It seems the level of sea level rise must be nonlinear and we'd be expected sea level rise more in the range of 50 m rather than 2 feet

[thidmir]

Most climate change forecasts predict sea level rise in the range of 3 feet by the end of the century if greenhouse gas emissions are not stopped, but if we think we are in the Ice age, and sea level rise during an ice age cycle tends to be more like 50 - 100 m for the same range of global temperature increase, it should be the same for abut 5 degrees Celsius of global temperature increase. The warming is a lot faster so its difficult to compare, but so far the global temperature increase has only been about 1.6 degrees resulting in only a feet or so of sea level rise, but it seems it getting dangerously high. What do you think? 

 

This is the temperature variation during the ice ages, and as you can see the temperature variation is about 5 degrees Celsius. 

See sea level rise is usually nonlinear 

The range of temperatures is not the same, and there is less ice around than during an ice age, but it still suggests something. 

 

One reason why the sea level rise may not have been that much in the past century is because the warming was very rapid. SO if I warm up a block of ice rapidly rather than slowly the result might not be noticeable immediately. 

 

Santosh Gupta

 

Edited December 2, 2023 by thidmir

[swansont]

1 hour ago, thidmir said:

if we think we are in the Ice age

Are we in an ice age? I though we were in a warm interglacial period.

[mistermack]

1 hour ago, swansont said:

Are we in an ice age? I though we were in a warm interglacial period.

We are both. A typical ice age consists of glacials and interglacials, which add together to be the actual ice age. So although we are in a warm interglacial, we are still in an actual ice age. Hence the ice sheets at the poles and Greenland and mountain glaciers. 

[swansont]

2 hours ago, thidmir said:

sea level rise during an ice age cycle tends to be more like 50 - 100 m for the same range of global temperature increase

Your graphs show we've already had ~120m of sea level rise for the ~ 9ºC rise in temperature from the glacial maximum.

Why would we expect an additional 50m?

 

[studiot]

3 hours ago, thidmir said:

One reason why the sea level rise may not have been that much in the past century is because the warming was very rapid

You  are right in thinking time is a factor, though not quite in the way you perhaps imagined.

Up to about the 1960s it was thought that the water was simply moved between stored ice in the cold periods, which lowered sea level and returned to sea water in the warm periods, which raised sea levels. This thus offered a simple calculation using the volume of the trapped and released water to estimate sea level change, the water simply moving from the land to the hydrosphere and back.

However it has become apparent that the distribution of both the water and the land is much more complicated than this.

Firstly isotasy plays a part.

Unloading of the continental crust from the melting of the last Scandinavian icesheet has led to a rise in the land, relative to the sea, of 300m.
A much more modest rise of 14m has been recorded with the corresponding loss of the much smaller Scottish ice sheet.

Secondly the increased water places an increased load on the thinner ocean crust depressing it and reduci ng the sea level rise.

Thirdly in warmer periods more of the water enters atmousphere and is retained there.

Fourthly we have discovered much more recently that significant amounts of water is subducted into techtonic processes, taking many thousands of years to reappear via igneous outbursts.

So the question should be when as well as how much.

[TheVat]

Melting all polar ice and glaciers would involve an enormous volume - estimates I've seen are around 70m further sea level rise.  

https://www.usgs.gov/faqs/how-would-sea-level-change-if-all-glaciers-melted

Clearly this would be an extreme scenario involving a runaway feedback effect made of various specific effects of reduced ice cover, e.g. albedo drop, release and dissociation of methane hydrates, particulates (both microbial and inorganic) blowing out of ancient bogs and other thawed permafrost, methane from thawed organic material decomposing, and others.  

As for tectonic processes that @studiot mentioned, yes, lots of unknowns there.   I will try to dig a bit more into that USGS estimate, given that it's a little higher than some.   

 

[studiot]

In the late 1970s a programme of measuring total ice volumes by isotopic dilution analysis was started.

In part this was calibrated against the sea level of a sea area that has seen no ice for thousands of years.

Here are 1979 results. Im sure there are more recent ones, but I don't have them.

