"We are losing the battle," Macron said at Tuesday's "One Planet" summit.  "We must all act because we will all be held to account."

The meeting was held on the second anniversary of the Paris Agreement, a pact ratified by 170 nations to cut Earth-warming greenhouse gas emissions.

US President Donald Trump, however, has since announced plans to withdraw from the accord, a move Macron described as "bad news".

"We are here in such great numbers because so many of us have decided not to accept the US government's decision to leave the agreement," he said.

Macron did not invite Trump to the summit. Several prominent American figures - including Arnold Schwarzenegger, Bill Gates, and Elon Musk - were in attendance.

Al Jazeera's Natacha Butler, reporting from Paris, said the US pullout has left "an enormous shortfall in the funding for the battle against climate change".

Trump, who has called climate change a "hoax", said he would withhold $2bn pledged to the Green Climate Fund, set up to help poorer countries tackle the effects of climate change.

Antonio Guterres, the UN chief, said the Green Climate Fund was indispensable, adding it was "only justice" that developed countries help poorer countries fight climate change.

"We are in a war for the very existence of life on our planet as we know it," said Guterres.

"There is no shortage of funds. What we are short on is trust and we must fix this. This means that the rich northern countries up their engagement and pledge $100bn a year until 2020 for developing countries."

Michael Bloomberg, the former mayor of New York, said environmentalists owed Trump a debt of gratitude for rallying thousands to action.

Speaking to reporters earlier in the day, Bloomberg added America's Pledge - a coalition of 1,000 US governors, mayors, business leaders, and academics, formed to honour US commitments in the Paris Accord - now "represents half of the US economy".

Other public and private financial institutions unveiled plans to invest in clean energy and divest from fossil fuels.

That included an announcement by the World Bank that it would not finance oil-and-gas exploration or production after 2019.

A group of more than 225 investment funds managing more than $26 trillion in assets pledged to step up pressure on the world's largest corporate greenhouse gas emitters to curb emissions and disclose climate-related financial information.

Here are some of the other commitments announced in Paris: 

- French insurer Axa said it would quadrupole investments in environmentally friendly projects, and pull out $2.9bn from companies that derive more than 30 percent of their revenues from coal 

- Dutch bank ING said it would have "close to zero exposure" to coal power generation by 2025 

- Norwegian pension fund Storebrand said it will expand its portfolio of fossil fuel-free investments to more than $3bn 

- The European Union pledged to invest 9 billion euros ($10.6bn) in clean energy, sustainable agriculture, and climate-resilient cities   

- The World Bank also announced a slew of other projects, including a $4.5bn fund for cities to fight the effects of climate change, and a plan to tackle erosion along the West African Coast

Margaret Kuhlow, the World Wide Fund, told Al Jazeera she was "encouraged" by the new commitments.

News24