It now seems that nowhere on the face of the Earth has been left untouched by the burning of fossil fuels. The last station on the planet without a reading of atmospheric carbon dioxide of 400 parts per million – the remote depths of Antarctica – has now for the first time recorded the breaching of this milestone, making it the first time it has hit such levels over the continent in perhaps 4 million years.

“The far southern hemisphere was the last place on Earth where CO₂ had not yet reached this mark,” explains Pieter Tans, the lead scientist of NOAA's Global Greenhouse Gas Reference Network, who recorded the carbon dioxide levels. “Global CO₂ levels will not return to values below 400 ppm in our lifetimes, and almost certainly for much longer.”

This news comes after an earlier report found that the levels of CO₂ in the atmosphere recorded at the Mauna Loa Observatory in Hawaii will likely be above 400 ppm for an entire year. Atmospheric carbon dioxide concentrations have not been this high for some 4 million years, when ground sloths and giant armadillos still roamed the Americas and our early hominin ancestors, australopithecines, first emerged during the Pliocene epoch.

While the figure of 400 parts per million is largely symbolic, it acts as good marker of just how dramatically we have changed the atmosphere of the planet. At the start of the industrial revolution, before the wholesale burning of coal, oil and gas, the concentration of atmospheric carbon dioxide was sitting at around 280 parts per million. Over the following century, this level has been increasing in tandem with the amount of fossil fuels we have been consuming, finally reaching 400 ppm for the first time in 2013.

Independently, another research station in Antarctica has also recorded the same figures. Reported by the British Antarctic Survey from their Halley VI Research Station, it seems that humans really have changed our planet “to the very poles.” With the CO₂ in the atmosphere trapping the heat from the Sun, it is hardly surprising then that 2016 is set to be the hottest on record.

“We know from abundant and solid evidence that the CO₂ increase is caused entirely by human activities,” says Tans. “Since emissions from fossil fuel burning have been at a record high during the last several years, the rate of CO2 increase has also been at a record high. And we know some of it will remain in the atmosphere for thousands of years.”

^{Image in text: NOAA}