My top 3 impressions up-front:
- The sea level projections for the year 2100 have been adjusted upwards again.
- The IPCC has introduced a new high-end risk scenario, stating that a global rise “approaching 2 m by 2100 and 5 m by 2150 under a very high greenhouse gas emissions scenario cannot be ruled out due to deep uncertainty in ice sheet processes.”
- The IPCC gives more consideration to the large long-term sea-level rise beyond the year 2100.
And here is the key sea-level graphic from the Summary for Policy Makers:
This is a pretty clear illustration of how sea level starts to rise slowly; but in the long run, sea-level rise caused by fossil-fuel burning and deforestation in our generation could literally go off the chart and inundate many coastal cities and wipe entire island nations off the map. But first things first.
Observed Past Rise
Let’s dive a little deeper into the full report and start with the observed sea level change. Since 1901 sea level has risen by 20 cm, a rise unprecedented in at least 3,000 years (disclosure: I co-authored some of the research behind the latter conclusion).
Since 1900 the rise has greatly accelerated. During the most recent period analyzed, 2006-2018, it’s been rising at a rate of 3.7 mm/year – nearly three times as fast as during 1901-1971 (1.3 mm/year). The IPCC calls this a “robust acceleration (high confidence) of global mean sea level rise over the 20th century”, as did the SROCC in 2019.
The finding of sea-level acceleration is not new. The AR4 already concluded in 2007: “There is high confidence that the rate of sea level rise has increased between the mid-19th and the mid-20th centuries.” And the AR5 found in 2013 that “there is high confidence that the rate of sea level rise has increased during the last two centuries, and it is likely that global mean sea level has accelerated since the early 1900’s.” (Which has not stopped “climate skeptics” from repeatedly claiming a lack of acceleration.)
The reason for earlier hedged wording by the IPCC was the possibility of natural decadal variability affecting the trend estimates, but the AR6 now concludes “that the main driver of the observed global mean sea-level rise since at least 1970 is very likely anthropogenic forcing”. That is the result of so-called “attribution studies” – attempts to differentiate with the help of a combination of data, models, pattern detection and statistics between all possible human-caused and natural factors in the observed changes. However, on the level of basic physical reasoning, it is of course a no-brainer that warming will cause land-ice to melt (and melt faster as it gets hotter) and ocean waters to expand, so sea-level rise is the inevitable result.
And there is this:
New observational evidence leads to an assessed sea level rise over the period 1901 to 2018 that is consistent with the sum of individual components contributing to sea level rise, including expansion due to ocean warming and melting of glaciers and ice sheets (high confidence).
IPCC AR6
That’s an important consistency check; the independent data add up to the overall observed rise.
The Future Until 2100
It is virtually certain that global mean sea level will continue to rise over the 21st century in response to continued warming of the climate system.
IPCC AR6
By how much? That depends on our emissions and is shown in the following figure. The take-away message is: for high emissions we’d likely get close to a meter, sticking to the Paris agreement would cut that down to half a meter.
And how does that compare to the recent previous reports? Here is the comparison the IPCC shows:
If you look at the 2100 projections for the last three reports (AR5, SROCC, AR6) you can see that the numbers have increased each time – and remember that the AR5 numbers had already increased by ~60% compared to the AR4. This illustrates the fact that IPCC has been too “cautious” in the past (which is not a virtue in risk assessment), having to correct itself upward again and again (all the while “climate skeptics” try to paint the IPCC as “alarmist”, for want of any better arguments to play down the climate crisis).
Related to that are notable changes in grappling with uncertainty and risk. The IPCC is now showing very likely (5-95 percentile) as well as likely (17-83 percentile) ranges. In the AR5, it had made the rather ad-hoc argument that “global mean sea level rise is likely (medium confidence) to be in the 5 to 95% range of projections from proces-based models”. So their likely range was actually the modelled very likely range.
The IPCC now splits the uncertainty into two types, hence the two different shadings in the uncertainty bars, in an attempt to also cover uncertainty in processes which we still cannot confidently model. They write:
Importantly, likely range projections do not include those ice-sheet-related processes whose quantification is highly uncertain or that are characterized by deep uncertainty. Higher amounts of global mean sea level rise before 2100 could be caused by earlier-than-projected disintegration of marine ice shelves, the abrupt, widespread onset of Marine Ice Sheet Instability (MISI) and Marine Ice Cliff Instability (MICI) around Antarctica, and faster-than-projected changes in the surface mass balance and dynamical ice loss from Greenland. In a low-likelihood, high-impact storyline and a high CO2 emissions scenario, such processes could in combination contribute more than one additional meter of sea level rise by 2100.
Note that this uncertainty goes to one side: up. For estimating this uncertainty they use an expert survey as well as a smaller but more detailed structured expert judgement. I co-authored the survey (see also 7-minute video about it) with Ben Horton and others, as well as a predecessor survey published in 2014, and I am happy to see that the IPCC now includes this type of expert judgement to assess risks that can’t yet be modelled reliably, but cannot be just ignored either. In dealing with the climate crisis, it simply is not enough to consider what is likely to happen – it is even more important to understand what the risks are.
Think about it: If someone builds a nuclear facility near to your house, would you be satisfied with knowing that it is “likely” to work well (say, 83% certain)? Or would you like to know about a few percent chance that it could blow up like Chernobyl in your lifetime?
With the high-end risk scenarios, the IPCC is catching up with other assessments such as the US National Climate Assessment of 2017, which already showed a “high” scenario of 2 meters and an “extreme” scenario of 2.5 meters of rise by 2100.
The Long Term Future
One of the headline statements of the AR6 is:
Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.
IPCC AR6
That’s because huge ice sheets take a long time to melt in a warmer climate, and the ocean waters take a long time to warm up as you go further down, away from the surface. So by what we are doing now in the next couple of decades we determine the rate and amount of sea-level rise for millennia to come, condemning many generations to continually changing coastlines and forcing them to abandon many coastal cities, large and small. That we cannot turn this back is the reason why the precautionary principle should be applied to the climate crisis.
Just look at the ranges expected by the year 2300, in the right-hand panel of the first image above. Even in the blue mitigation scenario, which limits warming to well below 2 °C, our descendants may well have to deal with 2-3 meters of sea-level rise, which would be catastrophic for the people living at the world’s coastlines. Not only would it be extremely hard and costly – if possible at all – to defend cities like New York during a storm surge with a so much higher sea level. We would see massive coastal erosion happening all around. And remember that “nuisance flooding” is already causing real problems after just 20 cm of sea-level rise, for example along the eastern seaboard of the US!
