Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements Stephen Pacala March 16, 2010

Committee Members Stephen Pacala, (Chair), Princeton University Clare Breidenich, Independent Consultant Peter Brewer, Monterey Bay Aquarium Research Institute Inez Fung, University Of California, Berkeley Michael Gunson, Jet Propulsion Laboratory Gemma Heddle, Chevron Corporation Beverly Law, Oregon State University Gregg Marland, Oak Ridge National Laboratory Keith Paustian, Colorado State University Michael Prather, University of California, Irvine James Randerson, University of California, Irvine Pieter Tans, National Oceanic and Atmospheric Administration Steven Wofsy, Harvard University NRC Staff: Anne Linn

Context for the Study Anthropogenic greenhouse gases are accumulating in the atmosphere International agreements to limit future greenhouse gas emissions will rest on the ability of each country to estimate emissions accurately and to monitor and verify changes over time Scripps CO 2 program

Committee Charge and Focus Charge: Review current methods and propose improved methods for estimating and verifying greenhouse gas emissions at different spatial (e.g., national, regional, global) and temporal (e.g., annual, decadal) scales. The committee focused on the gases, methods, and scales relevant to international climate agreements –National, annual emissions and decadal trends –Public domain information

Greenhouse Gases Covered Carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), sulfur hexafluoride (SF 6 ), chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and perfluorinated hydrocarbons (PFCs) –result from human activities –long lifetimes in the atmosphere –currently included in international agreements Particular focus on CO 2 –largest single contributor to global climate change

Bottom Line National fossil-fuel CO 2 emissions can be estimated by each nation accurately enough to support a climate treaty (error <10%). Strategic investments could enable accurate independent checks on self- reported estimates of CO 2 emissions from fossil fuel and deforestation within 5 years (<10% for critical countries) Estimates of emissions of other greenhouse gases will remain uncertain in the near term IPCC (2007)

One-quarter of countries are responsible for 80% of global emissions

Methods for Estimating Emissions UNFCCC National inventories –Estimates anthropogenic emissions and removals (sinks) –Based on measurements of human activities Tracer-transport inversion –Estimates net anthropogenic and natural sources and sinks –Based on atmospheric and/or oceanic measurements of the gases and models of air and water flow Land-use measurements and models –Estimates emissions and sinks of CO 2, CH 4, and N 2 O –Based on land cover information from satellite imagery and biogeochemical models

UNFCCC Inventory Emission = Activity Level X Emissions Factor (i.e. steel prod.) X (CO 2 per unit prod.) Current error: <10% for CO 2 from developed countries but up to 50% for CH 4 and 100% or more for N 2 O, CFC’s, PFC’s, HFC’s and SF 6.

Methods for Estimating Emissions UNFCCC National inventories –Estimates anthropogenic emissions and removals (sinks) –Based on measurements of human activities Tracer-transport inversion –Estimates net anthropogenic and natural sources and sinks –Based on atmospheric and/or oceanic measurements of the gases and models of air and water flow Land-use measurements and models –Estimates emissions and sinks of CO 2, CH 4, and N 2 O –Based on land cover information from satellite imagery and biogeochemical models

CO 2 Sampler LAND CO 2 Sampler Prevailing Wind CO 2 Tracer-Transport Inversion Current errors of 100% or more for all gases. Fossil-fuel CO 2 Emissions

Problems with Tracer Transport Method Transport Error Large and incompletely understood background fluctuations of natural emissions. Current sampling grid avoids urban areas and large industrial sources which generate most emissions. Current sampling grid is too sparse.

Atmospheric Sampling Network

Methods for Estimating Emissions UNFCCC National inventories –Estimates anthropogenic emissions and removals (sinks) –Based on measurements of human activities Tracer-transport inversion –Estimates net anthropogenic and natural sources and sinks –Based on atmospheric and/or oceanic measurements of the gases and models of air and water flow Land-use measurements and models –Estimates emissions and sinks of CO 2, CH 4, and N 2 O –Based on land cover information from satellite imagery and biogeochemical models

Methods for Estimating Emissions Models convert changes visible in the imagery into carbon emissions Errors up to 100% or more for all gases.

Categories of Recommendations Strengthening national greenhouse gas inventories Improving independent estimates of fossil-fuel CO 2 emissions Improving independent estimates of fluxes from land-use sources and sinks

Current Differences in Estimating and Reporting Emissions Developed countries –Produce annual estimates of sources and sinks of 6 greenhouse gases –Use the most rigorous methods → most accurate –UNFCCC review of methods and data sources Developing countries –Make periodic estimates of CO 2, CH 4, and N 2 O (many countries have produced only 1 inventory) –Use simplest methods → least accurate –No UNFCCC review

Recommendation UNFCCC parties should strengthen self-reported national emissions inventories by working toward Extending regular, rigorous reporting and review to developing countries Extending top-tier (most stringent) IPCC methods to the most important greenhouse gas sources in each country This would reduce errors to <10% for CO 2, and, depending on the country, from <10% to 50% for CH 4, from 10% to 100% for N 2 O, and from <10% to 50% for the fluorinated gases. Financial and technical assistance will be required to help developing countries collect, analyze, and report emissions regularly.

