The demonstrators, about two dozen of them, first showed up at Vanguard’s Malvern campus in June. Then a group appeared again in September, that time riding bicycles.

On Friday, just ahead of the United Nations’ global climate change summit, they’ll be in Malvern once more, to tell the investing giant that it has a climate problem.

The campaign — dubbed Vanguard’s Very Big Problem — is the latest by the Sunrise Project and its partners to take aim at asset managers over their fossil fuel investments as the risks of a warming planet grow more urgent.

Organizers launched a similar effort against investment giant BlackRock three years ago. Now, they say, it’s Vanguard’s turn.

With more than $7 trillion in assets under management, Vanguard’s stakes in a wide swath of companies give it “massive shareholder power,” said Tanya Kar, with the Sunrise Project.

The organization, based in Australia, fights climate change through building social movements, and has a focus on shifting financial support away from fossil fuels. It’s appealing to Vanguard customers to put pressure on the firm about how their money — held in retirement accounts and other products — is invested. In the Philadelphia area, Sunrise is working with environmental groups such as Earth Quaker Action Team (EQAT) and Fossil Free Penn.

For all its financial might, the company has been “silent” on important issues related to climate change and is one of the world’s largest investors in coal, Kar said. “That time for them to be flying under the radar is over.”

Friday’s rally at Vanguard is part of an international day of demonstrations that activists are holding before the U.N. climate conference in Glasgow, which starts on Sunday.

Vanguard did not give an interview for this story, and provided a statement saying: ”On behalf of our 30 million investors, it’s our fiduciary duty and our role as an index fund provider to protect their best interests by advocating for good governance principles at companies around the world; including how companies are mitigating, overseeing, and disclosing climate risk.”

The company said it takes “this role very seriously, and will continue to advocate on the risks related to climate change within our engagements with companies, industry regulators, and policymakers, and through aligned organizations and initiatives.”

A spokesperson cited Vanguard’s involvement in the Net Zero Asset Managers initiative. Participating firms say they’re “committed to supporting the goal of net zero greenhouse gas emissions by 2050 or sooner,” according to the initiative’s website.

Last year, the company began to disclose more details about how it votes on shareholder resolutions at publicly-traded companies, on issues such as executive compensation and climate change.

Campaign organizers say the firm needs to move faster, and take steps to exclude certain companies from their investments and exit some industries altogether.

“We need to see that the action matches the rhetoric,” Kar said, “and that means they will eventually need to phase out these kinds of sectors that have no viable climate transition plan” — such as coal.

As of earlier this year, Vanguard was the world’s top institutional investor in the coal industry, with nearly $86 billion invested, according to research published by a collection of nonprofits, including Urgewald, Reclaim Finance, and Rainforest Action Network.

Another goal of the campaign is to get Vanguard to vote more for climate-friendly proposals at company shareholder meetings.

In May, for instance, Vanguard threw its support behind two new directors for ExxonMobil’s board, contributing to a shakeup at the oil and gas company. Vanguard said the new board members would add “transformational energy perspectives” to the board.

Southampton resident Alice Maxfield, 74, has saved with Vanguard for over 40 years. She appreciated founder John Bogle’s ideas about keeping customer fees low, and how easy it was for her children to open their own retirement savings accounts with the firm.

But she’s also worried about climate change and thinks Vanguard should use its investments, and its influence with companies, to address it. Maxfield heard about the Very Big Problem campaign through her involvement with EQAT, and she and her husband were among those who marched to Vanguard’s Malvern campus in June.

“They really have a lot of clout,” Maxfield said of the firm. “But if the future is not going to be sustainable, then they’re letting us down.”

She was fascinated by the successful election of new board members at Exxon this past spring.

“That was indicative of what a small group of investors can do, particularly when a company like Vanguard puts their weight behind it as well,” Maxfield said.

Eve Gutman, a Pennsylvania organizer for the campaign, said customers she’s met are often not aware of how their money is being invested in fossil fuels.

“Large companies that are either funding or insuring or, in the case of Vanguard, investing in fossil fuel companies have an outsize obligation to move us away from this path that will take us over the cliff,” she added.

“We’re behind the times in investing in renewable energy,” said Russell Hicks, an outreach coordinator with the Very Big Problem campaign.

“Ultimately the goal is to shift some of the thinking, shift some of the investment, shift some of the money, to make sure the 99% has a voice as well,” he said.