At least with this Paris scenario and a good portion of sheer luck, we may get away with less than a meter rise. But with further unmitigated increase in emissions, a desastrous 2 meter rise is about as likely as an utterly devastating 7 meter rise. What would our descendants think we were doing?
Dear Prof. Stefan R.
Why is future sea level rise still so uncertain?
For my part, I will return this not entirely unimportant question with a very simple answer: “It will depend on whether humanity finds a concept that slows, stops or even reverses sea level rise.”
…and here it is:
A simple concept to stop SLR, increasing global temperatures, droughts, river & sea floods and
decreasing biodiversity,
As an explanatory introduction to this alternative, holistic climate protection, I would like to ask the question:
How do we bring falling groundwater levels and rising sea level together ?
– which specific measures and changes will protect us from droughts, river & sea floods, increasing global temperatures and decreasing biodiversity ?
Many answer this question that only a rapid reduction in emissions of greenhouse gases such as CO2 and methane, etc. alone can hold back climate disasters and tipping points.
A majority of climate scientists are also convinced:
– The rise in sea level is unstoppable and also irreversible, …
– That mankind cannot directly influence climate, solar radiation, rain, clouds and the water vapor content of the atmosphere.
I would like to counter this and claim:
“The lowering of the SLR and the earth temperature are directly related to the global radiation balance and the water cycles of the earth.”
“Water vapor, and not CO2, is the most important greenhouse gas and, due to the clouds albedo has a strong negative, net cooling radiative forcing”
“And of course humans can influence the climate, sea level and the water vapor content of the atmosphere.”
We are doing it every day – since centuries.
Mio. km² of rainforest, mostly eliminated by slash and burn, together with ~ 1.5 million km² of urban sealed area inevitably leads to the fact that much less water evaporates over these areas and precipitation and service water quickly drains off into the sea via the sewers and rivers.
The long-term global drainage of moors and wetlands also significantly reduces their ability to evaporate water. Spreading deserts rapidly increase these areas with reduced evaporation.
—
~49500 km³ of fresh water flows into the seas via rivers every year.
Even a high annual sea level rise of 3.7 mm corresponds to “only” ~ 1335 km³ (2,7% of global river discharge).
https://upload.wikimedia.org/wikipedia/commons/thumb/7/73/HumanIntegratedWaterCycle_%282%29.jpg/1024px-HumanIntegratedWaterCycle_%282%29.jpg
This corresponds to 9mm or 9L / m² over global land area and 27L / m² over the 50 Mio km² of agricultural area – far too little for a drought lasting 2 weeks to 2 months even in a (my) summer in the Rhine Valley at the 49th parallel north.
My climate protection strategy would be to retain this volume of annual SLR from the global rivers and creeks and bring it to evaporation. Thus not only stops the SLR – but also effects cloud cover and earth`s albedo.
If we convert this volume into little cumulus clouds e.g.(250m³ / 625t of water) we get ~ 2 billion clouds, which will improve the earth’s albedo in spring/summer drought periods (surface radiation is 5 times higher than winter times) on ~3.5 million km². The global cloud cover and evaporation rate will increase by ~ 1%, which will cause a negative, cooling radiative forcing of ~ 0.19 W / m².
The cloud radiative effect CRE = -19W/m²
https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter07_FINAL-1.pdf
— page 582
https://link.springer.com/article/10.1007/s00382-018-4413-y
— Martin Wild et.al.
That is far more than the current annual increase in radiative forcing caused by CO² – and would holistically resolve almost all problems caused by climate change.
My personal hit parade of desaster caused by global warming is:
1. dramatically decreasing biodiversity
2. slr with an immense cost for (a lost) infrastructure
3. Extreme drought / maximum temperatures / heavy rainfall and floods
The volume of 1335km³ of water will also ensure an additional assimilation of 1.3-2.6 Gt of carbon in agriculture and forests etc.
This climate protection concept starts with rain barrels, cisterns and larger rain retention basins which are equipped with an overflow onto unsealed terrain. But even the smallest stream and river can tolerate a small diversion (outside of the drought and low water) to rewet moors and forests and is upwards in the catchment areas usually much cleaner than in the vicinity of the larger cities.
The water management of the ancient Inca cultures is an excellent example of how one can fight against the desert, but also against floods, with the most primitive tools.
“Amunas” is the name of the water channels with which the Incas sow the water in order to harvest it weeks or months later.
https://hidraulicainca.com/lima/sistema-hidraulico-amunas/
Taking out of the atmosphere as much CO² emissions as possible …
but also evaporate as much water as possible by an increasing irrigation of plant growth
— is hopefully a global motto for the atmosphere of the future.
Artificial irrigation = artificial clouds
and thus an instantly faster climate protection and 1000times cheaper than the conversion of a fossil equipment into a renewable one and will have to be implemented anyway as an adaptation measure in many dry regions.
A large part of the evaporation energy specified in the averaged radiation balance of ~ 82W / m² is converted into water vapor over the area of 71% oceans and the volume of evaporation there increases with increasing air and water temperature, but over the 29% land area with spreading deserts and the causes described above, it tend to be the other way around.
The land climate changes regionally and seasonally from water to air cooling. Drought periods in summer, even up to the Arctic Circle, produce less and less evaporation and clouds, especially when the strongest solar radiation is acting.
The flow of energy from the surface in height and width takes place less and less by water vapor, but increasingly in the form of hot and dry air.
Rainforests transport clouds and rain inland – and deserts, conversely, spread blue skies and drought.
The amount of water vapor in the atmosphere is first of all very small, less than 4 cm of sea level (as 2 minutes with google can tell you). So even if you could double that somehow, you could prevent no more than 4 cm of sea level rise.
But second, you cannot increase the water content significantly by increasing evaporation, because any additional moisture you add by evaporation will simply rain out.
The water holding capacity of the atmosphere is limited and that is what controls the amount of water in it. It is not limited by lack of evaporation.
You can increase it by warming the atmosphere, then it will hold 7% more moisture per °C of warming, because this is how the saturation vapor pressure increases with temperature. -Stefan
Dear Stefan – sorry – you completely misunderstood me.
My climate protection strategy would like to take the volume of 3.7mm SLR(1335km³) from the global rivers discharge when their water levels are sufficient(&clean) or even specially in flood events after rain- !!! to store it in soil moisture and groundwater over the land mass.
