what do you make of the new study that that suggest a slow down in sea level rise with global warming?

Question

The“PALSEA” group short for PALeo SEA level working group did a paleo climate study. They wrote:

"Given this evidence for periods of rapid warming during TI, at least some of this warming occurred on decadal to centennial timescales. Because of the general similarity between the magnitude and rate of warming predicted for the 21st century and the warming that occurred during certain periods of TI, it is interesting to consider rates of sea-level rise during TI as a case study of the response of sea level to climate change."

They concluded:

Therefore, we suggest that option 1 (exponential sea-level rise) is extremely unlikely. …An exponential increase in rates of sea-level rise with respect to temperature would result in 21st-century sea-level rise an order of magnitude larger than estimates using alternative patterns of response – it is an important result that the palaeo-sea-level data rule out such a response.

Finally, they write “the palaeo sea-level data suggests that sea-level rise related to current warming may be rapid at first and slow over time.”

http://www.worldclimatereport.com/index.php/2010/08/09/sea-level-history-lesson/

Answer 1

The short answer is that there simply is not enough continental ice mass to support exponential sea level rises (or thermohaline catastrophes) during interglacial periods.



The so called consensus view is that a sea level rise of 6 feet by the year 2100 is somewhat likely. Sea level would have to rise at a rate seven times as fast as it is now for the next 90 years to rise by 6 feet by the year 2100. A seven-fold increase in sea level rise starts sounding just a bit exponential.







From 1993-2003 sea level rose at a rate of 3.45 mm/yr. Since 2003 it has been rising at a rate of 2.35 mm/yr...



http://i90.photobucket.com/albums/k247/d…



The satellite data fit very nicely into the long term trend of sea level rise since the end of the Little Ice Age...



http://i90.photobucket.com/albums/k247/d…



Here are the top ten decades of sea level rise (mm/yr) since 1700...





1804-1813 12.75

1803-1812 10.67

1728-1737 10.30

1789-1798 8.38

1842-1851 7.87

1858-1867 7.82

1788-1797 7.72

1861-1870 7.66

1808-1817 7.58

1785-1794 7.18



None of those 10-yr periods has come anywhere close to 22 mm/yr... And all of those periods occurred long before man started pumping CO2 into the atmosphere.





Here are the top ten decades (mm/yr) from 1950-2002...





1989-1998 4.66

1990-1999 3.95

1991-2000 3.86

1956-1965 3.79

1986-1995 3.78

1974-1983 3.71

1952-1961 3.65

1993-2002 3.63

1988-1997 3.44

1975-1984 3.30



Satellite altimetry data from 1993-2010 show that sea level rise has decelerated to less than 3 mm/yr.



Sea level has never risen more than 12.75 mm/yr on a decadal scale since 1700.



Sea level hasn't risen by more than 4.66 mm/yr on a decadal scale since 1950.



Sea level would have to rise at 20 mm/yr to rise by 6 feet by the end of the century.



The observational data support a sea level rise of no more than 11 inches by the year 2100.









Now for some "fun with geology!"



Here is the total Eustatic Sea Level (ESL) change since the Last Glacial Maximum (LGM) compared to the total ESL change since 1700 AD...



http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/18150BC.png



Now let's compare the last 300 years of ESL rise with the ESL changes of the last 2 million years (most of the Pleistocene)...



http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/2000000BC.png



Geologists have a very technical term for this. It's called "perspective."



The alarmists are Chicken Little-ing about a 1 meter rise in sea level over the next 90-100 years.



Could sea level rise another 1, 3 or even 5 meters before the end of the current interglacial? Sure. It rose that high in the previous interglacial.



Could sea level rise another 1 meter over the next 90 to 100 years? No. There is no historical or geological evidence to support such a scenario.



Assuming Earth stays in the warm phase of the 1,500-yr cycle until at least 2100 (not a huge assumption), the maximum possible sea level rise by then will be a bit more than 0.25m above current MSL…



http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/SeaLevelProjection-1.png



1/4 of a meter… A bit less than 1 foot… That’s it… That’s the worst case scenario that is actually possible in the real world.

