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Sea Level Rise Pt. 2

Re: Sea Level Rise Pt. 2

Unread postby Ibon » Sun 27 Oct 2019, 15:22:29

Cog wrote:At the current rate of sea level rise, a paraplegic snail could avoid the impending flood.


Cog, your an investor. The market signal always comes long before the event that triggers it.
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Re: Sea Level Rise Pt. 2

Unread postby Cog » Sun 27 Oct 2019, 19:23:59

If I were investing in the market the way you guys are in investing in sea level doom, I'd be long dead before I saw a profit.
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Re: Sea Level Rise Pt. 2

Unread postby Newfie » Sun 27 Oct 2019, 20:15:59

Cog,

I think that is partly true, people don’t understand the time frames we are dealing with.

OTOH it’s also not to dismiss CC, it’s just saying “I won’t pay the price, my grandkids will, but F em.”
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Sun 27 Oct 2019, 20:29:29

OTOH it’s also not to dismiss CC, it’s just saying “I won’t pay the price, my grandkids will, but F em.”


more likely your grandkids, grandkids (or even further out on the tree) assuming the earth isn't struck by an asteroid in the meantime, or yellowstone doesn't blow it's top.
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Re: Sea Level Rise Pt. 2

Unread postby Ibon » Sun 27 Oct 2019, 21:47:41

Cog wrote:If I were investing in the market the way you guys are in investing in sea level doom, I'd be long dead before I saw a profit.


That hurricane Dorian that stalled for 36 hours over the Greater Bahamas as a category 5 with 25 foot storm surges.

Had that happened anywhere from Miami to West Palm Beach the devastation of coastal properties would have been a

game changer for the insurance companies, game changer for affordability of coastal housing, game changer for property taxes

to build sea walls etc. That more than sea level rise was one of my considerations. I wanted to exit before the next big game

changing storm Interesting statistic a real estate agent told me in South Florida. More than 50% of homeowners that outright own their homes without mortgages do NOT have hurricane insurance. For the 10 years that we owned two coastal properties we also did not have insurance. I was not comfortable maintaining these assets not secured and the net income we made from doing short term rentals would have been too compromised had we insured those properties.

Statistics went into it. 2000 miles of vulnerable coast line and the core are of a hurricane that does the real damage is often only 30-40 miles wide. The odds still make the risk of not having insurance a fair bet but when you are older your become more risk averse.
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Re: Sea Level Rise Pt. 2

Unread postby Outcast_Searcher » Sun 27 Oct 2019, 23:06:34

rockdoc123 wrote:
I didn't know houses could move significantly by themselves. Our houses move in California, but usually back and forth only.


under the worst-case representative concentration pathway (i.e. CO2 emissions and accumulation in the atmosphere) 8.5 the IPCC in AR5 was predicting around 60 cm of sea-level rise overall. Not metres or tens of metres but cm. And under the more likely RCP 6.0 we are talking much less potential sea-level rise. But this is absolute sea-level rise. There are some areas in North America (for example) that are undergoing coastal uplift resulting in an actual fall in sea level (eg Alaska coastline -14 mm/yr) and there are some areas where natural and human-induced subsidence has resulted in quite high relative sea level rise (eg New Orleans).
The point is 3 mm of sea level rise over 80 years is 240 mm of sea level rise by 2100 or 24 cm (aoubt 9 inches), about half or less than half of what the IPCC were predicting. And that is over a 80 year period. In 5 years at that rate you would see 1.5 cm of sea level rise meaning you don't even have to pull the wellies out.

So you're going to completely ignore the fact that AGW and effects like sea level rise are accelerating? And how about all the feedback mechanisms? Pretending all nature is linear isn't exactly realistic.

We were talking about Miami above. Miami is already experiencing worsening significant flooding in areas at times -- despite the ongoing mitigation efforts including raising streets, flood walls, and lots of pumping capability being installed.

What happens there in 30 years? Or 100?

Too bad that when it happens the deniers who refused to support any mitigation don't get to pay for it.
Given the track record of the perma-doomer blogs, I wouldn't bet a fast crash doomer's money on their predictions.
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Sun 27 Oct 2019, 23:24:59

So you're going to completely ignore the fact that AGW and effects like sea level rise are accelerating? And how about all the feedback mechanisms? Pretending all nature is linear isn't exactly realistic.


