Associated Press

President Donald Trump listens during the United Nations Climate Action Summit during the General Assembly, Monday, Sept. 23, 2019, in New York.

• Though he wasn't slated to attend, President Donald Trump dropped in at the UN Climate Action Summit on Monday along with Vice President Mike Pence.
• The UN summit was organized by UN Secretary-General António Guterres to get countries to agree on stricter standards to slow the effects of climate change.
• Countries like the US, Japan, Australia, and South Africa were not invited to speak at the event due to the UN's disapproval of their greenhouse gas emissions.
• 16-year-old climate activist Greta Thunberg spoke at Monday's meeting, telling world leaders, "You have stolen my dreams and my childhood with your empty words."
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President Donald Trump crashed the UN Climate Action Summit late Monday morning along with Vice President Pence - even though they weren't invited to attend.

The US commander-in-chief dropped in for about 10 to 15 minutes before departing the General Assembly hall. A Business Insider reporter at the scene saw him sit with pursed lips in the US seat flanked by Pence, with secretary of state Pompeo and acting chief of staff Mick Mulvaney behind him. He stayed for Indian prime minister Narendra Modi and German chancellor Angela Merkel's speeches.

Trump clapped for the former politician's remarks, though seemingly not for the latter's.

Trump and his vice president were at the UN building in New York to deliver remarks at the Global Call to Protect Religious Freedom, which was happening simultaneously.

According to CNN's Jim Acosta, when asked why he attended the UN summit after all, the president responded: "I'm a big believer in clean air and clean water, and all countries should get together and do that, and they should do it for themselves. Very, very important."

The US was one of several countries not invited to speak at the summit

Over 100 other world leaders, including Merkel, Modi, and French President Emmanuel Macron attended the UN summit in New York, which was held ahead of the UN General Assembly meeting on Tuesday. UN Secretary-General António Guterres organized the meeting to pressure countries to slow the effects of climate change, according to the Financial Times.

Guterres plans to get countries to agree to stricter standards to slow the effects of climate change, citing the Paris climate change agreement as a benchmark. In December 2015, world leaders created the agreement, which states that countries will prevent global temperatures from rising above 1.5°C (2.7°F), and staying well below 2°C (3.6°F).

"I am appealing for leadership from politicians, from businesses and scientists and from the public everywhere," Guterres said in an announcement. "We face a direct existential threat. Climate change is moving faster than we are."

Countries that didn't have a climate action plan prepared for the summit, including Japan, South Africa, and Australia, were encouraged not to speak. Other countries, like Saudi Arabia and Brazil, chose not to take part in the summit whatsoever.

"Only the boldest and most transformative actions [will] make the stage," Amina Mohammed, UN deputy secretary-general, told the Financial Times. "We will see on Monday who is stepping up."

Climate activist Greta Thunberg gave an impassioned speech

Though the US was represented at the event by a diplomat, President Trump had previously made it clear that the US had no intentions of making long-term commitments to lower its carbon footprint. In June 2017, Trump announced that the US would drop out of the Paris climate change agreement, citing concerns that lowering fossil fuel consumption would take a toll on the US economy.

Last Friday, millions of demonstrators gathered in hundreds of cities around the world for the Global Climate Strike, a mass protest against inaction toward climate change timed near the eve of the summit. The catalyst for the demonstrations was 16-year old Greta Thunberg, a Swedish climate activist known for her direct, outspoken manner. Thunberg sailed across the Atlantic in a zero-emissions sailboat (Thunberg says flying has too big a carbon footprint) to attend the summit, among several other events, including New York's climate strike.

During Monday's summit event, Thunberg gave an impassioned speech on the dangers of climate change, telling world leaders, "You have stolen my dreams and my childhood with your empty words."

"The eyes of all future generations are upon you," she continued. "If you choose to fail us, I say we will never forgive you."