More than 150 nations, including the U.S. and China, are expected to sign the Paris Agreement on climate change on Friday—Earth Day—marking a huge step in the fight against global warming and the next phase for a growing and vibrant climate movement.

The magnitude of the single-day signing “clearly demonstrates the degree of support internationally for moving forward on climate,” said David Waskow, the director of the international climate initiative at the global research organziation World Resources Institute.

The deal aims to keep any further warming “well below” 2°C by working to reduce greenhouse gas emissions as soon as possible.

With that in mind, the COP21 agreement “could be the next nail in the coffin of the fossil fuel industry” says 350.org executive director May Boeve, “if governments actually follow through on their commitments.”

That’s the big question, of course—to what extent, and at what speed, governments will actually adhere to the pledges laid out in the Paris Agreement.

And even if they go whole hog, that won’t be good enough, according to a new analysis from Climate Interactive and MIT’s Sloan business school. That analysis shows that full implementation of the current pledges would result in expected warming by 2100 of 3.5°C (6.3°F)—far past the consensus threshold. To limit warming to no more than 2°C, “deeper, earlier emissions cuts are needed,” the groups say in their Climate Scoreboard.

That, in turn, would “catastrophic to the ecosystem of the world, including the ice culture of the Indigenous Peoples of the Arctic,” said Tom Goldtooth of the Indigenous Environmental Network, which on Wednesday joined other grassroots groups in releasing a report (pdf) that denounces the COP21 deal as a “dangerous distraction.”