 

 

[mistermack]

If you look at the sea level rise over time, it's very hard to attribute any of it so far to CO2 levels. The current CO2 level rise was tiny, up until 1950, when the acceleration began. Given that there must be a time lag between CO2 rising and sea level rise, it's reasonable to infer that the graph up to 1970 is of natural rises, due to other causes. It's very very hard to look at the graph, and see any effect as yet, after 1970, from CO2 level. It appears so far that it's just continuing the previous trend. If there is an effect in the graph, it's very very tiny. 

  

 

 

[swansont]

1 hour ago, mistermack said:

If you look at the sea level rise over time, it's very hard to attribute any of it so far to CO2 levels. The current CO2 level rise was tiny, up until 1950, when the acceleration began. Given that there must be a time lag between CO2 rising and sea level rise, it's reasonable to infer that the graph up to 1970 is of natural rises, due to other causes. It's very very hard to look at the graph, and see any effect as yet, after 1970, from CO2 level. It appears so far that it's just continuing the previous trend. If there is an effect in the graph, it's very very tiny. 

  

 

 

Or, instead of unsourced conjecture and opinion, we could go with what science says (bold added)

"Global mean sea level increased by 0.20 [0.15 to 0.25] m between 1901 and 2018. The average rate of sea level rise was 1.3 [0.6 to 2.1] mm yr–1 between 1901 and 1971, increasing to 1.9 [0.8 to 2.9] mm yr–1 between 1971 and 2006, and further increasing to 3.7 [3.2 to 4.2] mm yr–1 between 2006 and 2018 (high confidence). Human influence was very likely the main driver of these increases since at least 1971"

https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf

See also table 1 of the following, showing thermal expansion and ice melt numbers starting with 1972 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3758961/

[mistermack]

7 minutes ago, swansont said:

we could go with what science says

You seem to be confusing IPCC reports with science. Instead of responding to my post with any kind of logical point. 

I just posted the graph from wikipedia (as usual) and the rest of my post was easy enough to read and respond to, if you disagree with it. 

As for unsourced conjecture and opinion, I write my own posts. I would have thought that would be obvious by now. 

Sea level rise - Wikipedia  

If you think Wikipedia got it wrong, I'm sure you'll soon be writing your own pages. 

[swansont]

57 minutes ago, mistermack said:

You seem to be confusing IPCC reports with science. Instead of responding to my post with any kind of logical point. 

IPCC reports are based on science. My point was that the science disagrees with your opinion. I thought that was obvious. Apologies for assuming that.

57 minutes ago, mistermack said:

I just posted the graph from wikipedia (as usual) and the rest of my post was easy enough to read and respond to, if you disagree with it. 

As for unsourced conjecture and opinion, I write my own posts. I would have thought that would be obvious by now. 

Blatantly.

57 minutes ago, mistermack said:

Sea level rise - Wikipedia  

If you think Wikipedia got it wrong, I'm sure you'll soon be writing your own pages. 

I don’t see where Wikipedia backs your opinion. It says the sea level rise has accelerated, rather than being a continuation of the earlier trend.

“Between 1901 and 2018, the average global sea level rose by 15–25 cm (6–10 in), or an average of 1–2 mm per year.[2] This rate accelerated to 4.62 mm/yr for the decade 2013–2022”

(note that there’s an overlap, so the smaller trend up to 2018 includes the higher trend of the latest decade of data)

[Phi for All]

15 hours ago, mistermack said:

As for unsourced conjecture and opinion, I write my own posts. I would have thought that would be obvious by now. 

!

Moderator Note

It's been painfully obvious for a LONG time, but it's still frustrating that you don't bother to source your conjecture the way others do. You seem to think your raw opinions are meaningful without facts and evidential support. This has allowed you to post a whole lot of crap in otherwise scientific threads. You need to stop it. You seem very smart, and you often represent a POV that we need to see, but you ruin it with unevidenced opinion that you assert like it's fact. We can start trashing bad faith posts like that if you can't stop yourself, but we want to let you know our thinking on this.

 

[Ken Fabian]

@thidmir There are some scientists who think we underestimate the potential for non-linear ice sheet collapse but even a pessimistic James Hansen doesn't expect sea level rise of 50m to 100m 70m. The hypothetical maximum is around 70m - where Antarctica and Greenland lose all their ice sheets.

