Transcript Slide 1

“Our Great Geophysical Experiment”
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Questions to consider
1. The science of global warming.
2. The impacts of global warming on markets and
environmental systems.
3. Why global warming poses such difficult problems for
economic and environmental policy and the theory of
stock global public goods.
4. The use of integrated assessment models to analyze
trends and examine policies.
5. Alternative strategies for slowing climate change,
especially cap and trade, the Kyoto Protocol, and
carbon taxes.
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Emissions:
fossil fuel use
generates CO2
The
emissions
-climateimpactspolicy
nexus
Carbon cycle:
redistributes C around
atmosphere, oceans, etc.
Climate system:
change in radiation warming,
precip., ocean currents, etc..
Impacts on ecosystems,
agriculture, diseases,
skiing, golfing, …
Policies: Measures to control
emissions (limits, taxes,
subsidies, …)
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The Keeling curve of CO2
concentrations at Mauna Loa
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The Greenhouse Effect:
Fossil (C) fuel + O2 → Energy + CO2
CO2 has long atmospheric residence
time as gas.
CO2 is a “greenhouse” gas that
retains surface heat.
A CO2 Blanket
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Energy balance of the earth
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Radiative forcing and climate change
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Absorption on the spectrum
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Central notion of radiative forcings
“The radiative forcing of the surface-troposphere system due to the
perturbation (say, a change in greenhouse gas concentrations) is the
change in net (down minus up) irradiance (solar plus long-wave in
Wm-2) at the tropopause AFTER allowing for stratospheric
temperatures to readjust to radiative equilibrium, but with surface
and tropospheric temperatures and state held fixed at the
unperturbed values.” IPCC
Basic equation:
ΔT = λ ΔF
where T = mean surface temperature, F = forcings (W/m2),
and λ is a feedback parameter.
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From CO2
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All GHGs, 2005
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General Circulation Models
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These are the workhorses of climate change science.
They are 3D computerized time-stepped simulation models of the
atmosphere, oceans, cryosphere, and biosphere
Based on fundamental physics (conservation, etc.), geography
(where are oceans), and observations (initial conditions)
Used to predict weather first, now climate, both historically and in
the future
Large ones are still very coarse grid (200 x 200 km) and require
supercomputers (e.g., 8 TFLOP for GFDL).
Because of complex physics, large remaining errors in and across
GCMs (see next slide)
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Ocean carbonization
(a) Atmospheric CO2 emissions and changes in ocean pH and (b) projections
compared with history(A and C), uncontrolled C/W (D);
red + = uncontrolled WN; green triangle = “optimal” WN)
Caldeira and Wickett, Nature 2003
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