Answer 2

I am certainly not qualified to question the findings of published experts but I note that they refer specifically to sea level rise due to ice sheet melt. The IPPC projections are ice sheet melt plus thermal expansion.



In fact the sea level rise observed so far has been nearly all due to thermal expansion. As thermal expansion increases linearly, the yet-to-be-seen increases from ice sheet melt will cause the rate to be greater than linear at least for some time. It may well be that at some later point the sea level changes to increasing at a decreasing rate, but the PALSEA group does not seem to indicate when that point will be or how high sea levels will have rison by then. The PALSEA summary might not be in conflict with the IPCC projections at all, and/or this may be a small step towards better understanding how high to expect sea levels to rise to.

Answer 3

Nothing in nature ever increases exponentially indefinitely, so the conclusion is hardly surprising. I think the key is how rapidly it will rise in the short-term, and I don't see that this paper has a good answer for that. I think we can conclude from the paper that sea levels are unlikely to rise by tens of meters per century, but we already knew that.



By the way, does this mean that you've given up on disputing AGW is real, and are now just arguing about what effects it will have?



rightheousjohn, the physics may be simple, but you apparently flunked it. "water (aka: Ice) expands to 10 times it's volume as a liquid" How could you possibly believe this? As A Modest Proposal points out, haven't you ever made ice cubes? And then you say "Tectonic plate shifting has and will continue to have, more impact on relative sea levels than any changes in air temperature." Sure plate motion matters...over millions of years. Plates shift at about the same rate that fingernails grow, millimeters per year, tens of millimeters at the fastest. Tectonic motion is largely irrelevant to the discussion of short-term sea level rise.

Answer 4

Like Trevor, I prefer to actually read the study in question. The fact that sea level rise won't be exponential forever is hardly news.



"we are moving into a climate regime when the Greenland and West Antarctic ice sheets will become increasingly unstable"



"one may expect sea-level rise over the next century to fall between the lower limit of 20th-century sea-level rise (0.12m per century; Meehl et al., 2007) and the sea-level rise at the conclusion of TI (1m per century; Carlson et al., 2008)...while extreme upper bounds of 2m per century have been estimated by extrapolating the fastest observed ice stream responses to all of the ice streams of Greenland and West Antarctica (Pfeffer et al., 2008)"



So there's really nothing particularly new here. They conclude that sea level rise may be as much as 1-2 meters over the next century, which is consistent with several other recent studies which concluded that the IPCC underestimated possible sea level rise.



And by the way, current sea level rise is about 0.3 meters per century, so they are indeed anticipating that sea level rise will likely accelerate rapidly over the next century. Your claim that this report concludes that Greenland and Antarctic ice sheets won't contribute considerably to sea level rise over the next century is *completely* wrong. They will be the main contributors to the potential 1-2 meter sea level rise.



*edit* "where are you getting a 1-2 meter sea level rise as their conclusion?"



From the quote in my answer. Their claim that the worst case scenario is 1.4 meters (citing Rahmstorf) is wrong, because as they later note (and as I quoted), Pfeffer puts the maximum at 2 meters by 2100.

http://www.sciencemag.org/cgi/content/abstract/321/5894/1340

Answer 5

The most ice mass that would add to sea levels does not come from sea ice but from ice sheets and glaciers, which are not floating in the oceans. Simple physics means if those melt then sea levels rise. You also have thermal expansion of the oceans as they warm, on average at least.



