Prime Minister Justin Trudeau has brought cheers from the gathering by speaking up for developing countries, saying that "they shouldn't be punished for a problem they didn't create."
He says Canada will invest $2.56 billion over next five years to help such countries meet the goals of the climate agreement.
Trudeau also says Canada will ratify the climate agreement later this year.
"Climate change will test our intelligence, our compassion and our will," he says. "But we are equal to that challenge."
The agreement enters into force once it's signed by 55 countries accounting for 55 per cent of global emissions.
Most countries are expected to add their signatures today - on the first possible day.
The agreement creates a system to evaluate whether countries are keeping their commitments: Canada's is to reduce emissions 30 per cent by 2030. The country is not on target to meet that commitment.
The prime minister was pressed about his government's apparent support for oil pipelines, like Keystone XL, during a question-and-answer with students yesterday at New York University.
Trudeau replied that flexibility is key: he said a strong economy means more wealth, which can be invested in policies that lead to a clean-energy future.
The prime minister also went to a famous Brooklyn gym yesterday and boxed.
His New York trip concludes today with a meeting with Colombia's president and a press conference.
