2015 Global Sea Level Thread

[AvantHiatus]

 

If the average rate of sea level rise was 2 mm per year during the 20th Century, the past two decades have witnessed a more than 60% rate of increase over even that unprecedented rate. For current sea level rise measures show a 3.27 mm per year increase.

 

Most scientists expect an ever more extreme rate of atmospheric warming over the 21st Century to ramp this already rapid rate higher — with annual increases likely to exceed 1 cm before 2100 arrives. Such rates would push end 21st Century sea level rise well into the end ice age range of 1.2 meters every 100 years — with chances for even greater rates of increase going forward.

The IPCC has identified a likely sea level rise in the range of 2-3 feet by the end of this Century (60-100 cm), with many outside analysts identifying a range between 2-9 feet (60-300 cm) as possible given the potential for 3-5 C warming under business as usual fossil fuel emissions (Researchers at the Neils Bohr Institute recently established a range from 2-6 feetbut note that sea level rises of 80 cm [2.5 feet] are most likely this century and increases of greater than 6 feet have a probability of less than 5% through 2100).

 

[Sophisticated Skeptic]

Everybody's speechless.  

[AvantHiatus]

I suppose, there is an annual cycle to it for sure. A large chunk is probably from the South Pacific/ENSO. Thermal expansion city.

[dabize]

http://climatecrocks.com/2015/03/17/warm-oceans-wearing-away-antarcticas-plug/

 

The hell of it is, they keep finding new major sources of sea level rise that haven't been taken into account by the "official" predictions. Here is one - this is the first I've heard that EAST Antarctic (land-based) ice sheets are in imminent danger of "irreversible" melting. It is a rude surprise to me - I thought the EAIS was supposed to still be stable.

 

The Totten Glacier (see link) is pegged to produce 11 feet of SLR overall.  Even if that just means a foot or two on top of what is forecast for this century, that would be enough to make Florida uninhabitable.

 

Another point made in the post (which describes a Nature Geoscience paper - linked) is that very little is actually known about most of the rest of the EAIS - so that there may be more surprises in store - all of which will increase, rather than decrease, expected SLR over current estimates.

[chubbs]

A 14-minute talk glaciologist Richard Alley gave last summer on his work with the IPCC on sea level and the potential collapse of the WAIS. He closes by saying that  there is low risk of a much higher rise than projected by the IPCC.

 

https://royalsociety.org/people/fellowship/2014/richard-alley/

[skierinvermont]

A 14-minute talk glaciologist Richard Alley gave last summer on his work with the IPCC on sea level and the potential collapse of the WAIS. He closes by saying that  there is low risk of a much higher rise than projected by the IPCC.

 

https://royalsociety.org/people/fellowship/2014/richard-alley/

alley conclusion.png

 

They could have made it useful by summing up the probabilities of the whole right hand side of the tail into one probability such as:

 

"The probability of SLR >10 feet = X"

 

That would be something useful. If the 50% confidence interval is 2-5 feet, but there's a 25% chance of more than 10' that's a tail end risk that is very significant and useful for policy makers. That's basically what his chart shows, but it's not at all what they made clear in the IPCC report. 

 

However, I think they may have felt pressure not to be so bold about something we know so little about. 

[chubbs]

They could have made it useful by summing up the probabilities of the whole right hand side of the tail into one probability such as:

 

"The probability of SLR >10 feet = X"

 

That would be something useful. If the 50% confidence interval is 2-5 feet, but there's a 25% chance of more than 10' that's a tail end risk that is very significant and useful for policy makers. That's basically what his chart shows, but it's not at all what they made clear in the IPCC report. 

 

However, I think they may have felt pressure not to be so bold about something we know so little about.

 

 

Here is a 2014 paper (open source) that does what you suggest and gets roughly 6 feet but note the limitations.

 

S Jevrejeva et al 2014 Environ. Res. Lett. 9 104008 doi:10.1088/1748-9326/9/10/104008

Upper limit for sea level projections by 2100

OPEN ACCESS

 

S Jevrejeva¹, A Grinsted² and J C Moore^3,4

 

Letter

We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century.

[skierinvermont]

 

Here is a 2014 paper (open source) that does what you suggest and gets roughly 6 feet but note the limitations.

 

S Jevrejeva et al 2014 Environ. Res. Lett. 9 104008 doi:10.1088/1748-9326/9/10/104008

Upper limit for sea level projections by 2100

OPEN ACCESS

 

S Jevrejeva¹, A Grinsted² and J C Moore^3,4

 

Letter

We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century.