Anyways, interesting article, though notably biased. Did the PALSEA group discuss why they thought sea levels would rise in an asymptotic manner? Obviously they are comparing to the last warming period some 10,000 years ago, but considering that there was a leveling off of sea level rise at the same time temperatures leveled off, and also a notably larger rate of temperature increase now than during the last warming:

http://www.theoildrum.com/uploads/12/Post_Glacial_Sea_Level_present.jpg

http://www.uwsp.edu/geo/faculty/lemke/geog101/images/25b_ice_age_temperature_warmingart.png

(0.6˚C in 10,000 years or so)

http://www.trackforum.com/images/WARMING/Vostok+Temp-Co2-Mh4-Dust-Solar-Glacial.jpg

(0.8˚C in 100 years)

http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif



are sea levels going to rise rapidly for quite some time and then level off? In other words, I agree that sea levels will eventually stop when temperatures stop rising, but when? And what type of anomaly pattern will we see before?





righteousjohnson, I've placed ice trays in the freezer so I can get ice cubes. They don't expand to ten times their size. Maybe they increase in volume by 10% (they do), but not a factor of ten.



>>>This report says that with global warming sea levels will not accelerate but decelerate.



In the long run. You forgot about the "rapid at first" part, which is in coordinance with the observations of sea level rise during the last warming period, as you can see from the first link I gave and the actual report Trevor so kindly linked us to - Figures 1 and 3.

Answer 6

What do I think of it? I think that instead of relying on selectively edited, biased and misrepresented extracts from a report written by Exxon funded ‘scientists’, it would be infinitely better to read the original article in it’s entirety; in doing so it then takes on a whole new meaning.



The website you linked to conveniently only focuses on the possibility of a slow down in sea-level rises but conveniently forgets to mention that the report also concludes sea-levels could rise by 1000mm in the next century (2000mm in the extreme), this is 2½ times the IPCC’s estimates of between 190mm and 590mm.



Not surprisingly, the article also overlooks the fact that the report states “direct observational evidence confirms the assertion… [that] we are moving into a climate regime when the Greenland and West Antarctic ice sheets will become increasingly unstable”.



http://eis.bris.ac.uk/~glyms/PALSEAJQS2009.pdf



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EDIT: RE YOUR ADDED COMMENTS



This report does NOT contradict what the IPCC or myself have said. In fact, when you read it carefully, it ascribes potentially greater sea-level rises.



You’ve already mentioned the figures of 590mm and 1400mm. The figure of 590mm comes from the IPCC’s 4th Assessment Report (AR4) and is the upper limit on sea-level rises and is based on a 4°C temperature rise projected by SRES Scenario A1FI (Special Report on Emission Scenarios). The value of 1400mm is based on altimetric observations from the Gravity Recovery And Climate Experiment satellites (GRACE).



These are worst case scenario figures and are considerably less than the 2000mm value given in the PALSEA paper.



http://www.grida.no/publications/other/ipcc_sr/?src=/climate/ipcc/emission/

http://www.csr.utexas.edu/grace/

http://www.sciencemag.org/cgi/content/abstract/321/5894/1340

Answer 7

oh, eric, to get our hopes up like this! your link is to a climate change denier site, and i really cant be bothered to find the real reference, so i willjust say, oceanographers are a very conservative bunch, the are only just getting their heads around acidification.



as for 'exponential', what you show here is a mis-understanding; the easy way to think of a power law is is how often the thing (in this case sea level rise) doubles.

Answer 8

I think it is rather obvious. I don't think any scientist ever suggested that sea levels will rise exponentially for an indefinite amount of time. Over very short periods of time it may look exponential.

Answer 9

Makes sense. Simple Physics.



1. Frozen water (aka: Ice) expands it's volume by 10%, from it's liquid state. Therefore as the ice melts, it reduces the amount of area on the planet it displaces. Like ice melting in a glass, it will never overflow.

2. Higher temperatures will increase evaporation. There will be more rain, but the actual amount of water on the planet is finite. It will just be moving around from one state to another quicker.

3. Tectonic plate shifting has and will continue to have, more impact on relative sea levels than any changes in air temperature.

Answer 10

A slowdown in the rate of rising does not equate to a fall.

Answer 11

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No, it doesn't. Have you ever seen an ice cube melt?



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What are you trying to say?????

Answer 12

Neither of those needs to be true. Thanks for the example of scientific illiteracy, weak thought, and political bias that defines the denier agenda.