Greenland ice sheet climate disequilibrium and committed (274mm) sea-level rise | Hacker News Reader

Greenland ice sheet climate disequilibrium and committed (274mm) sea-level rise

nature.com

80 pointsKaibeezy65 comments

How much wiggle room is there in the conclusion that this is level of sea level rise is going to happen “regardless of twenty-first-century climate pathways”?

For example, and setting aside feasibility, if carbon dioxide levels were reduced back down to pre-industrial levels, would that amount of sea level rise still be locked in? Or would the ice stop melting and even gradually re-freeze?

It depends on who you ask, but I've seen estimates that suggest at least 10m of sea level rise is already "priced in", so to speak.

In the climate crisis discussion communities there's a saying that things are happening "faster than expected", which also applies to the fact that most of the accepted climate models are much more conservative than they should be. The IPCC models (for example) largely ignore tipping points and methane emissions, and their contribution to the exponential rate of increase in climate change.

At this point we're not going to do what's needed to make things less bad (i.e., keeping the carbon in the ground) so my suggestion is to plan for the worst and hope for the best.

Is there a map somewhere that simulates various coastline changes based on sea level rise?

Ex: the 10 meters mentioned above

Good question, there are several, but the one I've played with is this tool from the NOAA: https://coast.noaa.gov/slr/

I've used this tool to inform my decisions with regard to planning for my climate mitigation strategy.

A better question would be, is there a map that shows the extended inland reach of the more violent storms that we will get with a warmer atmosphere?

Planning on the basis of the ocean being a mill-pond won't go very well.

Both are important. New York City becoming an oyster bed is a catastrophic migration crisis waiting to happen.

It all depends on how long you want to wait. Last time CO2 levels were as high as today was the mid-Pliocene, with temperatures estimated 2-3C higher than today and sea levels estimated 16 meters higher than today. A slow steady melt of Greenland and West Antarctica would take hundreds or thousands of years:

> "We acknowledge that this sea-level rise would not happen overnight. It would take hundreds to thousands of years to melt such large amounts of ice. Another important finding of our study is that, under temperatures ~4 °C higher than pre-industrial values and elevated CO2 during Pliocene Climatic Optimum, the global mean sea level reached 23.5 m (with an uncertainty range of 9.0-26.7 m) higher than present. This indicates that significantly more ice will melt if temperatures stabilize at this level. This estimate can serve as a target for future ice sheet model calibrations."

https://thesciencebreaker.org/breaks/earth-space/pliocene-se...

This particular article seems to point to 2-3 meter sea level rise by 2100, which looks to be on the higher end of what NOAA puts on their website as the 'observed trend', which looks more like a 1-3 ft sea level rise estimate by 2100. According to their graphics, by 2030 or 2040 it should be more clear which way things are really going, real-world evidence wise.

https://www.climate.gov/news-features/understanding-climate/...

While I can see the logic behind how long it would take to melt all this ice, what about the risk that it will suddenly (in the long view) slide off and start floating around? That will raise sea level by the same amount without needing to melt.

It's worth noting, the last time there was this much CO2 in the atmosphere (>400ppm), sea levels were significantly higher. Estimates are all over the map, but most of them put global sea at least 10m above our current levels.

A few sources:

https://www.noaa.gov/news-release/carbon-dioxide-now-more-th...

https://www.nature.com/articles/s41586-019-1543-2?proof=t

https://www.science.org/doi/10.1126/science.1233137

https://royalsocietypublishing.org/doi/10.1098/rsta.2012.029...

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200...

EDIT: Fix words.

I mean, if you waved a magic wand and CO2 levels were back at 280ppm? Maybe you'd expect sea levels to stabilize at their current levels?

There's at least four pieces of inertia here that make preventing sea-level rise hard absent such a magic wand:

1. We're not at equilibrium temperature for our current CO2 levels; if you stopped generating CO2 at an industrial scale and we kept the atmosphere to 420ppm CO2, you'd still expect to see the mean global temperature rise.

2. Even absent increases in CO2, the ice that continues to melt until the new equilibrium is reached decreases the reflectivity of the Earth.

3. The ice that's already melted has decreased the weight on the continental places upon which it rested; the plates are still rebounding, and it can be easier for ice to fall off as they raise.