 

 

Look at all the uncertainties they note- this might be something done better qualitatively. Unless there is a mathematical model for scenarios of high uncertainty?

[PhillipS]

You may have already seen this but this 2012 lecture by Dr Richard Alley on ice sheets and sea level rise is informative and entertaining.  If the first few minutes he talks about a plot of CO2 versus sea level and now that we are at 400 ppm it's pretty clear that we have locked in more than 10 meters of sea level rise.

 

[A-L-E-K]

Dr. Alley might have the most stereotypical nerd voice on the planet. But thanks for the link!

[AvantHiatus]

[Msalgado]

You may have already seen this but this 2012 lecture by Dr Richard Alley on ice sheets and sea level rise is informative and entertaining.  If the first few minutes he talks about a plot of CO2 versus sea level and now that we are at 400 ppm it's pretty clear that we have locked in more than 10 meters of sea level rise.

 

 

He gave a series of lectures at the university I was attending back in 2012 and they were very good.  I would imagine the one you linked is basically one of the same talks he gave.  

[SVT450R]

So do you now understand how your SLR predictions are unrealistic based on the graphic? 

[AvantHiatus]

So do you now understand how your SLR predictions are unrealistic based on the graphic? 

Irrelevant, was just posting a different source in case one goes down and for accuracy checking.

 

It is sunny today so that means it will be sunny tommorow, dat logic.

 

 

color your skin with gold, and the violence remains

cover your eyes with rose, but the stain remains

will you escape your life

with all the walls you build?

smother your will and lead you into fashion...

morning comes in the dream before we rise

when we linger side by side

it's my heart that speaks this time:

we will ride the rising tide

[SVT450R]

Irrelevant, was just posting a different source in case one goes down and for accuracy checking.

It is sunny today so that means it will be sunny tommorow, dat logic.

 

What's exactly irrelevant here? So our current SLR rate is roughly 3.3mm a year. So when you make a statement of 6" in 10 years or 10' this century it looks pretty silly. Of course as the earth warms the yearly rise will increase over time but it's not like you will see in say a decade it double or triple within a short duration of time, which is what you seem to be pointing at. SLR observations have seen a mostly continuous slow rise over the last century.

 

[chubbs]

What's exactly irrelevant here? So our current SLR rate is roughly 3.3mm a year. So when you make a statement of 6" in 10 years or 10' this century it looks pretty silly. Of course as the earth warms the yearly rise will increase over time but it's not like you will see in say a decade it double or triple within a short duration of time, which is what you seem to be pointing at. SLR observations have seen a mostly continuous slow rise over the last century.

Watch the Alley video's posted above. If the Thwaites glacier in WAIS moves off its current pinning point it will be a whole new ballgame.

[SVT450R]

Watch the Alley video's posted above. If the Thwaites glacier in WAIS moves off its current pinning point it will be a whole new ballgame.

I'll try to watch the whole video when i get the time.  It's fine to talk about possible tipping points etc and when they may happen, but I'll stick with the observational data for the time being which shows a continued gradual increasing SLR rate.

[AvantHiatus]

2010-2014 there is a decent acceleration with a small return to the mean at the end. Not that it matters much.

[Msalgado]

I'll try to watch the whole video when i get the time.  It's fine to talk about possible tipping points etc and when they may happen, but I'll stick with the observational data for the time being which shows a continued gradual increasing SLR rate.

 

Alley is just discussing the large influx of a huge amount of ice due to the melting of a "dam" so to speak.  He's got observational data on the "dam" supporting this, but it isn't a high likelyhood event (although not insignificant either) chance in the next 100 years according to him.  

[wolfpackmet]

CU just updated their global mean sea level.  Seasonal removed GMSL is up ~4 mm since the last update.  The rate also had a slight bump to 3.3 mm/year from 3.2 mm/year.  Will be interesting to see what happens if the Nino/MEI continues to strengthen.  

 

http://sealevel.colorado.edu/

[chubbs]

 The study below (paywalled) was recently accepted for publication. This only covers a short 3-year period so is not definitive but recent data posted above indicates that the faster SLR identified in this paper has continued into early 2015.

