258 ■ CITIES AND CLIMATE CHANGE
scale. Currently, climate projections for the present century are provided by
the IPCC, most recently in its Fourth Assessment Report, but these have sev-
eral limitations that inhibit their application at the city scale. First, the projec-
tions are typically provided at coarse spatial (such as hundreds of kilometers)
and temporal (such as monthly) scales, and decisions have to be made at
fi ner regional or local scales and require information at submonthly time
scales. Second, the projections provide average temperature and precipita-
tion, whereas vulnerability assessments require a suite of climate informa-
tion (such as wet or dry and hot or cold spells, extreme events, and the like).
Last but not least, they do not capture urban features, and near-term decadal
projections are less skillful than long-term projections. Furthermore, climate
model projections have not been linked systematically with distribution of
vulnerabilities and societal capacities for adaptive governance. Th us, key
questions in the area of climate adaptation at the city scale include issues
such as the following:
- What are the best methods to downscale climate models while integrating
key urban features such as anthropogenic heat fl uxes and urban surface
characteristics? - What is the range of extreme events that can be expected in cities as a con-
sequence of climate change, and how are they diff erent from larger-scale
projections? - What are the available frameworks for translating climate impacts into haz-
ards, risks, and adaptive strategies in cities, as planners recognize the dispro-
portionate impacts on the most vulnerable populations?
Climate change is expected to generate a range of impacts that cities must
address in adaptation planning, including more frequent extreme heat events,
droughts, extreme precipitation and storm events, sea-level rise, and changes
in disease vectors. Such impacts can aff ect public health, ecosystems, and the
many infrastructure systems, including water, energy, transportation, and
sanitation systems, that serve cities. To better characterize these impacts,
climate models downscaled to the urban scale are gaining more attention.
McCarthy and Sanderson are leading the work in this arena, as presented in
their paper “Urban Heat Islands: Sensitivity of Urban Temperatures to Climate
Change and Heat Release in Four European Cities,” on preliminary results
from downscaling regional climate models using an improved urban surface
scheme (MOSES2). Th eir results indicate that when fi ner-scale urban layers
are included—particularly anthropogenic heat fl uxes and surface characteris-
tics of urban areas—more extreme temperature impacts may be seen in cities
than previously projected. For example, the number of hot nights in London
for the decade of 2050 is projected to be three times greater if urban areas and