4. Once we reverse course and ice is no longer melting, it will take a long time for the ice to re-form and the water to be removed from the oceans, lowering sea-levels (and storm surges). Some of the places the ice is disappearing from is effectively a desert, with very low rates of precipitation.

5. The ocean has warmed, and it would take time to cool down again. That will continue to affect Greenland for a century or more.

Oh yeah, a goodly portion of the sea level rise is thermal expansion, isn't it?

> We're not at equilibrium temperature for our current CO2 levels; if you stopped generating CO2 at an industrial scale and we kept the atmosphere to 420ppm CO2, you'd still expect to see the mean global temperature rise

Exactly.

We're really in uncharted territory. The IPCC et al can show the results of models etc but nobody really knows how bad things are going to get, even if a miracle happened and we reached zero emissions today.

Last time the Earth was above 400ppm of CO2 was during the Pliocene Epoch (2-5 million years ago). Temps were 2-3ºC higher and sea level was about 30 feet higher. We're now at about 420ppm and rising.

>How much wiggle room is there in the conclusion that this is level of sea level rise is going to happen “regardless of twenty-first-century climate pathways”?

No wiggle room.

https://www.e-education.psu.edu/earth107/node/1496

20,000 years ago we had the last glacial maximum aka ice age. Water levels increased 130 metres since. Your cities like "atlantis" were coastal cities gobbled up by rising water. Noah's ark was just this. When graphs are showing sea level rise over the last 200 years, they are illegtimately trying to imply the industrial age caused it. It has been a process that started 20,000 years ago. In fact, sea level rise hasn't changed at all during industrial age. Same rate nonstop.

So it's not really part of the 'excess carbon' problem but rather a natural process we cant stop.

Therefore you better not be a rich person living on the coast.

Global trend is higher population in cities. So the actual big scale problem is placing cities on shores, in historical flood zones, not minding historical records & ancestral wisdom, then blaming climate for own short-sightedness. Not changes in general but the inertia & radical fast-fixes with ability to create new problems never before existing.

Humanity can adapt to anything. But building non-durable way, consuming wastefully, getting away from nature & living in virtual "civilised" bubbles far from material reality is only asking for troubles when Earth & Sun reminds who truly rules here..

http://polarportal.dk/groenland/iskappens-overflade/#c7242

Here you can follow the accumulation - Greenland has a net accumulation of snow/ice every year - over the last months and years. This year has seen less melt/more accumulation than the average for the last 40 years. Go back to 2016 for the last period of high melt/low accumulation, 2010-2012 saw the highest melt/lowest accumulation in the last ~70 years. At this moment the runoff of water from Greenland is comparable to that in the 1950's [1 - select 'Run off' on polarportal.dk to get this graph].

As to why the authors suggest the application of the highest melt in 70 years - which, as is shown by the graph, clearly stands out from the rest - 'in perpetuity' I'll leave up to the readers to decide.

[1] http://polarportal.dk/fileadmin/_processed_/csm_tasersuaq_ce...

Just to ensure nobody is fooled by this idiot, the SMB clearly states: "It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater. "

English version at http://polarportal.dk/en/greenland/surface-conditions/

Nice snub. Realise why those glaciers calve off icebergs - it is related to the flow of the glacier which is in turn a function of the amount of mass accumulated. As to those icebergs 'melting in contact with warm seawater' I can add that this is what icebergs do when they come into contact with seawater - they melt. Did you think they just stayed around forever to accumulate somewhere in a giant iceberg pileup? Nope, they melt and return the water to the ocean from where it eventually evaporates for a new cycle.

So before you call someone an 'idiot' I'd suggest you read up on the subject so as to make yourself look like less of one.

> The high-melt year of 2012 applied in perpetuity yields an ice loss commitment of 782 ± 135 mm SLR, serving as an ominous prognosis for Greenland’s trajectory through a twenty-first century of warming.

It's been a decade now and we haven't had any years really even close to 2012 in terms of minimum sea ice extent.

