Can states meet their climate goals without a reliable GHG inventory?

September 8, 2023, by Olga Lyandres

The latest Intergovernmental Panel on Climate Change (IPCC) assessment report calls for net zero CO2 emissions by early 2050s to limit warming to 1.5oC. As a result, many U.S. states are putting forward statewide greenhouse gas (GHG) emission reduction actions and commitments. Currently over half of U.S. states have adopted GHG reduction targets[1] and 13 of those aim to reach net-zero by 2050 or sooner. But can the states meet these ambitious decarbonization goals? And would we (or they) know if they did?

States face many barriers, from an unfavorable political climate to market forces outside their control in taking climate actions. But, there is at least one step states can take that evades some of these barriers—building the internal technical capacity for climate change action, especially the development of a state GHG inventory system for tracking progress.

Despite adopting GHG reduction targets, most U.S. states lack technical familiarity of how to build the institutional and data collection systems that are essential for inventorying and tracking their GHG emissions and removals. States pursuing climate action are tasked with juggling numerous objectives, which include meeting state reporting requirements, aligning with national and/or international accounting methods, developing and implementing mitigation interventions, among other things. With limited staffing resources, states have to prioritize what they take on and reporting often falls by the wayside. Due to constrained staff resources, states may utilize a patchwork of ongoing efforts or outsource majority of the exercise to assemble an inventory. Consequently, many existing state inventories do not provide reliable results for policy decision making, including meaningfully comparing emission sources and discerning trends over time.

As state governments and other subnational jurisdictions develop policies and actions to address climate change, it is important that they employ a robust and transparent processes to monitor whether these policies are having the intended effect and whether the state is on track to achieve targets. This monitoring is largely done through the work of estimating and reporting on the GHG emissions and removals occurring within their jurisdictional boundaries. Inventories can also help illuminate data gaps and prioritize needs for future research initiatives designed to inform climate change mitigation policy making.

To support state GHG inventory development, the U.S. Environmental Protection Agency (EPA) provides state governments with disaggregated state-level data and an interactive spreadsheet tool, the State Inventory Tool (SIT). The SIT is pre-populated with default data from the national inventory and simplifies the work of producing emission estimates for a state. The SIT tool also allows states to enter state-specific data, but the ability to thoughtfully refine inputs is limited without proper training in GHG accounting and an understanding of the methodologies utilized by the SIT tool. In addition, the main barrier in utilizing state-specific data in compiling a GHG inventory is that states are still challenged by collecting and managing their own data needed to more accurately estimate GHG emissions and removals. Without improved data and analysis that is better tailored to their state-level policies and circumstances, states will be hard pressed to quantitatively demonstrate progress toward the emission reduction targets. And to obtain improved data and analysis, states need the technical infrastructure for data collection, data sharing across government units, and increased capacity to conduct the inventory process.

While some states may use the SIT to compile their inventory, other states have developed their own methodologies and tools, established collaborative partnerships with local academic institutions and other agencies, and/or relied on external consultants. These approaches can benefit a state’s GHG accounting efforts by supporting them to collect more representative activity data and emission factors and develop state-specific models. However, a robust GHG inventory system includes far more than just activity data and calculations.

GHGMI recently partnered with the State of Washington to help them build capacity in developing a GHG inventorying framework for their land use, land use change, and forestry (LULUCF) sector which included GHG emissions and removals from forests, grasslands, cropland, wetlands, and settlements. Specifically, GHGMI worked with the inventory team, led by Department of Ecology and staff from Department of Fish and Wildlife, to develop and pilot a LULUCF inventory manual for Washington to support future inventory development for the state. Our technical support was focused on helping them build an institutionally sustainable GHG inventory program within their departments, rather than a one-time research study.

Without good guidance and planning regarding the key elements of the inventory process, states face unnecessary barriers. For instance, some sectors are particularly challenging to estimate because obtaining relevant activity data calls for data collection and sharing that does not typically occur between state institutions. The agency that’s tasked with compiling the GHG inventory, say the Department of Environmental Quality, may need data on vehicle use from Department of Transportation or fertilizer application rates from the Department of Agriculture. The agency that ‘owns’ the data may be unwilling or legally unable to share the data. If the data exist, it may be aggregated or miscategorized and agencies may not have capacity to review and reprocess the data they do have.