In principle a simple, seasonal storage of retained river water to adapt to droughts and floods.
In dry seasons, this water will be mainly evaporated from agriculture, but also the above mentioned
“amunas” of the old inca culture and water management are a perfect way to rewet forests & moors
This in turn ensures an increasing relative (and specific) humidity and additional cloud formation over land in a regional drought season.
After an average of 8.5 – 10 days in the atmosphere it will return – even with a relatively high probability – as precipitation over another land area. There will be a multiplier effect that increase together with soil moisture and evaporation rate (wet regions become wetter).
As a result, the water cycle over the land areas is intensified by ~ 1% and the increasing size of the annual mean cloud cover leads to a higher CRE, which I estimate to be at least ~ -0.2W m-2 / year.
A really cooling, additional radiative forcing, which, in my opinion, can more than compensate for the current annual radiative forcing caused by CO² .
A holistic, functioning climate protection strategy,
(stopping SLR AND global temperature rise & adaptation to droughts and floods)
which works alternatively and independently of the reduction in CO² emissions, which only promises to stop the temperatures perhaps after ~ 2070 (if we as humanity can reduce emissions immediately – which I personally do not believe)
In the latest IPCC report / WG1 Chapter 7.4.2.4.3, the positive feedback of the cloud cover on an atmosphere warmer by 1 ° C is given with
CRF = +0.42W m-2 ° C-1.
We are slowly but steadily losing not only areas of ice and snow albedo, but also the clouds albedo due to decreasing global mean cloud cover an higher lapse rate.
The cooling CRE with ~-19W m-2 (chapter 7.2.1. in the same report) should decrease accordingly.
The slower warming of the oceans means that there has not been enough moisture evaporated into – and then held in – the air above the oceans to keep pace with the rising temperatures over land. This means that the air is not as saturated as it was and – as the chart below shows – relative humidity has decreased, desertification is spreading rapidly mainly caused by human activities.
Dryness is a temperature driver and cloud killer.
https://www.carbonbrief.org/wp-content/uploads/2020/11/Global-time-series-of-annual-average-relative-humidity-for-the-land-ocean-and-global-average-relative-to-1981-2010.jpg
That is why I (as an artist) think it`s a good idea to create “artificial” clouds by artificial irrigation retained from the superfluous sea water. – macias
In Permaculture we refer to similar structures as swales when they are made of trenches on contour. Of course, terracing is pretty much universal.
Water management is a key aspect of any good design. We start with water, sunlight, and wind move across a site and water management is the core of a regenerative design.
This is not coincidental: Permaculture principles and design process were drawn from direct observation of natural systems, including traditional practices (TEK.) Principle: Capture and Store Energy. This includes water, obviously. So, we seek ways to 1. follow the natural paths of water and design to those, 2. infiltrate water into the soils and 3. store water in ponds, cisterns, etc.
THE single best solution long-term is to restore global soils to high-carbon density: “Each 1 percent increase in soil organic matter helps soil hold 20,000 gallons more water per acre.” That’s PER SIX INCHES of depth. One yard deep would be 6x more water, 120,000 gallons. Add another meter and you’ve got 240,000 gallons.
This is why adding soil carbon is the single most effective, cheapest and fastest response for soil health, aquifer restocking, flood control, drought control, lower temperatures, etc.
@stefan: if you reply to a comment, you should have read the comment too.
The report’s SPM makes the following point: “The rate of ice sheet loss increased by a factor of four between 1992-1999 and 2010-2019 .. together ice mass loss and glacier loss were the dominant contributors to global sea level rise in 2006-2018” [in contrast to thermal expansion in the 20th century]..
Would like to hear your thoughts about this and what the trends in this driver may imply for future sea level rise. Thanks.
Forget the future of SLR and look to the actual.
3,7mm = 1335km³ / year
That`s a big number. If you bring it over the land area it`s 9mm = 9L/m².
That is ~ 1,5% of averaged yearly precipitation over land.
Retain this volume out of global river discharge and use it for additional irrigation/evaporation in drought season(s) for additional plant growth.
You will produce 1,5% more cloud cover over land clear sky regions.
This is a negative, cooling radiative forcing of about 0,1W/m² in a global mean energy balance and thus enough to compensate the AGW.
SLR is stopped / global temperature rise is stopped / adapted to drought & floods / additional absorbtion of 4,5 – 9Gt CO² / survival of creation is more secure…
I really wonder that so many members of RC don`t know how to use a bathtube.
Does sea level rise also have an influence on trade winds and ocean currents?
As more evidence/data accumulates, it seems to me that sea level projections for the year 2100 keep being adjusted upwards.
An important new paper in Nature (paywalled, except for Abstract) on Antarctic ice sheet loss was published on 5 May 2021, titled The Paris Climate Agreement and future sea-level rise from Antarctica, that missed the AR6 WG1 literature cutoff date (31 January 2021).
https://www.nature.com/articles/s41586-021-03427-0
The authors of the Nature paper have also provided an accessible post at CarbonBrief, with some sobering warnings, including:
Included are graphs of rates and total amounts of sea level rise from Antarctica ice sheet loss for 1.5, 2, 3 and 4.5 °C global mean warming (relative to pre-industrial age) by 2100 scenarios. The caveats and warnings include:
https://www.carbonbrief.org/guest-post-overshooting-2c-risks-rapid-and-unstoppable-sea-level-rise-from-antarctica
Indeed, what would our descendants think we were doing?
As an example of the value of expert opinion: in 1957, the First International Geophysical Year, Athol Rafter was an invited speaker at a conference to talk about how radiocarbon dating had changed our understanding of the carbon cycle. He was cited in the Otago Daily Times as saying “the industrial effect would undoubtedly continue and if the existing percentage of carbon dioxide in the air was doubled, the average temperature would be raised sufficiently for the masses of ice to melt and raise the levels of the oceans by tens of feet, swamping many major cities.”
Its good that the latest IPCC report acknowledges the possibility of rapid sea level rise this century of about 2 metres. The IPCC reports seem well written overall, but its always been inexplicable to me why earlier IPCC reports did not include this possibility. Such rapid sea level rise has happened in the past at around 1.5 – 3 degrees c of warming, so if it happened then its hard to see why it couldn’t happen this century. It’s not as if Greenland and Antarctica are short of ice sheets. Such possibilities should be in bold text in the IPCC reports. on page one.