The sea level impacts are likely to continue for a long time after reaching zero emissions, which, by necessity is a near term goal, within the next few decades, ie well before sea levels can stabilise. But there is an expectation amongst those that study the cryosphere aspects of climate change that the rate will slow with zero emissions. I suppose the worse case scenarios where emissions reductions are abandoned and there are ongoing high emissions that put us back on the RCP8.5 pathway, but even that looks like a trend that must top out, as fossil fuel stocks decline.

Better prediction can help us work out what to expect for varying emissions scenarios but we don't need precise sea level rise predictions to know we urgently need to bring emissions down. Sea level rise, however it develops, will require adaptation but apart from locally at small scale (levies, imported fill to raise ground levels, building better for those that can afford it) that looks like a global retreat to higher ground and accepting an irrevocable loss of environmental capital (land).

 

 

 

[iNow]

6 minutes ago, Ken Fabian said:

Better prediction can help us work out what to expect for varying emissions scenarios but we don't need precise sea level rise predictions to know we urgently need to bring emissions down.

Those better predictions also make it painfully simple to see where the ROI is on the expenditure of our tax revenues.

As you well know, we can either spend hundreds of billions reparing towns and restoring infrastructure (over and over and over again) after the storms, or we can instead invest those same revenues on risk mitigation at much lower orders of magnitude and much higher returns.

We're digging a hole and we can all agree that we need to stop digging, even if we disagree slightly on how much larger the hole will ultimately become if we continue unabated on our current path. 

[Ken Fabian]

8 minutes ago, iNow said:

We're digging a hole and we can all agree that we need to stop digging, even if we disagree slightly on how much larger the hole will ultimately become if we continue unabated on our current path. 

I think our current path has already changed in significant ways almost entirely due to the successes of renewable energy (and batteries and EV's). RCP8.5 scenarios are considered very unlikely now, not because climate science was wrong about the impacts of emissions but because we now expect renewable energy to - at the very least -  to displace growth of fossil fuel use significantly, with less emissions than otherwise. For all the disparaging it is an extraordinary achievement. To call it on purpose might be a stretch; for some it was on purpose, but those were initially considered fringe. More widely the supporting of renewables seemed more about empty gestures, with it actually working and being cost competitive coming as a surprise. Now that the renewable options are cost effective in most of the world it might still get some government support (as fossil fuels still do) but fundamentally, now and for the near future, it is market economics at work.

As well to channel Canute and get the tide to stop - but it is clear that Doubt, Deny, Delay politickers around here have shifted their focus to obstructing the things that will make renewables reliable as their scale grows - opposing transmission lines, battery farms and wind, especially off-shore wind. Astro turf nimby opposition and trying to wedge them between climate concerns and local environmental impacts. But I think that - having made up the for, by, about environmentalist framing themselves - they underestimate the wider community support for emissions reductions with renewables, from people who do not identify with environmentalism, who's commitment is because of the science based advice, not green politics.

Ultimately we will require strong, enduring commitment to climate stability at levels we are yet to see, but governments even being able to say they are committing to zero emissions is a remarkable shift. Economic alarmist fear of what has to be done to reach zero emissions (along with denying climate change's harms) has been one of the most successful denier memes, yet the most direct and effective and acceptable emissions reduction pathway is building an abundance of low emissions energy to displace fossil fuels and, hey, that is the one thing we are succeeding at. Much better than expected.

The enormous stocks of fossil fuel capacity in place make early contributions by renewables seem small but within just one decade of crossing price equivalence thresholds renewables have become the most built new capacity additions, by a very large margin. That quickly. Less than 7 years ago Australia installed a Big Tesla Battery, to widespread derision. More than 20 times that capacity of batteries are up and running. That quickly. Not just Tesla but multiple mega batteries factories are already up and running. That quickly.

Amongst all the cause for pessimism there is one thing going right - renewable energy. So we should not be surprised that the deniers are going all out to undermine public confidence in it.

[mistermack]

1 hour ago, Ken Fabian said:

The hypothetical maximum is around 70m - where Antarctica and Greenland lose all their ice sheets.

It that were to happen, it might be comforting to know that you and any children you might have will have been dead for at least 500 years, or more likely 1,000 years or more. And of course, that's assuming that the climate keeps warming for that long. Since the human population is projected to top out and start falling by the end of this century, and renewables keep increasing, and fossil fuels are getting used up, there's virtually no chance of MMGW still being the talk of the town in 500 years time. 

