How Are We Doing?

This graph shows trends over time and includes commercial and residential electricity and natural gas usage, vehicle miles traveled, compost and waste emissions, and waste water treatment emissions. Note that the data in this figure should be viewed as a best estimate using available data rather than an exact metric. Emissions data is calculated using raw utility data converted to emission estimates. This conversion is done with an EPA program called eGRID which calculates emission conversions that are regionally specific (i.e. "location-based"), but are not specific to one power utility. For more information about eGRID visit: https://tinyurl.com/eGRIDemissionfactors -- Note: eGRID emssions factors can vary from year to year, which can cause the columns in the graph to fluctuate.

The BLUE target line depicts Mercer Island's portion of the emission goals for all of King County, as part of the King County-Cities Climate Collaboration (See: https://tinyurl.com/K4Cinfo). This goal is based on a 25% reduction in 2007 emissions, to be achieved by the year 2020.

What Are the Biggest Sources of Our Emissions?

As is common for most Lake Washington area cities, Transportation (aka "Mobile Combustion") and Electricity Usage account for the vast majority (approx 75%) of community-wide emissions on Mercer Island. Seattle is the exception to this pattern because its electricity generation is almost entirely clean hydropower. In the transportation sector, SOV usage (i.e. solo commuters) is the area with the greatest potential for improvement.

Solutions such as carpooling, bike infrastructure, and mass transit are the only way to reduce per capita emissions from transportation. In the electricity sector, approximately 1/3 of the power served to the Island by Puget Sound Energy (PSE) is currently generated, on average, by coal-fired power. This is responsible for a disproportionate amount GHGs in the region, and is an arena in which the City of Mercer Island, along with its K4C partners, is working vigorously to expedite both the early closure of the Colstrip, Montana power station and replacement with cleaner energy sources.

 

 

Emissions Trends per Capita

In 2016, the population for Mercer Island was approximately 23,700; on average that year, each resident produced 8.41 metric tonnes of Greenhouse Gas Emissions (GHGs). King County's "geographic plus" emissions in 2008 were reported as 12.4 metric tonnes per capita (see: https://tinyurl.com/KingCountyInventory2008, Table 3).

The BLUE target line shows the K4C goal of 25% reduction from 2007 translated into an average per capita emissions level by 2020: approximately 8.5 metric tonnes (assuming a 1% population increase per year). The data presented in this figure include all residential, commercial and industrial emissions divided by the number of residents of Mercer Island, and do not depict GHG offsets from programs that can help prevent carbon emissions (e.g. recycling or composting instead of landfilling, etc.).

A Look into the Future

Based on current trends, if no additional GHG reduction programs were implemented on Mercer Island, over the next 30 years Mercer Island would emit a cumulative total of nearly 6.4 million tonnes of CO2e into the atmosphere (an average of 220,000 tonnes per year). The relative contribution of each major emissions component can be selected in the "Compare To" menu box -- the graph and Y-axis will adjust accordingly.