 

An increase in the rate of global mean sea level rise since 2010^†

 

Yi, Shuang; Sun, Wenke,  Heki, Kosuke,  Qian, An

 

Abstract

The global mean sea level (GMSL) was reported to have dropped 5 mm due to the 2010/11 La Niña and have recovered in one year. With longer observations, it is shown that the GMSL went further up to a total amount of 11.6 mm by the end of 2012, excluding the 3.0 mm/yr background trend. A reconciled sea level budget, based on observations by Argo project, altimeter and gravity satellites, reveals that the true GMSL rise has been masked by ENSO-related fluctuations and its rate has increased since 2010. After extracting the influence of land water storage, it is shown that the GMSL have been rising at a rate of 4.4 ± 0.5 mm/yr for more than three years, due to an increase in the rate of both land ice loss and steric change.

 

http://onlinelibrary.wiley.com/doi/10.1002/2015GL063902/abstract

JO  - Geophysical Research Letters;SN  - 1944-8007

 

http://dx.doi.org/10.1002/2015GL063902

[chubbs]

This is a repost from the ASIB comment section. WAIS is the elephant in the SLR room - the scientific uncertainty is striking and well conveyed by Alley.

 

Richard Alley at INSTAAR, April 2015.

Published on Apr 13, 2015.

Glaciologist Richard Alley shares recent research on the state of the West Antarctic Ice Sheet, climate change, and what it means for people living near the coasts in "Crumbling Ice Cliffs? Not-So-Good News for Low Coasts." INSTAAR Monday Seminar, 6 April 2015, University of Colorado Boulder.

https://www.youtube.com/watch?v=yCunWFmvUfo

[AvantHiatus]

This is a repost from the ASIB comment section. WAIS is the elephant in the SLR room - the scientific uncertainty is striking and well conveyed by Alley.

 

Richard Alley at INSTAAR, April 2015.

Published on Apr 13, 2015.

Glaciologist Richard Alley shares recent research on the state of the West Antarctic Ice Sheet, climate change, and what it means for people living near the coasts in "Crumbling Ice Cliffs? Not-So-Good News for Low Coasts." INSTAAR Monday Seminar, 6 April 2015, University of Colorado Boulder.

https://www.youtube.com/watch?v=yCunWFmvUfo

Dr. Alley is quite the character, very enthusiastic about his field of study. A rare sight these days. Nothing but hunks of shells and dead bugs from the Pleistocene so why not melt it? Lol

[chubbs]

Just the kind of marine glacier threshold behavior Alley discusses above. A change this large hasn't been seen in other studies so some caution is in order until confirmed.

 

Cryosat detects a sudden glacier loss in the Southern Antarctic Peninsula.

 

"A recent acceleration in ice loss in a previously stable region of Antarctica has been detected by ESA’s ice mission.The latest findings by a team of scientists from the UK’s University of Bristol show that with no sign of warning, multiple glaciers along the Southern Antarctic Peninsula suddenly started to shed ice into the ocean starting in 2009 at rate of about 60 cubic km each year.This makes the region one of the largest contributors to sea-level rise in Antarctica, having added about 300 cubic km of water into the ocean in the past six years. Some glaciers along the coastal expanse are currently lowering by as much as four m each year."

 

 http://www.esa.int/Our_Activities/Observing_the_Earth/CryoSat/CryoSat_detects_sudden_ice_loss_in_Southern_Antarctic_Peninsula

 

Science 22 May 2015:
Vol. 348 no. 6237 pp. 899-903
DOI: 10.1126/science.aaa5727

 

http://www.sciencemag.org/content/348/6237/899

[chubbs]

An OHC update was posted in the temperature thread. There is probably an OHC contribution to the increasing rate of SLR over the past couple of years.

 

[stadiumwave]

An OHC update was posted in the temperature thread. There is probably an OHC contribution to the increasing rate of SLR over the past couple of years.

 

SLROHC.png

 

 

Our ability to measure global deep ocean heat is pitiful.  It's so pitiful I'm not even sure why it's a talking point.

[nflwxman]

Our ability to measure global deep ocean heat is pitiful. It's so pitiful I'm not even sure why it's a talking point.

Go on...

How so? OHC is by far the consistent and useful measure of AGW. In fact, it's a remarkably stable rise 0-2000m and correlates more with CO2 rise than the surface temperature.

[Vandy]

How so? OHC is by far the consistent and useful measure of AGW. In fact, it's a remarkably stable rise 0-2000m and correlates more with CO2 rise than the surface temperature.

 

I'm going to go out on a limb and suggest that's why he is trying to discredit it.

[chubbs]

NOAA sea level chart updated through April. Not much change in the past two months - still tracking above the trendline.

 

[AvantHiatus]