They mentioned the possibility … and the fact that they simply didn’t have enough “confidence” (IPCC definition applies) in the large range produced by the various (ice-sheet dynamics) computer models at that moment in time.
AR5 (2013), in the Executive Summary of Chapter 13, “Sea Level Change”, page 1140 :
“Abrupt and irreversible ice loss from a potential instability of marine-based sectors of the Antarctic ice sheet in response to climate forcing is possible, but current evidence and understanding is insufficient to make a quantitative assessment.”
Thank’s for the information, but your quoted statement doesn’t mention 2 metres by year 2100. It just talks about abrupt ice loss without quantifying it, so it could mean anything. And it appears to be buried away in the report rather than highlighted in the summary for policy makers.
It was also “buried” in note (b) under Table SPM.2 of AR5 (page 21) :
“Based on current understanding, only the collapse of marine-based sectors of the Antarctic ice sheet, if initiated, could cause global mean sea level to rise substantially above the likely range during the 21st century. There is medium confidence that this additional contribution would not exceed several tenths of a meter of sea level rise during the 21st century.”
If the IPCC had decided to take on board your desire for every single “possibility” with equal “confidence” to be included “in bold text in the IPCC reports, on page one” then “page one” of the new AR6 report would have had to be around 4000 (A4) pages long (using bold text would take up slightly more room than the actual 3948 pages).
RC: “If the IPCC had decided to take on board your desire for every single “possibility” with equal “confidence” to be included “in bold text in the IPCC reports, on page one” then “page one” of the new AR6 report would have had to be around 4000 (A4) pages long (using bold text would take up slightly more room than the actual 3948 pages
Except I didn’t SAY any of that bullshit. I said it might be useful to include the MAIN warming projections and sea level rise projections on page one in bold print. That would take no more than a couple of brief sentences.
I agree. This report is migrating towards the unvarnished truth. I love that it has a much less timid vibe from it.
A long-overdue and badly needed change.
“2m” is roughly equal to “a third of the Greenland ice-sheet (GIS) plus less than half of the WAIS”.
“7m” ~= “80+% of the GIS + most of the WAIS”.
Saying those two options are “about as likely” for a fixed scenario and the same end date is … “counter-intuitive” ?
Please could you elaborate on the above “extraordinary claim” (hat-tip : Carl Sagan).
Mark BLR,
The GIS has a volume of 2.85M cu km. The WAIS has a volume of 2.2M cu km. So combined that is 5.05M cu km. If the oceans have an area of 361M sq km, the additional volume of GIS+WAIS would result in 14m SLR.
And do bear in mind that, while there is uncertainty on how much of the GIS & WAIS will melt out and also how quickly, there are other contributions to SLR.
With such large projections of multi-century SLR as 7m, the odd metre or so from a combination of thermal expansion and land glaciers (beyond Greenland & Antarctica) may appear minor but it remains a significant contribution.. And perhaps you also overlook the ice on Antarctica beyond the WAIS which represents the mother-load and a potential 64m of SLR. (The consideration centered on WAIS is usually the result of its potential for rapid disintegration, something which is less relevant when considering multi-century SLR.)
And I hope this meets the standards of science-communication set by Carl Sagan.
1) In 2300 total SLR [ including ice-sheet melt and thermal expansion ] will be [ on the order of ] 2 metres.
2) In 2300 total SLR will be 7 metres
Conjecture : Under SSPn-x.y option 1 is “about as likely as” option 2.
My “non-scientist” reaction : “Huh ?!? … I mean, please can you ‘expand’ on that assertion …”
Mark BLR,
The quote from the OP runs “But with further unmitigated increase in emissions [ie SSP5-8.5], a disastrous 2 meter rise is about as likely as an utterly devastating 7 meter rise,” this by 2300AD.
These values represent a spread of uncertainty which is shown in the OP above with IPCC AR6 Figure SMP.8d&e. The long vertical pink stripe in fig SMP.8e represents the most likely SLR relative to 1900 under scenario SSP5-8.5 with the assumption that there is no “low-likelihood, high-impact ice sheet processes that cannot be ruled out.”
So with this assumption, the expected SLR by 2300AD under SSP5-8.5 is somewhere in the range +2m to +7m. The likelihood of it being greater than +7m is about 13%, which is roughly the same likelihood of it being less than +2m. Thus “as likely.”
What lies behind that large spread? I don’t know having not read up on it. But under SSP5-8.5 the Greenland Ice Sheet would be undergoing melt-down by 2300AD and presumably there would be similar melting in parts of Antarctica. So I would expect the big spread is due to difficulties in assessing the speed of Greenland’s melt and the scope of Antarctic melt.
I have long been of the view that projections of SLR that stop at 2100AD were pretty useless, so I am pleased the 2300AD projections are more prominent in AR6. I don’t see the big spread as anything surprising.
And the “low-likelihood, high-impact ice sheet processes that cannot be ruled out” delivering +15m SLR by 2300AD; that requires a massive energy input, enough to put AGW into reverse for a period, the sort of thing modelled by Hansen et al (2015).
These values represent a spread of uncertainty which is shown in the OP above with IPCC AR6 Figure SMP.8 …
… the expected SLR by 2300AD under SSP5-8.5 is somewhere in the range +2m to +7m. The likelihood of it being greater than +7m is about 13%, which is roughly the same likelihood of it being less than +2m. Thus “as likely.”
OK, my bad. I should have spotted that.
Looking back I think the sentence preceding the extract in my OP threw me off :
“At least with this Paris scenario and a good portion of sheer luck, we may get away with less than a meter rise.”
For SSP1-2.6, which corresponds to the “Paris scenario” for limiting warming to 2°C (?), panel (e) gives a lower limit of less than 0.5m, which (probably …) made me think internally something along the lines of “Stefan has stopped talking about the ‘Just look at the ranges expected by the year 2300 …’ case of the previous paragraph”.
– – – – –
PS : It also undermines his “So by what we are doing now in the next couple of decades we determine the rate and amount of sea-level rise for millennia to come …” message, as the differences in GHG emissions between SSP1-2.6 (or even SSP1-1.9) and SSP5-8.5 up to 2040 are relatively minor compared to emissions after that date.
According to panel (e) the “amount” of SLR as soon as 2300 [ “200 years” is a lot less than “millennia” … ] is highly dependant on the (cumulative) amount of emissions after 2040 under different scenarios.
