Considerations for future IPCC inventory work on SLCF
(black carbon example)• Does policy context matter?
• A quick look at source categories• A quick look at methods• Implications

Bill Irving
USEPA
May 30, 2018• Policy context is important• For GHG inventories, IPCC focus is on
national totals, to facilitate international
cooperation (policy relevant but notprescriptive)• BC inventories are part of a broader
strategy on health & environment fornational, regional and local governments• Implications for potential IPCC work
• Additional inventory information needsfor BC?
• Timing during year
• Location (high latitude, other sensitiveregions, population centers)• Co-emitted pollutants, including negative
radiative forcers• Weather conditions & air quality
monitoring needs• Policy relevance of "annual national
totals" of BC?
• Growing importance, but part of abroader strategy• Individual countries are likely to needmore as their capacities increase

Comparison of priority (‘key’) sources• In the US (and other developed countries?) the largest sources of BC aretypically transportation and burning of biomass (forests fires &agricultural residue burning).
• Developing countries may have higher BC emissions from residential
cooking and industrial sectors, with growing mobile source sectors.

••

US Example
Transportation (diesel engines) is aleading sources of both GHGs and BC
Wildfires less important for CO2 than forBC

“On-road” Transportation – methodological comparison• US CO2 estimates (key category)• IPCC Tier 2: aggregate fuel use by mode x country-specific carbon content• Approximately 30% of total national emissions• US Non-CO2 estimates (N2O key category, CH4 non-key category)• IPCC Tier 2: Vehicle Miles Traveled by Vehicle Type, Fuel Type, Model Year, and Control Technology x CH4/N2O• Less than 1% of total national emissions• EMEP/EEA air pollutant emission inventory guidebook 2016 (Tier 2)• PM emissions = Number of vehicles by category/technology x distance traveled x technology-specific emission factor• BC = percentage of PM• US black carbon estimates for transportation (Report to Congress)• “MOVES” model calculates total PM2.5 emissions and BC emissions at the county level.
• Accounts for high emitters, deterioration of PM emissions (i.e., increase in PM mass) with higher mileage, and increased PMemissions at lower temperatures.
• Directly calculates BC emissions (as well as other exhaust PM components such as sulfates and OC), and accounts for thesignificantly reduced BC fraction emitted from on-road diesels due to application of diesel particulate filters (DPFs).
• Gasoline OC and BC emissions increase dramatically at lower ambient temperatures. To calculate this increase for gasoline vehicles,
an hourly grid-cell temperature adjustment was done as part of emissions processing at the county level for each of over 3,200counties.
• MOVES can also be used to calculate tire and brake wear PM2.5, with speciation factors applied to calculate BC.

Increasing
complexity

SimilarForest fires/wildfires – methodological comparison• US CO2 estimates (Forest Land remaining Forest Land - key category, IPCC Tier 3)• Total C stocks are estimated for each C storage pool, next the net changes in C stocks for each pool are estimated,
and then the changes in stocks are summed for all pools to estimate total net flux.
• Changes in C stocks from disturbances, such as forest fires or harvesting, are included in the net changes.

Method notcomparable• US Non-CO2 from forest fire estimates (non-key category)• IPCC Equation 2.27: Area burned x Fuel available x combustion factor x EF
• Data inputs from forest land survey data (FIA) and burn severity data (MTBS)• AP-42 (PM2.5 emissions) – similar to EMEP/EEA air pollutant emission inventory guidebook 2016
• Emissions = Pollutant yield/fuel consumed x fuel/area x area
• BC is % of PM• US black carbon estimates for fires (Report to Congress)• Process modeling and remote sensing data to estimate fire activity patterns and emissions from fires (Blue SkyFramework, 2010). Blue Sky can enable•••

Increasingcomplexity

the lookup of fuels information from fuel maps
the calculation of total and hourly fire consumption based on fuel loadings and weather information
the calculation of speciated emissions (such as CO2 or PM2.5) from a fireSimilarSummary• Policy context can have implications for inventory requirements and future work
• More to consider than just adding another column to IPCC tables• Similarities and differences in priority sources & methods for GHGs and BC• Alignment for some sources, and some methodological approaches, but not for others• Historical IPCC core strengths and limitations for methodological development• IPCC focus on complete and comparable national totals and Tier 1/Tier 2 methods• Limitations on utility for atmospheric modeling and setting/assessing domestic standards because of spatial/temporal
resolution, and tracking of mitigation efforts.

• IPCC Approach: incremental approach or one-stop shop?
• IPCC could focus on products that facilitate countries preparing GHG and SLCF inventories• Cross-walk IPCC categories with major sources to identify focus areas (e.g., for BC - forest fires, residueburning, transportation, some industrial sources• Detailed survey of available guidance to identify gaps
• Identify where methods and activity data converge (e.g., Tier 2 for non-CO2 and BC)• Identify where methods and AD do not converge (e.g., C stock changes, fluorinated gases)• Formats?
• Series of IPCC technical bulletins focused on particular sectors? (E.g., agricultural burning)• Emission Factor Database (EFDB) to include SLCF?
• IPCC methodological supplement?
• Longer-term planning?
• Process for getting feedback from inventory compilers and considering additional work? (no UNFCCC
inventory reports or reviews to