With regards to sea level rise I’ve posted a few papers here that speak to the fact that if you look at decadal variation rather than cherry pick you will find that it has accelerated, then decelerated then accelerated throughout both the satellite era and before that when all we had to go on was bouys, meaning it has happened before and during the period where man-made CO2 was being put into the atmosphere at significant levels. I can repost those references but I’ve done so several times before and nobody seems to bother to read them (BTW these were published in well known, peer-reviewed journals). As to other AGW, please show me some evidence of anything else somehow “accelerating” and I will point you to the actual research that suggests that isn’t the case. The best place to start with that is the actual IPCC working group publications from AR5.

We were talking about Miami above. Miami is already experiencing pretty annoying flooding in areas at times -- despite the ongoing mitigation efforts including raising streets, flood walls, and lots of pumping.


You obviously missed the point I made about subsidence. Miami and most of the Gulf Coast have been subsiding for a long, long time. A lot has to do with natural geologic subsidence (it is all somewhat related to heavy sedimentary loading along the delta system which has been ongoing throughout the Cenozoic) and some to do with groundwater removal. Natural subsidence in this region is a huge deal, hence relative sea-level rise is important (mostly unrelated to climate change).

What happens there in 30 years? Or 100?


Probably the same thing that has been happening for the last several hundred years…continued subsidence. People shouldn’t have built there in the first place. This wasn't something that hadn't been predicted decades ago.

Too bad that when it happens the deniers who refused to support any mitigation don't get to pay for it.


Jesus wept. You are the one “denying” actual science here (subsidence along the Gulf Coast has been well documented in the literature for decades and the information regarding sea level rise projections I posted are from the IPCC AR5). And I don’t think either Cog or I said anything about not supporting mitigation. When you're given lemons you have to either make lemonade or suck them.
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Re: Sea Level Rise Pt. 2

Unread postby kublikhan » Tue 29 Oct 2019, 04:05:11

rockdoc123 wrote:With regards to sea level rise I’ve posted a few papers here that speak to the fact that if you look at decadal variation rather than cherry pick you will find that it has accelerated, then decelerated then accelerated throughout both the satellite era and before that when all we had to go on was bouys, meaning it has happened before and during the period where man-made CO2 was being put into the atmosphere at significant levels. I can repost those references but I’ve done so several times before and nobody seems to bother to read them (BTW these were published in well known, peer-reviewed journals). As to other AGW, please show me some evidence of anything else somehow “accelerating” and I will point you to the actual research that suggests that isn’t the case. The best place to start with that is the actual IPCC working group publications from AR5.
I just went to the IPCC web page. I looked through their recent paper Special Report on the Ocean and Cryosphere in a Changing Climate. It says that overall, the rate of sea level rise has been increasing. And is projected to continue to increase in the future.

rockdoc123 wrote:under the worst-case representative concentration pathway (i.e. CO2 emissions and accumulation in the atmosphere) 8.5 the IPCC in AR5 was predicting around 60 cm of sea-level rise overall. Not metres or tens of metres but cm.
The IPCC have increased their projections for sea level rise since the AR5 due to increased ice sheet melting. Current projections for RCP8.5 put sea level rise at multiple meters.

Observed Physical Changes
It is virtually certain that the global ocean has warmed unabated since 1970 and has taken up more than 90% of the excess heat in the climate system (high confidence). Since 1993, the rate of ocean warming has more than doubled (likely). Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity (very high confidence).

Global mean sea level (GMSL) is rising, with acceleration in recent decades due to increasing rates of ice loss from the Greenland and Antarctic ice sheets (very high confidence), as well as continued glacier mass loss and ocean thermal expansion. Increases in tropical cyclone winds and rainfall, and increases in extreme waves, combined with relative sea level rise, exacerbate extreme sea level events and coastal hazards (high confidence).