I am curious about the projection for only a half a meter of SLR by 2100 if we cut emissions rapidly. At just the recent acceleration rate of ice sheet mass loss of 44 Gt/yr2 we get 78cm by 2100 from the ice sheets alone, thermal expansion and mountain glaciers another 20-30cm.
Which means we are already on pace for a meter by 2100. It seems a stretch to say in a warming world that the rate of acceleration would diminish.
SLR of “78 cm by 2100 from the ice sheets alone” would mean an average of one cm per year, which five times the current rate of 2 mm/yr. That acceleration seems inconsistent with the observed increases in SLR.
That acceleration seems inconsistent with the observed increases in SLR.
Don’t such accelerations only look inconsistent if we restrict our observations to the Holocene period, and the last century in particular.
The observations in Paleo-climatology should not be minimized, discounted or dismissed entirely. They tell a completely different story about rapid abrupt changes in SLR and global/regional temperatures.
One example being James White, Institute of Arctic and Alpine Research at the AGU https://youtu.be/hZdhPnsp4Is?t=800
There are many more examples like this urging caution about future assumptions.
another example is the research by Dr. Peter Ward, professor, Department of Earth and Space Sciences; professor, Department of Biology, University of Washington
https://www.ess.washington.edu/people/profile.php?pid=ward–peter
https://www.researchgate.net/profile/Peter-Ward-3
one example is this lecture What is the Worst That Global Warming Could Do?
https://www.youtube.com/watch?v=HP_Fvs48hb4
Can’t fit every thing known, every possibility and related to climate change into one AR.
The ice will not be melting in a linear fashion, it will be a parabolic curve.
Account for that and see how it seems to fit your expectations.
Thank you Stefan. I don’t envy your situation. Good luck.
Stephan,
Thank you for your summary of the IPCC AR6. I always enjoy your commentary on sea level rise. I used to live on a sailboat and sea level rise is important to me.
I think that the IPCC estimates of sea level rise are the low consensus. I.E. that the IPCC gives the low estimate as what a consensus of scientists think is the lowest possible low value and the high value as what a consensus thinks is the lowest possible high values. In your summaries you give a larger range of estimates. These include the consensus low values like the IPCC and the average assessments of experts which is substantially more than the consensus. You additionally give the high estimates which greatly exceed the IPCC reported values.
It seems that in AR6 that the writers are nodding to the higher values often proposed by some scientists, instead of just giving the low values.
I hope that you will have time to write a summary of what sea level scientists think on average and for extreme values again sometime. Unfortunately, it takes a lot of time to write good summaries.
Hansen in 2015 from (Ice Melt 2016) Interactive discussion
My present concern about group-think is not a criticism of IPCC (Intergovernmental Panel on
Climate Change), even though I strongly disagree with a very tiny subset of IPCC participants
who have controlled the message about the threat of sea level change. IPCC provides a crucial
service via generous unpaid efforts of volunteers including many of the best relevant scientists in
the world, who work for public well-being under intense scrutiny and often unfair criticism.
Most of the IPCC scientists, at least those that I have had contact with, share my concern that the
presentation of IPCC reports has led to under-appreciation of the threat of sea level rise. I
believe that the perspective we bring to the problem is welcomed by almost all IPCC scientists,
but we need to confront a small reticent subset. This task becomes feasible, in a more timely
way, because of the open interactive public ACPD review process, including Comments,
Reviews and Responses, all publicly available.
https://acp.copernicus.org/preprints/15/C8226/2015/acpd-15-C8226-2015-supplement.pdf
James Hansen is a treasure, even if I keep misspelling his name. Dr. Mann once said (approx) “we ignore Dr. Hansen at our peril”.
Hansen’s exponential melt hypothesis is scary and hard to accept, but the Jim with a floppy hat has been batting way over 900 for decades. Know anyone else over 500?
Dear Stefan – sorry – you completely misunderstood me.
My climate protection strategy would like to take the volume of 3.7mm SLR(1335km³) from the global rivers discharge when their water levels are sufficient(&clean) or even specially in flood events after rain- !!! to store it in soil moisture and groundwater over the land mass.
In principle a simple, seasonal storage of retained river water to adapt to droughts and floods.
In dry seasons, this water will be mainly evaporated from agriculture, but also the above mentioned
“amunas” of the old inca culture and water management are a perfect way to rewet forests & moors
This in turn ensures an increasing relative (and specific) humidity and additional cloud formation over land in a regional drought season.
After an average of 8.5 – 10 days in the atmosphere it will return – even with a relatively high probability – as precipitation over another land area. There will be a multiplier effect that increase together with soil moisture and evaporation rate (wet regions become wetter).
As a result, the water cycle over the land areas is intensified by ~ 1% and the increasing size of the annual mean cloud cover leads to a higher CRE, which I estimate to be at least ~ -0.2W m-2 / year.
A really cooling, additional radiative forcing, which, in my opinion, can more than compensate for the current annual radiative forcing caused by CO² .
A holistic, functioning climate protection strategy,
(stopping SLR AND global temperature rise & adaptation to droughts and floods)
which works alternatively and independently of the reduction in CO² emissions, which only promises to stop the temperatures perhaps after ~ 2070 (if we as humanity can reduce emissions immediately – which I personally do not believe)
In the latest IPCC report / WG1 Chapter 7.4.2.4.3, the positive feedback of the cloud cover on an atmosphere warmer by 1 ° C is given with
CRF = +0.42W m-2 ° C-1.
We are slowly but steadily losing not only areas of ice and snow albedo, but also the clouds albedo due to decreasing global mean cloud cover an higher lapse rate.
The cooling CRE with ~-19W m-2 (chapter 7.2.1. in the same report) should decrease accordingly.
The slower warming of the oceans means that there has not been enough moisture evaporated into – and then held in – the air above the oceans to keep pace with the rising temperatures over land. This means that the air is not as saturated as it was and – as the chart below shows – relative humidity has decreased, desertification is spreading rapidly mainly caused by human activities.
Dryness is a temperature driver and cloud killer.
https://www.carbonbrief.org/wp-content/uploads/2020/11/Global-time-series-of-annual-average-relative-humidity-for-the-land-ocean-and-global-average-relative-to-1981-2010.jpg
That is why I (as an artist) think it`s a good idea to create “artificial” clouds by artificial irrigation retained from the superfluous sea water. – macias
How can one claim sea level rise is driven by warming produced by CO2 emissions when that rise began at a time prior to 1880, when CO2 emissions were negligible and global temperatures were relatively stable? how can one claim sea level rise is driven by warming produced by CO2 emissions when the rate of rise has remained relatively stable from 1880 through the present, while both global land and sea temperatures have risen and fallen at varying rates during this same period? how can one reconcile the observations reported in Fasullo et al., acknowledging that sea level rise has actually decelerated during the satellite era, with the notion, claimed by the IPCC, that the rise has accelerated?
