Concentrations of carbon dioxide surged at a record breaking speed in 2016, according to the annual Greenhouse Gas bulletin compiled by the World Meteorological Organization.
The Geneva-based organization said that levels of the heat-trapping gas CO2 in the atmosphere are the highest in in 800,000 years.
"The abrupt changes in the atmosphere witnessed in the past 70 years are without precedent," WMO said in a statement.
The report cited a combination of "human activities and "a strong El Niño event" as the reason why carbon dioxide levels increased so swiftly.
"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 added.
The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago, the temperature was 2-3 degrees Celsius warmer and sea level was 10-20 meters higher than now, the WMO said.
The historic Paris agreement, approved by 195 countries two years ago, is facing a major setback following US president Donald Trump's announcement last June he would pull the US out of the agreement, a process that will be complete in 2020.
US officials will however attend the United Nation's annual climate meeting in Bonn, Germany, next month to work on a "rule book" for the 2015 Paris plan to shift the world economy from fossil fuels this century, according to a Reuters report.
A separate Emissions Gap Report by the UN Environment Programme will be released on 31 October. That report tracks the policy commitments made by countries to reduce greenhouse gas emissions and analyzes how these policies will cut emissions up until 2030.
"The numbers don't lie. We are still emitting far too much and this needs to be reversed," said Erik Solheim, head of UN Environment Programme, commenting on the WMO report.
"The last few years have seen enormous uptake of renewable energy, but we must now redouble our efforts to ensure these new low-carbon technologies are able to thrive. We have many of the solutions already to address this challenge. What we need now is global political will and a new sense of urgency."