"Disappointing is too weak of a word to express my feelings," Prince Albert tells PEOPLE exclusively 
Credit: CAROLINE SEIDEL/AFP/Getty; Mark Wilson/Getty

Monaco’s Prince Albert, one of the world leaders who warned about Donald Trump‘s environmental views before the U.S. election, has called the president’s withdrawal from the Paris Agreement a “historic mistake.”

“It’s a historical decision, in the wrong sense,” the 59-year old sovereign tells PEOPLE exclusively. “President Trump has made a historic mistake. Not only for the Paris Agreement but for the United States relations with the international community.”

Admitting frustration and bewilderment, the royal says Trump’s treaty abandonment “is incomprehensible. We were making great efforts, great progress, and the country — which has traditionally led us — is baling out.

“Disappointing is too weak of a word to express my feelings. There’s hope still, there are states and cities in America, and some businesses and civil agencies going ahead with their plans and if that movement continues to grow there’s hope. But it will take time to turn the tide.”

The prince, who recently attended a screening in Monaco of Al Gore‘s An Inconvenient Sequel, took the opportunity to note “there’s a sequence in that film, quite a long one on Florida and Miami and the difference in flooding they’ve experienced. They’ve huge, huge areas of flooding now.

“I know if I owned beachfront property in Florida that would scare me.”

While hoping there could still be some lobbying efforts, Albert stressed little belief in President Trump’s professed treaty renegotiation. Referring to French President Macron’s response that “there’ll be no new negotiations,” the sovereign says, “It’s difficult to see how there could be. It was difficult enough to get everyone to agree at all. I’ve been working on climate and environmental issues for 20 years and it wasn’t certain after years of negotiations that we’d get the Paris Agreement.

“Now, less than two years later, to have it thrown down the drain by a new administration is disheartening. It’s catastrophic.”

Recognized for his commitment and expertise to ecological causes, Albert was an extremely visible world leader at the COP 20 conference, which laid the groundwork for the Paris Agreement. The conference included an “Oceans Day” agenda championed by Prince Albert’s work to expand understanding among delegate nations.

In October, before the U.S. election, Albert told PEOPLE he believed that Trump’s lack of understanding of environmental issues was “dangerous” for the entire planet. “I was pretty shocked,” he warned at that time, “when I heard his climate change denial. It’s dangerous to have someone like this running for office, someone who can have people believing it’s all a conspiracy.”

Speaking to PEOPLE on Friday, Albert again criticized Trump’s refusal to consider scientific opinion.

“In a nutshell, what he did yesterday is too momentous of a decision to make without doing your homework,” he says. “When you are out on the campaign trail, making promises, you can’t be excused for not knowing things.

“But something this big, an issue this important to all citizens not only of America but to the world you have to do your homework before. When you are in office, and you have access to the sources, then you really have to do your homework.

“I really don’t understand how people can be so shortsighted or miss this completely. I don’t understand how when 97-98 percent of the world’s scientific community agrees that there is climate change impact, why anyone would want to be on the side of the 3 percent.

“Fifteen, 20 years ago, you might have had different arguments, but today? To reject it because it is inconvenient or to say it doesn’t make sense or that you think it will draw us back to the Stone Age, you really have to make an effort not to understand that we’re running out of time.”

He continues, “If your house is on fire, it is going to remain on fire, if you continue pouring gasoline on it.”

Earlier on Friday — in welcoming remarks to the second edition of the Energy Security Forum in Monaco — Prince Albert declared: “This decision constitutes a very serious misjudgment for our planet and for future generations. It also compromises America’s global leadership and its own economic interests by underestimating the prospective growth offered by a non-carbon based economy and on technological innovation.

“I want to believe that the states, people and cities of America which are already engaged in a virtuous cycle of transformation and those who understand the importance for future generations will continue their efforts to promote lower carbon levels and sustainable energy.

“The Principality of Monaco affirms more than ever its commitment in the fight against global warming with ambitious objectives greater than those envisaged by the Paris Agreement. I invite all the nations of the world, signatories of this Agreement, to continue and confirm their commitments for a cause that concerns the preservation of our Earth and Humanity.”

The prince’s remarks come on the verge of his departure for the U.S. On Wednesday, he’ll formally present his upcoming three-year oceanographic project Monaco Explorations to United Nations representatives in New York.