Cities Lead on Climate Problems, and Solutions

New Report Analyzes Urban Areas Across the World


Projected temperature changes for cities by the 2050s

Projected temperature changes for cities by the 2050s
(click to enlarge)

Cities are emerging as most threatened by climate change, and as the first responders to it, says a new international report. The report, led by researchers at Columbia University and the City University of New York (CUNY), is the most comprehensive study to date detailing the risks cities face, and how they are preparing for impacts such as increased heat waves, drought and rising sea level. Authors from 50 cities looked at urban areas in Asia, Latin America, Africa, Europe and North America, doing in-depth analyses of Athens, Dakar, Delhi, Harare, Kingston, London, Melbourne, New York, São Paulo, Shanghai, Tokyo and Toronto.

Cities are now home to half the world’s population, the authors note. This is a groundbreaking study that should serve as a wake-up call about the need to make cities a key focus of global climate change research and response efforts,” said Cynthia Rosenzweig, a climate impacts scientist at the NASA Goddard Institute for Space Studies and the Center for Climate Systems Research, part of the Earth Institute at Columbia University, who is one of the coeditors. Published by Cambridge University Press, the report was convened by the Urban Climate Change Research Network, a global coalition of researchers specializing in climate change from an urban perspective. The initiative was founded at the Earth Institute in 2007.

Some key findings and facts from the report, Climate Change and Cities: First Assessment Report of the Urban Climate Change Research Network:

- Cities already tend to be hotter than surrounding areas due to absorption of heat by building materials. In the 12 cities analyzed in detail, average temperatures are projected to rise between 1 and 4 degrees C by the 2050s, increasing extreme weather events including heat waves.

- Coastal cities should expect to experience more frequent and more damaging flooding related to storm events due to sea level rise. Particularly at risk are populations like those living in slums located in lagoon areas such as in Lagos.

- In many cities, the quantity and quality of energy, water, and transport systems will be strained by increases in flooding and droughts, and increased demand for air-conditioning and other services. Water-borne diseases, injuries and chronic health problems may increase with rising temperatures and frequency of extreme weather.

“Climate change will stress cities in many ways” said William Solecki, director of the CUNY Institute for Sustainable Cities at Hunter College, and coeditor of the study.  “There will be more heat waves, threatening the health of the elderly and infirm. Droughts will also become more commonplace in many cities, while in coastal communities too much water may be the problem.” 

Despite the grim forecasts, the report outlines actions already being undertaken by many cities. Affluent ones like New York and London have been developing plans, but many in developing countries are also looking ahead. “Cities are developing comprehensive climate action plans, but we’re a long way from being prepared, particularly to meet the needs of the world’s poorest urban residents, who are also the most vulnerable,” said Shagun Mehrotra, managing director of Climate and Cities at the Center for Climate Systems Research and coeditor of ARC3.  Mehrotra said that cities must be “acting decisively, and acting now. The greatest gains in city-climate-risk reduction will occur from mainstreaming science-based analysis into ongoing and planned infrastructure investments by private and public sectors.”  International organizations led by the World Bank, Cities Alliance, and UN-HABITAT, along with C40, a group of large cities committed to tackling climate change, and ICLEI-Local Governments for Sustainability, are enabling cities to scale up these efforts, said Mehrotra.

The report is structured around key themes, including local energy systems, water supply, transportation and public health. It offers guidance on how cities can assess their climate risks and tackle adaptation, as well as mitigation issues, providing examples from 48 different cities around the world.

“We’ve tried to create a comprehensive study that explains both the challenges and opportunities facing local government managers.  It’ll also be a great classroom tool, one that we hope will train the next generation of climate change researchers and policymakers,” said Stephen Hammer, an energy policy expert who served as coeditor and lead author of one of the chapters.

Rosenzweig and Mehrotra are participating at the C40 Large Cities Climate Summit in São Paulo, Brazil from May 31–June 3, 2011. The report will be launched, along with the United Nations “Cities and Climate Change: Global Report on Human Settlements 2011,” by Joan Clos, United Nations under-secretary general and executive director of UN-HABITAT, and Marcelo Ebrard, mayor of Mexico City and chair of the World Mayors Council on Climate Change, at the ICLEI Resilient Cities 2011 in Bonn, Germany from June 3–5.