From KQED Science (Andrew Alden):
This week [November 22, 2015], you can watch as Earth passes a threshold not seen for at least a million years. The concentration of carbon dioxide in the air will rise above 400 parts per million. And scientists predict neither you nor your children will ever see it go below 400 ppm again.
The World Meteorological Organization (WMO) said on Monday that this year’s El Niño combined with global warming puts the world “in uncharted territory.”
“This naturally occurring El Niño event and human induced climate change may interact and modify each other in ways which we have never before experienced,” said WMO Secretary-General Michel Jarraud.
‘An Icon of Climate Change’
When scientists talk about atmospheric CO2, their yardstick is the so-called Keeling curve. It’s the record of the air’s composition, made each day at a station run by the Scripps Institution of Oceanography in the pure air high on Mauna Loa volcano, in Hawaii.
Ralph Keeling, the custodian of the CO2 record, made his prediction last week in a blog post on the Keeling Curve website.
The Keeling curve was started in 1958 under the direction of Keeling’s father, Charles David “Dave” Keeling. Today it’s the longest series of such measurements in the world. It was named a National Historic Chemical Landmark this year.
The Keeling curve is an icon of climate change. What does it show?
In the 1960s, Dave Keeling’s measurements showed that the CO2 level in the air was rising steadily. That long-term increase is the mark of human influence. It comes overwhelmingly from the fossil fuels we burn — largely to generate electricity, but also to smelt metals, produce cement, run motors and so on. Other smaller sources of CO2 are from humans cutting down forests and from large-scale mechanical farming, which removes most of the carbon-rich humus contained in soil.
Since the 1960s, the long-term increase in CO2 has sped up. A little over half of the CO2 we produce is absorbed by the ocean and by growing plants. The rest stays in the air and acts as a greenhouse gas.