The former chief of United Nations climate negotiations is slamming the White House for, in her words, having "no understanding of the legal underpinning" of the Paris Agreement.

"I would call it a vacuous political melodrama," Christiana Figueres, former executive secretary of the UN Framework Convention on Climate Change, said of President Trump's Rose Garden announcement that the U.S. would turn its back on the Paris Agreement, a landmark international accord to reduce carbon emissions and build global capacity for clean energy.

The president's announcement misrepresented how withdrawal from the Paris Agreement actually works, Figueres said. In actuality, she explained, the process for withdrawing from the agreement signed by 195 nations is complex and lengthy, taking four years to complete.

Get Breaking News Delivered to Your Inbox

"Apparently the White House has no idea how an international treaty works," she said.

Figueres has been a prominent voice in recent years arguing that nations should embrace clean energy industries and abandon "dirty" industries, like coal, not only for the health of the planet but for the health and growth of their economies.

Speaking alongside Figueres in a conference call for reporters, California Governor Jerry Brown said his state remains "all in" in its commitment to reducing carbon emissions regardless of the federal government's decision.

"California will resist because his effort is misguided," Brown told reporters after the president's announcement. "I will even say this is an insane move by the president."

Brown pledged to continue his state's momentum towards a clean economy. California has a goal of 50 percent renewable energy by 2030.

In withdrawing from the Paris Agreement, the U.S. puts itself in the company of Syria and Nicaragua — the only two countries in the world who refused to sign the accord. The U.S. is the biggest carbon polluter in the world, according to data compiled by the United Nations.

Thus far, 147 countries have ratified the agreement, meaning it is the law of the land in those nations. In exiting the pact, some fear the U.S. could trigger a domino effect among other countries.

Anticipating U.S. withdrawal, climate change advocates have closely scrutinized world leaders' comments regarding their commitment to the Paris Agreement in recent weeks. Many have spoken out to confirm they remain committed to the deal.

Speaking in Berlin on Wednesday, Chinese Premier Li Keqiang said fighting climate change is a "global consensus" and an "international responsibility" and reaffirmed China's commitment to the deal.

"It's not invented by China," he said of climate change. It was a pointed reference to a 2012 tweet by Mr. Trump falsely claiming that "the concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive."

China plans to introduce a nationwide cap-and-trade system later this year.

The president's reversal of U.S. policy comes on the heels of his participation in the G7 Summit last week, where his relationship with world leaders, particularly German chancellor Angela Merkel, appeared strained. Merkel has long championed the Paris Agreement.

In pulling out of the climate accord, the president honors one of his core campaign promises. Here, then-candidate Donald Trump holds a sign supporting coal during a campaign rally at Mohegan Sun Arena in Wilkes-Barre, Pennsylvania on October 10, 2016. DOMINICK REUTER/AFP/Getty Images

Merkel alluded to lowering expectations for U.S. leadership on climate change and other issues after the summit.

"The times in which we could completely depend on others are on the way out. I've experienced that in the last few days," Merkel said at an election rally in Munich on Sunday.

She added: "We Europeans truly have to take our fate into our own hands."

The Kremlin has signaled that the nature of the Paris Agreement will fundamentally change if key participants pull out.

"President (Vladimir) Putin signed this convention in Paris. Russia attaches great significance to it," Kremlin spokesman Dmitry Peskov told reporters Thursday, while also adding a caveat: "At the same time, it goes without saying that the effectiveness of this convention is likely to be reduced without its key participants." Russia has not yet ratified the agreement.