Recommendation Annex I (developed) countries should develop and implement standardized methods for preparing and publishing inventories that are gridded at spatial and temporal resolutions appropriate for the particular greenhouse gas and source UNFCCC inventories report annual, national totals, even when more detailed information is collected Gridded inventories would facilitate independent checks using atmospheric data and models

Categories of Recommendations Strengthening national greenhouse gas inventories Improving independent estimates of fossil-fuel CO 2 emissions Improving independent estimates of fluxes from land-use sources and sinks

Improving Independent Estimates of Fossil-Fuel CO 2 Emissions Deploy a CO 2 -sensing satellite Establish new atmospheric sampling stations (ground, ocean surface, aircraft) in strategic locations Measure 14 C in the CO 2 samples already being collected

Recommendation NASA should build and launch a replacement for the Orbiting Carbon Observatory (OCO) Most fossil-fuel CO 2 emissions emanate from large local sources OCO’s high precision and small sampling area could detect these signals and attribute them to the emitting country Demonstrate the capability for monitoring CO 2 from space for a climate treaty –Improve lifetime and coverage in future designs

Comparison of Satellite Capabilities Example: 500 MW coal power plant 4 Mt CO 2 yr -1 3 m s -1 OCOGOSAT Instrument accuracy 1-2 ppm4 ppm CO 2 in air sampled 1.7 ppm0.4 ppm CO 2 signal would be detectable by OCO, but not by GOSAT (best available satellite)

Recommendation Extend the international atmospheric sampling network: (1) to research the atmospheric “domes” of greenhouse gases over a representative sample of large local emitters, such as cities and power plants Existing stations are located away from cities and power plants to study natural sources and sinks New measurements at locations radiating from the center of selected large emitters would: –Document shifts in fuel sources in urban areas –Provide data to calibrate satellite measurements –Demonstrate a ground and aircraft monitoring capability

Recommendation Extend the international atmospheric sampling network: (2) to fill in underrepresented regions globally, thereby improving national sampling of regional greenhouse gas emissions. Stations are capable of accurately detecting widespread, unconcentrated sources New stations in high-emitting countries would improve tracer-transport modeling → improve independent verification of emissions More frequent vertical profiles would constrain atmospheric transport → improve comparisons with satellite CO 2 measurements

Recommendation Extend the capability of the CO 2 sampling network to measure atmospheric 14 C Natural emissions of CO 2 fluctuate and can be as large as fossil-fuel sources CO 2 from fossil-fuel and non-fossil-fuel sources can be differentiated using radiocarbon ( 14 C) measurements –Modern organic material contains 14 C from cosmic rays and bomb tests, but the 14 C in fossil fuels has decayed away Measurements could be made in CO 2 samples that are already being collected at low cost

Problems with Tracer Transport Method Transport Error Large and incompletely understood background fluctuations of natural emissions. Current sampling grid avoids urban areas and large industrial sources which generate most emissions. Current sampling grid is too sparse.

Accuracy of Fossil-fuel CO 2 Emissions Estimates Sector or ActivityMethod Current Uncertainty Uncertainty of Improved Methods Fossil-fuel combustion UNFCCC inventory <10-25% (developed countries) <10% (all countries) Fossil-fuel combustion Atmospheric measurements and models 50->100%<10-50% (annual) <10-25% (decadal) Large local sources Atmospheric measurements and models >100%10-25% (annual) <10% (decadal)

Categories of Recommendations Strengthening national greenhouse gas inventories Improving the ability to independently estimate fossil-fuel CO 2 emissions Improving independent estimates of fluxes from land-use sources and sinks

Improving Independent Estimates of Land-Use Emissions and Sinks Produce global maps of land-use and land cover change Design a research program to improve methods for estimating AFOLU emissions

Recommendation Establish a standing group to produce a global map of land-use and land cover change at least every 2 years. This will require a commitment to maintaining the continuous availability, in the public domain, of Landsat (or an equivalent satellite) and high-resolution satellite imagery. Frequent mapping necessary to detect important changes (e.g., forest clearing or planting) Provide an independent check on dominant sources of AFOLU CO 2 emissions Enable more accurate land-use emissions reporting from developing countries

Global maps Based on Landsat –Publicly available, medium resolution Supplemented with targeted high- resolution imagery to monitor logging, forest degradation, and some agricultural practices (e.g., rice cultivation) NASA Earth Observatory

Recommendation An interagency group, with broad participation from the research community, should design a research program to improve and, where appropriate, implement methods for estimating agriculture, forestry, and other land-use emissions of CO 2, N 2 O, and CH 4 Research to make more accurate estimates of AFOLU emissions –Emission factors: CO 2 from deforestation and forest degradation, CH 4 from rice paddies and cattle, and N 2 O from fertilizer application –Natural cycles of CO 2, CH 4, and N 2 O Supporting observations, including flux measurements and ecosystem inventories (annual measurements of major carbon pools) Improved methods could become part of UNFCCC reporting

Accuracy of AFOLU CO 2 Emissions Estimates Sector or ActivityMethod Current Uncertainty Uncertainty of Improved Methods AFOLUUNFCCC inventory <10-100% (developed countries) <10-50% (all countries) AFOLULand-use measurements and models %10-50% Deforestation source, afforestation sink Land-use measurements and models % (forest area) % (emissions) <10-25% (forest area) 10-25% (emissions)

Implications for Climate Agreements Implementing the recommendations would Establish rigorous annual inventories for all countries as the core of a greenhouse gas monitoring system Enable independent checks (<10% accuracy) on fossil-fuel combustion and deforestation, which are responsible for three-fourths of UNFCCC greenhouse gas emissions Improve monitoring and verification of all greenhouse gases through targeted research

Simplifying the Monitoring and Verification Problem 90% of global emissions are from energy and AFOLU (agriculture, forestry, and other land use) → obvious focus for monitoring and verification