PROJECTED CHANGES AND RISKS
The Greenland and Antarctic Ice Sheets are projected to lose mass at an increasing rate throughout the 21st century and beyond (high confidence).The rates and magnitudes of these cryospheric changes are projected to increase further in the second half of the 21st century in a high greenhouse gas emissions scenario (high confidence).

Sea level continues to rise at an increasing rate. Extreme sea level events that are historically rare (once per century in the recent past) are projected to occur frequently (at least once per year) at many locations by 2050 in all RCP scenarios, especially in tropical regions (high confidence). The increasing frequency of high water levels can have severe impacts in many locations depending on exposure (high confidence).

Sea level rise is projected to continue beyond 2100 in all RCP scenarios. For a high emissions scenario (RCP8.5), projections of global sea level rise by 2100 are greater than in AR5 due to a larger contribution from the Antarctic Ice Sheet (medium confidence). In coming centuries under RCP8.5, sea level rise is projected to exceed rates of several centimetres per year resulting in multi-metre rise (medium confidence), while for RCP2.6 sea level rise is projected to be limited to around 1m in 2300 (low confidence). Extreme sea levels and coastal hazards will be exacerbated by projected increases in tropical cyclone intensity and precipitation (high confidence).
IPCC Special Report on the Ocean and Cryosphere in a Changing Climate
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Tue 29 Oct 2019, 10:46:59

The IPCC have increased their projections for sea level rise since the AR5 due to increased ice sheet melting. Current projections for RCP8.5 put sea level rise at multiple meters.


Not according to the actual research underlying the Guidance for Policy Makers (which you chose to read). You need to go to SROCC Chapter 4 Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities.

Projections
Future rise in global mean sea level caused by thermal expansion, melting of glaciers and ice sheets, and land water storage changes, is strongly dependent on which RCP emission scenario is followed. Sea level rise at the end of the century is projected to be faster under all scenarios, including those compatible with achieving the long-term temperature goal set out in the Paris Agreement. GMSL will rise between 0.43 m (0.29–0.59 m, likely range) (RCP2.6) and 0.84 m (0.61–1.10 m, likely range) (RCP8.5) by 2100 (medium confidence) relative to 1986-2005


Note also that 'medium confidence' refers to nothing much more than a coin flip

To get to those very high sea level rises requires using RCP 8.5 (which is a very unlikely estimate of future concentration pathways, especially if you believe in Peak Oil) and making some wild assumptions about very large increases from the Antarctic ice shelf collapse for which there is very little evidence and projecting out well beyond 2100 to multiple centuries and millennia.

Evolution of the Antarctic Ice Sheet beyond the end of the 21st century is characterized by deep uncertainty as ice sheet models lack realistic representations of some of the underlying physical processes. The few model studies available addressing timescales of centuries to millennia indicate multi-meter rise in sea level for RCP8.5 (medium confidence).


And this work doesn't take into account recent research (which I posted on the Antarctic thread) that indicates there is little chance of runaway ice sheet instability in Antarctica. That paper is also backed up by another one: Edwards, T et al, 2019. Revisiting Antarctic ice loss due to marine ice-cliff instability. Nature 566. PP 58-64 where they point out there is no evidence for marine ice-cliff instability and that all models suggest the lower end of contribution from Antarctica by 2100.
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Re: Sea Level Rise Pt. 2

Unread postby kublikhan » Tue 29 Oct 2019, 12:16:59

rockdoc123 wrote:Not according to the actual research underlying the Guidance for Policy Makers (which you chose to read). You need to go to SROCC Chapter 4 Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities.
Your quote is referring to 2100. However my quote metions that sea level rise does not stop in 2100 and will continue on for centuries:

Sea level rise is projected to continue beyond 2100 in all RCP scenarios. For a high emissions scenario (RCP8.5), projections of global sea level rise by 2100 are greater than in AR5 due to a larger contribution from the Antarctic Ice Sheet (medium confidence). In coming centuries under RCP8.5, sea level rise is projected to exceed rates of several centimetres per year resulting in multi-metre rise (medium confidence)
IPCC Special Report on the Ocean and Cryosphere in a Changing Climate

rockdoc123 wrote:Note also that 'medium confidence' refers to nothing much more than a coin flip

To get to those very high sea level rises requires using RCP 8.5 (which is a very unlikely estimate of future concentration pathways, especially if you believe in Peak Oil) and making some wild assumptions about very large increases from the Antarctic ice shelf collapse for which there is very little evidence and projecting out well beyond 2100 to multiple centuries and millennia.

