Point of No Return: Earth Reaches 400ppm Threshold Permanently

September’s carbon dioxide output failed to drop below 400 parts per million (ppm) despite historically being the year’s low point for CO2 emissions, which means the Earth has very likely passed that symbolic climate threshold forever.

The Earth has hit 400ppm before, but seasonal cycles have always reduced carbon dioxide output back below that level. Now, climate scientists say it is “almost impossible” that will ever happen again.

According to Climate Central:

“Is it possible that October 2016 will yield a lower monthly value than September and dip below 400 ppm? Almost impossible,” scientist Ralph Keeling, who runs the carbon dioxide monitoring program at the Scripps Institute for Oceanography, wrote in a blog post this week. “Brief excursions towards lower values are still possible but it already seems safe to conclude that we won’t be seeing a monthly value below 400 ppm this year—or ever again for the indefinite future.”