Greenhouse gas levels in the atmosphere have hit a new high and there is no sign of them slowing down, according to a report published by the United Nations.

Levels of carbon dioxide (CO2) – a byproduct of burning fossil fuels and the main force driving climate change – are almost 50 percent higher than they were in the pre-industrial era, around 1750. Measuring data from 2017, CO2 clocked in at 405.5 parts per million (ppm), up from 403.3 ppm in 2016 and 400.1 ppm the year before.

"The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago when the temperature was 2-3°C warmer," head of the World Meteorological Organization (WMO) Petteri Taalas said in a statement.

Levels of methane, a potent gas responsible for 17 percent of global warming, are 2.5 times higher while levels of nitrous oxide, a chemical known for destroying the Earth’s protective ozone layer, are 20 percent higher.

"Without rapid cuts in CO2 and other greenhouse gases, climate change will have increasingly destructive and irreversible impacts on life on Earth," said Taalas. "The window of opportunity for action is almost closed."

WMO is an intergovernmental agency tasked with tracking the content of dangerous gases in the atmosphere and publishes its findings annually in the Greenhouse Gas Bulletin. In order to keep global warming below 1.5°C (2.7°F), the UN Intergovernmental Panel on Climate Change (IPCC) reports net CO2 emissions need to be at net zero – the amount being pumped into the atmosphere must equal the amount removed through natural or technological processes. Even so, President Donald Trump continues to deny the effects of climate change after having pulled out of the Paris Climate Agreement last year.

“Brutal and Extended Cold Blast could shatter ALL RECORDS – Whatever happened to Global Warming?" he tweeted. (Read this write-up by the New York Times to understand why that math just doesn’t work out.)  

WMO has been able to estimate greenhouse gas levels dating back 800,000 years by studying ancient air bubbles trapped in ice core samples taken from Greenland and Antarctica while analyzing fossilized material has allowed them to estimate levels going back 5 million years.

"There is currently no magic wand to remove all the excess CO2 from the atmosphere," said WMO deputy chief Elena Manaenkova. "Every fraction of a degree of global warming matters, and so does every part per million of greenhouse gases."

China is the largest producer of greenhouse gas emissions, followed by the US, India, and Russia.