From Fasullo et al., “Is the detection of accelerated sea level rise imminent?” “Global mean sea level rise estimated from satellite altimetry provides a strong constraint on climate variability and change and is expected to accelerate as the rates of both ocean warming and cryospheric mass loss increase over time. In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era.” ( https://www.nature.com/articles/srep31245 )
If you read and understood the paper, rather than skimmed for sentences that appear to support your preconceived views, you would realise the authors are actually providing a rebuttal to your stance.
I am genuinely unable to tell if you are so stupid that you think the paper supports your position, or so cynical that you are working on the pemise most people won’t bother following the link. Either way, you have shown that your reputation as a troll is well deserved.
Yes, an answer to V’s supposed concerns is given in the sentences that immediately follow his quote from the abstract, to wit:
Also, it doesn’t take much digging to put V’s premises in doubt. Specifically, he speaks of “a time prior to 1880, when CO2 emissions were negligible and global temperatures were relatively stable”.
First of all, temperatures were probably generally warming slightly from ca. 1650 (Fig O5.c, here):
https://www.nap.edu/read/11676/chapter/3#17
(But no doubt there is more recent work.)
Second, CO was rising from at least 1850 and probably earlier, per this analysis at least:
https://www.semanticscholar.org/paper/Atmospheric-CO2-fluctuations-during-the-last-by-of-Kouwenberg-Wagner/920d043e2fff8dd0610fbcf39e7a1c2a2332582c/figure/2
But it’s in broad agreement with the Scripps version of the merged ice-core + instrumental data, which is much less ‘noisy’ and shows a pretty persistent increasing trend from 1750 or so:
https://scrippsco2.ucsd.edu/assets/graphics/png/merged_ice_core_record.png
Thirdly, per Jevrejeva et al (2014) sea level had been dropping, but reversed course around 1850-60 (Fig. 8, here):
https://core.ac.uk/reader/19530792
So, to sum up, these papers suggest the following sequence:
1) Temperatures (generally) rise as the LIA wanes from 1650 on. (There’s a large and sudden dip in the early 19th century that appears to be associated with the famous Tambora eruption in 1815 and possibly the suspected ‘mystery eruption’ of 1808, among other, lesser volcanic events.)
2) CO2 shows an accelerating rise from the early 19th century.
3) Sea levels fall during the first part of the 19th century, presumably in response to the volcanically-induced cooling mentioned above, but reverse around mid-century, initiating a still ongoing rise.
With these ice sheet parameters, what sea level rise occurs under SSP3-7? And does anyone know the values under RCP6.0?
maybe im missing something , but I have looked at hundreds of NOAA tide gauge graphs and none of them show any acceleration in sea level rise . why isn’t that the basis for sea level rise predictions ?
Because sea-level rise is global, and tidal gauges are local. There are many factors in addition to sea level that determine tidal gauge readings
I have looked at 4 NOAA tide gauge graphs and 50% show marked acceleration. So yes, you are missing something. Maybe you live in a part of the USA where regional isostatic or tectonic responses dominate and have looked only at local stations? But in any case the purpose of science and modelling is to make the most accurate predictions possible, and there is enough evidence of acceleration in the factors forcing SLR to assume that linear models wouldn’t provide a ‘best’ forecast.
Yes, you’re missing something.
Try reading the posts that show up from this search at Tamino’s:
https://tamino.wordpress.com/?s=sea+level+acceleration
Kevin McKinney: Yes, an answer to V’s supposed concerns is given in the sentences that immediately follow his quote from the abstract, to wit:
“Here, a combined analysis of altimeter data and specially designed climate model simulations shows the 1991 eruption of Mt Pinatubo to likely have masked the acceleration that would have otherwise occurred. . . ”
V: You’ve apparently missed my response to a similar assertion, posted on the Unforced Variations thread. When accused of not reading the whole paper, I responded, in part, as follows:
“I certainly did read the whole paper. However, what’s important to me, as it should be to any real scientist, is the data itself, not an ad hoc hypothesis which remains to be proven.”
“[The authors’ report regarding a deceleration of sea level rise is based on] actual data, the [Pinatubo reference is] a hypothesis formulated in an attempt to explain why the data fails to support the expected result. As far as I’m concerned the data itself should take precedence over any attempt to massage it.”
KM: Also, it doesn’t take much digging to put V’s premises in doubt. Specifically, he speaks of “a time prior to 1880, when CO2 emissions were negligible and global temperatures were relatively stable”.
First of all, temperatures were probably generally warming slightly from ca. 1650 (Fig O5.c, here):
https://www.nap.edu/read/11676/chapter/3#17
(But no doubt there is more recent work.)
V: According to this graph, based on evidence compiled by Hadley, NASA and NOAA, we see little to no sign of global temperature rise from 1850 through 1910, a period of 60 years: https://royalsociety.org/-/media/Royal_Society_Content/policy/projects/climate-evidence-causes/fig1a-large.jpg?la=en-GB&hash=14D5026DA62ADB4652A18BA13758F84A
Yet sea levels began to rise steadily from at least 1880 and probably sooner: https://www.globalchange.gov/sites/globalchange/files/seal_level_rise_052021.png
If this evidence is correct, then it’s difficult to see how sea level rise could have been a response to a rise in global temperatures that began at least 30 years later. It’s difficult also to understand how sea levels have continued to rise at a relatively steady pace while temperatures cooled or remained steady for a period of 40 years during the mid 20th century, not to mention the 21st century “hiatus.”
KM: Second, CO was rising from at least 1850 and probably earlier, per this analysis at least:
https://www.semanticscholar.org/paper/Atmospheric-CO2-fluctuations-during-the-last-by-of-Kouwenberg-Wagner/920d043e2fff8dd0610fbcf39e7a1c2a2332582c/figure/2
V: Well pardon me for being so “stupid” Kevin, but CO2 levels in themselves can have no direct influence on sea level.
