Image copyright Google Image caption While young people have been demonstrating against climate change, big financial players are putting on pressure from a different direction

While young people throng the streets demanding action on man-made climate change, an older, more sober group of activists is fighting a green campaign: big investors.

The men and women who control trillions of dollars' worth of assets are flexing their muscles. And as shareholders they are in a position to put pressure on companies to do the right thing.

Climate Action 100+ is a group of more than 360 investors with more than $34tn (£28tn) in assets under management.

They are worried not just about damage to the planet, but about the long-term viability of their investments. In short, irreversible harm to the environment would reduce or even wipe out the value of those investments.

This group, which includes influential institutional investors such as the Church of England Commissioners, aims to engage with "systemically important emitters" in which they hold shares to curb greenhouse gas emissions and improve governance.

One of those firms is the oil giant BP, which recently had its annual general meeting.

Climate Action 100+ put forward a shareholder resolution to get BP to demonstrate that its strategy was consistent with the goals of the Paris climate agreement, the international plan to limit global warming to 1.5C.

The resolution, which was supported by the BP board was approved and is now legally binding.

Various institutional investors were behind the BP resolution including Hermes, HSBC, Legal and General, and Aviva Investors.

Image copyright Aviva Investors Image caption Steve Waygood says we only have a short time to head off potentially catastrophic climate change

"The economic and financial risks associated with climate change are very real," says Steve Waygood, chief responsible investment officer at Aviva Investors.

"We only have the next five to 10 years to deal with the risks associated with climate change and make sure they don't become real."

If there is no action taken, the risks "will become real in the next 20 to 30 to 40 years," and in the "very long term, a potentially catastrophic issue".

As an investor, Aviva is concerned about risks to its holdings and as an insurer Aviva is exposed to flood risks, fire, drought, and to a lesser extent crop damage.

"If global governments, if humanity doesn't prevent climate change.... $43tn could be wiped off global shares - roughly a third of their value," says Mr Waygood.

He is confident that humanity already has the technology to stop ripping up our life support system. We just need to put it into action - and while big firms have a role to play, they can't do it on their own.

He is calling for coordinated action between with businesses, governments and regulators to come up with "a Marshall plan" to transition to a low carbon economy. He likens such action to the US programme to help rebuild western Europe after World War Two.

"BP is one small cog in a giant economic system that has to be retuned to deliver the Paris agreement."

Nonetheless, he says there is a mismatch between the vast sums that oil firms spend on exploiting new or existing fossil fuel reserves - and the goals of the Paris Agreement.

"A significant amount of oil and gas capital expenditure assumptions could turn out to be very awry if governments deliver with Paris," he says. Those oil and gas assets could become stranded.

Image copyright Getty Images Image caption A malfunction at ExxonMobil's Fife Ethylene Plant in April caused concern among residents

For example, ExxonMobil, one of the firms under pressure from Climate Action 100+, plans to spend $46-48bn in 2019/2020 on oil and gas investments, including fracking.

In a recent presentation to investors it said global population growth, coupled with a rise in the middle class, would underpin energy demand.

It told investors that the International Energy Agency estimates that $21tn investment in oil and gas will be needed by 2040, and that ExxonMobil itself would spend an estimated average £30-35bn a year to meet demand.

Despite its climate commitments, BP still devotes £12bn of its £15bn annual capital expenditure on oil and gas explorations and extraction, and just $500m into its new energy businesses such as biofuels, solar energy and electric car charging. It also puts $200m into promising startups.

BP says this is consistent with its Paris accord targets, but Greenpeace senior climate advisor Charlie Kronick says it still investing too much in oil and gas.

"There is no way they are conforming to or even aligned with the Paris Agreement," he says. "BP feel they are doing enough, and they clearly aren't. That should be an indication that [investor] engagement with this industry has to be more robust."

In addition to its success with BP, Climate Action 100+ has had some notable wins, including persuading Glencore, one of the world's biggest coal producers, to cap production. Shell will start to set targets for its net carbon footprint, and has agreed to review its climate change lobbying.

Image copyright Per-Anders Pettersson Image caption Glencore is one of the world's largest mining companies

However, the investor group has also not made much headway with some companies, including ExxonMobil.

In April US regulator the SEC allowed the firm to throw out a resolution calling on the company to set emissions targets.

"Exxon has not been very supportive," says Stephanie Pfeifer, a member of the global Climate Action 100+ steering committee and the chief executive of the Institutional Investors Group on Climate Change (IIGC).

She says the regulatory environment in the US is part of the problem. Corporate bosses have a 'fiduciary duty' to act in the best interests of their shareholders - but does that mean maximising profits now by producing as much oil as possible, or doing everything they can to limit climate change in the future?

"In the US there is this question mark about how you should be dealing with environmental, social and corporate governance as a fiduciary duty. That is not helpful," says Ms Pfeifer.

Nonetheless, "Climate Action 100+ has demonstrated that investor pressure can work," she says, adding that "$34tn has a lot of clout".

ExxonMobil did not reply to requests for comment.

Pressure from charities and environmental activists such as Extinction Rebellion and youth climate strikers also can't be ignored, she says.

But can investors get firms to change direction soon enough to make a difference while also not harming their investment? Ms Pfeiffer says they can.

"We do recognise that action needs to be taken now, and it will be much more costly if action is not taken now."