How much will global sea level rise this century?

By: Dr. Jeff Masters , 2:49 PM GMT on July 13, 2009

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How much will global sea level rise this century? Well, global sea level rise began in the late 1700s, and accelerated to 1.2 inches (3 cm) per decade over the past 25 years (see my post, Sea level rise: what has happened so far). If the conditions that led to this acceleration continue, we can expect sea level will rise an additional 1.1 ft (0.34 m) by 2100 (Jevrejeva et al., 2008). At a minimum, sea level rise during the 21st century should equal that of the 20th century, about seven inches (0.6 ft, 0.18 meters). This is the lower bound given by the IPCC in its 2007 assessment, which projected sea level rise of 0.6 - 1.9 ft (0.18 - 0.59 m) by 2100. However, they cautioned in their report that due to the lack of knowledge about how melting glaciers behave, the actual sea level rise might be higher. There is a growing consensus that the 2007 IPCC sea level rise estimates are much too low.


Figure 1. Observed global sea level from tide gauges (red line, pink color is the uncertainty range) and satellite measurements (green line), with forecasts for the future. The blue colors show the range of projections for three different forecasts (the forecasts overlap, but this overlap is not shown). Image modified from U.S. EPA.

The 2007 IPCC report: too conservative?
Three major sea level rise studies published since the 2007 IPCC report have argued that the IPCC's projections of sea level rise are too conservative. A paper published in 2008 in Science by Pfeffer et al. (2008) concluded that the "most likely" range of sea level rise by 2100 is 2.6 - 6.6 ft (0.8 - 2.0 meters). Their estimates came from a detailed analysis of the processes the IPCC said were understood too poorly to model--the ice flow dynamics of glaciers in Greenland and Antarctica. For example, increased glacial flow may result when water draining from melt water lakes on the surface of the glacier to the base of the glacier, where it acts as a lubricant. The authors cautioned that "substantial uncertainties" exist in their estimates, and that the cost of building higher levees to protect against sea level rise is not trivial.

Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany looked at the observed relationship between changes in sea level and global temperatures since 1900 (Rahmstorf, 2007). Rahmstorf showed that that there has been a direct relationship between sea level rise and global average temperature: 0.1 - 0.3 meters of sea level rise occurs per °C increase in global temperature. Using this relationship, Rahmstorf predicted 1.6 - 4.6 ft (0.5 - 1.4 m) of sea level rise by 2100, since the IPCC predicts that global temperatures will rise 1.4° to 5.8°C. Rahmstorf concluded, "very low sea-level rise values as reported in the 2007 IPCC report now appear rather implausible in the light of the observational data".

A similar approach was taken by Grinsted et al. (2009), but they extended the relationship between sea level and global average temperature all the way back to 200 A.D. using proxy records. They concluded that ice sheets respond more quickly to temperature changes than the computer models used in the 2007 IPCC assessment. The authors estimated that "IPCC projections of sea level rise 2090 - 2099 are underestimated by roughly a factor of three". The authors predicted that global sea level will be rising 11 mm/year by 2050--four times faster than the 20th century rise. By the last decade of this century, they forecasted that sea level will rise 3.0 - 4.3 feet (0.9 - 1.3 meters), using the IPCC's A1B "business as usual" scenario.

The long-range forecast: using paleohistory to forecast sea level rise
We can also look at times in Earth's past that had similar climate to what we expect by the year 2100. The best time to look at is probably just before the most recent ice age--the Eemian. This interglacial period 130,000 - 114,000 years ago featured temperatures near the poles that were 2°C warmer than present-day temperatures. Tree line lay about 500 miles farther north in the Canadian Arctic, and the hippopotamus ranged as far north as the Thames River in England. A similar climate is expected under some of the more moderate global warming scenarios envisioned by the IPCC. Sea level is believed to have been 4 - 6 meters (13 - 20 feet) higher than at present during the Eemian, but there is at least one unpublished study that presents evidence that global sea level was 6 - 9 meters (20 - 30 feet) higher. If the climate does warm to levels seen in the Eemian, it is widely believed that we would again see sea levels at least 4 - 6 meters higher than the present-day levels. Clearly, sea level rises of this magnitude would be ruinous to society. However, most climate change scientists believe that it would take many centuries for enough ice to melt from the Greenland and West Antarctic ice sheets to create sea level rises of 4 - 6 meters.

