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Thread: Extreme climate change - how much and how fast

  1. #61
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    Quote Originally Posted by Gigabyte View Post
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  2. #62
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    The AMOC is driven by heat and salinity. In the arctic region evaporation and cooling increase the density of the ocean water. The net result is an expected weakening from an already weakened flow. There might be some feedback in terms of the ice melt and freeze cycle. But that seems to work in reverse. The lesser cold store from less ice, weakens the cold dense downflow. The increased heat in the equatorial and southern oceans does not seem to make up for that. While the total flows are gigantic, the drivers may only need slight encouragement.

    It was Benjamin Franklin who discovered the Gulf stream, dangling a thermometer on a string. Surely we can build on that, now that we see the threat?
    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

  3. #63
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    I happen to have some arctic scientist connections. I will, I hope, report back with their view of geo engineering up there.
    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

  4. #64
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    Excellent XKCD from a couple of days ago.
    And of course there's this one.
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

  5. #65
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    My concern about artificially "correcting" the damage done is that it could make the future habitability of Earth dependent on humans. We are simply not stable enough to make the Earth dependent on us. At least not right now.

    We are a bit like the proverbial frog in a pot of water being heated up. The changes may be fast geologically but on human scales change isn't happening fast enough. People aren't noticing the changes because they are happening over many years, they just mentally adjust what "normal" is.

    Although it would be fairly catastrophic what it might take to finally get people to notice is a fast transition. Two possibilities are a major disruption of the Atlantic currents as mentioned above and/or a major collapse into the ocean of an ice sheet. An ice sheet collapse could happen in either Greenland or Antarctica and could result in sea levels rising many feet in a matter of a few years, or less. That would be hard to pass off as a temporary weather event.

    By Ice sheet collapse I mean a large land based ice sheet breaking off and sliding into the ocean. There are some large ice sheets in Antarctica that have some researchers concerned. The melting ice ends up falling through the cracks and resting below the ice, effectively lubricating the bottom of the ice sheet. If the sheet breaks off from the main continental mass then it could slide into the ocean relatively quickly. There is the potential for ice sheets the size of an average U.S. state and thousands of feet thick to slide into the ocean. The resulting sea level increase would swamp coasts the world over.

    There are indications in the geologic record that previous warming periods did not just result in slow increases in sea level but those increases were punctuated by rapid rises over short periods of time. The ice sheets collapsing are a prime suspect in those rapid rises.

    There are other possibilities for a rapid change but the two I mention are two of the big ones. Siberia's permafrost melt is another.

  6. #66
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    The weakening of the AMOC will not have effects that are localised to the Atlantic. It would probably allow the antarctic currents to move north, which will result in more warming of the southern polar region. This will lead to faster ice melt. Of course, this means all the worlds oceans will become affected, destabilising the whole system.
    We have an example of the social inertia in my town. Situated by the sea, but at approximate sea level, the town is protected by what is essentially a sand bank. This is grassed over and has roads and some walls and buildings built on top.

    The local council has determined that we need to construct a wall around 1.5m high to protect against sea level rise. This would be built along the highest part of the sand bank. The local holiday businesses are campaigning against the wall because they say it will interrupt the view of the sea from their properties and impact their business.

    They have constructed a small section of wall to demonstrate the proposed height, which ironically is approximately the sea level height around their properties if the wall does not get built.

    Houses built on sand...

  7. #67
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    I found this article from phys.org interesting.

    Planting trees and replenishing forests are among the simplest and most appealing natural climate solutions, but the impact of trees on atmospheric temperature is more complex than meets the eye.

    One question among scientists is whether reforesting midlatitude locations such as North America or Europe could in fact make the planet hotter. Forests absorb large amounts of solar radiation as a result of having a low albedo, which is the measure of a surface's ability to reflect sunlight. In the tropics, low albedo is offset by the higher uptake of carbon dioxide by the dense, year-round vegetation. But in temperate climates, the concern is that the sun's trapped heat could counteract any cooling effect forests would provide by removing carbon dioxide from the atmosphere.

