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Defining a ‘Carbon Neutral’ City

by Justus Stewart and Pete Erickson

Last November, Alex Steffen gave a two-night talk at Seattle’s Town Hall. In those talks, he issued a challenge to the government and the residents of Seattle: to be bigger and bolder with our goals; to stake our claim as the environmental and civic leaders of the bright green future. He challenged us to conceive of Seattle as the first carbon neutral city in North America, and to get there by 2030.

Since then, the idea has spread, and been debated, among Seattle’s civic leaders and innovative thinkers. One question that moved immediately to the fore is this: What does carbon neutral even mean? A critical first step in pursuing ‘carbon neutrality’ is defining it.
Of the many considerations that go into defining carbon neutrality for a city the size of Seattle, a few stand out for their significance.

1. How does carbon neutrality relate to the global limits that scientists warn us we must not exceed – 350 ppm CO2 (or 2 degrees C over pre-industrial levels)?

2. Would a city have to actually quit emitting greenhouse gases, or could it use offsets (purchase carbon credits) to reach its goal?

3. Are we trying to account for only emissions that occur within city limits, or all emissions for which Seattleites are responsible?

This is wonky stuff; catnip for the carbon emissions accounting crowd (yes, they exist, and yes, there are technically enough of them to constitute a crowd…). Let’s take them one at a time.

How does Seattle’s goal relate to the global limits that scientists warn us we must not exceed – for example, 350 ppm (or 2 degrees C)?

Well over 1,000 cities in the US have adopted greenhouse gas emissions reduction goals. Many of those cities, including Seattle, express their goals in alignment with a science-based goal of an 80% reduction (from 1990 levels) by 2050. This "80 by 50" target is reflected in some national policies as well. However, we often lose sight of the fact that this is a global goal, not a local one. Meeting an aggressive global goal (whether 350 ppm, 450 ppm, or whatever is required to limit warming to 2 degrees C) will require the rich countries of the world to reduce their emissions at least 80% by 2050 -- and in addition, to help finance emission reductions in poor nations. If we only hit 80% of our own emissions by mid-century -- and don't help poor nations invest in clean energy and other emission-reducing projects -- then we overshoot our global emissions target, with potentially devastating consequences.

What does this mean? It means we may want to define carbon neutrality in a way that accounts for both our actual emissions and our fair share of global emissions. This does not have to be guesswork: frameworks exist to apportion emissions according to measures of historical responsibility and capacity to act. These frameworks - often called burden sharing or carbon budgeting -- suggest that to contribute equitably to a 2 degree goal, the U.S. may need to take responsibility for emission reductions greater than its total emissions. One calculation found that the U.S. would need to go well below zero (substantially “carbon negative”) by 2030.

The reasoning behind a burden-sharing approach is simple: because wealthy nations (and their wealthy cities) are responsible for the lion’s share of historical emissions, which helped fuel our prosperity and now threaten the whole planet, we must take greater action to reduce those emissions than poor countries with less responsibility and less capacity to act. After all, we cannot ethically (or even legally) restrict emissions from developing nations if it means they remain in poverty. If they are to reduce their emissions, we must help fund their cleaner path to prosperity. That’s point two.

Does the City have to actual quit emitting greenhouse gases, or can it use offsets (purchase carbon credits) to reach its goal?

While carbon emissions in Seattle can be reduced significantly from their current levels, it is unrealistic to actually stop local emissions completely. Doing so would be prohibitively expensive. In terms of achieving global targets, then, it is at some point more cost effective to reduce emissions in other places than here in Seattle. Furthermore, as described above, we may want to accept a greater share of global responsibility for emission reductions, perhaps going beyond zero, and financing emission reductions (likely as offset credits) in poor nations. But how do we determine where the threshold should be between our own reductions and those we fund elsewhere as offsets? How deep of a reduction should Seattle make in its own emissions? Considerations include whether to honor Seattle's existing 80% by 2050 goal, cost-effectiveness, global responsibility, the value of branding Seattle as a global leader in green innovation, and other in-city benefits promoted by advocates of carbon neutrality.

Are we trying to account for only emissions that occur within city limits, or all emissions for which Seattleites are responsible?

Finally, and crucially, is the distinction between the elimination of emissions within the geographic boundary of the city, and the elimination of emissions for which the city and its citizens are responsible, wherever in the world they occur. Both methods -- termed "production-based" and "consumption-based" inventories, respectively -- have their merits in emissions accounting. For a goal of neutrality, the latter approach -- based at least partly on consumption -- should at least be considered. One traditional example used to support a consumption-based approach is this: imagine a cement plant operating within the city limits, with significant GHG emissions. If we attempt to reduce those emissions while accounting only for what’s emitted within city limits, then we simply move the cement plant! It’s now operating in another city, and no longer our problem. Taking a broader view of the emissions for which Seattleites are responsible, and therefore accounting for emissions associated with our food, our clothes, or are gadgets, does provide a more complete picture of the role of Seattle residents in global emissions, and would make every choice we make count: our meals, our trip to work, our new phone. Would counting emissions in his way unlock the potential for radical innovation and currently unimagined ways of living well in this city? Or would it be just too difficult to count in a meaningful way and distract from things we can more easily influence?


IMAGE CAPTION: Greenhouse gas emissions sources in both Production and Consumption-based inventories.

There are many other issues to be tackled as well, in this process of crafting a definition. Who takes responsibility for military bases? For ports that ship goods all over the country? For regional airports that draw from many cities? Do you include the mines that dug the ore, or just the plant that made the car? What about deforestation indirectly induced by purchasing crops or biofuels? These and other decisions are made on a case-by-case basis; if that sounds a little ad-hoc remember that no city has done this before…

To engage the task of creating a working definition for climate neutrality that addresses the above concerns and provides a scientifically sound path forward, a citizen-led technical working group is beginning to form, with the goal of crafting a definition for Seattle.

Want to weigh in on the choices above? Want to help? If you have expertise in the field of climate emissions accounting and want to be a part of this group, or would like to submit comments to the group, please email the Climate Neutral Seattle Technical Working Group at

Image source: Stockholm Environment Institute

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Don't count out the 667 colleges that are going for carbon neutrality, and publicly reporting on how they plan to get their and their progress = some great lessons for cities, and a few within Seattle's city limits...

Posted by: atlas1776 on 22 Feb 10

To accomplish true carbon neutrality an entity such as Seattle would require expertise beyond climate emissions accounting; it would need to draw upon life cycle analysis and regional/industrial metabolism expertise, which has been applied on the level of industries or parts of cities for almost two decades.

Posted by: Warren K. on 22 Feb 10

What about me(thane)? Methane radiative forcing appears to equate to about half of CO2's RF value. Might be good to cover both gases, perhaps. Don't Seattle folks consume plenty of steaks, butter, milk, lattes, hot coco and... beans? :)

Seems to me that talk about CO2 may partly be a cover story for dealing w/ peak oil without talking about peak oil -- a more consumption-friendly fig leaf. Not that we don't need to deal with it.

Posted by: Ken Ott on 23 Feb 10

Achieving Carbon neutrality is essential and i m glad that many organization have started initiative to accomplish that, like switching to Eco-friendly solutions like Billing Tracker, Replicon Timesheet,etc

Posted by: Mohit on 24 Feb 10

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