Stabilization and Global Climate Policy in a Multi-Gas World Marcus - - PowerPoint PPT Presentation

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Stabilization and Global Climate Policy in a Multi-Gas World Marcus - - PowerPoint PPT Presentation

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Stabilization and Global Climate Policy in a Multi-Gas World Marcus C Sarofim*, Chris E Forest*, David M Reiner , John M Reilly* *Joint Program on the Science and Policy of Global Change, MIT Judge Institute of Management Studies,

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Stabilization and Global Climate Policy in a Multi-Gas World

Marcus C Sarofim*, Chris E Forest*, David M Reiner†, John M Reilly*

*Joint Program on the Science and Policy

  • f Global Change, MIT

†Judge Institute of Management Studies,

Cambridge University NIES and EMF Stabilization Workshop Tsukuba, Japan, Jan. 22-23, 2004

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Aim of the Research

  • To examine the issues involved in current

discussions of stabilization policy given a multi-greenhouse gas world

– To encourage tighter definition of stabilization in academic and political discussion. – To reemphasize the importance of non-CO2 greenhouse gases for effective, inexpensive temperature reduction on the two century time scale. – To examine stabilization under uncertainty.

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Article 2 of the Framework Convention on Climate Change

  • “The ultimate objective of this Convention... is

to achieve... stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt... to ensure that food production is not threatened, and to allow economic development to proceed in a sustainable manner.”

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Definitions of Stabilization

  • Many anthropogenic greenhouse gases exist:

– CO2, CH4, N2O, SF6, HFCs, etc. – Not including “climatically important substances” such as SO2, black carbon, ozone precursors, etc.

  • Stabilize CO2 only? (EU 550 ppm position)

– What are assumptions about other gases? – SRES A1B is often used for non- CO2 gases.

  • Stabilize overall radiative forcing?

– Separate targets for each gas? CO2 equivalents?

  • Trading between gases?

– The use of Global Warming Potentials (GWPs) is incompatible with stabilization.

  • When? 2100? 2150? 2500? 3000?
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Nature of Two Scenarios: CO2ONLY and GHGTRADE

  • Estimate cumulative CO2 emissions to 2100

consistent with ‘stabilization’ of CO2 at 550 ppm

– Actually 530 ppm in 2100 to allow for gradual stabilization after 2100.

  • Allocate CO2 reductions optimally over time.

– Discounted marginal abatement equalized over time— price rises at the discount rate.

  • Expand constraint to Other GHGs

– Allow GHG trading using 100-year GWP to achieve reductions equal to CO2 only case – Considered proportional reduction case (not shown)

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Considerations

  • Emissions path consistent with a frequently

discussed policy target, reinterpreted in multigas terms.

– Other interpretations possible.

  • Economic rationale for initial allocation of

reductions over time

– but once expanded to other GHGs its no longer quite true

  • Known concentration and climate outcomes

associated with these emissions scenario

  • Economic and climate outcomes are true for

EPPA/MIT IGSM—not necessarily for other models.

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Further Considerations

  • Initial CO2 path was achieved with a globally

uniform carbon tax– equal marginal costs.

  • After adding other GHGs, reinterpreted as a

quantity constraint

  • Concentration and climate effects depend

little on the regional allocation

– Regionally reallocate global totals as desired, and still be consistent with concentration and climate results.

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EPPA: An Economic/Emissions Model

  • CGE model of the world economy with all human

activities and all CIS’s. – GHGs: CO2, CH4, N2O, SF6, PFC, HFC . – Other air pollutants: NOX, SOX, CO, NMVOC, NH3 and carbonaceous particulates. – Activities: Energy combustion and production, agriculture and land use, industrial processes, waste disposal (sewage & landfills).

  • Designed for the 100 year time scale.
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Emission paths (550 ppm)

5 10 15 20 25 30 2000 2020 2040 2060 2080 2100

Year GtC/year CO2ONLY GHGTRADE BAU 100 200 300 400 500 600 700 800 900 1000 2000 2020 2040 2060 2080 2100 Year Tg CH4 BAU CO2ONLY GHGTRADE

Carbon Path Methane Path

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The MIT IGSM

A coupled chemistry, climate, ocean, and ecosystem model.

