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Sea Level Rise Pt. 2

Re: Sea Level Rise Pt. 2

Unread postby diemos » Sun 22 Sep 2019, 19:02:46

Newfie wrote:So you are saying we have 3.3mm of SLR and that is a linear, not exponential?


The graph is consistent with linear. If there were a 5 year doubling trend it would be clearly visible. There's not one at this time.

Newfie wrote:I’m not so sure about your claim that a BOE would be the end of positive feedback loops. Your statement is vague. The way I see it a BOE does not END the feedback loop. It would possibly cause ONE feedback loop to slow down.
The BOE would likely happen in Sept but the sun is at its apex months earlier when there would still be a lot of ice around. I think you are confusing a BOE with the year round end of all ice which would be a very long way in the future.

But there are other feedback loops, just the changed albido itself is a feedback loop.


That's just the arctic albedo feedback loop. There are others. And you're right that we'll still get increased absorption until the pole is ice free year round. But that effect will taper off between BOE and year round ice free.

Newfie wrote:Just considering this now I would say the steady loss of sea ice creates warming (feedback 1) which in itself warms the air and changes air circulation patterns (feedback 2). So after some point halting feedback 1 would not stop or reverse feedback 2.


But until this 5 year doubling shows up in the data or someone will specify exactly which feedback loop is going to kick in I remain dubious. Beckwith maybe keeping his youtube stuff geared for a general audience and avoiding details, but he hasn't published. If he tried to publish the reviewers would insist on these kind of details.
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Re: Sea Level Rise Pt. 2

Unread postby Newfie » Sun 22 Sep 2019, 20:03:11

Thanks for clarification of your point.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Sun 22 Sep 2019, 21:15:41

More on impacts of slr in the US:

https://www.ucsusa.org/global-warming/g ... plications

https://www.ucsusa.org/global-warming/g ... level-rise

Feedbacks can get quite complex and hard to model as they all interact with each other with potentially great or small exacerbating or damping effects.

The albedo of the GIS is decreasing, and will likely continue to decrease--that's one feedback specific to GIS

As is the shift of albedo as the GIS itself melts and reveals more dark land

As is the lowering of elevation of the ice sheet as it melts, bringing the higher parts ever further down into warmer altitudes

See the video below on ice cliff instability and marine ice-sheet instability

Then there are various biological feedbacks, also mostly having to do with albedo

There are any number of other known and unknown feedbacks of greater or lesser (or unknown) importance. Most I know are positive/exacerbating, but some are negative/damping to some extent and for some period of time.

The Antarctic is a whole other can of worms, but major sections now seem to have destabilized irrecoverably. And some recent advances in our understanding of glaciers suggest strongly that when they destabilize, they can to quite fast.

And some places will see / are seeing much faster sea level rises due to shifts in ocean currents as well as other factors.

Again, I agree that Beckwith tends to overstate things, and with a level of certainty that is certainly unwarrented.

I just think that we should avoid also the opposite extreme of being absolutely certain that we can rule out fairly rapid rates of slr within this century with so many uncertainties involved.

ETA: RCP 2.6 is the only projection that shows anything like a continued linear trend, and we all know that it is utterly unrealistic. All others, that is the projections based on reality, show exponential growth in sea level rise from here on out.

Here's something to ponder on this subject: https://www.youtube.com/watch?v=Pp5kK0Td-Vc

At about 2:30 he points out that the collapse of just two Antarctic glaciers could contribute up to 11 feet ( ~3 and a half meters) to sea level rise in as little as 20 years. This is based on studies and statements of very well established and well published scientists.

Richard Alley has elsewhere said that Thwaites will collapse in 50 yrs, +/- 50 years!

Also note that estimated rates of global warming have increased dramatically in the last couple years, with most of the best and latest models talking about 7C increases above pre-industrial global temperatures by the end of the century.

Faster and higher increases in global temps than earlier models suggested should pretty clearly translate into faster and higher increases in sea level rise.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Sun 22 Sep 2019, 23:19:41

A PNAS paper from last years showed SLR accelerating at .08mm/yr^2.

One can look at the doubling time of each component and there we see Antarctic Ice Sheets have a relatively low contribution now, though the shortest doubling time, on the order of 6 years.

The overall doubling rate of the rise is roughly 35 years.

http://www.pnas.org/content/early/2018/02/06/1717312115

(Thanks to salbers at asif for text and link)
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Re: Sea Level Rise Pt. 2

Unread postby diemos » Sun 22 Sep 2019, 23:42:00

dohboi wrote:A PNAS paper from last years showed SLR accelerating at .08mm/yr^2.


From your link:
"If sea level continues to change at this rate and acceleration, sea-level rise by 2100 (∼65 cm) will be more than double the amount if the rate was constant at 3 mm/y."

