The concentration of carbon dioxide in the Earth’s atmosphere surged last year at the highest pace in hundreds of thousands of years, the World Meteorological Organization (WMO) said Monday.

Carbon dioxide, the emission of which has been growing rapidly over recent decades due to human activity like fossil fuel use, accounted for 403.3 parts per million in the atmosphere, averaged around the world for the entire year, in 2016, according to the WMO.

WMO made its conclusion based both in recordings in recent years and fossils and other artifacts.

ADVERTISEMENT

The United Nations group is warning that the greenhouse gas level is dangerous and unsustainable and used the announcement to call for actions to reduce emissions.

“Without rapid cuts in CO2 and other greenhouse gas emissions, we will be heading for dangerous temperature increases by the end of this century, well above the target set by the Paris climate change agreement,” said WMO Secretary-General Petteri Taalas. “Future generations will inherit a much more inhospitable planet," he said.

The last time the Earth had this much carbon dioxide in its atmosphere was between 3 million and 5 million years ago, the WMO said. Surface temperatures were then between 2 and 3 degrees Celsius warmer and sea levels were 10 to 20 meters higher than present day.

Last year had previously been confirmed as the hottest year on record, breaking the record set in 2015.

President Trump in June announced he would pull the United States out of the Paris climate agreement. It was reached in 2015 by nearly 200 countries with pledges to reduce greenhouse gas emissions, with a goal of limiting global warming to 2 degrees Celsius above pre-industrial levels.