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King County Community Greenhouse Gas (GHG) Emissions Inventory and Wedge Analysis


Start: March 2019
End: August 2019
Client or funder: King County, WA, in partnership with King County Cities Climate Collaboration (K4C)


Offering some of the highest leadership on local climate action and regional coordination, King County and its 39 cities have established the collective goal to reduce countywide sources of greenhouse gas (GHG) emissions 25% by 2020, 50% by 2030, and 80% by 2050, all compared to a 2007 baseline. To understand what it would take to achieve adopted GHG targets, King County and partners of the King County-Cities Climate Collaboration (K4C) established specific, quantifiable pathways nicknamed the “wedge analysis”. In light of changing federal and state policies the County contracted ICLEI USA to update its wedge analysis in 2019.

Project Activity

To support the approach, ICLEI developed a community-scale geographic-based GHG for calendar year 2018 in a way that ensured consistency and comparability with previous inventories. The County’s 2018 GHG inventory was used to quantify progress toward meeting its existing “absolute” target, plus a per-capita target, based on a 2007 baseline. The analysis looked at recent trends and projected future changes based on: population growth; impacts of regulatory standards and codes, cleaner fuels, fewer vehicle miles, improved building energy efficiency, and increased renewable energy use. The results were used to project potential impact of 2019 Washington State policies on clean electricity, vehicle fuels, and related GHG reduction strategies; and to identify how sector targets may need to be updated to achieve the 50% reduction in GHG by 2030.

Adding an additional layer of investigation, ICLEI’s Contribution Analysis quantified causes of changes in emissions between 2008 and 2018. Finally, using the emissions inventory ICLEI then updated the 2015 Strategic Climate Action Plan (SCAP) wedge analysis (see graphic). Taken together, these analyses inform pathways for the County to achieve its 2030 community-scale GHG reduction target using updated assumptions about government policies and sector-specific targets.


Provided 3 pieces of analysis in the final report: a GHG inventory, a contribution analysis, and a wedge analysis.

See the full analysis.

Those Involved

King County, WA

“In the last decade, the population in King County has grown by more than 10%, but emissions have remained flat. While we’ve seen an important decoupling of emissions and population growth, ICLEI’s Contribution Analysis showed that we need to do much more to phase in renewable energy sources, develop clean transportation options, and make our homes and buildings more efficient.” – Matt Kuharic, Climate Change Program Coordinator for King County, WA