65 cm by 2100 is a bit different than Paul's statement of 700 cm by 2070 and 0.084 ± 0.025 mm/y2 is a doubling time of 40 years and quite consistent with my statement that there is no sign of a 5 year doubling time in the data. Until Paul specifically states what he thinks is wrong with the IPCC models there's no way to evaluate the credibility of his estimate. Since his estimate is 20 times the upper end of the IPCC estimate of 50 cm by 2100 I definitely want a concrete answer for what they got wrong before I'll take his estimate seriously.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Mon 23 Sep 2019, 14:17:44

Soooo, if you accept that part of the paper/abstract, do you also accept from it the finding that there is now already an exponential increase going on, exactly counter to your earlier claim that "There's no sign of exponential increase" ?
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Re: Sea Level Rise Pt. 2

Unread postby diemos » Tue 24 Sep 2019, 20:13:49

Traditionally in science you wait for a result that is 5 sigma away from zero before claiming observation of an effect.

His results of 0.084 ± 0.025 mm/y2 is only a little over 3 sigma away from zero. Which is why there's no obvious visible curvature to the line.

For the quadratic function that he's fitting to give you 7 meters in 50 years the quadratic term would need to be 2.734 which is 100 sigma away from his result. Which is why I say that if we were on track to reach 7 meters in 50 years there would already be a blatantly obvious curvature to the plot. Which there isn't.

If we had perfectly precise data we might be able to tell the difference between 0.000 and 0.084 but it would still be small even if it was there.

What will happen in the future I do not know. But there's no sign of any significant acceleration in the data at the present time.
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Re: Sea Level Rise Pt. 2

Unread postby dissident » Tue 24 Sep 2019, 21:41:51

The debate is utterly pointless. We will only see the actual sea level rise curve in the rear-view mirror. Extrapolating from the conditions over the last 50 years is not valid. Future land ice melt is not a function of current or historic melt.

The missing detail in IPCC assessments is the looming inflection of atmospheric warming as the ocean deep water sink for heat gets clamped by the steepening of the thermocline. The oceans have done a good job hiding the global warming but will fail in this role in the coming decades. Estimates of sea level rise by Hansen et al. are rather plausible with a lot of melt happening after 2070.

https://phys.org/news/2015-09-eyes-ocea ... n-sea.html
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Re: Sea Level Rise Pt. 2

Unread postby diemos » Tue 24 Sep 2019, 22:56:59

dissident wrote:The debate is utterly pointless. We will only see the actual sea level rise curve in the rear-view mirror. Extrapolating from the conditions over the last 50 years is not valid. Future land ice melt is not a function of current or historic melt.


Correct. Without a model there is no way to relate past performance to future behavior. All we can say is that it's not happening now. But it's academically interesting even if it has no relevance to any decisions I'm going to be making in the near future.

dissident wrote:The missing detail in IPCC assessments is the looming inflection of atmospheric warming as the ocean deep water sink for heat gets clamped by the steepening of the thermocline. The oceans have done a good job hiding the global warming but will fail in this role in the coming decades. Estimates of sea level rise by Hansen et al. are rather plausible with a lot of melt happening after 2070.

https://phys.org/news/2015-09-eyes-ocea ... n-sea.html


Let's bound the problem.

A forcing of 2 W/m2 is 3.3e22 J/yr

if all of that went into melting ice that would be 9.9e13 m3/yr which spread out over the surface area of the ocean would give 269 mm/yr of rise. So there plenty of energy available to melt lots of ice. But at the moment we're only getting 3.3 mm/yr of rise.

if all of that went into heating up the ocean instead that would be 0.0058 C/yr spread out over the entire ocean, which is a gross oversimplification. Cutting off the deep ocean would indeed increase the rate of surface temperature increase and could jack up the melt rate. I'll eagerly wait to see when it shows up in the sea level rise data. Or the greenland ice mass balance data.

"The suspense is killing me ... I hope it lasts." -- Willy Wonka
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Wed 25 Sep 2019, 10:16:18

"Without a model there is no way to relate past performance to future behavior"

Right. But of course we do have lots and lots and lots of models. And pretty much all of them (that aren't based on fairy dust/massive carbon sequestration within the decade or bringing all carbon emissions to zero in the next few years or both) predict exponential growth in sea level rise.

That you choose to ignore them tells us much more about you than about the science.
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Re: Sea Level Rise Pt. 2

Unread postby diemos » Wed 25 Sep 2019, 10:20:38

dohboi wrote:That you choose to ignore them tells us much more about you than about the science.


I don't ignore them. The exponential increase hasn't shown up in the data yet. Keyword: yet.

If and when it does all these models will get tuned and revised to match the data. This is a good thing. This is science.

I do not tell the Universe what it is.
The Universe tells me what it is, if I will listen to the data.
A model is a collection of ideas. The test of those ideas is how well they match the data. Various and sundry people have various and sundry ideas and so there is no firm consensus yet as to exactly what is going to happen and as the data comes in we'll have a better and better idea of who was right.

