In his memo to employees, Cook said he spoke to Trump on Tuesday to try to persuade him to keep the U.S.in the Paris deal.
"Today's announcement from President Trump that the United States will not honor the agreement is a huge disappointment".
As President Donald Trump backs out of the historical Paris climate agreement, the recently elected French President Emmanuel Macron sent out a message to all American climate scientists welcoming them to France. "And they won't be". That means it could take another three-and-half years for the U.S.to formally withdraw, though Trump promised to stop implementation immediately.
Trump noted in his June 1 statement that he would attempt to negotiate a fairer deal for the US.
During this time, nations in the agreement theoretically could attempt to get the U.S. to rejoin, but this is unlikely.
In a TV broadcast made both in French and English, Macron said he believed that Trump had made a historic mistake, and invited frustrated USA climate scientists and entrepreneurs to come and work in France.
That idea was unceremoniously slapped down by furious allies in Europe, who joined figures from around the United States in condemning the move. Some 61 USA mayors have vowed to uphold the commitments of the worldwide agreement.
Democratic governors aren't the only politicians vowing to counter Trump's Paris pact decision.
Ehlers said he sees the Paris Accord as a path toward making sure the current generation leaves the planet better, not worse for his children.
Republicans, however, lauded the decision, saying Mr Trump's move should be "commended".
In Berlin, Chancellor Angela Merkel expressed "regret" at the decision, and called for a continuation of "climate policies which preserve our world".
"Unfortunately, the first to suffer from this injudicious decision is the American people", the group, an alliance of climate activists, said.
In an interview on Thursday, the president of the World Coal Association, Benjamin Sporton, told Reuters that he had mixed feelings about Trump's announcement, adding he was eager to see a USA policy that actively promotes a place for coal in the global energy mix.
Opponents of withdrawal - said to include Trump's own daughter Ivanka - had warned that America's reputation and its leadership role on the world stage was at stake, along with the environment.
The main goal of the Paris deal was to limit global temperature rise to 2 degrees Celsius. Chief strategist Steve Bannon supports an exit, as does Environmental Protection Agency Administrator Scott Pruitt.
American corporate leaders have also appealed to the businessman-turned-president to stay in the pact.
"Climate change is not an issue that the US can solve on its own".
Paris City Hall was symbolically bathed in green light on Thursday night following the American president's announcement.
A spokesperson for Dell, whose founder and CEO sits on Trump's council on manufacturing, said that there was "no change in engaging with the Trump administration and governments around the globe to share our perspective on policy issues that affect our company, our customers and our employees". "Industry must now lead and not depend on government", tweeted General Electric Co's Jeff Immelt. And less than a third support measures like the Clean Power Plan - Obama's principal tool for meeting America's Paris climate commitments. Countries like China, and other developing nations, are still going to pump carbon into the atmosphere and they will gladly watch us damage our economy and put ourselves at a competitive disadvantage.