LONDON—Fatih Birol, the head of the International Energy Agency (IEA), faced renewed calls to take a bolder stance on climate change on May 29 from investors concerned the organization’s reports enable damaging levels of investment in fossil fuels.

In an open letter, investor groups said an IEA report on options for green economic recoveries from the coronavirus pandemic, due out in June, should be aligned with the 2015 Paris accord goal of capping the rise in global temperatures at 1.5C.

The more than 60 signatories included the Institutional Investors Group on Climate Change, whose members have 30 trillion euros of assets under management, scientists and advocacy group Oil Change International.

“Bold, not incremental, action is required,” the letter said.

The Paris-based IEA said it appreciated feedback and would bear the letter’s suggestions in mind. It also said it had been recognized for leading calls on governments to put clean energy at the heart of their economic stimulus packages.

“We have backed up that call with a wide range of analysis, policy recommendations and high-level events with government ministers, CEOs, leading investors and thought leaders,” the IEA said.

Birol has faced mounting pressure in the last year from critics who say oil, gas and coal companies use the IEA’s flagship World Energy Outlook (WEO) annual report to justify further investment—undermining the Paris goals.

Birol has dismissed the criticism, saying the WEO helps governments understand the potential climate implications of their energy policies, and downplaying its influence on investment decisions.

But campaigners want Birol to overhaul the WEO to chart a more reliable 1.5C path. The world is on track for more than double that amount of heating, which would render the planet increasingly uninhabitable, scientists say.

The joint letter followed similar demands last year, and was published by Mission 2020, an initiative backed by former U.N. climate chief Christiana Figueres.