That’s false. Compare 1980 was 7.54 million, 2000 was 5.98 million, 2012 was 3.39 million, and 2020 was 3.82 million. https://climate.nasa.gov/vital-signs/arctic-sea-ice/

It is noisy data with few data points, so yes 2013 was 5.05 million but both the peaks and troughs are dropping.

that's over a 10% difference between 2020 & 2012, and it was the only year under 4 million, so my point still stands.

What is the point that still stands, exactly? There are peaks and troughs with a clear downward trend. If your point is that in that trend, some years over 10 year periods look similar, then you would be correct. But in making that point, you risk drawing the wrong conclusion from the data.

My point was that you shouldn't base a prognosis on a melt year that has happened once in a 40 year record, when it so far has been an anomaly.

data that I don't like is an abberation. data that I do like is proof!

that's nonsense. It hasn't happened again in a decade despite the last 5 years being some of the warmest on record, and there was a cyclone that ripped through arctic dispersing sea ice in early August that year. It's clearly an anomaly.

Being 2 standard deviations from the trend line is hardly an anomaly, just expected variance over a sample that size.

0.05 * 40 = 2.

Your definition of "really even close" is either absurd or you don't much care about the data nearly as much as the point you wanted to make.

Do you understand the point I'm trying to make? Because it doesn't really seem like it.

The 20 years leading up to 2004 the average was > 6 million square km. 2012 was 3.4. 2020 was 3.8. In the context of the previous average, that does seem close. What was your point?

My point was don't base a prognosis on an anomaly, but clearly everyone has taken it as something else entirely, based on the tones of the replies.

2012 isn’t an anomaly just normal variation, by area it’s the current low point by volume it isn’t.

I gotta say that it really looks like you're using motivating reasoning here. That graph plainly shows the direction, and it's not upwards or even stable.

A different visualization of the same data here, https://nsidc.org/arcticseaicenews/charctic-interactive-sea-...

I guess it depends how you define "close".

All years from the last decade look pretty close to me:

http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger...

See the PIOMAS project data:

http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volum...

I'm not sure how they got data going to the end of 2022? This also doesn't show a low point in 2012, so can't be what they're basing it on.

The red line (2022 data) stops at July, and while it's hard to tell exactly it looks to me like the diamond line (not sure what to call that color) for 2012 is the lowest line between August and October.

Ahhh i see it now, 2 red lines with pluses. I was looking at 2015. That makes wayyy more sense.

There are multiple years show.

The PIOMAS project has been collecting data with a satellite over the Arctic since 1979 IIRC.

The PIOMAS project is just a calculation based on other satellite observations, the model has been verified using 2 different satellites, one launched in 2003, and another in 2010. [0] Their paper on the model was released in 2003. My mistake was that I was looking at the 2015 line, because the color and design looks exactly like 2022.

[0] - https://en.wikipedia.org/wiki/Measurement_of_sea_ice#Sea_ice...

If you read that part in Wikipedia again you will see those dates are about the ICESat and Cryosat projects (that are now contributing to PIOMAS).

But PIOMAS has been collecting Arctic ice data since 1979.

For example:

http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger...

If you don't believe, download the PIOMAS data and check it yourself.

https://psc.apl.uw.edu/research/projects/arctic-sea-ice-volu...

I understand that they've been using data collected by satellites since 1979, but they didn't even come up with the model until 99, and released the paper on it in 2003, so the model was used retrospectively on data previously collected, not specifically collected for that project.

You can see that in your own link.

Extent tends to be a noisier signal that total ice mass.

I agree entirely, but it seems that they're basing their calculation off of extent rather than volume, because 2012 isn't the low point volume.

The West Antarctic Ice Sheet is much bigger a problem, and is following suite.

Source: https://www.nationalgeographic.com/environment/article/west-...

No mention to this small detail in that article: https://www.sciencedaily.com/releases/2020/12/201207102105.h...

Greenland Ice Melt Today http://nsidc.org/greenland-today/

if we start mass desalination (just assume we can), would that have any impact on sea levels? what if it were on a scale of irrigating deserts, etc?

At some point all excess water flows to the sea or evaporates into the atmosphere, where it turns to rain and then to the sea. So sea (ocean, really) levels do not change.

I mean at a fundamental level if you can take out the same amount of water(or more) as is melting, yes. But I think from the shear size of the problem, most people have a hard time reasoning about just how much water we are talking about.

