1 “Our Great Geophysical Experiment” Source: NOAA, Hurricane Katrina shortly before landfall

2 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.

3 Emissions: fossil fuel use generates CO2 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, …) The emissions -climate- impacts- policy nexus

4 The Keeling curve of CO2 concentrations at Mauna Loa

5 Fossil (C) fuel + O 2 → Energy + CO 2 CO 2 has long atmospheric residence time as gas. CO 2 is a “greenhouse” gas that retains surface heat. The Greenhouse Effect: A CO 2 Blanket

Energy balance of the earth 6

Radiative forcing and climate change 7

Absorption on the spectrum 8

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. 9

From CO 2 10

All GHGs,

12 General Circulation Models -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)

13 (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 Ocean carbonization