Burning All Fossil Fuels Would Push CO2 to Levels Last Seen Before Forests

By Eric Betz | April 4, 2017 10:00 am
NASA scientists modeled Earth's CO2 as it shifts through the seasons using data from the Orbiting Carbon Observatory-2. (Credit: NASA's Scientific Visualization Studio)

NASA scientists modeled Earth’s CO2 as it shifts through the seasons using data from the Orbiting Carbon Observatory-2. (Credit: NASA’s Scientific Visualization Studio)

Earth’s been around for 4.5 billion years. And during that time, our star has gotten stronger with age. Yet the planet’s climate has stayed relatively stable.

That apparent contradiction recently prompted an investigation by Gavin Foster of the University of Southampton and his colleagues. The scientists suspected that as the sun’s power increased throughout Earth’s history, greenhouse gases must have declined.

To find out, they combed through more than 100 papers in search of an answer, compiling 1,500 estimates of carbon dioxide levels covering the last 420 million years. Their hunch about Earth’s history was right — greenhouse gases were much higher in the distant geological past — but it’s actually the future that’s most shocking.

Once the team had charted past CO2 levels, they plotted them alongside future predictions from the United Nations’ Intergovernmental Panel on Climate Change.

Their research, published Tuesday in Nature Communications, found that future carbon dioxide levels could eventually surpass anything in the geological record.

CO2 levels could hit a record 410 parts per million (ppm) by next month. That’s already the highest since humans existed. And atmospheric scientist Ralph Keeling, who’s in charge of tracking global CO2 levels at Scripps, recently told me he thinks we can count on hitting at least 450 ppm based on current activity.

But Foster’s study shows that if humanity sticks to business as usual, by next century, Earth will have more carbon dioxide than at any time in the last 50 million years. That’s roughly 700 to 900 ppm. If you visited the planet back then, a time period called the Eocene, you’d find a world with Arctic crocodiles and Alaskan palm trees.

Burn fossil fuels for another couple centuries and we’ll have atmospheric greenhouse gas levels not seen since 420 million years ago. Alarmingly, that’s taking Earth back to conditions that existed before land plants expanded enough to help create a nice, habitable planet for complex life to take hold.

It’s clear that life will have a hard time holding on at all if humanity pushes toward 5,000 ppm — a number that doesn’t factor in the sun’s increased power. Some scientists think we’d hit that level by burning all of the planet’s fossil fuels.

Of course, it’s unlikely that would happen. But this study does show the awesome power humanity now wields over its environment.

“There’s enough (fossil fuels) in the ground to take you to 1,000 ppm or more, but I don’t think that’s going to happen,” former NASA scientist James Hansen told me earlier this year. But even much lower CO2 levels aren’t considered safe.

“[A level of] 450 ppm would guarantee disaster,” Hansen said. “If you leave it in place long enough, it would guarantee that you do lose the coastal cities.”

Eric Betz is an associate editor of Discover. He’s on Twitter: @ericbetz.

  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    www dot dw dot com slash image slash 16516395_401 dot jpg
    …Extinguishing all wildfires and agricultural clearing fires would reduce atmospheric [CO2] to about 300 ppm.

    Beer’s law, A = εbc is not true past about A = 1.5 (about 3% transmission). It becomes A = εb√c. As atmospheric CO2 has A = 2000 at its 15µ maximum and about A = 100 at 2.7µ and 4.3µ. IPCC doom versus [CO2] is inflated by a factor of ~80. CO2 A=1 at ground level is about 50 vertical meters, a 16 story building

    “If you leave it in place long enough,” Christ returns. Two millennia of payments up front have not delivered the hamburger promised for Tuesday.

    • https://ridingtheirownmelting.wordpress.com/ cgs

      Is the 300ppm number you report coming from an analysis someone has published?

      Also, neither form of the Beer-Lambert law you post above is relevant for the atmosphere. See section “First Step – Absorption” here for the correct formula:

      Scienceofdoom dot com slash 2010 slash 01 slash 31 slash co2-an-insignificant-trace-gas-part-three

      Also, it’s not clear why you bring this up. Don’t forget that there is emission at all layers of the atmosphere too. and other physically relevant issues, that would prevent drawing any conclusions from a simple application of Beer-Lambert. See “Flaws in the Model” here:

      Scienceofdoom dot com slash 2011 slash 01 slash 23 slash understanding-atmospheric-radiation-and-the-%E2%80%9Cgreenhouse%E2%80%9D-effect-%E2%80%93-part-two

  • CB


    “Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme global warming events (hyperthermals) superimposed on a long-term warming trend. The first and largest of these events, the Palaeocene–Eocene Thermal Maximum (PETM), is characterized by a massive input of carbon, ocean acidification and an increase in global temperature of about 5-6C within a few thousand years.”

    (Yale, The People of Geology & Geophysics, “Paleocene/Eocene Thermal Maximum”, DeConto, et al)

  • OWilson

    James Hansen is still flogging “tipping points” to the great unwashed?

    He’s been at it since at least 2008.

    It’s always, “right around the corner”. :)

  • Brian McInnis

    How to Write an Acronym

    Right: P.P.M.
    Wrong: PPM
    Wrongest: ppm

  • RealOldOne2

    “CO2 levels could hit a record 410 parts per million (ppm) by next month. That’s already the highest since humans existed.”
    That’s nonsense. Peer reviewed science has documented many many previous measurements of CO2 at levels higher than that. Beck(2007) documents them from 180 peer reviewed papers written 1812 and 1961. Here is a plot of the 5-yr averaged CO2 levels compare with ice core levels: https://uploads.disquscdn.com/images/eb47bebd2236fe9c7f5e8ba043d8ae54e78a4a6d3ba11af6e8ec085286d5ca27.png

    Fig.1 from Fonselius(1956) ‘Carbon Dioxide Variations in the Atmosphere’ shows how Callendar cherry picked low values consistent with ice core data and ignored many direct atmospheric measured CO2 data that disagreed with his CO2 hypothesis: https://uploads.disquscdn.com/images/05ddd31685ebd76cf05a2acb5c6854dcaa7cf286a072e7389ea84f52baad78fb.png

    Plus the latest peer reviewed science shows that 85% of the increase in CO2 since the Industrial Era is natural, not anthropogenic:

    “The anthropogenic contribution to the actual CO2 concentration is found to be 4.3%, its fraction to the CO2 increase over the Industrial Era is 15% and the average residence time is 4 years.” – Harde(2017) ‘Scrutinizing the carbon cycle and CO2 residence time in the atmosphere’

    The real world empirical data shows that CO2 is an insignificant factor in causing climate warming.

    • OWilson

      If you are correct, and NOAA is correct (satellite data shows a statistically insignificant 0.12 degree warming anomaly over it’s 38 year history)

      Then Co2 is an “insignificant factor in insignificant global warming”.

      Shakespeare made fun of this stuff in his “Much Ado About Nothing!”

      Cue the “true believers”! :)

  • Brian Weatherall

    I thought we only had like 40 years left of fossil fuels if we continued burning at the current rate… how might we continue burning for centuries then?


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