Irving-based oil giant Exxon Mobil, one of the world's largest producers of greenhouse gases, announced Wednesday it would reduce its methane emissions by 15 percent in the next two years.

The company also set a 2020 deadline for reducing flaring — burning of natural gas at oil or gas drilling sites — by 25 percent.

In a statement Wednesday, the company did not mention climate change, but that would be one of the significant benefits of this move. Methane is a much more potent greenhouse gas than carbon dioxide, although methane does not last as long in the atmosphere.

Increasingly, Exxon and other major oil and gas companies have been under fire for their emissions. Since last year, at least 10 governments have sued Exxon and other large oil and gas companies for their contributions to climate change and those effects, from rising sea level to a reduced snow pack that supplies water for cities and regions.

The cities of San Francisco and Oakland are suing Exxon, BP, Chevron ConocoPhillips and Royal Dutch Shell. A federal judge in San Francisco is scheduled to hear arguments on Thursday about whether this case should go forward.

The environmental nonprofit CDP, formerly known as the Carbon Disclosure Project, determined that 100 companies were responsible for 71 percent of global industrial greenhouse gas emissions between 1988 and 2015. Exxon was number five on the list of top emitters, accounting for 2 percent of industrial greenhouse gas emissions.

Exxon officials said they have spent more than $9 billion on lowering emissions since 2000. Last year, Exxon's XTO Energy subsidiary announced it was switching to newer technology to reduce the amount of methane it releases into the atmosphere.

"We have a longstanding commitment to improve efficiency and mitigate greenhouse gas emissions," said CEO and chairman Darren Woods in a written statement Wednesday. "Today's announcement builds on that commitment and will help further drive improvements in our business."

Exxon was also one of eight major oil and gas companies that announced a collective commitment to reducing methane emissions. Last year, the companies signed a set of "Guiding Principles" that was developed with the help of the Environmental Defense Fund, United Nations Environment, the Rocky Mountain Institute and others.

And BP committed last month to keeping greenhouse gas emission at or below 2015 levels through 2025.

"With increased scrutiny from consumers and investors, setting strong methane targets — and delivering on those reductions in ways that are transparent and verifiable — is simply good business, positioning industry leaders to be more competitive in the transition to a cleaner energy future," said Matt Watson, associate vice president of climate and energy for the Environmental Defense Fund, in a written statement about the Exxon announcement.

But he also wrote that this is an "important and welcomed step, but greater ambition will be required."

Exxon recently began providing the public a more detailed report of the risks climate change poses to its business. The company started that reporting in response to pressure from investors at last year's annual meeting; Exxon management had recommended that shareholders vote against that initiative.

In February, the company released that report at the same time as its 2017 fourth-quarter earning. The Exxon analysis estimated that oil demand would drop by .4 percent annually from 2010 to 2040, but that natural gas demand would increase by .9 percent annually. And it said that the company's current reserves "face little risk."

"Even under a 2°C pathway, significant investment will be required in oil and natural gas capacity, as well as other energy sources," the report said, referring the global warming target set in the Paris Agreement.

The Carbon Tracker Initiative, a London-based financial think tank focused on fossil fuels, recently released a report looking at the latest climate change disclosures by eight large oil and gas companies.

It rated Exxon, BP and ConocoPhillips as moderate in their analysis of scenario modelling and carbon pricing and poor in market/price risk and scenario outputs.

Robert Schuwerk, executive director of Carbon Tracker North American, said there was a lack of transparency in the U.S. companies' price assumptions. Also, he said some of Exxon's modelling included older data and unrealistic assumptions on renewable energy.

Schuwerk said he somewhat agreed with Exxon's assumption that all its proven reserves would be needed. But there are more important questions.

"What prices would you obtain in a low-demand scenario?" he said. "Even if the volume may be safe, the value is a question that the company still needs to answer."