At the meeting of the C40 Cities Climate Leadership Group in Brazil, city leaders are trumpeting their efforts to fight climate change. New York City Mayor Michael Bloomberg, who's a C40 chair, released a report yesterday on the carbon emissions of some of the world's largest cities and took the opportunity to give his "you can't start solving a problem until you've got data" spiel. And, yes, data is great! But quite a few cities have kept their emissions number to themselves. In America, Houston bowed out. (Classic.) A group of European cities usually thought of as progressive on green issues -- including Barcelona, Paris, and Stockholm -- didn't participate. But among those who didn't disclose were the few cities that the global community should be most anxious to monitor: Beijing and Shanghai, in China, and Delhi and Mumbai, in India. Without emissions numbers from these large and growing cities, this set of data is much less useful. The report also identified effects of climate change that many cites are already experiencing or are expected to exoerience soon. Top on that list was temperature increases and heat waves, which, since it's 90 degrees today, the first day of June, in New York City, feels a bit obvious. But it also underscores how much more work cities have to do in order to address climate issues. Heat in cities lingers later and longer each day because the hard, dry surfaces of city buildings and roads trap more heat and then release it more slowly than greener, rural areas. Trapped heat from air conditioning units also contributes. One of the simplest policy answers to the urban heat island effect is to promote white roofs, which reflect sunlight back into the atmosphere, decreasing the amount of heat that enters the city to begin with. Bloomberg has pursued that policy in New York, and in the past year the city says more than 1,368,000 square feet of rooftop surfaces have been painted. It turns out, though, that white roofs get dirty and therefore less effective rather quickly. The city is studying how fast the heat-lessening impact of a white roofs declines. (More data!) But like so many of the ideas cities are looking at to fight climate change, this one's new and still has kinks to work out. In the meantime, us city-dwellers will be sweltering long into the evening.
