Up Close: NYC's sustainability work and politics

New York Mayor Bill de Blasio proposed a bold, new environmental plan this week at a climate summit at the Vatican.

He promised to reduce greenhouse gas emissions in New York City by 40 percent in the next 15 years.

Nilda Mesa, director of the mayor's Office of Sustainability, said the mayor has unveiled two plans about the city's sustainability with four main themes.

"We have buildings, power, waste, and transportation," she said.

Building structure sustainability is key, she said.

Seventy-four percent of the city's greenhouse gas emissions, which are the major cause of man-made climate change, come from our buildings," she said. "We've reached out to key people in the city, from the real-estate industry, building owners, architects, engineers, all kinds of experts on this to join us in figuring out, you know, really what are the best strategies."

She said the city has collected data that shows which approaches work and it will result in a set of recommendations in the beginning of 2016.