And this work doesn't take into account recent research (which I posted on the Antarctic thread) that indicates there is little chance of runaway ice sheet instability in Antarctica. That paper is also backed up by another one: Edwards, T et al, 2019. Revisiting Antarctic ice loss due to marine ice-cliff instability. Nature 566. PP 58-64 where they point out there is no evidence for marine ice-cliff instability and that all models suggest the lower end of contribution from Antarctica by 2100.
The IPCC said they have very high confidence that the Antarctic ice sheet is losing ice at increasing rates. And they have high confidence that the projected loss of mass will continue to increase going forward.

Global mean sea level (GMSL) is rising, with acceleration in recent decades due to increasing rates of ice loss from the Greenland and Antarctic ice sheets (very high confidence). as well as continued glacier mass loss and ocean thermal expansion.

The Greenland and Antarctic Ice Sheets are projected to lose mass at an increasing rate throughout the 21st century and beyond (high confidence).
IPCC Special Report on the Ocean and Cryosphere in a Changing Climate

Ice loss from Antarctica's ice sheet tripled from 2007 to 2016, relative to 1997-2006. During that same period, ice mass loss doubled in Greenland, largely from surface melting.
Image
From Antarctica to the Oceans, Climate Change Damage Is About to Get a Lot Worse, IPCC Warns
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Tue 29 Oct 2019, 14:31:02

Your quote is referring to 2100. However my quote metions that sea level rise does not stop in 2100 and will continue on for centuries


my reference in my note was to 2100, forecasting anywhere beyond that is ridiculous at best as IPCC notes by stating there is low confidence associated with that information. Also as I pointed out there are recent papers suggesting the ice cliff mass wasting worry in Antarctica (which is what is required for rapid losses in Antarctica and the high sea level rise case ) is likely without merit.

The IPCC said they have very high confidence that the Antarctic ice sheet is losing ice at increasing rates. And they have high confidence that the projected loss of mass will continue to increase going forward.


and in that statement they do not speak to how long in the future. But also there is considerable disagreement in the literature with their approach given they put extreme emphasis on the satellite data which is relatively short lived whereas the longer term sea level data measurements show considerable disagreement (and a lack of meaningful acceleration)

but you run in circles trying to argue somehow that the IPCC is suggesting metres and metres of sea level rise by 2100. They are not. As I said in a quote from their research even the worst possible scenario that is extremely unlikely RCP8.5 results in sea level rise that is not anywhere near the tens of metres that some here claim is possible.
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Re: Sea Level Rise Pt. 2

Unread postby kublikhan » Tue 29 Oct 2019, 18:52:24

rockdoc123 wrote:but you run in circles trying to argue somehow that the IPCC is suggesting metres and metres of sea level rise by 2100.
Incorrect. I never said IPCC was predicting meters and meters of sea level rise by 2100. Not once. Are you mixing me up with another poster? I said they were predicting meters of sea level rise and then quoted a statement with projections out to 2300. Apparently you missed the date in my quote and instead inferred that I was talking about 2100 when I was not. Your inference was incorrect. Thus the error was yours. Compounding this error you seem to be trying to present an argument that the acceleration in sea level rise is BS with the data going up and down. However this is not the case the IPCC makes. Their case is the rise in the sea level is accelerating, and they have very high confidence in this:

Global mean sea level (GMSL) is rising, with acceleration in recent decades due to increasing rates of ice loss from the Greenland and Antarctic ice sheets (very high confidence). as well as continued glacier mass loss and ocean thermal expansion.The Greenland and Antarctic Ice Sheets are projected to lose mass at an increasing rate throughout the 21st century and beyond (high confidence).
IPCC Special Report on the Ocean and Cryosphere in a Changing Climate

rockdoc123 wrote:forecasting anywhere beyond that is ridiculous at best as IPCC notes by stating there is low confidence associated with that information.
Incorrect again. IPCC says with high confidence that sea level will continue to rise for centuries.

