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Thread: Extreme climate change - how much and how fast

  1. #1
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    Exclamation Extreme climate change - how much and how fast

    The Atlantic has an excellent and fact-heavy article on past extreme climates, and how changes in CO2 brought them about.

    The Planet Could Have Catastrophic Surprises in Store. The geologic record carries a terrifying warning.
    https://www.theatlantic.com/magazine...istory/617793/
    Do good work. —Virgil Ivan "Gus" Grissom

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    Excellent summary article. One factoid not covered was the human population pinch points in the last, say, 20,000 years, covering the deep ice age to now. If you include the impacts and volcanoes, there have been periods that seem hard to survive and certainly reduced the population while forcing migrations. It is thought pestilence and famine easily out pace conflicts in reducing populations and destroying civilisations. Maybe those also outpace sea level rise although that seems drastic to us now when we can view the many underwater cities of the past. How vulnerable is the population to current warming?

    How vulnerable civilisations that support those populations? Right now we are reminded how our international world has allowed a new disease to give pause.

    We are so bad at factoring in unusual but catastrophic possibilities. So good at solving last year’s problems! But I guess we will lumber on until we get a real kick in the pants, we should start building pyramids that might survive us!
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Of more immediate interest today, a variation in the composition of the Earth’s atmosphere of as little as 0.1 percent has meant the difference between sweltering Arctic rainforests and a half mile of ice atop Boston.
    That is not settled science, not even close. The last million years of ice ages does not support that conclusion, nor do the dramatic changes that have happened since the end of the last glacier building phase of our current ice age.

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    Quote Originally Posted by nota View Post
    That cold blob might be the butterly flap that that changes the world. But, no panic, it should correct itself in a thousand years.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Thanks for sharing this excellent article from The Atlantic.

    It has two points that deserve clarification.

    1. The article compares the current CO2 level of 410ppm (actually now close to 417ppm) to past periods, asking about likely equivalence. However, it does not mention the current warming role of other greenhouse gases such as methane which mean that compared to the Holocene 280ppm the current radiative forcing is equivalent to a CO2 level of over 500 ppm, according to data cited at https://en.wikipedia.org/wiki/Radiat...#Recent_trends .

    2. The article makes the statement "The good news is the inertia of the Earth’s climate system is such that we still have time to rapidly reverse course, heading off an encore of this world, or that of the Miocene, or even the Pliocene, in the coming decades. All it will require is instantaneously halting the super-eruption of CO2 disgorged into the atmosphere that began with the Industrial Revolution." While true that we have time to rapidly reverse course, "halting the super-eruption of CO2" is not enough to do it. The warming problem is mainly due to past emissions, which cause about forty times as much radiative forcing as annual emissions according to https://www.globalwarmingindex.org/ . Therefore totally halting emissions, which means ending all burning, would only address 2% of the problem. The other 98% requires physical removal of the excess greenhouse gases from the air, ideally by converting them into valuable carbon products. And since that is such a big job, stopping dangerous warming also means that brightening the planet would be needed to limit overshoots while we bring GHGs back to a stable level. "Net zero emissions" may have to mainly be delivered by carbon dioxide conversion, not by decarbonisation of the world economy as implied in the article.

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    Quote Originally Posted by Robert Tulip View Post
    Thanks for sharing this excellent article from The Atlantic.

    It has two points that deserve clarification.

    1. The article compares the current CO2 level of 410ppm (actually now close to 417ppm) to past periods, asking about likely equivalence. However, it does not mention the current warming role of other greenhouse gases such as methane which mean that compared to the Holocene 280ppm the current radiative forcing is equivalent to a CO2 level of over 500 ppm, according to data cited at https://en.wikipedia.org/wiki/Radiat...#Recent_trends .

