NOV 4 2017, 2:37 PM ET Alarming Rise in CO2 Levels Looms Over Global Climate Change Summit

Image: Seagulls flying over the roofs tops of Paris
Seagulls flying over the roofs tops of Paris on Dec. 29, 2016. Lionel Bonaventure / AFP - Getty Images file
"We are actually moving in the wrong direction," Taalas said.

The United Nations is sounding the alarm: The last time carbon dioxide concentrations in the atmosphere were this high was three to five million years ago.

In a report this week, the World Meteorological Organization (WMO) warned that temperatures could continue to spike, hitting perilous levels by 2100 — unless world leaders take drastic action.

"Without rapid cuts in CO2 and other greenhouse gas emissions, we will be heading for dangerous temperature increases by the end of this century," Petteri Taalas, the WMO's secretary-general, said in a statement.

That alarming prediction will likely loom over a major climate summit, known as COP 23, that starts next week in Bonn, Germany, and will bring together leaders from around the world.

Related: Are NYC’s Preparations Amid Climate Change Enough?

Among the topics on the agenda: the Paris climate agreement, the landmark pact in which nearly 200 nations agreed to set plans for cutting greenhouse gas emissions. The accord has faced intense scrutiny in recent months after President Donald Trump announced plans to pull the United States out of it.

The State Department has said the U.S. will continue to play a role in international meetings on climate deals.

Trump is "open to re-engaging in the Paris agreement if the United States can identify terms that are more favorable to it, its business, its workers, its people and its taxpayers," the State Department said.