Johannesburg — More than half of the world's population lives in cities. This week, mayors from the world's major cities met in Johannesburg to discuss the impact of climate change - and what they can do to fight it.
In recent years, bad weather has hit cities harder than ever - from hurricanes in Hong Kong and snowstorms in New York to heat waves in Rio de Janeiro.
More than 3.5 billion people around the world live in cities. Cities consume more than two-thirds of the world's energy - and put out more than than 70 percent of global carbon dioxide emissions.
Mayors from more than 40 major cities gathered this week in Johannesburg to discuss taking the fight against climate change all the way to their respective city halls.
The event's host, Johannesburg executive mayor Mpho Parks Tau, says cities understand the effect they have on the world's climate.
"Cities are really where the rubber hits the road, figuratively and literally," said Park. "We are responsible for public transport planning, public transport provision. We are also responsible for the management of the electricity distribution network, water, sanitation, the management of the built environment, therefore building control and building standards, in the city of Johannesburg. And we're convinced that those are the areas that in fact impact on climate change."
Across the world, Houston mayor Annise Parker says her city, known as a headquarters for oil companies, is making great strides.
"In the last seven years, the city of Houston has reduced its greenhouse gas emissions by 26 percent. Today, I made a commitment of the next two years, 5 percent each year, we would reduce it another 10 percent," said Parker.
The mayor widely credited with leading the charge is New York's former leader, Michael Bloomberg.
"Our efforts to clean the air in New York City has raised life expectancy. Life expectancy in New York City is now three years greater than the average across America. And it has improved three years in just the last 12 years. So you really can make a difference," he said.
The mayors say they are convinced their efforts will help the fight against climate change - and keep residents of their cities a little more comfortable in the long run.