    2. The article makes the statement "The good news is the inertia of the Earth’s climate system is such that we still have time to rapidly reverse course, heading off an encore of this world, or that of the Miocene, or even the Pliocene, in the coming decades. All it will require is instantaneously halting the super-eruption of CO2 disgorged into the atmosphere that began with the Industrial Revolution." While true that we have time to rapidly reverse course, "halting the super-eruption of CO2" is not enough to do it. The warming problem is mainly due to past emissions, which cause about forty times as much radiative forcing as annual emissions according to https://www.globalwarmingindex.org/ . Therefore totally halting emissions, which means ending all burning, would only address 2% of the problem. The other 98% requires physical removal of the excess greenhouse gases from the air, ideally by converting them into valuable carbon products. And since that is such a big job, stopping dangerous warming also means that brightening the planet would be needed to limit overshoots while we bring GHGs back to a stable level. "Net zero emissions" may have to mainly be delivered by carbon dioxide conversion, not by decarbonisation of the world economy as implied in the article.
    Good point about brightening, recent modeling suggests bad news about clouds. Earlier it was unknown whether the increased water vapour would change cloud cover, and further unclear whether that would be positive or negative feedback to warming. Now , although “it’s only a model” and clouds are very complex, the models are pessimistic. Refective cloud cover may diminish, leading to even worse climate predictions than before. Progress on sequestering CO2 seems way too slow.
    https://e360.yale.edu/features/why-c...ons-on-warming
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    I'll admit I only skimmed the article, but I love this quote
    When hucksters tell you that the climate is always changing, they’re right, but that’s not the good news they think it is. “The climate system is an angry beast,” the late Columbia climate scientist Wally Broecker was fond of saying, “and we are poking it with sticks.”
    .

    Good points, Robert Tulip, and I'll add another thought. The thing that troubles me the most is not any specific concentration of CO2 in the atmosphere, but the rate at which we are changing it (and other greenhouse gases), which does not allow ecosystems to stabilize and species to adopt. Other than sudden, dramatic events (like the Chicxulub impactor 66 million years ago), I suspect this is the fastest that the Earth's climate has changed this much.
    At night the stars put on a show for free (Carole King)

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    Number of insect species has already declined by a third.
    Birds and amphibians face similar challenges. Bugs have lived through a lot of extinction events, but apparently not this one. From the ice numbers I've heard for Antarctica and Greenlland, it looks like we may face an Atlantic sea level rise of 6" a year by 2040. What I find scariest are the methane seeps and blowouts in Siberia. Methane eats oxygen as it burns, and our supply of that is limited by plant biomass. Methane release is not an easily reversible problem. It's more of a positive feedback loop, waiting to be triggered.

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    I mentionedthe Netflix documentary Seaspiracy in another thread. The state of life in our oceans is dire and there is an important link to climate change. The oceans are the biggest, by far, sink of carbon and that’s due to life, both tiny and huge. I see no human chance to end that until it becomes uneconomical to fish with thousands of large fishing boats. That is coming soon, tens of years perhaps. We humans have really gone and done it this time. Like addicts of other sorts, we must go through the bottom part of the cycle, the upheavals, the deaths, and hopefully survive wiser and determined to do better.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by Gigabyte View Post
    That is not settled science, not even close. The last million years of ice ages does not support that conclusion, nor do the dramatic changes that have happened since the end of the last glacier building phase of our current ice age.
    The claim that "variation in the composition of the Earth’s atmosphere of as little as 0.1 percent has meant the difference between sweltering Arctic rainforests and a half mile of ice atop Boston" refers to the cyclic variation between glacial maxima and interglacials, with the CO2 level regularly swinging between about 180 and 280 ppm over the hundred thousand year sawtooth pattern seen in ice core data, a variation of 100 ppm.

    100 ppm = 0.01% of the atmosphere. The 0.1% figure in the article overstates the cyclic variation of CO2 by ten times, an easy mistake. Also, I suspect the ice thickness at Boston twenty thousand years ago was more than half a mile, since the North American Laurentide Ice Sheet was up to two miles high. Otherwise, the claim is settled science.

    Correction: The 0.1% figure seems to refer to the difference between the Ice Age CO2 level of ~200 parts per million and the Eocene level, fifty million years ago, which is when there were rainforests in the Arctic. But the article explains that estimates of the Eocene CO2 level vary from 600 to 1000 ppm, ie a change between 0.04% and 0.08% of the atmosphere.
    Last edited by Robert Tulip; 2021-Apr-05 at 10:35 AM.

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