However, the scientist who is arguably the most visible and authoritative climate scientist in the world, Dr. James Hansen of NASA, stated (Hansen, 2007) "I find it almost inconceivable that business-as-usual climate change would not yield a sea level change of the order of meters on the century timescale" (IPCC business-as-usual (BAU) scenarios assume that emissions of CO2 and other greenhouse gases will continue to increase year after year). Hansen gave a hypothetical but potentially realistic scenario where the sea level rise due to ice sheet disintegration doubles every decade, leading to a 16 foot (5 meter) sea level increase by 2100. He noted that during the Plio-Pleistocene period 2 - 3 million years ago, CO2 levels were similar to today (350 - 450 ppm), and global temperatures were 2 - 3°C warmer, similar to what we expect by the end of the century. Yet, this Plio-Pleistocene world was "a dramatically different planet, without Arctic sea ice in the warm seasons and with a sea level 25 ± 10 m higher."

Summary
To summarize, here are some predictions of how high global sea level might rise by 2100:

0.6 ft (0.18 m): Constant linear rise, equal to 20th century rise
1.1 ft (0.34 m): Constant acceleration model (Jevrejeva et al., 2008)
0.6 - 1.9 ft (0.18 - 0.59 m): Primitive models of ice sheets (IPCC, 2007)
1.6 - 4.6 ft (0.5 - 1.4 m): Relationship between temperature and sea level rise since 1900 (Rahmstorf, 2007)
3.0 - 4.3 feet (0.9 - 1.3 m): Relationship between temperature and sea level rise since 200 A.D. (Grinsted et al., 2009)
2.6 - 6.6 ft (0.8 - 2.0 meters): Considering glacier ice flow dynamics not included by the IPCC (Pfeffer et al., 2008)

In a 2009 interview with New Scientist magazine, sea level expert Stephan Rahmstorf said, "I sense that now a majority of sea level experts would agree with me that the IPCC projections are much too low." This sentiment was echoed by glaciologist Robert Bindschadler of the NASA Goddard Space Flight Center in Greenbelt, Maryland, who commented, "most of my community is comfortable expecting at least a metre by the end of this century."

In forthcoming posts in this series, I'll explore how a meter (3.28 feet) of sea level rise will affect the U.S. coast, the Caribbean, and other vulnerable locations world-wide. It would be wise to begin preparing now for a potential rise in sea level of a meter this century. In particular, development near the coasts should be severely restricted in low-elevation zones. It will be very expensive to protect or move infrastructure away from rising seas later this century. However, even if the rate of sea level rise doubles every decade, those of us who are over the age of 50 will not live to see sea level rise cause a significant disruption to society. There is time for society to prepare for the rising sea.

References
Jevrejeva, S., J.C. Moore, A. Grinsted,, and P.L. Woodworth, 2008, "Recent global sea level acceleration started over 200 years ago?", Geophysical Research Letters, 35, L08715, doi:10.1029/2008GL033611, 2008.

Grinsted, A., J.C. Moore, and S. Jevrejeva, 2009, "Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD", Climate Dynamics, DOI 10.1007/s00382-008-0507-2, 06 January 2009.

Hansen, J., 2007, "Scientific reticence and sea level rise",, Environ. Res. Lett. 2 (April-June 2007) 024002 doi:10.1088/1748-9326/2/2/024002.

IPCC (Intergovernmental Panel on Climate Change), 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York, 996 pp.

Pfeffer, W.T., J.T. Harper, and S. O'Neel, 2008, "Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise", Science 321 no. 5894, pp. 1340-1343, 5 September 2008. DOI: 10.1126/science.1159099

Rahmstorf, Stefan. "Sea-Level Rise: A Semi-Empirical Approach to Projecting Future." Science 315 (2007): 368–370.

Other posts in this series
Sea level rise: what has happened so far
U.S. vulnerability to sea level rise

Wednesday, I'll take a look at the Atlantic hurricane forecast for the remainder of July. There's currently nothing out there worth discussing--will it stay that way?

Dr. Ricky Rood has some interesting commentary on the new climate change legislation that passed the House last month, and will go to the Senate in September.

Jeff Masters

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We could have an invest when they issue the 8pm update.
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Quoting AllStar17:


Well, seems like we will indeed have something to watch.


Wouldn't surprise me if the NHC put that area in yellow. Perhaps orange.
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
New QuikSCAT

Center at 9N/32W

The higher resolution pass should reveal a possible LLCC since it's hinted here.

There is also another possible circulation further west near 40W.




