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Sea Level Rise Pt. 3

Sea Level Rise Pt. 3

Unread postby dissident » Wed 30 Oct 2019, 22:14:59

EnergyUnlimited wrote:Rockdoc & Kublikhan

Lets admit that we don't know how much warming we are likely to experience by the end of century.
It is probably between 3 and 10 *C.
Perhaps more likely 3 than 10 but still.
There are different models, different groups of scientists working on these models and different opinions.
Also unknown latent switches and obscure feedbacks.
So a lot can change in all these models.
Science has its limitations too and quality of scientific work is falling down during last 2-3 decades, so published results, even if constitute best guess we might have, need to be taken with a grain of salt.
Have red many entirely incompetent articles published in chemical journals so I do not expect situation to be very different elsewhere.
These aguments may go on ad nauseum so lets wait and see.
Even if we don't see it ourselves, our grandchildren surely will. Those of us who live for 10-30 years more may see some indications (or even spectacular catastrophies in places like India).
One way or another we are going to be dead by the end of this century, so entire exercise is very much like discussions of turkeys what they will eat on the Christmas.


I know these models and they are not as different as you believe. And for sure there is no disagreement between the scientists unless you are talking about the fringe like Richard "Linear" Lindzen. The variation between models shows you how are reasonable range of differences in the coding and parameter selection can produce a spread of results. The best approach is to take the average of this ensemble.

But the problem is that the current generation of models are not complete in terms of physical process resolution. Comparison between the model results in the last 20 years we see that they have been failing to fully capture the sensitivity of the atmosphere-ocean system to greenhouse gas induced warming. This flies in the face of all the denier BS about "climate alarmism". This issue does not make modeling a pointless activity and we have actually learned that there are missing aspects to known processes or unknown processes that have to be researched and implemented into the models. If the lunatic deniers had their way, we would have been sitting on our a**ses and been at the science level of the 1940s today.
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Wed 30 Oct 2019, 23:29:31

Comparison between the model results in the last 20 years we see that they have been failing to fully capture the sensitivity of the atmosphere-ocean system to greenhouse gas induced warming. This flies in the face of all the denier BS about "climate alarmism".
 

If that were the case you would be seeing all measured temperatures higher than predicted from the range of coupled models used by IPCC in AR5 (CMIP 5) which is actually the opposite of what is recognized. Here is a plot that Curry updated from AR5 with data out to 2015 for her presentation to Senate (note that Gavin Schmidt and numerous others had the opportunity to comment on her presentation prior to it being made and she edited some material accordingly). Note that temperatures from Had Crut 4.3 along with uncertainties all plot at the bottom of the range of modeled predictions. The red hashered area is what the IPCC used as their lowered projections out to 2035 based on expert judgement of the authors who participated in that chapter reflecting on their concern that some of the models were too sensitive to anthropogenic forcing. Suggesting the authors of that chapter believed the models at that time (CMIP 5) were over-estimating projected temperatures, not under-estimating them.

Image

We are now at CMIP 6 and results are starting to trickle out with projected temperatures that are even hotter presumably as a result of increased sensitivity in the models. I suspect when those models are published the mismatch will probably be worse.
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Re: Sea Level Rise Pt. 2

Unread postby Plantagenet » Thu 31 Oct 2019, 00:53:45

New Climate Models run "hotter" then previous climate models and predict higher future temperatures

SCIENCE: new-climate-models-predict-warming-surge

Prior IPCC predictions were based on averages of numerous different climate models. But some models run "hotter" then others. It turns out that that models that predict lower amounts of global warming are usually very simple and don't include feedback effects from things like decreased ice cover in the Arctic Ocean. This explains why their predictions aren't very reliable.

The newest GCMs are more sophisticated and capture more natural processes. In addition, the newer models include some of the more significant feedback effects. The best new models are predicting we are in for higher temperatures then suggested by prior IPCC assessments.

Image

Cheers!
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Thu 31 Oct 2019, 11:48:07

New Climate Models run "hotter" then previous climate models and predict higher future temperatures


interestingly enough if you look at the range of those predicted temperatures from CMIP 6 and compare them to the package of 5%-95% of all CMIP5 from IPCC AR5 they are almost exactly the same. Will have to wait for a number of papers to be published in order to ascertain how they arrived at their statistics but the one thing that is certain measured temperatures are still showing up at the bottom of the range.
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Re: Sea Level Rise Pt. 2

Unread postby Plantagenet » Thu 31 Oct 2019, 12:15:40

.... the one thing that is certain measured temperatures are still showing up at the bottom of the range.


There is another thing that is certain.....the rate of increase in temperature is accelerating.