Beyond 2100, sea level will continue to rise for centuries due to continuing deep ocean heat uptake and mass loss of the Greenland and Antarctic ice sheets (4.2.3.5), and will remain elevated for thousands of years (high confidence).
Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities

rockdoc123 wrote:Also as I pointed out there are recent papers suggesting the ice cliff mass wasting worry in Antarctica (which is what is required for rapid losses in Antarctica and the high sea level rise case ) is likely without merit.
Personally I think even a half a meter to one meter rise in sea levels by 2100 is worrying enough:

Due to projected global mean sea level rise, extreme sea level events (ESLs) that are historically rare (for example, today’s hundred-year event) will become common by 2100 under all RCPs (high confidence). Many low-lying megacities and small islands at almost all latitudes will experience such events annually by 2050.

Risk related to sea level rise (including erosion, flooding and salinization) is expected to significantly increase by the end of this century along all low-lying coasts in the absence of major additional adaptation efforts (very high confidence).
Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities

However there are also recent papers that suggest the probability of faster melting should not be dismissed so easily.

Climate change-induced melting will raise global sea levels for decades to come. Antarctica experienced a sixfold increase in yearly ice mass loss between 1979 and 2017, according to a study published today in Proceedings of the National Academy of Sciences. “That’s just the tip of the iceberg, so to speak,” said lead author Eric Rignot, Donald Bren Professor and chair of Earth system science at UCI. “As the Antarctic ice sheet continues to melt away, we expect multi-meter sea level rise from Antarctica in the coming centuries.”

The team was able to discern that between 1979 and 1990, Antarctica shed an average of 40 gigatons of ice mass annually. (A gigaton is 1 billion tons.) From 2009 to 2017, about 252 gigatons per year were lost. Rignot said that one of the key findings of the project is the contribution East Antarctica has made to the total ice mass loss picture in recent decades. “The Wilkes Land sector of East Antarctica has, overall, always been an important participant in the mass loss, even as far back as the 1980s, as our research has shown,” he said. “This region is probably more sensitive to climate [change] than has traditionally been assumed, and that’s important to know, because it holds even more ice than West Antarctica and the Antarctic Peninsula together.” He added that the sectors losing the most ice mass are adjacent to warm ocean water. “As climate warming and ozone depletion send more ocean heat toward those sectors, they will continue to contribute to sea level rise from Antarctica in decades to come.”
Antarctica losing six times more ice mass annually now than 40 years ago

We know that our planet has experienced warmer periods in the past, during the Pliocene geological epoch around three million years ago. Our research, published today, shows that up to one third of Antarctica's ice sheet melted during this period, causing sea levels to rise by as much as 20 meters above present levels in coming centuries. We show that warming of more than 2°C could set off widespread melting in Antarctica once again and our planet could be hurtling back to the future, towards a climate that existed three million years ago.

Our study has important implications for the stability and sensitivity of the Antarctic ice sheet and its potential to contribute to future sea levels. It supports the concept that a tipping point in the Antarctic ice sheet may be crossed if global temperatures are allowed to rise by more than 2℃. This could result in large parts of the ice sheet being committed to melt-down over the coming centuries, reshaping shorelines around the world.
If warming exceeds 2 C, Antarctica's melting ice sheets could raise seas 20 meters in coming centuries

Rising temperatures have sped up the melting of West Antarctica’s ice fivefold in the past 25 years, resulting in a quarter of the region’s glaciers being classified as unstable, according to a new study published in the journal Geophysical Research Letters. Parts of the West Antarctic Ice Sheet have thinned by as much as 400 feet since 1992.
A Quarter of West Antarctica’s Ice Now Considered Unstable, Scientists Find
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Tue 29 Oct 2019, 19:49:50

However there are also recent papers that suggest the probability of faster melting should not be dismissed so easily