Another component of an inventory system is record keeping and improvements. Lack of proper documentation and archival of previous work on the inventory makes it challenging to prioritize methodological improvements, and ensure that estimates can be compared over time, and build institutional knowledge of the inventory system. Without a structured framework to guide how an inventory should be compiled (e.g., staff roles and responsibilities, outlined methodological approaches, plans to conduct quality assurance and control, archival and compilation of the whole inventory) producing consistent timeseries of GHG emissions and removals is even harder. And inventories that fail to generate a consistent time series can do more harm than good by misleading policy makers about the actual trends in sectoral and overall emissions.

Fortunately, the U.S. EPA does offer useful resources for establishing national GHG inventory procedures, although they are not targeted toward states. For example, the Toolkit for Building National GHG Inventory Systems is a suite of documents including guidance, templates, and analysis tools to build capacity for national governments to meet national reporting obligations under the Paris Agreement, which are aligned with Intergovernmental Panel on Climate Change (IPCC) methodological guidelines. States are in no way required to follow them, but many already utilize some components of the national reporting frameworks. States looking to develop GHG inventories for the first time or to enhance their current efforts should take note.

Figure 1. Parts of an Information Management System. Source: U.S. EPA.

Many of the same elements that are present in the national GHG inventory system are also needed in a state inventory or when inventorying sector specific emissions. The different components of a GHG inventory system in the Toolkit are shown in Figure 1. They include: inventory planning, institutional arrangements (IA), methods and data documentation (MDD), QA/QC procedures (QA/QC), key category analysis (KCA), archiving system (AS), and the national inventory improvement plan (NIIP). Each inventory system element is described in Table 1. The toolkit can be adapted to support states in developing their own inventory systems. A system with these elements enables transparency and accountability in the process because the framework specifies when data collection is supposed to occur, who is responsible, what methods are used and why, how is the quality control of the data and calculations conducted, where the information is saved, and what improvements can and should be made.

Table 1. Descriptions of inventory system elements

The manual that GHGMI developed along with the state of Washington (WA) was based on the U.S. EPA Toolkit for Building National GHG Inventory Systems. The tool was adapted for the LULUCF sector and is set up to be regularly updated by the WA state inventory team as they further develop and refine their data collection and methodologies and make decisions regarding staff roles and responsibilities around the inventory process. The process of adapting the national toolkit to state needs involved consultation with agency staff leading the GHG inventory compilation process as well as other agencies and technical experts. States may feel overwhelmed by having to consider all this information as they work on their inventories, but the effort is well worth it because it lays the groundwork for proper GHG accounting for the state, which is essential for the implementation of state mitigation mandates. Other states seeking to improve their GHG inventorying systems could similarly start this work by focusing just on one sector at a time, recognizing resource constraints.

GHGMI’s approach centers on fostering internal capacity within government agencies (and other organizations and companies) to manage GHG accounting process into the future. GHGMI further supports staff capacity building with online courses on data management and IPCC methods provided through GHGMI’s education program. The enduring result of this capacity building approach is that the analysis can be replicated yearly by current and future inventory teams.

Other efforts to bolster state capacity and offer technical support are on the rise. For instance, NASA’s Carbon Monitoring System (CMS) Program supports national and subnational governments with carbon monitoring using satellite remote sensing on vegetation and land use. CMS is working with the State of Maryland to assist with GHG inventory of forest land and urban trees. Another example is the Blue Carbon Network established by Pew Charitable Trust. One of the goals for the network is to help find data and approaches for developing GHG inventories for state coastal wetlands. Through this effort, Oregon and North Carolina have an accounting of carbon storage and fluxes in coastal wetlands.

As states and other subnational governments strengthen their GHG inventory management capacity, they will be in a better position to effectively measure, manage, and mitigate GHG emissions, reach their GHG reduction targets, and thereby contribute to global efforts to combat climate change.

Cover image was developed using and is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.


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