Key Heat Trapping Gas Crosses 410 Parts Per Million Threshold — Highest Level in Past 5-20 Million Years

This past week, atmospheric carbon dioxide levels passed a new ominous milestone.

Clocking in at 410.7 parts per million at the Mauna Loa Observatory, this key heat trapping gas hit a range not seen on Earth for many millions of years.

(The world crossed the 410 part per million milestone in the daily measure this week. Image source: The Keeling Curve.)

These levels now correspond with the Miocene Climate Epoch when seas were 120 to 190 feet higher than today and when global temperatures ranged from 3 to 5 degrees Celsius hotter than preindustrial averages.

Record Rates of Accumulation

These new records come following two years of record rates of atmospheric CO2 accumulation. According to NOAA, carbon dioxide accumulated by 3.03 parts per million during 2015 and by 3.00 parts per million during 2016. These now represent the two fastest rates of carbon dioxide accumulation in the climate record to date. By comparison, the substantial warming at the end of the last ice age was accompanied by an approximate 0.01 part per million per year rate of CO2 increase averaged over 10,000 years.

2017 rates of atmospheric CO2 accumulation, according to NOAA, appear to have backed off somewhat in the first quarter. Comparative gains from Q1 2016 to Q1 2017 are about 2.8 parts per million. A weak La Nina in the Pacific during late 2016 probably helped ocean surfaces to cool and to draw down a bit more CO2. However, the rate of increase is still disturbingly rapid. A 2.8 ppm increase in 2017, should it emerge, would be the 4th highest annual rate of increase in the record and would be substantially above past decadal averages. Hopefully, this still-disturbingly-rapid rate of increase will continue to tail off a bit through the year. But it is increasingly clear that the time for urgent action to reduce carbon emissions and this very harmful related rate of accumulation is now upon us.

(The CO2 growth rate has recently been ramping higher due to record carbon emissions during the present decade. Rates of carbon emission will need to fall away from record high rates in order to tamp down the presently high rate of accumulation which will tend to trend higher even if such emissions remain at plateau due to various faltering carbon sinks and leaking natural carbon stores. Image source: NOAA.)

The total CO2 increase since major fossil fuel burning began in the 19th Century is now in the range of 130 parts per million from 280 (ppm) to today’s high of 410 (ppm). By comparison, during the end of the last ice age, levels of this heat trapping gas jumped by about 100 (ppm) from around 180 (ppm) to 280 (ppm). Atmospheric averages for 2017 should range about 3-4 ppm lower than the April-May high mark (which might still hit daily highs of 411 ppm or more). But at present rates of increase, we’ll be leaving the 410 ppm threshold level in even the lower average months behind in just a handful of years.

Depending on How You Look at it, We’re 5 to 30 Million Years Out of the Holocene Context

The primary driver of the present extreme rate of CO2 increase is global carbon emissions (primarily from fossil fuel burning) in a record range near 11 billion tons per year (or nearly 50 billion tons of CO2 equivalent gas each year). Though 2014 through 2016 saw a plateau in the rate of global carbon emission, the decadal average accumulation of this emission is still at record highs. Meanwhile, it appears that warming oceans, lands more susceptible to deluges and wildfires, increasingly deforested regions like the Amazon, and thawing Arctic permafrost are less able to take in this record excess. As a result of these factors, human fossil fuel emissions will need to fall for a number of years before we are likely to see an impact on the average annual rate of atmospheric accumulation of this potent heat-trapping gas.

(Past paleoclimate proxy records show that we are millions of years out of the Holocene context when it comes to present levels of atmospheric CO2 accumulation. Image source: Skeptical Science.)

Paleoclimate studies of past epochs are unable to provide 100 percent accuracy for past atmospheric CO2 levels. However, proxy data provides a good range of estimates. Based on these measures, it appears that the most recent likely time when atmospheric CO2 levels were comparable to those we now see today occurred around 5 million years ago. Meanwhile, it appears possible that the last time CO2 levels were so high extended as far back as 20 to 25 million years ago.

Unfortunately, carbon dioxide is not the only heat trapping gas humans have emitted into the atmosphere. Add in methane and other greenhouse gasses and you end up with a heat forcing roughly equivalent to 493 parts per million of CO2 (CO2e) during 2017 at present rates of increase. This level is very close to the maximum Miocene boundary level of 500 parts per million — a total amount of heat forcing that likely hasn’t been seen in 20-30 million years.

