No Turning Back As Earth Permanently Passes CO2 Threshold

It's a brave new world. rdonar/Shutterstock

Under the imperfect but groundbreaking Paris agreement, now ratified by the world’s two largest carbon emitters, it’s hoped that the world will not warm by more than 2°C (3.6°F) by 2100. Sadly, we have registered so many high-temperature records this year alone that it’s looking doubtful that this will be achieved – and it appears that the most ominous record has just been broken.

According to data provided by the National Oceanic and Atmospheric Administration (NOAA), the concentration of atmospheric carbon dioxide hasn’t dropped below 400 parts per million (ppm) all September. During this time of year, climatological processes normally render the atmospheric concentration quite low, so the fact that this happened at all is astonishing.

It seems then that 2016 will be the year that the world permanently passed the 400ppm threshold. Although this value is mostly symbolic, it does represent just how significantly we’ve altered the climate.

“Is it possible that October 2016 will yield a lower monthly value than September and dip below 400ppm?” Ralph Keeling, a professor at the Scripps Institution of Oceanography, wrote in a blog post accompanying the ignominious milestone. “Almost impossible.”

“By November, we will be marching up the rising half of the cycle, pushing towards new highs and perhaps even breaking the 410ppm barrier,” he added.

Pre-industrial levels were around 280ppm, which means that since the late-18th century, there’s been an unprecedented 43 percent increase in atmospheric carbon dioxide. This has led to a warming rate that’s 10 times faster than what would be naturally expected during an interglacial period.

Spare a thought for the oceans, though, the largest carbon sink on the planet. There may be a lot more carbon dioxide in the atmosphere, but the oceans have already absorbed so much that if they were to expunge it all back out overnight, the world would warm 360 times faster than the natural rate.

The daily (yellow circles) averaged carbon dioxide values as measured from atop Mauna Loa, Hawaii. NOAA

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