256 ■ CITIES AND CLIMATE CHANGE
Such transboundary activities confound measurements of GHG emissions
at the city scale and raise many important questions, such as the following:
- What are the best methods to measure GHG emissions from cities when
human activities in cities transcend the small geographic-administrative
boundary of cities? - What are the principles by which GHG emissions are allocated to urban
residents? How is trade between cities, national and international, incorpo-
rated into GHG accounting? - How can city-scale GHG accounting techniques be more policy relevant
and compatible with existing methodologies established to promote carbon
trading? - Can city-scale GHG emissions be benchmarked and compared with
national-scale GHG emissions and with other cities? - What do we know about current baseline energy-use benchmarks in build-
ings and transport sectors in cities across the world? - How can urban design—the layout and choice or urban materials—enhance
GHG mitigation in the buildings sector?
In the commissioned research paper “Greenhouse Gas Emission Baselines for
Global Cities and Metropolitan Regions,” Kennedy, Ramaswami, Carney, and
Dhakal address the question of GHG accounting to incorporate transbound-
ary urban activities. Th e paper reviews key methodologies for measuring GHG
emissions from cities and covers multiple activity sectors—energy use in sta-
tionary and mobile combustion addressing building and transport sectors,
industrial nonenergy process emissions, waste emissions, and land-use change.
A major breakthrough of this paper is to harmonize diff erent methods in the
literature for estimating GHG emissions associated with cities and to develop
a resulting consistent methodology that is applied to 43 cities across the globe.
Th e methodology distinguishes between energy-use and direct GHG emis-
sions within urban boundaries (Scope 1 emissions) computed consistently with
Intergovernmental Panel on Climate Change (IPCC) methods, transbound-
ary contributions associated with electricity generation for use within cities
(Scope 2), and emissions associated with marine and airline travel from cit-
ies (Scope 3). Th e paper demonstrates that data are available and that overall
GHG emissions can indeed be computed in a consistent manner for numerous
cities across the world. A key fi nding of the paper is that required reporting
on Scope 1 and Scope 2 emissions, supplemented with optional reporting of
Scope 3 items, off ers a robust methodology for representing GHG emissions
associated with urban activities.
Growing interest exists in assessing spatial variation in GHG emissions both
within urban areas as a function of urban form and across the urban-rural gra-