The Hot 15 Million Year Time Machine — 415 Parts Per Million CO2

The clanking, wheezing, gasping, choking engines of fossil fuel burning are propelling us backwards toward hotter and hotter geological contexts. And with new atmospheric CO2 records shattered this week, it is, once again, time to take stock.

Jonathan Overpeck, dean of the School for Environment and Sustainability yesterday noted:

“We keep breaking records, but what makes the current levels of CO2 in the atmosphere most troubling is that we are now well into the ‘danger zone’ where large tipping points in the Earth’s climate could be crossed.”

One way we can get a sense of how far we’ve crossed into Overpeck’s ‘danger zone’ is by looking at how present atmospheric heat trapping gas levels compare to past climate ages. Taking measure, we find that over the last few days, carbon dioxide levels have spiked to over 415 parts per million. An ominous new record driven by fossil fuel burning that spells more warming and climate disruption for a planet already in crisis.

As a report in LiveScience yesterday noted — the present spike in atmospheric CO2 is unprecedented in the past 800,000 years. A span of time when we are able to directly measure historic atmospheric carbon dioxide due to air bubbles trapped in the ice of ancient glaciers in Antarctica and Greenland.

But as we can see in the above image, 415 parts per million is not only the highest atmospheric CO2 level in the last 800,000 years, it significantly exceeds all historic measures in this time period. The 2nd highest reading came in about 320,000 years ago at around 300 parts per million. 415 parts per million is nearly 40 percent higher than this peak value. It’s more than double the heat-trapping atmospheric CO2 averages seen during ice ages.

We have to go far, far back, much further back, to find a time when atmospheric CO2 values were likely similar to those experienced today. Indirect proxy readings indicate that the last time levels of this heat trapping gas were so high extend not hundreds of thousands, but millions of years.

(Atmospheric CO2 levels are now the highest since the Middle Miocene of 15 to 17 million years ago. Image source: Skeptical Science.)

In fact, we have to push into a period of time about 15 million years ago to see similar atmospheric CO2 readings. In other words, present CO2 levels are comparable to the Middle Miocene climate epoch when global temperatures were 3-4 degrees Celsius hotter than late 19th Century levels. And if we keep burning fossil fuels at present rates over the coming decade, we will keep elevating CO2 by around 3 parts per million each year. This continued activity would put us near the 450 part per million mark in just one decade further solidifying a Middle Miocene to early Ogliocene climate context.

Dr Michael Mann yesterday noted to Livescience:

“If you do the math, well, it’s pretty sobering. We’ll cross 450 ppm in just over a decade. [Such high levels of CO2] are likely to lock in dangerous and irreversible changes in our climate.”

What this means is that our continued fossil fuel burning brings with it heightening climate disruption. More heatwaves, wildfires, powerful storms, blows to ocean health, sea level rise, and harm to those living on Earth. The only way to significantly blunt that disruption is to rapidly reduce the fossil fuel based emission and transition to clean energy.

(CO2 hitting 415 ppm in the Mauna Loa Observatory puts us far out on a global warming limb.)

Present energy forecasts show a leveling off of fossil fuel burning over the ten year horizon. But clean energy substitution will have to ramp up considerably to prevent rapidly hitting new major and dangerous climate thresholds — driving not just a leveling off, but a decline in fossil fuel burning.

It is worth noting that adding in other greenhouse gasses such as methane puts us even further over the mark — at around 495 parts per million CO2 equivalent in 2019 and near 550 ppm CO2e within about 15 years if projected fossil fuel burning and extraction continue. However, since methane is a short lived gas, fossil fuel extraction reductions and changes to agriculture could tamp down a portion of the CO2e overshoot.

It’s time to get very, very serious about reducing fossil fuel burning and rapidly building out clean energy. The climate disruption that is coming won’t hold back. We need to pull out all the reasonable stops to prevent it. This is why everything from individual action to climate change focused policies like the Green New Deal are so important.

(Want to help fight climate change by transitioning to a clean energy vehicle? Get 1,000 to 5,000 free supercharger miles at this link.)

 

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Entering the Middle Miocene — CO2 Likely to Hit 404 Parts Per Million by May

The Pliocene. A period of time 2-5 million years ago hosting carbon dioxide levels ranging from 350 to 405 parts per million and global average temperatures that were 2-3 degrees Celsius hotter than 1880s levels. The great ice sheets of Greenland and West Antarctica were feeble, if they existed at all. And seas were about 25-80 feet higher than today.

mlo_two_years

(CO2 hit above 401.84 parts per million on March 9, 2015, and above 403 parts per million on March 10 — levels that test the upper boundary of CO2 last seen during the Pliocene and entering a range more similar to the Miocene. Image source: The Keeling Curve.)

In the context of human warming, the amount of heat forcing we’ve added to the global atmosphere from carbon dioxide emissions alone has been hovering in the range of the Pliocene for the past two decades. A heat forcing that, if it remained steady over a substantial period of time, would almost certainly revert the world to a climate state last seen during that time.

But by 2015, the global human heat forcing from carbon dioxide emissions had begun to exit the period of the Pliocene. Now we are entering a period in which atmospheres are more similar to those seen during the Middle Miocene Climate Optimum — the last time CO2 measures exceeded a threshold of roughly 405 parts per million (see here and here)

The Middle Miocene Climate Optimum occurred between about 15 and 17 million years ago. It hosted an atmosphere in which carbon dioxide levels varied wildly from 300 parts per million to 500 parts per million. Temperatures were between 3 to 5 degrees Celsius hotter than the 19th Century. And sea levels were about 120 to 190 feet higher. During this period, the world was still cooling down from the heat of the Paleocene and Eocene epocs. Carbon was being sequestered. And it was the first time the world broke significantly below a 500 part per million CO2 plateau that had been established during the Oligocene 24 to 33 million years ago.

The great glaciers in East Antarctica were mostly well established, even though their scope was a mere shadow of what we see today. The Greenland and West Antarctic glaciers did not exist. They would have to wait for about another 5-10 million years for the Earth to cool further.

glaciation-since-petm

(Glaciation since PETM. Image source: Dr James Hansen.)

As of March 9, 2015, atmospheric CO2 levels had reached 401.84 parts per million. Already a level testing the Pliocene-Miocene boundary, this measure will continue to increase through the rest of March, on into April, and keep rising until middle or late May. At that point, global CO2 levels will have reached around 404 parts per million. At least the highest levels seen in the last 3 million years and possibly the highest levels seen in 15 to 18 million years.

If the greater portion of this range is correct, then we are now breathing air that none among our species or even our hominid relatives have ever breathed since their setting foot on this world.

But CO2 alone doesn’t tell the whole story. Equivalent CO2 levels (CO2e) including all human emitted greenhouse gasses — methane and a host of industrial gasses — will reach about 484 ppm CO2e this year (see here and here). And that forcing puts us easily within the range of the warmest periods of the Miocene. A brew of heat trapping gasses including exotic chemicals that no creature has likely ever breathed while living on the Earth.

Links:

The Pliocene

Middle Miocene Climate Instability Associated With CO2 Variability

CO2 and Climate Closely Linked During Middle Miocene

Sea Level and Ice Volume Variations

IPCC 2007 Chapter 6 — Paleoclimate

Dr James Hansen

The Keeling Curve

NOAA ESRL CO2 Measure

CO2 Levels for February Eclipsed Prehistoric Highs

A Faustian Bargain on the Short Road to Hell — Living in a world at 480 CO2e

400 PPM CO2? Add in All other Gasses and it’s 478 CO2e

Hat tip to Aldous

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