Did you even bother to read that paper? The historic net ice mass loss they are referring to is inline precisely with what I have mentioned numerous times from scores of papers in the Antarctic thread. It is easy to get mislead because they talk about losses not overall net mass balance which takes into account increases from snowfall. The total net losses from Antarctica amount to anywhere from 0.25 to 0.3 mm/yr sea level equivalent or around 25 mm sea level rise by 2100. IPCC acknowledges that it requires ice shelf collapse at high rates (as was suggested by Pollard and DeConto several years ago) in order to come up with massive losses any higher than this from Antarctica. The Tamsin Edwards paper of 2019 I pointed to quantifies their assessment of what the actual potential loss from ice cliff mass wasting going forward is on a statistical basis and that is 45 cm by 2100 or a little more than double the current rate of overall losses. The Clerc et al paper of 2019 I referenced on the Antarctic thread speaks to the self-limiting process of ice cliff collapse meaning that runaway cliff collapse would be mitigated. If you take that into context with another recent paper by Wang et al. Wang, Y. et al, 2019. A new 200-year spatial reconstruction of West Antarctic Surface Mass Balance. JGR Atmospheres, pp 5282-5295 which spells out surface mass balance changes in Western Antarctic and the Pennisula suggesting that almost all net losses have been due to mechanical losses at the ice sheet toe and not melt you are left with being very hard-pressed to argue for any sort of huge increase over time with regard to Antarctic ice loss. AR5 spoke to this at some length and the SR Ocean and Cryosphere. Of course, this recent work is not included in the models that IPCC uses for their long term projections.

And with reference to projecting beyond 2100 out say nearly 3 centuries I don’t see the reason why this has any relevance. In that period of time any number of other more impactful events could take place and given the performance of models just in the period from 2005 through to 2015 (most predicted temperatures much higher than actually occurred) it seems predicting out 30 times that length of time would not be a very insightful exercise.
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Re: Sea Level Rise Pt. 2

Unread postby kublikhan » Wed 30 Oct 2019, 04:33:49

rockdoc123 wrote:Did you even bother to read that paper? The historic net ice mass loss they are referring to is inline precisely with what I have mentioned numerous times from scores of papers in the Antarctic thread. It is easy to get mislead because they talk about losses not overall net mass balance which takes into account increases from snowfall. The total net losses from Antarctica amount to anywhere from 0.25 to 0.3 mm/yr sea level equivalent or around 25 mm sea level rise by 2100.
'That' paper? I linked to 3. If you are referring to the first link it said:

As the Antarctic ice sheet continues to melt away, we expect multi-meter sea level rise from Antarctica in the coming centuries.
The second paper spoke of 20 meters of sea level rise during previous warming periods of Earth and the third spoke of growing instability of the West Antartica's ice.

And while we are on the subject, in the future I would appreciate if you could actually provide links to backup your arguments. "I did in the past and no one read them" doesn't really cut it since I wasn't here then. Then when I finally track down your links, they are behind a paywall.

"A lot can happen by 2300" doesn't really change the fact that the experts say we have a lot of sea level rise locked in by 2300, only the amount is debated. Did you look at some of the values the IPCC is projecting for 2300? Best case scenario, around 1 meter of sea level rise. Worst case, over 5 meters of sea level rise:
Past and future changes in the ocean and cryosphere

And given that we are not on track to meet the pledges in the Paris Accord, I would not put much stock in meeting the best case scenario. In fact the 2 degree warming scenario seems more like a pipe dream considering we are on track for a significantly higher amount of warming.

Global temperatures are on course for a 3-5 degrees Celsius (5.4-9.0 degrees Fahrenheit) rise this century, far overshooting a global target of limiting the increase to 2C (3.6F) or less, the U.N. World Meteorological Organization said on Thursday. “Greenhouse gas concentrations are once again at record levels and if the current trend continues we may see temperature increases 3-5 degrees C by the end of the century.”

Scientists say that it is vital to limit the rise in global temperatures to 2 Celsius to avert more extreme weather, rising sea levels and the loss of plant and animal species, although limiting the rise to 1.5C would have a far greater benefit.

