceans
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What factors affect future CO2 levels?
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



Global Population
Type of energy generation
– Fossil intensive
– Renewable energy
Growth of Economy
Type of Economy
– Material based
– Service and information based
Cooperation among countries
– More homogeneous - share technologies
– More isolated - larger divide between rich/poor
countries
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In 10 years, what do you expect you’ll earn
annually?
1.
2.
3.
4.
5.
6.
7.
Less than $20k
Between $20-40k
Between $40-60k
Between $60-80k
Between $80-100k
Between $100-150k
Over $150k
What kind of car will you most likely purchase
next?
1.
2.
3.
4.
5.
6.
7.
8.
SUV
Truck
Sportcar
Minivan
Station wagon
4 door sedan
Hybrid (gas/electric)
Electric
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What best explains your eating patterns now?
1. Eat meat most meals
2. Eat meat a few times a
week (3-5 times)
3. Eat meat occasionally
(1-2 times per week)
4. Eat meat very
occasionally (1-2 per
month)
5. Vegetarian
6. Vegan
Scenarios (1)
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Scenarios (2)
 A1 storyline
– World of rapid economic growth
– Population peaks 2050
– Different branches dependent on energy type/use
 A1FI – Fossil intensive – continued dependence on
coal/oil
 A1T – Non-fossil intensive energy use (Technology)
 A1B – Balance between fossil and non-fossil
 A2 storyline
– Heteorogenous world –technologies are not shared
across borders,
– population continues to increase
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Scenarios (3)
 B1 storyline
– Similar population as A1
– Global exchange/cooperation
– Change in economic structures from product
oriented to service oriented.
– Focus on social and economic sustainability
 B2 storyline
– Population like A2
– Similar environmental and social focus
– More regionally oriented (not as much
exchange between countries).
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Figure 4.16 Emissions scenarios (Part 1)
Figure 4.16 Emissions scenarios (Part 2)
Figure 4.18 Past and predicted changes in global average atmospheric CO2 concentration
Climate Model
 A climate model is a mathematical
representation of the physical processes that
control climate
– Basically everything that affects climate
– Sun, atmosphere (greenhouse gases,
aerosols), hydrosphere, land surface,
cryosphere
 Equations are very complicated
– Some of the world’s largest supercomputers
are running climate models
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Model Schematic
Changes in greenhouse-gas
concentrations and changes
in albedo due to aerosols
Climate Model
Climate change (i.e.
temperature,
precipitation etc.)
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Model Verification: Can it be done?
 Before you can trust any of these models, they
must be verified.
– We can use past climate as a test.
If your model can simulate the past climate,
then there is a reasonable chance that the
model can accurately predict future
climate.
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Can we predict changes in past climate?
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Figure 4.29 Observed global temperature changes versus simulations via the HadGEM1 GCM
What conclusions can you infer from these
model experiments?
1.
2.
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These experiments demonstrate that
1. The warming of the entire 20th
century is largely due to humans
2. The warming of the last 50 years is
largely due to humans.
3. Natural factors are largely
responsible for the warming of the
20th century
4. Natural factors are not important in
the early 20th century, but more
important in the last part of the 20th
century.
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Climate models
1.
2.
3.
4.
Are not useful for predicting the temperature
changes observed during the 20th century.
Show that volcanic eruptions and changes in
sunlight are responsible for most of the
changes observed over the 20th century.
Can predict the 20th century observed
temperature changes with natural factors only.
Can only predict the 20th century observed
temperature changes when they include both
human and natural contributions.
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What conclusions can you infer from these
model experiments?
1. Models can reasonably predict
temperature variations over the last
150 years.
2. Most of the observed warming in the
past 50 years is attributable to human
activities.
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Future Projections
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Carbon Emissions
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UNEP 2003
Figure SPM.5
Figure 4.34 Projected changes in surface temperatures comparing data (Part 2)
Figure 4.38 Projections of 21 GCMs about changes over the present century in precipitation
Figure 4.35 Past and future sea ice and sea level
Future predictions: main changes in
climate
 Higher temperatures - especially on land
– Arctic shows the largest warming
 Hydrological cycle more intense
– More rain overall
 Sea levels rise
– Why?
 Changes at regional level –hard to predict
 More intense weather (extremes)
– Floods, droughts etc.
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Activity 4
1. Based on the A2 scenario, what is the
predicted CO2 concentration, temperature
change and sea level change in 2100?
2. Based on the B1 scenario, what is the
predicted CO2 concentration, temperature
change and sea level change in 2100?
3. Explain the differences.
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 Therefore, stabilizing emissions is not enough
to reduce the radiative forcing
 Based on above, how much will emissions have
to decline in % to stabilize CO2 at 550ppm?
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A
B
C
Mean Temperature (2050):
relative to 1961-90
A1FI is A, B or C?
B2 is A, B or C?
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Indicate the correct matching
1.
2.
3.
4.
5.
6.
A1FI – A, B2 - B
A1FI – B, B2 – A
A1FI – C, B2 – A
A1FI – A, B2 – C
A1FI – B, B2 - C
A1FI – C, B2 – B
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Mean Temperature (2050):
relative to 1961-90
A1F
A2
B2
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A
B
C
Constant Aerosols ____
Increasing aerosols____
Decreasing aerosols____
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The correct order of the graph is (Constant,
Increasing Aerosols and Decreasing Aerosols)
1.
2.
3.
4.
5.
6.
ABC
ACB
BAC
BCA
CAB
CBA
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A
B
C
Constant Aerosols
Increasing aerosols
Decreasing aerosols
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If CO2 emissions were stabilized at present
day values, CO2 concentrations would
1. Continue to increase
2. Stabilize
3. Start to decrease
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