Transcript Sys-2 Daisyworld [text KKC, pp.23-31]

Chapter 3 Daisyworld
Objectives:
• Albedo
• Couplings between daisy coverage & T
• Equilibrium states in Daisyworld
• Response of Daisyworld to incr. solar
output
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A view of Daisyworld from outer space
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Couplings between daisy coverage & T
• Incr. daisy coverage of planet => decr. T.
T
Daisy
coverage
Daisy
Coverage
albedo
Daisy
Coverage
T
T
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• Daisies can live between a min.T & a max. T
daisy
coverage
Daisy coverage
T
T
daisy
coverage
optimum
min.
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max.
T
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• Intersection of 2 curves means the 2 effects
are balanced => equilibrium points P1 & P2.
Daisy coverage
T
daisy
coverage
daisy
coverage
T
Effects of daisy coverage on T
P1
Effects of T on
daisy coverage
P2
T
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Feedback loops
Daisy coverage
Effects of daisy coverage on T
P1
Effects of T on
daisy coverage
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P2
T
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• Perturb daisy coverage at P1 => sys. returns to P1
Daisy coverage
(stable equil. pt.)
P1
A large perturb.
=> daisies all die
from extreme T
P2
T
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• From P2, incr. daisy cov. => decr. T =>
Daisy coverage
further incr. in daisy cov. => converge to P1
daisy
T
coverage
P1
unstable
P2 equilib. pt.
T
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Daisy coverage
Gradual incr. in solar luminosity
For any particular value
of daisy cov., T incr.
P1
The effect of T on
Daisy unchanged
P1
To
Teq
P2
Tf
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P2
T
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Lessons from Daisyworld
• Despite change in forcing, climate sys. can
counter part of the change by negative
feedback loops.
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Uncertainty in Climate Change Study
Scenario uncertainty --- due to uncertainty of future
emissions of GHGs and other forcing agents;
Model uncertainty --- associated with climate models;
Natural variability --- Stochastic and Nonlinear problem;
Initial condition and forcing and boundary –
the limitation of observation data and assimilation
technique
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A1 Family is based on the following hypothesis
A1
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Rapid economic growth.
A global population that reaches 9
billion in 2050 and then gradually
declines.
The quick spread of new and efficient
technologies.
A convergent world - income and way
of life converge between regions.
Extensive social and cultural
interactions worldwide.
There are subsets to the A1 family
based on their technological emphasis:
A1FI - An emphasis on fossil-fuels.
A1B - A balanced emphasis on all
energy sources.
A1T - Emphasis on non-fossil energy
sources.
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Representative Concentration Pathways (RCPs)
The four RCPs --- RCP2.6, RCP4.5, RCP6, and RCP8.5
a possible range of radiative forcing values in the year 2100
relative to pre-industrial values (+2.6, +4.5, +6.0, and +8.5 W/m2,
respectively).
RCP 2.6 assumes that global annual GHG emissions peak
between 2010-2020, with emissions declining substantially
thereafter.
Emissions in RCP 4.5 peak around 2040, then decline.
In RCP 6, emissions peak around 2080, then decline.
In RCP 8.5, emissions continue to rise throughout the 21st
century.
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Long lived GHGs
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Uncertainty in Model
Model parameter uncertainty
Model physics
Model Resolution
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Uncertainty in Climate Change Study
Natural variability --- Stochastic and Nonlinear problem;
Initial condition and boundary condition–
the limitation of observation data and assimilation
technique
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As observational records lengthen and models
improve, researchers should be able, within the
limitations of the range of natural variability, to
narrow that range in probable temperature in the
next few decades . It is also possible to use
information about the current state of the oceans
and cryosphere to produce better projections up
to a few years ahead.
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