Emissions Inventory - Stage 2

01 Update your plan

As you advance from Stage 1 efforts that focused on developing a Tier 1 GHG inventory to Stage 2, where you will focus more on adding in criteria pollutant emission factors and adding activity categories that are relevant to air pollution while also solidifying institutional relationships and data reporting protocols, update your plan to ensure you have staff resources and clearly designated roles for data collection, inventory compilation as well as quality assurance steps. Staffing may remain broadly comparable to Stage 1, but the team should have secure access to laptops and, where feasible, a shared server or equivalent system for storing and managing the expanding inventory datasets .At Stage 2, your inventory should be aligned with a GHG Monitoring, Reporting and Verification (MRV) framework and housed in a secure and redundant database that enables IPCC reporting and easy conversion to emissions inputs for Source Attribution work (See Source Attribution Stage 2, Step 4) and Decision Support (See Decision Support Stage 2, Step 3).  

02 Review ambient air pollution inventory guidelines

Unlike Stage 1 work, which focused on the IPCC guidance for GHG inventory development, Stage 2 will focus on integrating criteria pollutant emission factors and sectors into an integrated inventory.  Here, you should ensure you are familiar with guidance and methods for air pollution inventory development before you dive in to the development process. Begin by familiarizing yourself with existing guidance and methodologies, such as the EMEP/EEA guidelines and methodologies for PM, SO2, NOx, VOC, and CO which are aligned with the IPCC guidelines. Other examples are also referenced below. Understand the specific requirements outlined in the IPCC guidelines related to GHG inventory development, and any new SLCP IPCC guidelines that are published, then identify additional steps needed to include air pollution aspects and sectors in your assessment. Pay special attention to high-emission sources, such as  so-called "high emitter" diesel engines and municipal waste burning, as these can significantly impact overall emissions. You should never forget that removing a source/subsector for its small emission​​s​​ must be demonstrated not to exceed a certain threshold. Check the IPCC guidelines for such estimations and thresholds. As you review the guidelines, critically compare objectives for data collection and compilation tasks, considering how they differ for GHG and air pollution inventories. This comprehensive understanding will enable you to establish a robust inventory that meets both national and international reporting requirements while addressing air quality management goals effectively.  

03 Clarify mandates and institutional relationships

UNFCCC prioritizes the EI for greenhouse gases but also CO, NOx, SO2, and VOC, which are common compounds of interest for air quality alongside other species (PM, NH3, etc.). The same database should be used to promote consistency (see Step 5), but could lead to duplication unless an agreement is established over which staff are responsible for which aspects of data collection and maintenance.  This is especially true where the different methodologies converge. Establish clear mandates for staff of both the climate change and air quality departments on how data is to be collected, managed and quality assured. 

04 Carry out a benchmark analysis

Carry out a benchmark of international, regional, and national literature to identify context-relevant emission factors where they exist and updating Stage 1 estimates where better, local data is identified for all compounds (i.e., GHGs, SLCPs and air pollutants). Systematically review existing studies, reports, and databases that pertain to your specific emissions sources. Focus on sources that align with your region’s economic activities and practices, ensuring data relevance. Document variations in emission factors across different contexts and reconcile discrepancies.  Where region-specific emission factors cannot be identified, continue to use default values from IPCC and EMEP/EEA but note where improvements are needed for your review in Step 9 below.   

05 Establish a common database

In addition to data obtained from ministries and other sources, it is crucial to derive information from the established monitoring, reporting, and verification (MRV) system. Consider expanding this MRV system (database/server) to accommodate spatialized activity data for future gridded emissions assessments. If a greenhouse gas (GHG) MRV system does not already exist, you should establish one that integrates your emission inventory database, including air pollutants, into a unified structure. Begin by identifying gaps in data collection and storage capabilities related to spatialized activity.  
Engage with stakeholders to identify the necessary types of activity data, such as energy consumption, transportation metrics, waste burning practices, agricultural and forestry operations, and land use patterns. Establish standardized data formats and protocols for consistent input and quality control.  
Finally, consider developing a user-friendly interface for data access that promotes transparency and enables users to visualize and interpret emission inventories effectively, supporting informed policy decisions and efficient resource allocation. 

06 Replicate steps 3-10 from Stage 1 including all pollutants

Decide on a common base year for both GHG and air pollutants and repeat the process used for your Stage 1 inventory ensuring that you include all air pollutant relevant sectors and the full complement of GHG, and priority air pollutants (PM, SO​2​, NOx, VOC, and CO) emission factors.  ​If your country is a party to the Convention on the Long-Range Transport of Air Pollution (CLRTAP) convention, also include NH​​​3​​​, Black Carbon (BC), and PM​​​10​​​ and PM​​​2.5 Quality checks from Step 6 can compare your data against global inventories like CEDS, EDGAR, and GEIA. Look for discrepancies in emissions totals, trends, and source contributions. Utilize these benchmarks to identify potential errors or gaps in your inventory and adjust methodologies or data sources to enhance accuracy and reliability. Bear in mind that local emission inventories are generally more accurate than global ones.

07 Develop data visualizations

When developing data visualizations for an air pollution emission inventory, choose clear and effective methods to illustrate findings. Use pie charts to visually represent the proportion of different emission sources relative to total emissions. Bar graphs can help compare emissions across different species or sectors, while histograms can illustrate the distribution of emissions data over time or locations. Waterfall graphs are effective for showing cumulative contributions of various species to overall emissions totals. Incorporate color coding to enhance readability and ensure that each graph has a clear title and legend. Finally, provide contextual information to help viewers interpret the visualizations accurately, aiding in data understanding and decision-making. 

08 Report to UNFCCC, LRTAP or other regional agreements

When reporting emissions data to the UNFCCC or the Convention on the Long-Range Transport of Air Pollution, ensure adherence to specific guidelines and formats outlined by these organizations through the authorized and mandated Ministry. Maintain accuracy and transparency by using standardized methodologies for data collection and calculation. Regularly update your emissions inventory to reflect the latest information and verify data consistency. Engage stakeholders throughout the process to facilitate collaboration and ensure comprehensive reporting, thereby enhancing the credibility and effectiveness of your submissions.

09 Develop an emissions inventory improvement plan

Begin with your key category analysis (Stage 1, Step 8) to identify sectors contributing significantly to total emissions. Assess the relative uncertainty of existing data through statistical analysis and expert judgment, prioritizing categories with high uncertainty. Based on this analysis, determine which sectors should advance to Tier 2 methodologies, which offer more detailed data and improved emission factors. Document clear objectives and timelines for upgrading methodologies, allocate resources and training for staff, and outline procedures for ongoing data verification and quality control. Engaging stakeholders will enhance the plan's effectiveness and ensure it is aligned with national and international reporting requirements. Although the improvement plan should identify the timing of future work, Stage 2 inventories may still be updated in response to reporting or project needs rather than according to a fixed recurring schedule.​