The NOAA website states: "According to the NOAA 2018 Global Climate Summary, the combined land and ocean temperature has increased at an average rate of 0.07°C (0.13°F) per decade since 1880; however, the average rate of increase since 1981 (0.17°C / 0.31°F) is more than twice as great."

The fact that the rate of temperature increase is going up so much is significant because it is one of the main predictions of the GCM models. The observation that the rate of T increase now is more then twice what it was only a few decades is an important confirmation of the validity of GCM modeling, which predicts non-linear increases in T over the coming decades. And since GCM modeling predicts the rate of T increase will continue to accelerate as more and more greenhouse gas accumulates in the atmosphere, it is likely the rate of increase will double again in coming decades. This means observed temperatures will increase much more rapidly in the future then they have in the past and may ultimately match or even exceed the GCM predictions for coming decades.

Cheers!
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Thu 31 Oct 2019, 13:36:00

The observation that the rate of T increase now is more then twice what it was only a few decades is an important confirmation of the validity of GCM modeling, which predicts non-linear increases in T over the coming decades.


Look at the IPCC plot. They lowered the model estimate range for the sake of forecasting as their expert groups believed the models were running too hot and that was with CMIP 5. There is no way based on plotting the actual data that you can argue otherwise unless you select a baseline other than what IPCC has traditionally used.
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Re: Sea Level Rise Pt. 2

Unread postby dissident » Thu 31 Oct 2019, 19:13:07

Plantagenet wrote:New Climate Models run "hotter" then previous climate models and predict higher future temperatures

SCIENCE: new-climate-models-predict-warming-surge

Prior IPCC predictions were based on averages of numerous different climate models. But some models run "hotter" then others. It turns out that that models that predict lower amounts of global warming are usually very simple and don't include feedback effects from things like decreased ice cover in the Arctic Ocean. This explains why their predictions aren't very reliable.

The newest GCMs are more sophisticated and capture more natural processes. In addition, the newer models include some of the more significant feedback effects. The best new models are predicting we are in for higher temperatures then suggested by prior IPCC assessments.

Image

Cheers!


Thanks for posting this. The IPCC was comparing apples and oranges if it was putting models with substantial differences in process implementation in the same ensemble. Doing such an ensemble is interesting to see how much of an effect leaving out some processes has. But then, reality does not leave any process that exists out. So a proper "forecast" ensemble of climate change would exclude all the models that are too simple. So these recent findings are in the "no sh*t Sherlock" category.
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Re: Sea Level Rise Pt. 2

Unread postby dohboi » Wed 12 Feb 2020, 17:05:16

Posted this in Antarctic thread, but even more relevant here:

Ancient Antarctic ice melt increased sea levels by 3+ meters—and it could happen again

https://phys.org/news/2020-02-ancient-a ... rsand.html

Using data gained from their fieldwork, the team ran model simulations to investigate how warming might affect the floating ice shelves. These shelves currently buttress the ice sheets and help slow the flow of ice off the continent.

The results suggest a 3.8m sea level rise during the first thousand years of a 2°C warmer ocean. Most of the modelled sea level rise occurred after the loss of the ice shelves, which collapsed within the first two hundred years of higher temperatures.

Notably, the researchers warn that this tipping point may be closer than we think...
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Re: Sea Level Rise Pt. 2

Unread postby vtsnowedin » Wed 12 Feb 2020, 17:41:44

The test for any model is to set it at some known point say 1950 and let it run to see if it can go forward for any length of time and still match what actually happened. Last I knew no model yet devised runs good for more then a year. How do these latest models do?
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Wed 12 Feb 2020, 18:47:06

The model used in this study is an ice sheet model and not a comprehensive ice/atmosphere model. As a consequence, all you look at is the potential loss of ice under the assumed conditions since it does not take into account snowfall which is expected to increase and has been noticeably increasing over the past decade in Antarctica. As a consequence pretty hard to compare with past data unless you look at ice losses alone in the data which is only half the story in terms of net mass balance which is the key factor in sea level change.

Two observations.

1. they identify two new tephra horizons and this area is characterized by a number of ancient volcanoes. The data as to when such volcanoes were active is not well constrained but the authors are arguing they can correlate tephra over very large areas for several horizons. This means extensive, long lasting volcanic activity. And the nature of the glass shards are basaltic, not ryholitic meaning we are talking shield volcanoes which tend to have a longer impact on heat flow over a specific area. The authors did not consider the possibility that higher heat flow at the base of the glaciers during the LIA due to volcanic activity or at least shallow magma chambers would contribute to glacier flow. IF it did then the amount of ice losses in the ancient event described where WAIS is thought to have largely vanished may not have as much to do with warm oceans as proposed. There is a very large mission now active looking at volcanic activity past and present in Antarctica in hopes of solving these questions. The latest identified active vulcanism below Pine Island Glacier with heat flows well above melting temperature for ice at the base of the ice sheet.
2. When you start talking about what is going to happen 1000 or 5000 years in the future it all becomes more and more model limited given assumptions may not hold up for anywhere near that long. But taking the worst-case their prediction if for about 200 mm of additional sea-level equivalent (which they show as happening by 2100) due to ice loss alone and you assume there is no increase in snowfall (which is a poor assumption) then you end up with, according to IPCC predictions a total of 620 mm or 2 feet of sea-level rise by 2100 rather than 450 mm. You could argue 2 feet is going to cause problems for places that are low lying such as Galveston or New Orleans but for the vast majority of the earths surface this is not problematic. And one would think that 80 years is a lot of time for mitigation efforts if you believed this to be the case.

