Wednesday, August 7, 2013

How Can Cities Best Measure Greenhouse Gas Emissions?

What metrics best reflect the energy and carbon intensity of cities? Insights from theory and modeling of 20 US cities?(12 page pdf, Anu Ramaswamiand Abel Chavez, Environmental Research Letters, Jul. 3, 2013)

Today we review a research paper that examines various ways cities use to measure and compare GHG emissions: top down and bottom up- and the advantages or disadvantages of these approaches. The authors conclude that normalizing the output in terms of carbon-energy per unit GDP.

GHG cities
Key Quotes:

“no guidance is yet provided on how to normalize the aggregate GHG emissions computed by the different methods to help cities compare their local energy intensity and carbon intensity features with other cities.”

“a key question that arises is: what metrics best represent the energy intensity of cities at the local or regional scale?”

“The major conclusion of this paper is that a dual approach of GHG accounting for cities, with CIF and a separate CBF, as is being recommended by ICLEI-USA and BSI, demands different metrics. Our modeling of 20 US cities shows the GHGCIF (all metabolic community-wide GHG accounts) are best represented as per unit GDP.”

“Our paper suggests that using the appropriate GHG accounting method (CIF) with the suitable normalization (per unit GDP) is important to better uncover relationships with urban form; the per GDP metric has the added advantage that downturns in the economy are readily accounted for.”

“Our results suggest cities should use GHG per capita metrics for consumption-based accounts and GHG per GDP metrics for the infrastructure-supply chain accounts.”
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