When Norway moved forward with a plan to divest from as many as 150 oil explorers earlier this month, thousands of investors that follow its lead saw a clear signal: The days for oil drillers are numbered.

While it’s keeping investments in the big, integrated oil companies, it said that’s because of their early commitment to renewable energy. At the same time, the government sees little use for companies that exist purely to find more oil.

That’s a clear signal, experts and activists say. Only so much carbon can be spent if countries and companies are serious about keeping global warming below globally catastrophic levels, says Andrew Grant, a senior analyst at U.K. climate data firm Carbon Tracker.

As of now, the world’s proven oil reserves are already about double what could be burned without warming the planet beyond the widely accepted 2-degree Celsius threshold.

The $1 trillion fund is still figuring out how it will unwind up to $8 billion in investments in a group of companies that include U.S.-based EOG Resources Inc. and India’s Reliance Industries Ltd, but other investors are almost certain to follow suit. Already the $356 billion California Public Employees’ Retirement System faced pressure over its own holdings from activists at a board meeting last week.

“Like Norway, stop investing in companies that explore for needless new drilling sites -- they’re wasting their money and ours,” Deborah Silvey, president of Fossil Free California, told the board of the largest U.S. public pension fund.

Norway is often at the forefront of divestment for ethical reasons. The wealth fund was one of the first to sell out of the tobacco industry in 2008, and when in 2015 Norway said it planned to divest $8 billion in shares of coal companies, hundreds of investors eventually did the same. Bankruptcy risk in the sector increased, and international banks have largely banned financing of new projects.

“Having such a large institutional investor that clearly knows the energy industry well make this choice gives you some cover,” said Elizabeth Levy, a senior vice president at Trillium Asset Management, a $2.5 billion responsible investment firm in Boston.

Governments around the world could soon face a new round of hard choices about their use of fossil fuels. In May, United Nations climate scientists will update and expand how greenhouse gas emissions are measured, and countries that want to limit global warming will have to re-calibrate how much fossil fuel they can burn.

Coal demand has fallen so much at this point that oil might be an easier target for emissions reduction. Electric buses are already making a dent in demand, and drilling for shale oil is more costly -- both in terms of dollars and emissions -- than extracting conventional reserves. That said, existing oil demand growth would have to decline 20 percent annually to reach global climate goals by 2040, according to the International Energy Agency.

A shift away from oil explorers could also push capital from pension and sovereign wealth funds more rapidly into clean energy stocks, which are outperforming oil companies in the market.

It’s the beginning of a “shift in the direction of significantly fewer fossil fuels,” said Lisa Woll, CEO of the Forum for Sustainable and Responsible Investment. “The question is, how quickly can you get clean energy moving so it makes up the difference.”

Norway still has plenty of investment in oil. Its sovereign wealth fund was built from profits on its own vast oil reserves, and the country’s own oil output is set to increase after hitting a 31-year low this year.

The fund is keeping its substantial stakes in companies such as Royal Dutch Shell Plc, Exxon Mobil Corp., BP Plc and Chevron Corp., a move the government said is justified by the firms’ initial commitments to renewables, though they still explore for oil. In fact, those four companies hold about as much carbon dioxide in their oil reserves as reported by the group of explorers Norway named as candidates for divestment.