Trustees of three New York City pension funds are pledging to develop an investment portfolio that would generate net-zero carbon emissions by 2040, making New York the first city in the country to take such a step in trying to combat climate change through conscientious investing.

Mayor Bill de Blasio made the announcement on Thursday at City Hall, where he was joined by City Comptroller Scott Stringer and Representative Alexandria Ocasio-Cortez, a progressive star in the Democratic party who has long been advocating for her own climate proposal called the Green New Deal. Altogether, the city's five pension funds have assets valued at around $270 billion. New York City ranks as having one of the biggest public retirement funds in the world.

"This is revolutionary," de Blasio said, adding that the commitment — which will redirect the city's retirement fund away from fossil fuel and toward investments in clean and renewable energy — was an example to other cities and states on "how to invest your money in a way that protects the earth."

As part of the plan, the city is promising to invest $50 billion of its municipal retirement funds in renewable energy by 2035. Ocasio-Cortez noted that although her legislation has faced opposition in Congress, its ideas have been adopted in places like New York City, Austin, Los Angeles, and Maine. Back in January, city pension trustees announced that they would drop $4 billion in investments from fossil fuel companies.

"What today's announcement really indicates is a next level in our ability to combat the climate crisis. And that is essentially a full divestment from fossil fuels from our public pension funds," she said.

The appearance with Ocasio-Cortez comes as the mayor has been trying to burnish his legacy as a progressive leader in his final few months of office. De Blasio, who recently said that he is "feeling more energy than ever" and wants to remain in public life, is also reportedly mulling a run for governor. In late 2020, the Cuomo administration said that New York State's pension fund would divest $226 billion from its fossil fuel investments by 2040.

Stringer, who earlier this year lost a primary bid for mayor and has been highly critical of de Blasio, offered high praise during the press briefing.

"There has never been a conversation I've had with Bill about climate change where he didn't give us three more things to do," Stringer said. "So once we were done with divestment, we were only beginning."

As of 2018, the city's pension funds had about $5 billion of assets tied to fossil fuel, according to John Adler, the mayor's chief pension investment adviser. He said fiduciary rules prohibited from saying how much had been already sold.

Adler defined fossil fuel investments as companies that own below-ground reserves of oil, gas, coal, and tar sands. Each retirement fund, he said, selects its own list of securities from which they want to divest.

Thursday's announcement came one day after three city's retirement funds — the New York City Employees’ Retirement System, which covers most civilian municipal employees, the New York City Teachers’ Retirement System, and the New York City Board of Education Retirement System — each sealed their commitment to the plan with a formal vote.

Two other municipal pension funds, for police and firefighters, have not made the same pledge, according to the mayor's office.