Biggest buildings in the world’s biggest cities are turning sustainable. On Thursday, 19 leaders from the C40 coalition committed to reducing carbon emissions by signing the Net Zero Carbon Buildings Declaration.

The nineteen cities are Copenhagen, Johannesburg, London, Los Angeles, Montreal, New York City, Newburyport, Paris, Portland, San Francisco, San Jose, Santa Monica, Stockholm, Sydney, Tokyo, Toronto, Tshwane, Vancouver and Washington, DC. These cities are home to many big and iconic skyscrapers and 130 million people.

The mayors of the cities came together to ensure that all the buildings, whether new or old, meet the net-zero carbon standards by 2050 which will help to significantly cut down on greenhouse gas emissions, air pollution and energy consumption from the cities.

The zero-emission buildings would not be running on fossil fuels but on renewables and driven by environmentally and socially beneficial ways. The cost of operation is also estimated to be lower in the future.

“Combating climate change is a moral necessity, an environmental imperative, and an economic opportunity—and Los Angeles is proud to be a leader in creating our clean energy future,” said Mayor Eric Garcetti in a statement. “By pledging to reduce the carbon footprint of our buildings, cities are moving us another step closer to the goals of the Paris Agreement–and the promise of lower emissions, less pollution, and more renewable energy innovation”.

“Delivering on the commitments made today will require a united effort, as city governments do not have direct control over all the buildings in a city. This commitment includes a pledge to work together with state and regional governments and the private sector to drive this transformation, and calls on national governments for equal action,” quoted the press

The pledge is signed in support of the Paris Agreement to keep the global temperatures below 2 degrees. Each year a progress report would be released to measure the progress.

“Action is needed today because most buildings will be standing for generations to come. Missing this opportunity locks in the problem for our children and grandchildren,” the declaration reads.