More than 200 institutional investors with $26 trillion in assets under management said on Tuesday they would step up pressure on the world's biggest corporate greenhouse gas emitters to combat climate change.

Two years to the day since 195 governments adopted the Paris climate agreement, investors including Pacific Investment Management Co, Amundi, Legal & General Investment Management, Northern Trust, and Aegon said they aimed to work with the 100 biggest polluting companies to curb emissions under a five-year plan.

That, they said, would be more effective than threatening to pull the plug on their investments in such companies, which include Coal India, Gazprom, Exxon Mobil, and China Petroleum & Chemical Corp.

"We will be asking companies ... to curb emissions and bring them down in line with the Paris goals," said Anne Simpson, investment director of sustainability at the California Public Employees' Retirement System.

That would mean roughly an 80 percent cut in greenhouse gas emissions by 2050, she told reporters on a teleconference, beyond the ambition of most companies.

The investors said they were also calling on companies to improve disclosure of greenhouse gas emissions, including those from the use of their products, and to step up governance of climate risks and opportunities.

French President Emmanuel Macron will hold a summit in Paris on Tuesday to build on the 2015 climate accord, which has been weakened by President Trump's plan to pull the United States out and instead bolster the US fossil fuel industry.

Under the investors' plan, divestment would only be a last resort. If big emitters refuse to cooperate with them, shareholders could ratchet up pressure with public statements, resolutions, and votes.

Such measures can work, they said. In May, for instance, 62 percent of shareholders in Exxon Mobil voted for greater transparency about climate risks of oil and gas despite opposition from the board.

"To talk about this as 'if you don't do what we want we're selling' in a way lets the companies off the hook," said Stephanie Maier, director of responsible investment at HSBC Global Asset Management.

She said it was better to cooperate with major emitters because they contributed to droughts, mudslides, heatwaves, and rising sea levels that threatened investors' other holdings.

In the past, some big investors have divested from high polluting coal or from companies they judge to be out of line with the Paris agreement's goals.

Stephanie Pfeifer, chief executive of the Institutional Investors Group on Climate Change which is among those coordinating the five-year plan, said investors were increasingly looking for ways to align their portfolios with the Paris goals.

"We're two years on from Paris – this is a way to showcase there is momentum," she told Reuters.

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Among pension funds with strong green goals, for instance, Denmark's $40 billion PKA aims to raise climate-related investments such as in wind turbines and green bonds to 10 percent of its holdings by 2020 from almost seven now.

This story was reported by Reuters.