Taalas said that the lower end of the range, a 3C rise in temperatures, came from a model assuming that countries acted on their pledges to meet the Paris targets.
Global temperatures on track for 3-5 degree rise by 2100: U.N.
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Wed 30 Oct 2019, 10:57:37

The second paper spoke of 20 meters of sea level rise during previous warming periods of Earth and the third spoke of growing instability of the West Antartica's ice.


not sure what it is you are trying to argue here. Are you trying to argue that the contribution from Antarctica is more than the 0.25 to 0.3 mm/yr? Are you arguing that the new research suggesting the worries that Pollard and DeConto were waxing lyrical on a couple of years ago are incorrect? If so, why?

And while we are on the subject, in the future I would appreciate if you could actually provide links to backup your arguments. "I did in the past and no one read them" doesn't really cut it since I wasn't here then. Then when I finally track down your links, they are behind a paywall.


I link to actual research, not to press releases that tend to be both inaccurate and usually biased. My reasoning is that in peer reviewed journal articles authors are kept from making statements that are not substantiated either by their own observations, evidence etc or published research by other authors. This isn't the case in journal article interviews where you see some pretty wild speculation that would never pass muster in a journal. On the Antarctic thread I've pointed to scads of research papers that have been accomplished, all of which I've read (I don't reference an article I haven't read). Some I have access to others I simply read at the local University that subscribes to pretty much every major journal you could imagine. I can't control what journals have paywalls and which ones don't but all of these journals would be available at your local university/college.

"A lot can happen by 2300" doesn't really change the fact that the experts say we have a lot of sea level rise locked in by 2300, only the amount is debated. Did you look at some of the values the IPCC is projecting for 2300? Best case scenario, around 1 meter of sea level rise. Worst case, over 5 meters of sea level rise:


I say a lot can happen because these projections are all model-based and include assumptions regarding future emissions and climate sensitivity that are widely disputed. As an example the newest models have ECP's that are higher than the range IPCC outlined in AR5 (1.5 -3 C for a doubling of CO2). Given a comparison of models run with a 2005 start date generally run much hotter than instrumental data (Hadcrut 4) to current time frame why would you suddenly expect them to be more accurate in their predictive ability over a time period 30 times longer?

And given that we are not on track to meet the pledges in the Paris Accord, I would not put much stock in meeting the best case scenario. In fact the 2 degree warming scenario seems more like a pipe dream considering we are on track for a significantly higher amount of warming.


Here is a useful discussion that wanders through the origins of RCP 8.5. The author of the discussion points out that RCP 8.5 might be a useful absolute worst-case scenario to be contemplated but that it is unrealistic. Judith Curry suggests it might be useful as a scare tactic but shouldn't be used for policy planning.
https://judithcurry.com/2015/12/13/a-closer-look-at-scenario-rcp8-5/
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Re: Sea Level Rise Pt. 2

Unread postby kublikhan » Wed 30 Oct 2019, 12:12:24

As I understand it, there is still a large amount of uncertainty on the amount of future ice melt and on the stability of the ice. However I have noticed that the projected rates given for ice melt and sea level rise seem to go up over time. IE, the more we know, the higher the projections for sea level rise become. Thus I am guessing this trend to continue into the future. IE, AR6 will have higher projected sea level rises than AR5, AR7 more than AR6, etc.

As for 8.5 being unrealistic, new research coming out has suggested that if current trends continue we may be in store for even more warming. Thus they are including even hotter scenarios in AR6. IE, 8.5 is no longer the worst case scenario:

New climate models unveiled by French researchers Tuesday showed Earth's average temperature could rise a "terrifying" 6.5-7.0°C above pre-industrial levels by the end of the century if dramatic action is not immediately taken to slash carbon emissions. The findings, presented at a press conference in Paris, suggest the planet may be warming significantly faster than scientists previously believed as the world's major economies continue to burn fossil fuels at unsustainable rates.

The new models are expected to form part of the U.N. Intergovernmental Panel on Climate Change's Sixth Assessment Report, which is set to be published in 2021. The IPCC's Fifth Assessment Report, published in 2014, presented a worst-case scenario of five degrees Celsius of warming by the end of the century.

Olivier Boucher, head of the Institute Pierre Simon Laplace Climate Modeling Center in Paris, which developed one of the new models, said the latest data provide a better look at where the climate is heading without drastic changes to global energy production. "We have better models now," Boucher told AFP on Tuesday. "They have better resolution, and they represent current climate trends more accurately."

