Activists representing more than 350 environmental, civic, and college student organizations held a press conference in Downtown manhattan and delivered a letter to New York Attorney General Eric Schneiderman in support of his investigation of ExxonMobil.

U.S. oil giants Exxon Mobil, Chevron and Occidental Petroleum will join a coalition that aims to reduce greenhouse gas emissions from the oil and gas industry.

The move marks a reversal for the American oil heavyweights, which did not join the Oil and Gas Climate Initiative when it was formed in 2014. The initiative currently has 10 members, including European oil majors Total, Royal Dutch Shell and BP, as well as state oil companies Saudi Aramco, Mexico's Pemex and China's CNPC.

The addition of the three companies means the initiative's members account for 30 percent of worldwide oil and gas output, the group said in a statement. The initiative made the announcement after a report by Axios broke the news.

Members of the initiative pledge to take action to reduce methane and transport emissions, improve their energy efficiency, and move forward technology to capture and store carbon emissions. They also contribute to a $1 billion fund that invests in new technologies and business models with the potential to cut planet-warming emissions.

"It will take the collective efforts of many in the energy industry and society to develop scalable, affordable solutions that will be needed to address the risks of climate change," Exxon Chairman and CEO Darren Woods said in a statement.

Exxon in particular has come under fire in recent years following a series of investigations that showed the company's scientists warned internally about the dangers of climate change while publicly downplaying the risks.

The so-called #ExxonKnew campaign has sparked a lawsuit by state attorneys general alleging Exxon misled investors. Exxon calls the #ExxonKnew movement "an orchestrated campaign that seeks to delegitimize ExxonMobil and misinterpret our climate change position and research."



A number of cities and counties, as well as Rhode Island, have sued oil and gas firms over the cost of mitigating the impact of climate change, though suits brought by San Francisco, Oakland and New York City have been dismissed by federal judges.

Exxon, Chevron and Occidental will become official members on Monday.