To keep things in perspective over the instrumental period when research in Antarctica has been active the annual net losses from Antarctica have been somewhere between 0.2 mm/yr (most recent work) and 0.3 mm/yr (largest estimates).
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Re: Sea Level Rise Pt. 3

Unread postby dohboi » Thu 13 Feb 2020, 10:20:50

vt, what do you mean by 'run good'?
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Re: Sea Level Rise Pt. 3

Unread postby vtsnowedin » Thu 13 Feb 2020, 13:42:09

dohboi wrote:vt, what do you mean by 'run good'?

Being reasonable accurate for the future time after run start about the parameters being modeled. Can you set it to the conditions of 1900 and have it predict the dust bowel of the 1930s, That sort of thing.
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Re: Sea Level Rise Pt. 3

Unread postby dohboi » Thu 13 Feb 2020, 20:44:10

Well, you know, all models fail.

If they didn't they wouldn't be models, they'd be reality.

It is how they fail that is interesting.

The point here is how specific of an occurrence you are trying to model based on how accurate of data.

Someone in 1900 could not have known about the roll out of manifest destiny and the vast and rapid settlement of the plains, as well as the dominant disregard for good land care practices, and stupid assumptions like 'rain follows the plow' that lead a lot of people to do a lot of stupid things.

That's vastly different from predicting how fast ice melts when you heat it up (which we know is and will be happening), which is the basic physics of sea level rise.

Of course, ice sheets dynamics can be a bit more complex than this suggests, but all the complexities are about physics, which is in principle predictable, versus human idiocy, which is unpredictable beyond that always has and always will exist (and usually prevail).

(And as I get older, I'm feeling more and more often like I'm suffering from 'dust bowel' without knowing it--so thanks for the term! :) )
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Re: Sea Level Rise Pt. 3

Unread postby rockdoc123 » Thu 13 Feb 2020, 21:07:12

So, in other words, he has absolutely no idea given he doesn't actually read the published literature. :roll:
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Re: Sea Level Rise Pt. 3

Unread postby vtsnowedin » Fri 14 Feb 2020, 09:41:43

dohboi wrote:
(And as I get older, I'm feeling more and more often like I'm suffering from 'dust bowel' without knowing it--so thanks for the term! :) )

Thank my spell checker that can't tell the difference between bowl and bowel. :oops:
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Re: Sea Level Rise Pt. 3

Unread postby dohboi » Mon 23 Mar 2020, 14:23:16

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Re: Sea Level Rise Pt. 3

Unread postby Tanada » Tue 24 Mar 2020, 09:09:45

dohboi wrote:potential 5 feet of sea level rise:

https://www.washingtonpost.com/climate- ... te-change/


A sadly large portion of my personality wishes one of these precariously balanced subsea trench ice situations would bust loose and demonstrate beyond all doubt that significant melting is taking place every day.
I should be able to change a diaper, plan an invasion, butcher a hog, design a building, write, balance accounts, build a wall, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, pitch manure, program a computer, cook, fight efficiently, die gallantly. Specialization is for insects.
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Re: Sea Level Rise Pt. 3

Unread postby Newfie » Fri 27 Mar 2020, 08:59:17

Tanada,


I think I understand your feeling exactly. Humanity needs a sever shock to awaken from its stupor. If it’s possible to awaken, it may be a coma.
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Re: Sea Level Rise Pt. 3

Unread postby GHung » Fri 27 Mar 2020, 16:09:07

Blessed are the Meek, for they shall inherit nothing but their Souls. - Anonymous Ghung Person
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Re: Sea Level Rise Pt. 3

Unread postby Keith_McClary » Fri 19 Jun 2020, 00:07:37

Tiny sand grains trigger massive glacial surges
"It's within the realm of possibility that we could get 1 to 3 meters of sea-level rise from West Antarctica within our lifetimes," Minchew says. This type of shearing mechanism in glacial surges could play a major role in determining the rates of sea-level rise you'd get from West Antarctica."
Facebook knows you're a dog.
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