In brief: The Trump administration may have started the process of withdrawing from the Paris climate accord, but that hasn’t stopped tech leaders signing an open letter urging the US to stay in the agreement.

In June 2017, the US joined Nicaragua and Syria as the only nations not part of the Paris Agreement. Donald Trump said at the time that withdrawing was to “protect America and its citizens.” He added that it's "very unfair, at the highest level, to the United States," and would impose "draconian financial and economic burdens."

A few days after Trump announced the withdrawal, top tech firms signed an open letter pledging to support the accord. Now, the CEOs of companies including Apple, Adobe, Google, HP, Microsoft, and Tesla have signed another open letter—United For The Paris Agreement—which calls on the US not to leave the agreement.

"There has been progress, but not enough," states the letter. "This moment calls for greater, more accelerated action than we've seen. It calls for the strong policy framework the Paris Agreement provides, one that allows the US the freedom to choose our own path to emissions reductions."

Two big names conspicuously absent from the letter are Facebook and Amazon. In Greenpeace’s 2017 “Clicking Clean” report, which rates companies on how environmentally friendly they are, Facebook scored an A grade in all but one category, where it received a B. Amazon, on the other hand, was awarded an F, D, two Cs, and a B. And in September, more than 900 of the retail giant’s employees protested its failure to take action in the fight against climate change.

It’s unlikely that the letter will change the government’s stance on the Paris accord, but it’s clear where the majority of tech firms stand on the issue.