Meanwhile in the real world, today's more pessimistic models are pushing up the forecast sea-level rise by the end of this century to between 10 and 15 inches.         How quickly are Antarctica's glaciers melting? | World Economic Forum (weforum.org)  

They might even be in a nuclear winter in 500 years time. That's always an option in a desperate situation. Solve the population problem and AGW by pressing a few buttons. 

Nuclear winter - Wikipedia   

[TheVat]

For those following, I thought it might be useful to define the acronym RCP 8.5 which is being used here.

RCP 8.5 is one several scenarios (Representative Concentration Pathways) that yields a particular concentration of carbon in the atmosphere. RCP 8.5 is the concentration of carbon that delivers global warming at an average of 8.5 watts per square meter across the planet.  (at the surface, at noon on a summer day in the temperate zone, we get about 1000 w/m² total insolation - I got this figure from Woods Hole)  The RCP 8.5 pathway delivers a temperature increase of about 4.3˚C by 2100, relative to pre-industrial temperatures. RCP 8.5 is often contrasted with RCP 2.6, which would deliver a total warming of about 1.8˚C by 2100. 

@Ken Fabian has neatly summarized all the political and market forces that are smoothing the path for renewables and decreasing the chances of the dystopian RCP 8.5 scenario.  I would only add that the driver of an alternative like wind is its fundamental simplicity and ease of construction once production of components is scaled up.   There's something almost surreal about looking back at the history of power generation and seeing how humanity breezed (npi) right past a 19th century technology that ran on free fuel.  

[thidmir]

There's one other thing, the there is a strong correlation between level of CO2 and global temperature, so greenhouse gases definiely need to be mitigate to avoid having to see what would happen if Earth warmed by 4 degrees Celsius. 

 

From the ice ages

and 

almost linear. 

Anyone not understand? 

 

Santosh Gupta

Edited February 15 by thidmir

[Bufofrog]

On 2/15/2024 at 3:56 PM, thidmir said:

almost linear. 

Anyone not understand?

Apparently you don't. 

The graph is only linear because the spacing of the years is not linear.  Look at the 20 year spacing between 2000 and 2020 then look at the spacing between 1884 and 1902.  The spacing is clearly not linear and this misleading graph gives the false impression that the temperature increase is linear.

Based on this apparently purposely misleading graph I would assume that this is from a climate denial site.

Edited February 17 by Bufofrog

[swansont]

On 2/15/2024 at 3:56 PM, thidmir said:

almost linear. 

Linear in concentration. As Bufofrog notes, this is not linear in time.

[J.C.MacSwell]

1 hour ago, swansont said:

Linear in concentration. As Bufofrog notes, this is not linear in time.

Wasn't that the context thidmir intended?

 

On 2/15/2024 at 4:56 PM, thidmir said:

There's one other thing, the there is a strong correlation between level of CO2 and global temperature, so greenhouse gases definiely need to be mitigate to avoid having to see what would happen if Earth warmed by 4 degrees Celsius. 

 

[swansont]

17 minutes ago, J.C.MacSwell said:

Wasn't that the context thidmir intended?

I was just pointing it out. The context of the thread is sea level rise in time, so knowing the variation in time is relevant. And the OP has yet to engaged with other participants, so who knows what their intent was?

[J.C.MacSwell]

1 minute ago, swansont said:

I was just pointing it out. The context of the thread is sea level rise in time, so knowing the variation in time is relevant. And the OP has yet to engaged with other participants, so who knows what their intent was?

I don't know for certain but the statement and graph didn't seem to be in support of climate denial...quite the opposite, though I really should have directed my post more at Bufofrog.

Hopefully thidmir will clarify.

 

[Bufofrog]

16 minutes ago, J.C.MacSwell said:

I don't know for certain but the statement and graph didn't seem to be in support of climate denial...quite the opposite, though I really should have directed my post more at Bufofrog.

I certainly may be misunderstanding the point of the graph.  If the point was that there is a linear relationship between the greenhouse gases and warming then my comment about the timeline was off the mark.

Edited February 17 by Bufofrog

[J.C.MacSwell]

4 minutes ago, Bufofrog said:

I certainly may be misunderstanding the point of the graph.  If the point was that there is a linear relationship between the greenhouse gases and warming then my comment about the timeline was off the mark.

Thanks. Hopefully thidmir will clarify and expand on the purpose of that post.