There's Now More Carbon Dioxide In Earth's Atmosphere Than At Any Other Time In Human History

Yesterday, carbon dioxide levels in Earth’s atmosphere reached a major milestone: a daily average above 400 parts per million. The new high — the highest in human history — was recorded at two separate stations — one in Hawaii and the other in San Diego, California.

That number — expressed in parts per million — means that out of a million molecules of “air,” about 400 are molecules of carbon dioxide. The measurement at the Mauna Loa, Hawaii air sampling station, which has been tracking carbon dioxide levels since the 1950s, was 400.03 on May 9. Last year at this time, the level was at 396.81. 10 years ago it was 378.50.

fluctuations in carbon dioxide levelsDaily and weekly carbon dioxide means at NOAA’s Mauna Loa observatory.

These levels are higher than humanity has ever seen. Higher than they have been for at least the last 3 million years.

“We are creating a prehistoric climate in which human societies will face huge and potentially catastrophic risks,” Bob Ward of the London School of Economics and Political Science, told the AFP. “Only by urgently reducing global emissions will we be able to bring carbon dioxide levels down and avoid the full consequences of [global warming].”

Since the beginning of humanity, up until about 200 years ago, the atmosphere held steady at 275 ppm of carbon dioxide. Along with the industrial revolution came carbon dioxide being pumped into the air, causing a steady and unyielding increase of the green house gas.

As we plucked carbon out of the ground as coal, then burnt it as fuel and released that carbon into the air as carbon dioxide, we’ve steadily increased the carbon dioxide level in the atmosphere.

Carbon dioxide is called a greenhouse gas because it locks in heat. This is really important, because without greenhouse gasses in the atmosphere, our planet would be a lifeless, icy rock. But, when we accumulate too much of these gasses the planet heats up, which, when done in a short amount of time, leads to drastic changes in the environment — changes that plants and animals can’t keep up with.

“There is no precedent in Earth’s history for such an abrupt increase in greenhouse gas concentrations,” Michael Mann, of Penn State University, told the AFP. “While living things can adapt to slow changes that took place over tens of millions of years, there is no reason to believe that they — and we — can adapt to changes that are a million years faster than the natural background rates of change.”

The level of carbon dioxide in the air will dip again over the summer, because levels fluctuate during the year — peaking in May and dropping to its minimum levels (last year that was around 390 ppm) in October — after plants spend the summer sucking 10 billion tons of carbon from the air. But, these levels have been increasing about two parts per million every year, so soon the time will come when there is no longer a day with a carbon dioxide reading under 400.

The milestone is symbolic, but it’s also a scary number. According to, the safe level of carbon dioxide to have in the atmosphere is 350 ppm:

Unless we are able to rapidly return to below 350 ppm this century, we risk reaching tipping points and irreversible impacts such as the melting of the Greenland ice sheet and major methane releases from increased permafrost melt.

“The last time we’re confident that CO2 was sustained at these levels is more than 10 million years ago, during the middle of the Miocene period,” climate scientist Michael Mann told The Huffington Post. “This was a time when global temperatures were substantially warmer than today, and there was very little ice around anywhere on the planet.”

Governments have set our official targets at a maximum of 450 ppm carbon dioxide in the air. 

Ralph Keeling, a climate researcher at the Scripps Institution of Oceanography told The New York Times he estimates we will reach that level in “well under” 25 years.

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