State of the Planet

News from the Columbia Climate School


Cities Can Lead Nations

This is the second of a continuing series of essays and interviews from Earth Institute scientists on the prospects for a global climate-change treaty. Check with us daily for news and perspectives, and to make comments, as events unfold throughout the Copenhagen meetings.

Shagun Mehrotra
Shagun Mehrotra

By Cynthia Rosenzweig

At the Copenhagen climate summit, nations must answer a call for action—but local governments may help show the way.

Climate change is no longer predicted; it has arrived. A plethora of studies shows that global changes in physical and biological systems are being caused by human-induced warming. Building on the 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report, recent research have demonstrated that increased extreme weather events, melting of glaciers, increases in water flow, ocean salinity changes, advances in spring life-cycle events for plants and animals and many other impacts are outside the range of natural variability.

These lines of evidence have already caused hundreds of cities across the globe to lay out strategies to combat climate change. The world climate summit coincides with another important event: the Copenhagen Climate Summit for Mayors, where groups such as the Urban Climate Change Research Network (UCCRN) will present key findings from their first Assessment Report on Climate Change in Cities.

Initiated at a workshop at Columbia University, this report has been conducted by a group of specialists in urban climate-change topics.  Its aim is to provide the science needed to develop effective urban climate-change policies and programs. Urban areas are already leading the way with efforts to mitigate their contribution to climate change through efficient transportation and energy projects.  They must also begin to adapt themselves to climate change, given threats to their vulnerable populations, particularly the urban poor in developing countries, from potential flooding, heat waves, disease outbreaks and losses in water supply.

Cities such as New York and Chicago have already begun to use science-based projections to foresee and plan for threats.  For instance, the New York City Panel on Climate Change has developed the specific risk information necessary to support the development of a local adaptation plan for critical infrastructure. Risks include flooding in the airports, subways, and roads, as well as increased peak electricity load, with a greater likelihood of power outages.

In order to be truly effective, nations and cities must act in unison. In Copenhagen, heads of state have an important opportunity to move forward in concert with local governments to both mitigate and adapt to climate change.  In an increasingly urbanized world, such coordinated action is required to build a sustainable future.

Cynthia Rosenzweig is senior scientist at Columbia University’s Center for Climate Systems Research and Goddard Institute for Space Studies.

Stephen Hammer is head of the Urban Energy Program at Columbia’s School of International and Public Affairs.

Shagun Mehrotra is Faculty Fellow, Columbia University

Banner featuring a collage of extreme heat images.

Recent record-breaking heat waves have affected communities across the world. The Extreme Heat Workshop will bring together researchers and practitioners to advance the state of knowledge, identify community needs, and develop a framework for evaluating risks with a focus on climate justice. Register by June 15

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