Our thin blue line will be less blue over time thanks to how much carbon dioxide we're pumping into the sky. Dima Zel/Shutterstock

Last year, a grim landmark was reached. Concentrations of carbon dioxide in the atmosphere persisted at levels above 400 parts per million for the first time in recorded history, signposting a “point of no return”.

A new global analysis by the World Meteorological Organization (WMO) makes it clear just how serious this event was. As it turns out, Earth’s atmospheric concentration of the long-lasting greenhouse gas is the highest it’s been for 800,000 years.

Methane – a shorter-lived but far more potent greenhouse gas – is also present in the atmosphere in far higher quantities than expected, something that is also linked to human activities.

Apart from the ignition of fossil fuels, this record was also down to an extremely powerful El Niño event – a natural phenomenon that is exacerbated by man-made climate change.

El Niño restricts the ability of flora to absorb carbon dioxide whenever it causes extensive droughts. Normally, much of this excess carbon would be absorbed by the oceans – the planet’s most significant carbon sink – but they’re becoming increasingly saturated these days.

The last time the Earth experienced a comparable concentration of CO 2 was 3-5 million years ago. Back then, the temperature was 3°C (5.4°F) warmer and sea level was up to 20 meters (66 feet) higher.

Things are only set to get worse. Yes, planetwide carbon emissions have been stalling in recent years. However, the time lag between the burning of fossil fuels and the appearance of greenhouse gases in the atmosphere means concentrations will continue to rise for some time.

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It's not the quantity that's most significant here, though, but the pace of change. Measurements taken in 51 different countries revealed that 2016’s increase was 50 percent higher than the average of the past 10 years.

“The rate of increase of atmospheric CO 2 over the past 70 years is nearly 100 times larger than that at the end of the last ice age,” the authors of the report explained in a statement. “Such abrupt changes in the atmospheric levels of CO 2 have never before been seen.”

This all spells trouble for the Paris agreement.

A recent study suggested that the more ambitious target of restricting the warming to just 1.5°C (2.7°F) was possible thanks to an underestimation of how “sensitive” the atmosphere is to carbon dioxide’s heat-trapping effect. This new analysis, sadly, notes that we’ve pumped so much of the gas into the sky so suddenly that the upper 2°C (3.6°F) limit will likely be breached.

This will bolster support for plans that aim to actively draw down atmospheric carbon dioxide that’s already in the atmosphere – conceptions like carbon capture and storage, for example. Their development will need to be sped up somewhat if we are to have any hope of saving the world.

[H/T: BBC News]