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Some Aspects of the MIT IGSM

  • Natural systems (ocean and terrestrial) integrated

part of the coupled atmosphere-ocean model

– ocean and terrestrial biology of C uptake – natural CH4, N2O, C affected by climate and atmospheric concentrations of CO2

  • Carbon from human land use assumed to be

neutral over the century

  • Active and integrated atmospheric chemistry

resolved for urban and rural conditions

– Tropospheric ozone as an additional warming effect – Sulfate aerosols as cooling effect – Oxidation of CH4 explicit so lifetime is endogenous

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Total GHG Forcing (change since 1990)

1 2 3 4 5 6 7 8 2000 2020 2040 2060 2080 2100 Year ∆ total forcing since 1990 (W/m 2) CO2ONLY GHGTRADE BAU

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Results in 2100

Temperature Reduction (From 2.8 ºC) Reduction in Net Present Consumption

CO2ONLY

0.75 ºC 1.2%

GHGTRADE

1.18 ºC 0.5%

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0.5 1 1.5 2 2.5 3 2000 2050 2100 2150 2200 2250 2300

Year Temperature change since 1990 (ºC)

0.2 0.4 0.6 0.8 1 1.2

Sea level rise since 1990 (m)

CO2ONLY Temperature GHGTRADE Temperature CO2ONLY Sea Level Rise GHGTRADE Sea Level Rise

Long Term Studies (to 2300)

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Uncertainty in Policy Costs

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 2 3 4 5 6 Percentage Loss of Net Present Consumption Cumulative probability density CO2ONLY: Mean 1.1 5/95 bounds: 0.02 / 3.9 GHGTRADE: Mean 0.67 5/95 bounds: 0.01 / 2.6

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Uncertainty in Climate System Parameters

550 ppm CO2ONLY emissions scenario

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1 2 3 4 Temperature Rise from 1990 (°C) Probability Density

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

490 540 590 CO2 concentration (ppm)

Probability Density (x 10 -2)

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Carbon Uptake

1 2 3 4 5 6 7 8 9 10 2000 2050 2100 2150 2200 2250 2300 Year Pg C/year 100 200 300 400 500 600

ppm CO2

Carbon emissions CO2 concentration CO2 emissions Ocean uptake

Terrestrial uptake Total uptake

550 ppm CO2ONLY emissions scenario

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CAVEATS

  • Modeling

– Results depend heavily on abatement curves and technology assumptions in model. – Discount rate impacts emissions path and cost calculations: Absolute numbers but not conclusions are sensitive to choice of rate.

  • Policy Implementation

– Non-CO2 sources are hard to monitor. – Reducing CO2 emissions may require capital investments which should be started early.

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Future Work

  • Uncertainty:

– Impact of other gas emission uncertainty on global temperature change results. – Determining carbon emissions pathways given carbon uptake uncertainty. – Tradeoffs between cost and damages.

  • Policy Improvements

– Devising an “optimum cost over time” all-GHG policy. – More realistic policies: developing countries should have differentiated goals.

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Conclusions

  • Stabilization of carbon dioxide concentrations

can be met at reasonable costs. However, these costs will be much less if trading is allowed between all gases. Additionally, an all-gas policy is much more effective than CO2 only policies on the two century scale.

  • Uncertainty in costs and uncertainty in

impacts should be incorporated into the determination of appropriate targets.

  • Imprecision in language should be addressed

before creating long term policy frameworks.

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Carbon-Equivalent Prices 2005-2050

50 100 150 200 250 300 2000 2010 2020 2030 2040 2050 Year Cost of Carbon (1995 US $/ton C eq) Year 2005 Prices: $30.48 $1.46

CO2 only All GHG Proportional

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Total GHG Emissions, GWP weighted

5 10 15 20 25 30 35 2000 2020 2040 2060 2080 2100 Years Carbon equivalents by GWP (Gt C) Reference CO2 only GWP Equiv. All GHG Proportional Reduction

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Total Carbon Emissions

5 10 15 20 25 2000 2020 2040 2060 2080 2100 Year CO2 emissions (Gt C) GWP Equivalent CO2 only Reference Proportional Reductions

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Total Methane Emissions

100 200 300 400 500 600 700 800 900 1000 2000 2020 2040 2060 2080 2100 Year CH4 emissions (MT)

Reference All GHGs Proportional Reductions CO2 only All GHGs GWP equivalent

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CO2 Concentrations

300 400 500 600 700 800 2000 2020 2040 2060 2080 2100 Year CO2 Concentration (ppm)

CO

2 only

All GH Gs Proportional Reference

A ll GHGs GWP Eq.

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Methane Concentration

1 2 3 4 5 6 2000 2020 2040 2060 2080 2100 Year CH

4 Concentration (ppm)

Reference CO2 only All GHGs Proportional Reductions All GHGs GWP equivalent

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Total N2O Emissions

5 10 15 20 25 2000 2020 2040 2060 2080 2100 Year N2O Emissions (Tg) Reference CO2 only All GHGs GWP equivalent All GHGs Proportional reduction

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N2O Concentration

300 320 340 360 380 400 420 440 460 480 500 2000 2020 2040 2060 2080 2100 Year N2O Concentration (ppb) All GHGs Proportional reduction CO2 only Reference GWP eq.

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Ozone Concentration

30 35 40 45 50 55 2000 2020 2040 2060 2080 2100 Year O3 concentration

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Global Mean Temperature Change: 2000-2100

0.5 1 1.5 2 2.5 3 2000 2020 2040 2060 2080 2100 Year Mean Temperature Change from 1990 (°C) All GHGs Proportional Reduction CO2 only Reference