Serious, Concerted Action Required to Avoid Worsening Disasters

The only safe and reliable way to halt the rapid rise of heat trapping gasses and concurrent warming is to cease emitting carbon to the atmosphere. Such an undertaking would primarily involve a major shift away from fossil fuel burning machines and infrastructure. Present low-cost renewable energy provides a powerful option for just such a transition. In addition, various forms of atmospheric carbon capture from changes to land use, to biofuel-based carbon capture, to materials-based carbon capture will be necessary to draw down the extraordinarily high level of carbon overburden that has already been emitted. Failing such an undertaking, however ambitious, would consign the world to increasingly harmful temperature increases and related damaging geophysical changes for the foreseeable future.


The Keeling Curve


Skeptical Science

Entering the Middle Miocene

Renewable Energy Technology is Now Powerful Enough to Significantly Soften the Climate Crisis

Hat tip to Ryan in New England

Hat tip to Wili

Hat tip to Erik Frederickson

Increasingly Out of the Human Context: Atmospheric CO2 Likely to Hit Monthly Peak Near 410 ppm in 2017

“The rate of CO2 growth over the last decade is 100 to 200 times faster than what the Earth experienced during the transition from the last ice age. This is a real shock to the atmosphere.” — Pieter Tans, lead scientist at NOAA’s Global Greenhouse Gas Reference Network


It wasn’t too long ago that we were talking about atmospheric CO2 crossing the key 400 parts per million threshold. That was 2014. But now, just three years later, atmospheric levels of this key heat-trapping gas are climbing to within striking distance of another, and still more dangerous, atmospheric milestone. 410 ppm.

That’s an increase in the peak atmospheric CO2 value of around 3 ppm per year or more. One that gibes with record annual rates of atmospheric accumulation of this heat trapping gas during 2015 and 2016. And as we approach a new high water mark for atmospheric carbon, we’ve left the 400 ppm level so far behind that it’s likely that we’ll never see even a single day where values at the Mauna Loa Observatory fall below that threshold.

Approaching Another Milestone for Key Heat-Trapping Gas

Instead, primarily through our rampant and incessant burning of fossil fuels, we are racing head-long into an ever-more uncertain climate future:

(The world hasn’t seen such high levels of atmospheric carbon in millions of years. And all that extra carbon is sucking a considerable amount of Earth-altering heat into its atmosphere and oceans. Image source: The Keeling Curve.)

Since late February, weekly and daily CO2 values have ranged between 405 and 409 parts per million. But as CO2 typically peaks during April and May before Northern Hemisphere vegetation begins to draw down carbon in the months of June through September, it appears that we are likely to see top monthly atmospheric CO2 values hit between 409 and 410 parts per million during 2017.

Out of Context Problem

Back in 2014, we were talking about how atmospheric CO2 levels hadn’t been so high in about 3 million years. But a near 410 ppm high water mark would push those comparative timeframes back to between 5 and 15 million years when the world was about 3-4 degrees Celsius hotter than today and atmospheric CO2 ranged from 400 to 500 parts per million (to this point it’s worth noting that atmospheric CO2 equivalent gasses like methane, when added to presently high CO2 levels, will produce a combined total forcing equal to around 493 ppm CO2e by end 2017).

Back then, ocean levels were meters to tens of meters higher than today, the glacial ice of Greenland and West Antarctica was gone or greatly reduced, and even East Antarctic Ice Sheets were smaller. It’s also worth noting that back then, the great apes had just begun to appear and that the first fully developed ancestors of modern humans were still far off.

(NASA provides a new 3-D visualization of carbon dioxide accumulating in the Earth’s atmosphere. Video source: NASA and The Hindustan Times.)

Human beings, and even our furthest distant ancestors, have not experienced climates of the kind we are locking in now.

But as increasingly tough as our present climate situation may seem, there’s another wrinkle to the tale. For from 5-15 million years ago to now, billions of tons of carbon in the form of plant and animal remains has been sequestered in the world’s forests, peatlands, permafrost and oceans. And as the heat-trapping gasses that we have now placed into the atmosphere, primarily through fossil fuel burning, stresses those stores, we risk creating a further warming response coming from the Earth System. Such high atmospheric thresholds should, therefore, be viewed as in a range that produces considerable risk of crossing key climate tipping points and of locking in harmful Earth System changes for very long time periods. And we continue to add to that risk by burning more fossil fuels.


The Keeling Curve


Following Carbon Dioxide Through the Atmosphere

Human Evolution

Climate Epochs: Miocene

Atmospheric Carbon Dioxide Hits Record Levels

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