Cities are warmer and more pleasant. Trees grow faster and leaf earlier. And that’s just the beginning of the bad news.

To get a real sense of how global warming is affecting our planet, we just need to look at what’s happening on a much smaller scale in the cities where we live. Cities have a metabolism of their own, consuming energy in the form of fuel and resources, and producing waste — including carbon dioxide. Our researchers have followed the flow of carbon dioxide through urban areas — and have uncovered alarming facts about its impact on climate and vegetation. And while 70 percent of the world’s carbon dioxide emissions come from cities, Boston University is one of the few leading research institutions to actively study urban ecosystems. Another example of how thinking differently about our world begins with BU.