Last time CO2 levels were this high we lived in trees


The difference between 399 parts per million of carbon dioxide and 400 ppm isn’t much, but new data from NOAA shows that that thresh-hold has now been crossed. The last time earth saw levels this high it was a very different place:

Real Climate — This period of Arctic warmth “coincides, in part with a long interval of 1.2 million years when the West Antarctic Ice sheet did not exist.” Indeed, sea levels during the mid-Pliocine were about 25 m [82 feet] higher than today!

It is worth noting that a 2009 analysis in Science found that when CO2 levels were this high 15 to 20 million years ago, it was 5° to 10°F warmer globally and seas were also 75 to 120 feet higher.

Paleo-climate Professor Michael Mann, author of The Hockey Stick (And now a DKos diarist), emailed noting that, “The last time we’re confident CO2 levels breached 400ppm, was the mid Miocene, around 10 million years ago, though it could have been a bit later, e.g. 4 million years. In either case, we know that the globe was quite a bit warmer than today, with much less ice around, and much higher sea level.” When I asked, Mann added he could think of no significant factor present millions of years and not present now that might dampen warming.

The new data and recent work solidly linking past CO2 levels to much warmer temperatures, lends further credence to the views expressed by climate scientists like NASA’s James Hansen. That even maintaining CO2 at current levels, let alone raising them further through ongoing carbon emissions, could lead to dangerous, irreversible changes in the climate.


  1. badgersdaughter says

    I don’t know what I can do about it except small and ineffectual things to reduce my own consumption, and despair.

  2. says

    I’ve been seeing the climate change denialists insist that Mauna Loa is an active volcano and that the sensors are picking up concentrations of CO2 being released by the mountain, or that stray winds are blowing CO2 from Kilauea or other nearby volcanos into the sensors, and so the results are “clearly bad science being used to fraudulently promote a hoax.”


    These people will be denying climate change right up to the point where their beach front homes are swallowed by the rising tides.

  3. says

    Is it bad that my reaction to a lot of climate change talks nowadays is something along the lines of: I hope whatever species (regardless of what world they come from) that deciphers our communications gets to read such zingers as Gregory In Seattle because at least then they’ll know that there were people who tried to prevent the tragedy.


  4. timberwoof says

    We’ll put a fence around Colorado and admit only people who can confirm that they were not global warming deniers (we need a word like antidisestablishmentarianism for this). No one from North Carolina can come in.

  5. lanir says

    @Gregory in Seattle #3:
    Sadly I suspect when their beach front homes are swallowed up, I suspect they’ll blame offshore windfarms. Hmm. Maybe we could sell the right on climate change if we blame it all on poor people breathing? It’s utter, batshit crazy nonsense but it’s -their- kind of utter batshit crazy nonsense. Maybe someone smarter than me could figure out how to pull off the bait and switch at that point, once they admit there’s “A” problem even if they don’t admit to “THE” problem.

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