There was a proposal to just pump seawater inland to the center of Antarctica. That would consume a monumental amount of energy, of course, but is technologically feasible.

Assuming that the center of Antarctica is still frozen after increasing energy consumption that much…

Wind or tidal power would be zero emissions and the most practical. You can use them directly without electrical conversion.

Considering manufacturing, nothing is emissions free. Sea waves energy turbines are well engineered & safe for fauna not affecting water oxygenation unlike the other thing.

Surface area of the oceans is 361e6 km², let’s say each of 7e9 people using 200 liters of water daily (obviously way more in the developed world but a lot of the world still living in huts), 1e8 dm² in km² (since liters are dm³) you have

(7e9 * 200) / (361e6 * 1e8) = 0.00003878116 decimeters of sealevel/day = basically imperceptible

The only brute force solution to reducing sea level rise that might be reasonable is to pump sea water into a dammed desert basin, e.g. Sahara or Australia.

The mass of water you would have to displace to handle what's melting off Greenland and Antarctica on top of thermal expansion of the oceans due to hotter water[0] would make this the biggest mega project humanity has ever attempted, by several orders of magnitude.

From a purely economic and technical perspective, it probably makes drastically more sense to just gradually abandon parts of our coastal cities as they submerge and retreat inland.

[0] - https://sealevel.nasa.gov/understanding-sea-level/global-sea...

Building a canal from that makes the Qattara Depression in Egypt a part of the Mediterranean would lower ocean levels by 4cm.

Seems worth doing just to bring life to the desert.

> Seems worth doing just to bring life to the desert.

Possibly. But you also have to consider the knock on effects of making such a drastic change to Earth's ecosystem.

Life to the desert could lead to death to the rainforest...

https://www.nasa.gov/content/goddard/nasa-satellite-reveals-...

Neil Stephenson's Termination Shock is a great narrative about how any kind of active attempt to address climate change chaos could lead to near hopeless geopolitical complexities.

You can always make a "you never know" argument, and you'll always be right.

I'm really tired of the "let's not do anything, just to be safe" attitude. Systemic inaction has a huge cost of its own.

When did I say we shouldn't do anything?

You should read Termination Shock. It makes a great case for why doing things is hard, but also worth it. Sometimes it just takes someone with sufficient power and courage to do what's right and accept the hatred and violence that will inevitably come their way for disrupting the establishment order.

But sadly, most modern people are too weak to stick their necks out like this.

You didn't say that, to be fair.

I think it's a serious problem of this era, and your post sounded like those arguments to me.

Let's do nothing is more reasonable comparing to do something now not minding consequences. This overreaction "2019 syndrome" brought grave results to humanity. If sea rise is result of warming, flooding deserts is opposite to role of deserts which reflect heat back to space through vapour-free sky. Logically there is more sense in deserting bigger part of world to increase this process what global depopulation promoters would also love. But problem with global solutions is they are assuming totalitarian centralised global Earth management which is undemocratic, political & tends to promote particular big corporate interests not common good. It replaces scientific discourse & convincing through arguments, building organic non-obligatory consensus with censoring free speech & access to raw data, political pressure, coercing tactics building unhealthy psychosis in people, through emotions killing reason and objective truth. That's not the world & humanity we want to save. I don't understand why we don't paint all roofs white yet. It's something anybody can do to help reflect heat if he believes warming is a problem (not historically low oxygen level in atmosphere earth's life breaths with or possibility of freezing people & soils to death..).

I can't even imagine how it would impact sea levels at all.

A mechanical thing that would work is digging up material from the seafloor and dumping it on land.

The costs have to be astronomical though, aside from environmental considerations.

In The Ministry for the Future, which is speculative fiction about attempts to mitigate climate change and its impacts,

one small sub-plot is the idea of seeking to freeze the motion of ice sheets and glaciers, by pumping the water serving to lubricate their motion to the surface to refreeze. Not exactly the same idea, but similarly ambitious.

If it's instead of pumping out inland aquifers, yes.

Sea level rise would be reduced by maybe a quarter of a millimeter per year.

This is nonsense. Climate change isn't science because it's not falsifiable. Next.

Reply on news.ycombinator.com