Measuring urban greenhouse gas emissions
Posted on July 3, 2009
Filed Under General
I’ve just returned from the 5th Urban Research Symposium in Marseille, which this year focused on cities and climate change. We were presenting our work on the modelling of urban energy systems and it was a great chance to talk shop and see what others were doing in the same area.
One of the main themes running through the event was how to measure greenhouse gas emissions from cities. There have been numerous figures published recently, such as the IEA’s estimate that cities are responsible for 71% of global direct and fossil-fuel related emissions. There was much hand-wringing among the conference participants though about whether the methods for compiling such inventories are sufficiently mature to facilitate comparative studies or for use in international trading arrangements.
Some of the worry seems misplaced. Of course better data is always desirable but as a representatitve from ICLEI pointed out, the world hadn’t even agreed on the official list of greenhouse gases in 1992. Now 17 years later, we’re complaining about too many competing methods. And anyway, if the world is aiming for massive emission reductions on the order of 80% by 2050, then surely we have enough information to act.
This pragmatic view was best expressed in a paper by Chris Kennedy, Anu Ramaswami and others titled A protocol for City based GHG emission indices. Using the corporate emissions protocol of the World Resource Institute, they suggest that the emissions of a city should include:
- Scope 1 emissions from the consumption of fossil-fuels directly within the city boundary (e.g. natural gas);
- Scope 2 emissions from the indirect consumption of imported fuels like electricity, heat or steam; and
- a limited set of Scope 3 indirect emissions from key resources consumed within the city (e.g. cement, steel, food) and a share of major cross-boundary transport (e.g. air travel, freight).
The key thing about this approach is that by using a reduced set of Scope 3 emissions, you can capture the open nature of cities, i.e. their dependence on resources imported from other regions, without introducing too much administrative hassle. It’s a question of diminishing returns and this proposal seems like a sensible one if a practicable international framework for urban emissions inventories is to be established.
The full paper, and the accompanying presentation, should be available from the URS website in the coming days.
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