LONDON (Reuters) - A group of the world’s top oil and gas companies pledged on Monday to slash emissions of a potent greenhouse gas by a fifth by 2025 in an effort to battle climate change.

FILE PHOTO: The Exxon Mobil gas station in Denver, Colorado United States July 28, 2017. REUTERS/Rick Wilking/File Photo

The Oil and Gas Climate Initiative (OGCI), which U.S. giants Exxon Mobil and Chevron joined recently, committed to cutting methane emissions to an intensity of 0.25 percent of the group’s total fossil fuel production, it said in a statement.

Such a reduction would equate to 350,000 tonnes of methane annually. It compares with a baseline intensity of 0.32 percent in 2017, excluding new members.

The pledge, which could be lowered further to 0.20 percent intensity, echoes targets set individually by members BP, Royal Dutch Shell and Exxon to reduce methane emissions.

“Our aim is to work towards near zero methane emissions from the full gas value chain in support of achieving the goals of the Paris (Climate) Agreement,” the heads of the OGCI members said in a statement, referring to an international agreement aimed at limiting global warming.

The OGCI today represents nearly a third of global oil and gas production. It also includes BP, Royal Dutch Shell, France’s Total as well as national oil companies of China, Mexico, Brazil and Saudi Arabia.

The U.S.-based Environment Defense Fund (EDF), a non-governmental organization, said OGCI needs to adopt more, and transparent, ways of measuring methane emissions to meet the target.

“It will be critical now for companies to follow through on their commitment, reporting on progress with actual measured emissions, fully and publicly disclosed,” EDF President Fred Krupp said in a statement.

“A second challenge for OGCI is the risk that laggards in the industry hide behind their efforts, falsely claiming that the actions of an important few represent what all in the industry are doing.”

In a separate announcement, timed to coincide with the start of Climate Week in New York, OGCI announced the creation of a $100 million China-focused climate investment fund with China National Petroleum Corporation (CNPC).

The group is investing in new technologies, including satellite imagery, to help measure and detect methane leaks from pipelines, wells and other infrastructure, said Pratima Rangarajan, head of OGCI Climate Investments.

“Today there is no global measurement, so what you don’t measure you don’t fix or operate as well as you should,” she told Reuters in an interview.