NY became the largest American city to sue Big Oil, demanding that ExxonMobil, Chevron, BP, Royal Dutch Shell and ConocoPhillips pay for the cost of protecting the city from the "existential threat" of climate change.
"As climate change continues to worsen", de Blasio said, "it's up to the fossil fuel companies whose greed put us in this position to shoulder the cost of making NY safer and more resilient".
The lawsuit seeks to recover billions of dollars in damages from BP, Chevron, ConocoPhillips, Exxon Mobil, and Royal Dutch Shell for their role in creating - and perpetuating - climate change.
Mayor Bill de Blasio says the city will be seeking billions in the lawsuit to recoup money spent by the city for resiliency efforts related to climate change.
Beyond the climate lawsuit, New York City also announced a goal of divesting the city's pension funds from all fossil fuel reserve owners within five years; the city's five pension funds now contain some $5 billion in fossil fuel investments.
Curtis Smith, a spokesman for Shell, said by email: "We believe climate change is a complex societal challenge that should be addressed through sound government policy and cultural change to drive low-carbon choices for businesses and consumers, not by the courts".
The lawsuit follows the city's announcement that it plans to divest its pension funds from fossil fuel companies.
With 8.5 million residents, NY is America's most populous city, and also serves as its financial and entertainment capital.
Kenneth P. Cohen, a representative for Exxon, flatly denied suppressing climate change research.
In response to the California lawsuits, Exxon recently asked a federal judge in Texas to allow the company to depose municipal officials involved with the suits, arguing that depositions would allow the company to uncover "abuse of process, civil conspiracy and violations of Exxon Mobil's constitutional rights".
San Francisco and Oakland filed similar suits in September against the same five companies.
Greenpeace USA Executive Director Annie Leonard said, "New York City's impressive leadership makes me hopeful for the future".
Some of the oil companies being sued by New York City over claims they contributed to global warming are disputing the allegation. The funds invest the pensions of hundreds of thousands of active and retired city teachers, firefighters, police officers and other employees. City officials plan to submit a joint resolution instructing pension fund trustees to begin analysizing how it can be done in a responsible way.
"It's complex, it will take time, and there are going to be many steps, but we're breaking new ground, and we are committed to forging a path forward while remaining laser-focused on our role as fiduciaries to the systems and beneficiaries we serve", Stringer said in a written statement.