    But a new study from Princeton University researchers found that these concerns may be overlooking a crucial component—clouds. They report in the Proceedings of the National Academy of Sciences that the denser cloud formations associated with forested areas means that reforestation would likely be more effective at cooling Earth's atmosphere than previously thought.

    "The main thing is that nobody has known whether planting trees at midlatitudes is good or bad because of the albedo problem," said corresponding author Amilcare Porporato, Princeton's Thomas J. Wu '94 Professor of Civil and Environmental Engineering and the High Meadows Environmental Institute. "We show that if one considers that clouds tend to form more frequently over forested areas, then planting trees over large areas is advantageous and should be done for climate purposes."
    Here is the journal link

    Abstract:
    Because of the large carbon sequestration potential, reforestation and afforestation (R&A) are among the most prominent natural climate solutions. However, while their effectiveness is well established for wet tropics, it is often argued that R&A are less advantageous or even detrimental at higher latitudes, where the reduction of forest albedo (the amount of reflected solar radiation by a surface) tends to nullify or even overcome the carbon benefits. Here, we carefully analyze the situation for R&A at midlatitudes, where the warming effects due to vegetation albedo are regarded to be almost balanced by the cooling effects from an increased carbon storage. Using both satellite data and atmospheric boundary-layer models, we show that by including cloud–albedo effects due to land–atmosphere interactions, the R&A cooling at midlatitudes becomes prevalent. This points to a much greater potential of R&A for wet temperate regions than previously considered.
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  8. #68
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    I think one complication with comparison of reforestation at different latitudes is that temperate latitudes have more deciduous trees. These trees will result in active carbon capture for only part of the year and presumably result in more carbon emissions as the fallen leaves break down.
    How this compares with overall capture by tropical forests is difficult to judge.

  9. #69
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    Quote Originally Posted by headrush View Post
    I think one complication with comparison of reforestation at different latitudes is that temperate latitudes have more deciduous trees. These trees will result in active carbon capture for only part of the year and presumably result in more carbon emissions as the fallen leaves break down.
    How this compares with overall capture by tropical forests is difficult to judge.
    I seem to remember from something I read a very long time ago that mature tropical forests are pretty much in carbon balance, neither gaining nor losing much net carbon. Carbon release is from fallen leaves and other decaying plant matter, but new growth requires carbon too.

    Growing new forest is different and one plan I remember reading was to grow rapidly maturing trees or other plants, then regularly cut them down, bury them, and grow a new crop to sequester carbon for a time.

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  10. #70
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    Quote Originally Posted by Van Rijn View Post
    I seem to remember from something I read a very long time ago that mature tropical forests are pretty much in carbon balance, neither gaining nor losing much net carbon. Carbon release is from fallen leaves and other decaying plant matter, but new growth requires carbon too.

    Growing new forest is different and one plan I remember reading was to grow rapidly maturing trees or other plants, then regularly cut them down, bury them, and grow a new crop to sequester carbon for a time.
    I wonder how burning the crop, with appropriate co2 capture, would contribute to biofuel energy generation. I think there's some controversy over the current method (wood pellets).

  11. #71
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    I hope this is not the only forum where the collapse of the AMOC is discussed.

    profloater, the Arctic Sea Ice Forum discusses it heavily.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  12. #72
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    Quote Originally Posted by Tom Mazanec View Post
    I hope this is not the only forum where the collapse of the AMOC is discussed.

    profloater, the Arctic Sea Ice Forum discusses it heavily.
    Thank you I will check it while waiting to meet the researchers, travel easing day by day. Of course the Actic and Greenland ice melt
    Are in the news and at a centre of attention. I notice that geo engineering is not yet mainstream. It is hoped reduction of emissions will come in time. Maybe. Maybe not. The downside could be very disadvantageous for many people, and it could be the first reallt significant change.
    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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