Publication Abstracts

Blake et al. 2011

Blake, R., A. Grimm, T. Ichinose, R. Horton, S. Gaffin, S. Jiong, D.A. Bader, and L.D. Cecil, 2011: Urban climate: Processes, trends, and projections. In Climate Change and Cities: First Assessment Report of the Urban Climate Change Research Network. C. Rosenzweig, W.D. Solecki, S.A. Hammer, and S. Mehrotra, Eds., Cambridge University Press, pp. 43-81.

Cities play a multidimensional role in the climate change story. Urban climate effects, in particular the urban heat island effect, comprise some of the oldest observations in climatology, dating from the early nineteenth century work of meteorologist Luke Howard. This substantially predates the earliest scientific thought about human fossil fuel combustion and global warming by chemist Svante Arrhenius. As areas of high population density and economic activity, cities may be responsible for upwards of 40 percent of total worldwide greenhouse gas emissions, although various sources have claimed percentages as high as 80 percent. Figure 3.1 shows a remotely sensed map of nocturnal lighting from urban areas that is visible from space and vividly illustrates one prodigious source of energy use in cities. Megacities, often located on the coasts and often containing vulnerable population s, are also highly susceptible to climate change impacts, in particular sea level rise. At the same time, as centers of economic growth, information, and technological innovation, cities will play a positive role in both climate change adaptation and mitigation strategies.

Urban population recently surpassed non-urban population worldwide and is projected to grow from 50 percent currently to 70 percent by 2050. The urban population growth rate will be even more rapid in developing countries. In terms of absolute numbers, urban population will grow from ∼3.33 billion today to ∼6.4 billion in 2050, about a 90 percent increase. These numbers underscore the fact that urban climate is becoming the dominant environment for most of humanity.

This chapter presents information on four interrelated components of urban climate: (i) the urban heat island effect and air pollution, (ii) the current climate and historical climate trends, (iii) the role of natural climate variability, and (iv) climate change projections due to worldwide greenhouse gas increases.

Teasing out the relative infl uences of these components on urban climate is challenging. Natural variability can occur at multidecadal timescales, comparable to the timescales used for historical analysis and to long-term greenhouse gas forcing. Another challenge is that different climate factors may not be independent. For example, climate change may infl uence the amplitude and periodicity of natural variability, such as the intensity and frequency of the El Niño-Southern Oscillation (ENSO).

To survey these issues, twelve cities are selected as examples. The twelve focus cities in this chapter — Athens (Greece), Dakar (Senegal), Delhi (India), Harare (Zimbabwe), Kingston (Jamaica), London (UK), Melbourne (Australia), New York City (USA), São Paulo (Brazil), Shanghai (China), Tokyo (Japan), and Toronto (Canada) — share a range of characteristics but also differ in key respects. They are all large, dynamic, and vibrant urban areas, and act as hubs of social and economic activity. They also feature long-term twentieth-century climate records that allow trend detection, projections, and impact analysis. All the cities selected are likely to experience signifi cant climate change this century, and several illustrate the infl uence of climate variability systems such as ENSO. Some of the city examples demonstrate unique vulnerabilities to extreme climate events.

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BibTeX Citation

  author={Blake, R. and Grimm, A. and Ichinose, T. and Horton, R. and Gaffin, S. and Jiong, S. and Bader, D. A. and Cecil, L. D.},
  editor={Rosenzweig, C. and Solecki, W. D. and Hammer, S. A. and Mehrotra, S.},
  title={Urban climate: Processes, trends, and projections},
  booktitle={Climate Change and Cities: First Assessment Report of the Urban Climate Change Research Network},
  publisher={Cambridge University Press},
  address={Cambridge, U.K.},

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RIS Citation

ID  - bl01100r
AU  - Blake, R.
AU  - Grimm, A.
AU  - Ichinose, T.
AU  - Horton, R.
AU  - Gaffin, S.
AU  - Jiong, S.
AU  - Bader, D. A.
AU  - Cecil, L. D.
ED  - Rosenzweig, C.
ED  - Solecki, W. D.
ED  - Hammer, S. A.
ED  - Mehrotra, S.
PY  - 2011
TI  - Urban climate: Processes, trends, and projections
BT  - Climate Change and Cities: First Assessment Report of the Urban Climate Change Research Network
SP  - 43
EP  - 81
PB  - Cambridge University Press
CY  - Cambridge, U.K.
ER  -

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