Citibank promised Wednesday to lend and invest $100 billion over the next decade in projects to reduce the effects of climate change, in a plan that was developed with help from a Boston environmental advocacy group.

Ceres enlists institutional investors to persuade businesses to follow environmentally sensitive practices. Citibank will look for opportunities to finance programs that reduce greenhouse gases, increase access to clean water, and provide affordable housing.

Getting a bank the size of Citi to commit to large clean-energy investments is crucial, as it helps guide money and other businesses toward more environmentally sensitive practices, said Mindy Lubber, Ceres’s president.

“When you think about their breadth and ability to move the agenda and their resources,” Lubber said, “they are tremendous.”

Citi made a $50 billion commitment in 2007 and was able to lend that money three years ahead of schedule.

“The core mission hasn’t changed, but the way we approach it has,” said Michael Corbat, Citi’s chief executive. “Incorporating the principals of sustainability into everything we do improves our own operations, enhances our clients’ work, and contributes to a better world.”

Even as it announced its investment in clean energy, Citi remains heavily involved in the oil and gas business. In 2014, Citi made $492 million in investment banking revenue from the oil and gas sector, the highest of any bank, according to a January article in The New York Times.

Lubber said it’s unrealistic to expect companies to avoid fossil fuels entirely, but Citi’s announcement is a move in the right direction and could encourage other companies to follow.