At the moment there's an energy imbalance, so the earth is going to get hotter until the incoming and outgoing energy is in balance again. That is also an idea, but it's one that's grounded in well tested basic physics and so I'm quite confident in it. As to how fast this is going to happen, well, the IPCC has their ideas and Hansen has his ideas and Beckwith has his own ideas and eventually we'll have the data to know who was right.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Wed 25 Sep 2019, 13:45:13

Lotsa false equivalence, there, buddy. What's up with that?

Soooo, you're saying you are rejecting that the vast majority of science-based models, which show exponential growth from here to at least the end of the century, have essentially no probative value? That they all just add up to one of many equally possible outcomes?

That doesn't sound very...scientific... :roll:
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Re: Sea Level Rise Pt. 2

Unread postby diemos » Wed 25 Sep 2019, 14:49:23

dohboi wrote:Soooo, you're saying you are rejecting that the vast majority of science-based models, which show exponential growth from here to at least the end of the century, have essentially no probative value?


No, I'm saying that the timing of the rise isn't settled science yet. As demonstrated by the fact that credentialed scientists are proposing numbers that vary by an order of magnitude. And I'm going to wait to see what the data says before I decide which one was right.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Wed 25 Sep 2019, 15:12:05

Great. So you accept the overwhelming scientific consensus that sea level rise is likely to go exponential in the coming years to decades.

That's all I was interested in.

It's nice to know what we agree on and what we don't so we don't waste time on minor details.

Gotta go now. Have a good one!
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Re: Sea Level Rise Pt. 2

Unread postby jedrider » Thu 26 Sep 2019, 01:13:44

diemos wrote:No, I'm saying that the timing of the rise isn't settled science yet. As demonstrated by the fact that credentialed scientists are proposing numbers that vary by an order of magnitude. And I'm going to wait to see what the data says before I decide which one was right.


It will NEVER be settled science. That's just an excuse to do nothing. The science does have good bounds on it, though, half-a-meter to several meters. Yes, a wide range, but there is good reason to believe at least one meter is possible by then and to be exceeded significantly soon afterwards.

Half-a-meter, I suppose we can do something about, but more than that, I suggest a run to the hills. I'm hoping the rise is gradual, but at some point I suppose, the ice regions just start collapsing. Hansen said the prehistorical record is of rather rapid changes that can impact us. Only twenty, or so, years ago, the polar ice was thought to be stable, but now scientists are exploring how they are actually disintegrating and not just melting. Not settled, but ominous.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Sun 29 Sep 2019, 09:12:31

Well put, as usual, jed. Meanwhile:

It’s a slow-motion emergency.

America’s Great Climate Exodus Is Starting in the Florida Keys

Mass migration begins as coastal homes are bulldozed in the state facing the biggest threat from climate-driven inundation.

The Great Climate Retreat is beginning with tiny steps, like taxpayer buyouts for homeowners in flood-prone areas from Staten Island, New York, to Houston and New Orleans — and now Rittel’s Marathon Key. Florida, the state with the most people and real estate at risk, is just starting to buy homes, wrecked or not, and bulldoze them to clear a path for swelling seas before whole neighborhoods get wiped off the map.

By the end of the century, 13 million Americans will need to move just because of rising sea levels, at a cost of $1 million each, according to Florida State University demographer Mathew Haeur, who studies climate migration. Even in a “managed retreat,” coordinated and funded at the federal level, the economic disruption could resemble the housing crash of 2008. ...

https://www.bloomberg.com/news/features ... orida-keys
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Re: Sea Level Rise Pt. 2

Unread postby Ibon » Sun 29 Sep 2019, 09:39:36

jedrider wrote: The science does have good bounds on it, though..................


The problem is that ignorance doesn't
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Re: Sea Level Rise Pt. 2

Unread postby asg70 » Thu 03 Oct 2019, 13:49:20

Here is a followup phys.org article from the earlier one.

https://phys.org/news/2019-10-antarctic ... 6yZxCVqYEY

And so it goes...

HALL OF SHAME:
-Short welched on a bet and should be shunned.
-Frequent-flyers should not cry crocodile-tears over climate-change.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Fri 04 Oct 2019, 07:07:03

From asg's just-cited article:

If warming exceeds 2 C, Antarctica's melting ice sheets could raise seas 20 meters in coming centuries

...At the current rate of global emissions we may be back in the Pliocene by 2030 and we will have exceeded the 2°C Paris target. One of the most critical questions facing humanity is how much and how fast global sea levels will rise...


Don't we already have enough CO2 equivalent already in the atmosphere to push us to, or close to, 2C?
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Re: Sea Level Rise Pt. 2

Unread postby Newfie » Fri 04 Oct 2019, 08:01:50

If we don’t we will, we are working on it.

The inevitable is, well, inevitable.
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