The IPCC warned last year that even limiting planetary warming to 1.5°C by the end of the century, the goal of the Paris Climate Agreement, would not prevent many of the disastrous effects of the climate crisis. Warming of 6.5-7.0°C would be catastrophic. "Higher warming would allow less time to adapt and mean a greater likelihood of passing climate 'tipping points' such as thawing of permafrost, which would further accelerate warming," said Boucher.
'Terrifying' New Climate Models Warn of 6-7°C of Warming by 2100 If Emissions Not Slashed
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Re: Sea Level Rise Pt. 2

Unread postby Newfie » Wed 30 Oct 2019, 12:30:41

There was a terrific amount of ice coming down the Labrador Current last year.

Some folks see that and say “See all the ice bergs, no warming”, but they are wrong. It’s more like ice flowing down a river in the spring after a break up. Info it is of a “warming” that breaks up the once solid ice. Except here there is a one or two year delay.
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Re: Sea Level Rise Pt. 2

Unread postby rockdoc123 » Wed 30 Oct 2019, 12:44:44

As for 8.5 being unrealistic, new research coming out has suggested that if current trends continue we may be in store for even more warming. Thus they are including even hotter scenarios in AR6. IE, 8.5 is no longer the worst case scenario:


Apparently you didn't read the article I posted. The new models do not incorporate worse emission scenarios than RCP 8.5 (not sure how you could get worse given the over the top suggestions on coal) what they do is have much higher ECS (I would have to look for the reference where that number was arrived at) when much of the recent research is suggesting lower sensitivities (in the range of 2.5 C) based on historical information and bottoms up calculations. To get the sort of scenario they are talking about probably needs ECS >5.
Here is a plot showing published results for ECS and TCR calculations versus year of publication. It is telling that over time the values have dropped, not increased, which is in-line with the disconnect between model predictions and actual results
Image
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Re: Sea Level Rise Pt. 2

Unread postby kublikhan » Wed 30 Oct 2019, 13:20:39

The point was a trend of projected sea levels rising with each new report. I expect the trend to continue with AR6.

Higher projections than in the past
To those who remember the much-discussed sea-level range of 18-59 cm from the 4th IPCC report, it is clear that the new numbers are far higher, both at the low and the high end. But how much higher they are is not straightforward to compare, given that IPCC now uses different time intervals and different emissions scenarios. But a direct comparison is made possible by table 13.6 of the report, which allows a comparison of old and new projections for the same emissions scenario (the moderate A1B scenario) over the time interval 1990-2100(*). Here the numbers:

AR4: 37 cm (this is the standard case that belongs to the 18-59 cm range).
AR4+suisd: 43 cm (this is the case with “scaled-up ice sheet discharge” – a questionable calculation that was never validated, emphasised or widely reported).
AR5: 60 cm.

We see that the new estimate is about 60% higher than the old standard estimate, and also a lot higher than the AR4 attempt at including rapid ice sheet discharge.

Outlook
For the past six years since publication of the AR4, the UN global climate negotiations were conducted on the basis that even without serious mitigation policies global sea-level would rise only between 18 and 59 cm, with perhaps 10 or 20 cm more due to ice dynamics. Now they are being told that the best estimate for unmitigated emissions is 74 cm, and even with the most stringent mitigation efforts, sea level rise could exceed 60 cm by the end of century. It is basically too late to implement measures that would very likely prevent half a meter rise in sea level. Early mitigation is the key to avoiding higher sea level rise, given the slow response time of sea level (Schaeffer et al. 2012). This is where the “conservative” estimates of IPCC, seen by some as a virtue, have lulled policy makers into a false sense of security, with the price having to be paid later by those living in vulnerable coastal areas.

Is the IPCC AR5 now the final word on process-based sea-level modelling? I don’t think so. I see several reasons that suggest that process models are still not fully mature, and that in future they might continue to evolve towards higher sea-level projections.
Sea level in the 5th IPCC report
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Re: Sea Level Rise Pt. 2

Unread postby EnergyUnlimited » Wed 30 Oct 2019, 14:05:55

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.
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