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Greenhouse gas concentrations continued to rise in 2018, with carbon dioxide levels hitting an all-time high of 407.8 parts per million, according to a report released by the World Meteorological Organization on Monday. The grim assessment comes just days before the UN Climate Change conference begins on Dec. 2, highlighting the increasing levels of three greenhouse gases contributing to global heating as a result of human activities.

The last time the Earth had comparable concentrations of carbon dioxide in the atmosphere was approximately 3 million years ago, when the temperature was approximately 3 degrees Celsius (5.4 degrees Fahrenheit) warmer and sea levels were up to 20 meters (65 feet) higher.

"There is no sign of a slowdown, let alone a decline, in greenhouse gases concentration in the atmosphere despite all the commitments under the Paris Agreement on Climate Change," said Petteri Taalas, secretary-general of the WMO, in a press release.

The report details concentrations of three greenhouse gases known to greatly contribute to global heating: carbon dioxide, methane and nitrous oxide. These gases can remain in the atmosphere for long periods of time, trapping heat. The higher the concentration, the more heat they can trap. Of the measured gases, CO2 contributes the most to heating and is also absorbed by the oceans, lowering their pH and wreaking havoc on marine life.

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Data is obtained by a suite of over 100 monitoring stations around the globe. The stations are able to assess the minute changes in gas concentrations at any given location and this information is used to work out a global average. The average has been rising at a rate much faster than previous natural increases, driven by fossil fuel combustion, agriculture activities and industrial sources. Notably, the levells will continue to rise.

"I can tell you they're going to go up next year and the following one and then the next decade and the following decade," said Pep Canadell, climate scientist with Australia's CSIRO and executive director of the Global Carbon Project. "It's not until you bring those emissions to zero that you can begin to inspire stabilization in the atmosphere."

The Global Carbon Project is expected to release its yearly "carbon budget" report on Dec. 4, revealing where CO2 is being generated and how limiting emissions can stabilize concentrations in the atmosphere. "The budget is truly like your household finance budget," said Canadell. "[It measures] how much carbon we put into the atmosphere, how much carbon accumulates in the atmosphere and how much carbon gets pulled out of the atmosphere through the oceans and land."

The Project also measures atmospheric CO2 and provides its own measure for the current year. The rise in carbon dioxide concentration will continue, as Canadell noted, unless emissions are drastically reduced.

That poses a huge threat for all life on Earth. The climate crisis is already having negative effects on human health, threatening species with extinction and sending temperatures soaring. On Nov. 5, over 11,000 scientists declared a climate emergency.

Correction 12:58 p.m. PT: Carbon dioxide lowers ocean pH, not ocean acidity.