Carbon dioxide levels lower than thought during super greenhouse period

Posted: October 12, 2017 by oldbrew in climate, History, research
Tags: , , ,

Alaskan permafrost [image credit: insideclimatenews.org]


The idea, so heavily pushed these days, that we are on the brink of ‘hot’ times looks more than a bit weak when compared to some earlier epochs on Earth. Regarding raised CO2 levels, the finding that ‘the most likely source of the carbon [dioxide] came from thawing permafrost during the period studied’ strongly suggests that the thaw would be causing the gas release, not the other way round. Phys.org reporting.

Concentration of carbon dioxide during an intense period of global warmth may have been as low as half the level previously suggested by scientists, according to a new Dartmouth College study.

The study found that carbon dioxide may have been less than 1000 parts per million, or ppm, during the Earth’s early Eocene period. This runs counter to thinking that concentration levels were as high as 2000 ppm in the same time frame.

By comparison, current levels of carbon dioxide observed at NOAA’s Mauna Loa Observatory are around 400 ppm.


“This research provides important information about the planet’s climate past and adds an important chapter to the Earth’s history book,” said Ying Cui, Obering Postdoctoral Fellow at Dartmouth College. Climate researchers focus on the early Eocene, a so-called “super greenhouse” period, to better understand how the Earth historically responds to changes in carbon dioxide levels, and to help make better climate projections.

Both the Arctic and Antarctic were ice-free in this time period as temperatures averaged about 10 degrees Celsius warmer than present day. The early Eocene was also characterized by five periods of extreme warmth—known as hyperthermals—that occurred between 52-56 million years ago when the Earth warmed an additional 2C – 8C above the already higher temperatures.

Although there were no cars or power plants 56 million years ago, the same carbon rich in the isotope carbon-12 was released into the atmosphere. Up until now, researchers have grappled with where that carbon came from, what triggered its release, and to what extent carbon dioxide accounted for warming relative to other greenhouse gases.

Unable to access information on carbon dioxide from ice cores that only date back approximately 800,000 years, the research team used a new method to reconstruct levels of carbon dioxide associated with the temperature spikes within the early Eocene.

The Dartmouth research result was derived by assessing past carbon dioxide concentrations using sediment samples found in terrestrial and deep-sea drilling sites. The ratio of carbon-12 to carbon-13 isotopes in those samples helped the team determine that the most likely source of the carbon came from thawing permafrost during the period studied.

“This changes our understanding of what the concentration of carbon dioxide should be in relationship to global temperature as well as how we should revisit climate models in order to better project future climate change,” Cui said.

While the Dartmouth research, published in the journal Earth and Planetary Science Letters, finds that the carbon was most likely released by permafrost thaw, there is still question as to what triggered the warming that caused the release of extra carbon into the atmosphere. Separate research points to the roles of extreme volcanic activity and water vapor during Earth’s earlier warming periods.

“The challenge is to reconstruct what the past carbon dioxide concentration is and to utilize these geochemistry proxies the best we can – essentially, how can we best interpret these records using geological archives,” said Cui.

Continued here.

Comments
  1. BoyfromTottenham says:

    Does NOAA operate the Mauna Loa observatory? I though this lab was (uniquely) privately owned and operated.

    [reply] yes it does but see opening para. here: http://en.wikipedia.org/wiki/Keeling_Curve#Mauna_Loa_measurements

  2. p.g.sharrow says:

    Carbon Dioxide levels in the atmosphere is a result, not the cause of warm periods.
    Density Altitude is the cause. Look to changes in the Amount of atmospheric gases and things that might change that…pg

  3. p.g.sharrow says:

    Cold water holds more gasses then warm…pg

  4. I agree with p.g. but that still leaves the question………what caused the PETM temperature rise?

  5. Richard111 says:

    What ever caused the temperature rise certainly wasn’t CO2.

    At STP, one cubic meter of pure, dry air, has a mass of 1,290 grams and contains 8 grams of H2O (1%) plus 0.78 grams of CO2 (0.04%). With ten times the number of H2O molecules to CO2 molecules just how much heating is due to CO2?

  6. oldbrew says:

    “This changes our understanding of what the concentration of carbon dioxide should be in relationship to global temperature as well as how we should revisit climate models in order to better project future climate change,” Cui said.

    So that’s about as clear as it can get – ‘the science’ is not settled.
    – – –
    Wikipedia – …during the Paleocene–Eocene Thermal Maximum, the planet was essentially ice-free. However, the amount of released carbon, according to a recent study, suggest a modest 0.2 gigatonnes a year (at peaks 0.58 gigatonnes), humans today add about 10 gigatonnes a year. [bold added]

    http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum

    No ice and a fraction of today’s CO2?

  7. p.g.sharrow says:

    cold sea water is a very good solvent to capture carbon dioxide in fume scrubbers but it does cause buildup of carbonate deposits…pg

  8. oldbrew says:

    We’re at the right hand edge, note warm and cold zones…ready for -6C compared to present?

    Istid = “ice age” in Swedish
    (intervals between last 4 peaks = 2 @ ~120,000y and 2 @ ~80,000y)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s