We have now had 3 months in a row of CO2 ambient atmospheric gas concentrations above 400 PPM, this has not happened since between 800,000 thousand years and 15 million years ago.
The world first passed the 400 ppm milestone on May 9, 2013. The first 400 ppm measurement of 2014 came two months earlier. CO2 concentrations at the Mauna Loa observatory in Hawaii, which have been monitored since 1958, have been steadily above that level since the beginning of April, which marked the first full month with an average CO2 level above 400 ppm.Though we know that this was coming it is still terrifying to see that the atmosphere is on it's way to perhaps surpass the Permian period of extinction. The planet does not care how the carbon is released into the atmosphere whether it is caused by human activity or by a meteor.
While concentrations of CO2 have begun their seasonal decline from their May peak (which was just shy of 402 ppm), the daily averages have stayed consistently above 400 ppm. With the month almost at an end, June’s average will be above 400 ppm.
Given the typical rate of decrease in concentrations, which happens as vegetation in the Northern Hemisphere sucks up CO2, they may only dip consistently below 400 ppm come the third week of July, Tans said.
The levels of CO2 in the atmosphere vary not only through humanity’s addition of the gas through industrial processes, but also with the biological cycle. Concentrations begin their rise in the winter, when plants are dormant, and continue rising through spring. They reach their peak in May and then begin to decline because plants are in full bloom and are pulling CO2 from the atmosphere to fuel photosynthesis.
But plants only pull so much CO2 out of the atmosphere in a given growing season. Each year they leave a growing excess of about 2 ppm behind, which is why the 400 ppm mark came earlier this year than last and will come earlier still next year.
Tans expects the first 400 ppm measurement of 2015 to happen in February, and for concentrations to stay above that mark through July — a full six months. In just another year or so of CO2 building in the atmosphere, the world will be above 400 ppm year-round.
“As long as human society continues to emit CO2 from burning fossil fuels, CO2 in the atmosphere and oceans will continue to increase,” Tans said.