Jacob Scherr, Director, Global Strategy & Advocacy, Washington, DC

On January 31st, UN Secretary General Ban Ki-moon named former New York City Mayor Michael Bloomberg as a Special Envoy for Cities and Climate Change.  This appointment reflects the growing recognition of the global impact of cities which, according to Bloomberg,  account for  "more than 70 percent of global greenhouse gas emissions and two-thirds of the world's energy use today."  Sarah Glazer reports here on the current efforts by C40 - a network of major cities - to work together to take local actions to address climate change.  The UN hopes that Bloomberg, also chair of C40's Board, will in his new role stimulate even more commitments by municipalities to reduce emissions and increase their capacity to adapt to a changing climate.  UN Photo/Eskinder Debebe

Last May, New York City packed 100 geeks into a room for 14 hours on a Saturday, fueled them with coke and pizza, and offered them cash prizes for new apps that could improve the city’s environment.  By the end of day 16 projects emerged, from crossword-style games that teach energy literacy to a Google street view to visualize future flood levels. First prize for the best energy, environment and resilience app went to a solar evaluation calculated on a smartphone to figure out a homeowner’s costs for going solar.

This type of hackathon is just one of the many ideas that cities are sharing with one another through C40, a global network of 66 mega-cities from Beijing to New York that have made a commitment to do something about climate change.

Hackathons like New York’s are catching on in cities around the world, James Alexander, C40’s finance and economic development initiative director, told me in a conversation near his London office. Rio de Janeiro, he told me, has run hackathons to solve big city problems like complaints about broken street lights and tree pruning.

Although C40’s member cities are spread across Europe, Asia, Africa, and North and South America, the network makes extensive use of video-conferencing and webinars to share ideas, says Alexander. “Using these platforms, major global cities have the freedom to say, ‘You know guys, this didn’t work and we could have saved ourselves three months of running around if we’d just known this… so don’t go down that alleyway.’”

The learning among cities is a two-way street. A key part of C40’s philosophy is “If one city is trying to do something, either another city has already done it and can share their successes and battle scars, or someone else probably wants to do it,” Alexander says.  “So why not all learn together how to do it rather than each individually inventing the wheel?”

While the hackathon may sound like a big party, it’s actually part of a serious effort by cities to take advantage of the green economy—saving the city money, improving urban life and creating new jobs.

The winner of New York’s CleanWeb hackathon last May, SolarList, trains students and young entrepreneurs to educate homeowners about their solar options with its phone-based free home assessment, then refers homeowners to its preferred list of installers. Along the way, homeowners pay less, installers sell more solar and young entrepreneurs get paid.

 It’s estimated that New York City could install enough rooftop solar to supply 40 percent of the city’s electricity during peak demand, but so far the city has tapped less than 1 percent of that potential.

 A recent survey found that over the last two years C40 cities have nearly doubled the number of actions they have taken to reduce greenhouse gas emissions and to improve urban resilience to climate change. Ideas are flowing not just from rich to poor countries, but from cities in developing countries to mayors in wealthier cities.

 For example, a 2011 survey showed that every C40 city in South America already had or was planning a Bus Rapid Transit system—which usually provides dedicated lanes to protect buses from traffic congestion-- providing efficient bus service at low cost to large numbers of passengers. Following the lead of cities like Curitiba, Brazil, which pioneered the idea, and Bogota, Colombia, which greatly expanded it, 35 cities have started or plan to develop such systems, and more than half are in the more developed northern hemisphere, the survey found.

Even as national and international leaders seem to have trouble reaching climate agreements, mayors realize that if a severe climate crisis hits their city there’s nowhere to hide. As a result many are taking matters into their own hands: 62 percent of the cities have established their own funds to invest in energy efficiency, renewable energy or carbon reduction projects.

But funding projects like new Bus Rapid Transit systems or waste- -to-energy costs money—sometimes a lot of money. “Many of our cities would say the financing barriers are as big if not bigger challenges than technical problems” around building this infrastructure needed to combat climate change, Alexander says.

Remarkably, more than a third of the network’s mega-cities do not even have a credit rating, which means they either cannot borrow money or can’t borrow at affordable rates. That’s particularly true of cities in developing areas of Africa, Latin America and Asia. “We’re helping them find out what they need to do to get credit-rated,” Alexander says, partly by sharing learning on how other cities do it.

 C40 is also looking into what cities need to do to make their projects more attractive to investors. This May, cities from the network will be presenting their proposed projects to investors at a summit in Basel, Switzerland, sponsored by Global Infrastructure Basel, a non-profit foundation with Swiss government backing. The foundation is acting as a matchmaker between investors like pension funds and cities looking to finance sustainable projects.

Cities that have already seen the benefits of such projects hope their case will be convincing to investors and their electorate alike. For example, efforts to make buildings more energy-efficient by installing double-glazed windows and insulation on a wide-scale can create thousands of jobs for installers.

If you’re the mayor of a big city, Alexander points out, “You start saying, even if we ignore the positive impact of this project on the environment, this would still be worthwhile to do because it would help the economy grow, it would create jobs, it would save on energy bills and give people more money in their pocket to spend in the city.”