KM: Thirdly, per Jevrejeva et al (2014) sea level had been dropping, but reversed course around 1850-60
V: Yes, of course. But as illustrated by the graph I’ve referenced, global temps didn’t begin to rise until ca. 1910. CO2 levels are beside the point as far as sea level rise is concerned unless it can be shown that they affected the temperature, which, theoretically, should have affected sea level. If they rose and the temperature failed to rise then it’s impossible to establish the necessary link. Duh.
I have now read a few more pages of the IPCC AR6 that continues to blame manmade CO2 and other gases for global warming and severe weather events.
I am astounded, flabbergasted, and greatly disturbed by the apparent, blatant, misinterpretation of the facts, of the actual data. In the Summary for Policymakers, at Section A.3.4 on page 41 of the IPCC AR6, the Report states, “It is likely that the global proportion of major (Category 3-5)tropical cyclone occurrence has increased over the last four decades …”. The Report then expands this statement throughout the Report by stating that the number and severity of such cyclones will continue to increase in the future because of manmade impacts.
The actual, real, data contradicts the IPCC statement. I have researched data from the Australian Bureau of Meteorology for the Australian region and from Dr Ryan Maue for the global data, both posted by me on my Facebook page on 24 July 2021 (copied below). Both sets of data show decreasing frequency and intensity of tropical cyclones over the last five decades.
I have just now double-checked with the data base of the US National Oceanic and Atmospheric Administration (NOAA). The image here is on its website at https://www.ncdc.noaa.gov/sotc/tropical-cyclones/202013… under the selection ‘Global’. Again, there is no support for the IPCC statement.
This evidence about tropical cyclones is enough to indicate to me that the IPCC continues to be ruled by its chosen ideology, not by science. Seemingly, it has dug a hole too deep for it to be able to escape, to admit its errors.
fwiw your cyclone occurrence reference is on Page 12 of the SPM, not page 41.
Please consoider the following observations:
1) tropical cyclone occurrence has increased over the last four decade
Response: the NOAA ref only goes back 30 years, recent occurrences post 2012 seem higher on the graph.
2) Section A.3.4 on page 12 goes onto say: “There is low confidence in long-term (multi-decadal to centennial) trends in the frequency of all-category tropical cyclones.”
3) no links to facebook refs
4) looking at Dr Maue data from http://climatlas.com/tropical/global_major_freq.png
I see a general increase in major hurricane frequency (aka cyclone occurrence) per year towards the right side of the graph. This seems to fit the general point being made in the SPM ref. Yes?
5) Regional data from Australia is not global data, which the SPM refs. specifically.
6) In the SPM page 12 notice REFS to {8.2, 11.7, Box TS.10 and {11.6, 11.7, 11.8, 12.3, 12.4, TS.2.6, Table TS.5, TS.10} Box
– go here
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_08.pdf
and here
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_11.pdf
PLUS HERE the TECHNICAL SUMMARY
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf
– to track down Sub-Headings, and Boxes, Tables, Data, Explanations and especially Paper/Study Citations etc. that relate back to the very short summarised SPM comments.
For example use the web-browser function *find in page* the phrase “Tropical Cyclone” which appears hundreds of times.
IOW there one can find “The actual, real, data…. “ upon which the AR6 says it is relying upon.
It is very complicated and not easy to follow. And is far above my Pay Grade.
But I can place directional signs reasonably well. But others here could do it far better than I ever could, if they wished to, had the time, and interest.
So good luck with that.
Hey, maybe my help / suggestions is as good as it gets? :)
@Lindsay Hackett I’m afraid that the NOAA image you referenced doesn’t support your assertion because the IPCC statement specified the last four decades and the relevant graph only shows the last 30 years.
Sure, Dr Ryan Maue:
Gosh, I’m convinced. Anyone hired by the former president must be really good with a sharpie.
I’m as liberal as they get (lived in Pelosi’s district quite happily for years). Ryan Maue is an honest, hard working guy. He may be wrong. He may be pissed at all the guff he’s taken from climate activists over the years (and he’s taken a lot). But he’s an honest, hard working meteorologist.
Thomas:
“I’m as liberal as they get (lived in Pelosi’s district quite happily for years).”
With credentials like that, who could doubt you? It’s not as if it sounds like what someone in the right-wing bubble would say because they are so immersed in Fox-Talk that they don’t realize what an obvious tell it is….
Tom,
Someone who is hired to propagate Cato’s bespoke AGW-denialism, or Trump’s, might be considered “hard working”. IMHO, however, they cannot be considered honest, because AGW-denialism is fundamentally dishonest.
Worse than “fundamentally dishonest”. INTENTIONALLY dishonest for political and personal gain. That, in many people’s books is pretty much a definition of at least corruption and well along the dimension labeled “Evil”.
Yes, and professional disinformers who achieve self-awareness are open about their regrets. Jerry Taylor, a former staff director for the energy and environment task force at the American Legislative Exchange Council (ALEC) and Vice President for Development at the Cato Institute, says (my bold):
I became increasingly uncomfortable with my position at the Cato Institute …. I decided it was time to liberate myself from the constraints of institutional orthodoxy and to re-engage with libertarian rhetoric not just on climate but on a whole host of issues.
…
I know conservative Republicans very well …. I have a good relationship with them, and I can sit there with credibility and say: Look, I used to believe exactly what you believe. Hell, I wrote your talking points.
I wish earlier in my career I had done the due diligence with the arguments that I was tracking in. I do regret that, so that’s something that I feel I have a lot to make up for.
IMHO, Taylor speaks persuasively, and I too wish he had recognized the Libertarian motive for AGW-denial from the start. Is he condemned for his past bad acts? Those of us who’ve been through our own gate of self-discovery may be inclined to absolve him, saying “go, and sin no more”. Especially since he’s now an effective counter to those Republican talking points!
Mal Adapted,
When a Republican waves a flag of truce, the only thing it means is that they’re running short of ammo. If they had any shame, they wouldn’t be Republicans.
Lindsay, your belief that your ability to evaluate complex data is superior to that of the expert climate scientists in Working Group 1, and your willingness to trust the opinion of a demonstrated pseudo-skeptic (see zebra’s comment) over the consensus of his scientific peers, suggests you are afflicted with the Dunning-Kruger Effect. Your claim that WG1 is motivated by ideology, advertises your own ideology. As my go-to ex-Libertarian Jerry Taylor observes, “Ideology = motivated cognition”. You’ll find little support here, I’m afraid.
“By how much? That depends on our emissions and is shown in the following figure. The take-away message is: for high emissions we’d likely get close to a meter, sticking to the Paris agreement would cut that down to half a meter”. Professor Stefan Rahmstorf
Just who is one to believe on this issue? Professor Stefan Rahmstorf or Steve Nerem, who is the leader of NASA’s Sea Level Change team. His project, Observation-Driven Projections of Future Regional Sea Level Change, focuses on using NASA satellite and in situ observations and climate modeling to estimate future regional sea level change.
Dr. Steve Nerem said this:
“In the last 50 years sea level has risen at an estimated rate of .18 centimeters (.07 inches) per year, but in the last 12 years that rate appears to be .3 centimeters (.12 inches) per year. Roughly half of that is attributed to the expansion of ocean water as it has increased in temperature, with the rest coming from other sources, “said Dr. Steve Nerem, associate professor, Colorado Center for Astrodynamics Research, University of Colorado, Boulder.
https://mynasadata.larc.nasa.gov/stem-career-connections/meet-dr-steve-nerem-sea-level-scientist
Not sure why you think that there’s a conflict between those two statements. Dr. Rahmstorf was describing an end-of-century scenario; Dr. Nerem about SLR *to date.* Very different things.
If you are somehow assuming that Dr. Nerem’s 0.3 cm/yr is a maximum or physical limit of some sort, you are sadly mistaken. The acceleration so far–0.18 cm/yr to 0.3, per Nerem–is not the end of the acceleration, especially if we keep raising atmospheric CO2.
Churchill, Canada is relatively close to Greenland where you must want me to believe that the water to make the seas rise is coming from; so, why does the Relative Sea Level Trend for Churchill, Canada show a
a change of -3.02 feet in 100 years.?
Relative Sea Level Trend
970-141 Churchill, Canada
• EXPORT TO TEXT | EXPORT TO CSV | SAVE IMAGE
The relative sea level trend is -9.21 millimeters/year with a 95% confidence
interval of +/- 0.49 mm/yr based on monthly mean sea level data from
1940 to 2018 which is equivalent to a change of -3.02 feet in 100 years.
https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?id=970-141
Raw data presented without a bit of context along with a nearly audible “Aha, gotcha!” is an old–classic even–propaganda trick. Works as propaganda in the correct outlets but doesn’t really fly in a science discussion.
So. Well for starters Mazzotti et. al, 2011 (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011GL049846) measured the land uplift in Churchill at 1.1 cm/yr. (There was this little thing called the Laurentide ice sheet that was around 2 miles thick in the area not so long ago.) On that score alone that would imply that sea level rise in the area is about .2 cm/yr . But things are more complicated than than that. There are other issues as well. These are reported and discussed by Richard D. Ray in “On Measurements of the Tide at Churchill, Hudson Bay” 2015 (https://www.tandfonline.com/doi/full/10.1080/07055900.2016.1139540). Then of course there are gravity effects mass loss in Greenland to consider that neither of these look into.
Both are open access, so you can read fully, not just the abstract, and possibly even learn.
Oh, Churchill is about 3000km from Cape Farewell. That is a goodly portion of the Earth’s 40,000km circumference and not exactly “close”. You remind me of a Texan student who once told me that Maine and Minnesota were right next to each other in US. Upon inquiry–Montana and Michigan too I found– it turned out she had a single “North” dimension in her brain and lumped anything US-northish into the place.
JDS says : “Churchill, Canada is relatively close to Greenland where you must want me to believe that the water to make the seas rise is coming from; so, why does the Relative Sea Level Trend for Churchill, Canada show a a change of -3.02 feet in 100 years.?”
Here is the reason. Firstly Churchill is a town in northern Manitoba, Canada, on the west shore of Hudson Bay. According to published research “Hudson Bay is a shallow bay in northern Canada surrounded by coastal communities and ecosystems that are vulnerable to future sea level change. The bay was ice covered 21,000 years ago, and sea level is currently falling there due to ongoing land uplift since the ice retreated. It is unclear if this trend will continue as the Greenland and Antarctic ice sheets melt, contributing to spatially variable sea level changes. ”
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JC015104
So clearly there are physical reasons why some places have falling sea levels, and that this doesn’t mean sea level isn’t rising in most places, and that AGW isn’t causing sea level rise. Please put JDS in the borehole.
“Relative Sea Level” is relative to the level of the land. The land around Hudson Bay, including Churchill, is still rebounding rapidly. The great weight of the ice sheet over eastern Canada during the last ice age caused the land to sag in the region, as rock was displaced in the mantle where it is somewhat plastic. As you might guess, this is a slow process, taking many thousands of years to reach equilibrium. Now, with the weight of the ice off, the mantle rock is still pushing back into the region, and raising the land level overall. On the other hand, the extra rock is retreating well to the south, and sea level rises are higher than the global average.
John Pollack says; “The great weight of the ice sheet over eastern Canada during the last ice age caused the land to sag in the region, as rock was displaced in the mantle where it is somewhat plastic.” For obvious reason, Professor Stefan Rahmstorf, will never allow this information to be seen by the ones who post their nonsense on this site.
https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?id=999-001
Yet ANOTHER context-free, cherry-picked factoid from the troll!
Hint: There was a lot of ice in Antarctica during the ice age as well. Plus the mantle is quite soft in many areas of the W. Antarctic due to vulcanism.
Open access to a Science article on the subject at (actually) nearby Amundsen Sea discussing uplift in the area: https://www.researchgate.net/publication/325920708_Observed_rapid_bedrock_uplift_in_Amundsen_Sea_Embayment_promotes_ice-sheet_stability
I am sure that in grade school geography they would have mentioned isostatic rebound? The weight of ice on northern Canada was sufficient to depress the land surface by several hundred metres. When the ice melted the land began to rise. So it is perfectly common, and not at all surprising, to see relative sea levels fall in areas that were once glaciated.
Duh! Because Churchill, Manitoba was under thick ice sheets relatively recently in geological time, and is still rising, relieved of that massive overburden.
It’s called “isostatic rebound”.
https://www.dmr.nd.gov/ndgs/ndnotes/Rebound/Glacial%20Rebound.htm
While estimates discussed here are averages, the SSP3.7 projections also feature values in excess of 1.4 meters by 2100, for instance in the Gulf of Mexico. https://sealevel.nasa.gov/ipcc-ar6-sea-level-projection-tool
See also https://www.realclimate.org/index.php/archives/2021/10/unforced-variations-oct-2021/#comment-796401