Well, seems like we will indeed have something to watch.
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maybe yellow circle on the map on the 18z map on nhc
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New QuikSCAT

Center at 9N/32W

The higher resolution pass should reveal a possible LLCC since it's hinted here.

There is also another possible circulation further west near 40W.


Member Since: July 24, 2005 Posts: 407 Comments: 19076
I hope that doesn't happen to be an OBX event. I'm vacationing in Hatteras there in about 3 weeks. But the models long range forecasts are a bit sketchy so you never know what could happen.
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A close shave.


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Shucks a shuttle scrub. Wednesday @ 5:58 PM.
Member Since: July 8, 2005 Posts: 259 Comments: 23627
Quoting tennisgirl08:
Per Dr. Steve Lyons - no concern for the low pressure system. Said it would be entering a very stable air mass and would have a hard time developing.

Sounds about right. I still dont like the longwave pattern for any development anytime soon.
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Good Afternoon...

Looks like GFS is coming inline with ECMWF. Due to the current AZ/BER HIGH strength... I would lean more towards ECMWF for its initial track as is not underestimating its strength... remember IKE and how troublesome that omega block was and its development.

I believe ingredients will become better combined for development later this week.
Member Since: August 14, 2008 Posts: 4 Comments: 4938
With a negative NAO in place, less likely a fish event. Not to mention the possible slow rate of deepening. It might recurve eventually but probably in close proximity to the Bahamas and E USA.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting futuremet:


I will no longer use the term "fish", I will use "go out to sea" instead. It is more tenable.


I 2nd that notion lol
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Per Dr. Steve Lyons - no concern for the low pressure system. Said it would be entering a very stable air mass and would have a hard time developing.
Member Since: July 17, 2008 Posts: 0 Comments: 1242
Quoting weatherwatcher12:

You can't call it a fish for 2 reasons:

1.Long range forecasting has some flaws
2.There is Bermuda out there too

IMO


I will no longer use the term "fish", I will use "go out to sea" instead. It is more tenable. Many gets mad when "fish" is used. It caused quite a commotion when Bertha was going "out to sea" last year.
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Should I put BenIbogger on ignore? He has really been annoying me the past week or so.
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Quoting reedzone:
Also we have a strong (2004) like High in the Atlantic, I don't see recurvatures unless a strong trough can digg in.. I basically see a WNW trend for the next few weeks.

Wel, well, well...
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Showing an OBX event:

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Quoting HurricaneSwirl:


why is it in this blog whenever someone asks a question they have to get ridiculed?? this blog is terrible for someone who actually plans on learning something.

I just wanted to ask that IF it ended up developing and IF it made it that far and IF there was a trough coming, that the high would be too strong and it would do a jeanne.

I honestly dont care if im a person "who just cant stop thereselves lol" because if i want to learn about what a certain pattern would do to a storm i can and i dont have to stop myself for people like you.

That is burnedafterposting, if he/she doesnt believe it then it cant be true haha.
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Quoting HurricaneSwirl:


why is it in this blog whenever someone asks a question they have to get ridiculed?? this blog is terrible for someone who actually plans on learning something.

I just wanted to ask that IF it ended up developing and IF it made it that far and IF there was a trough coming, that the high would be too strong and it would do a jeanne.

I honestly dont care if im a person "who just cant stop thereselves lol" because if i want to learn about what a certain pattern would do to a storm i can and i dont have to stop myself for people like you.


Fine you want an answer

Yes it could do a track like Jeanne, it could do a Frances, a Andrew, a Isabel, a Fabian.

It COULD do about a hundred different things at this point and that is if it even develops


Thats the point, now you get ridiculed no matter what, some chastize people for talking long range and some chastize you for not; you will learn pretty quick here, you cant win either way.
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What kind of fuel does this potential system have under its potential path? Do we have any depth to the TCHP in that area ? The water where it is currently is barely 81ºF from reading an earlier discussion.
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Quoting BenBIogger:


agree


Why do you always agree with downcasters?
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The bigger question is - will this disturbance actually develop. Then we can talk about forecast tracks. Also, I do see possible invest by this time tomorrow.
Member Since: July 17, 2008 Posts: 0 Comments: 1242
Quoting BurnedAfterPosting:


Why are we even talking about what it may do 7 days down the road? Again no matter how many times it is said some just can't stop themselves lol


why is it in this blog whenever someone asks a question they have to get ridiculed?? this blog is terrible for someone who actually plans on learning something.

I just wanted to ask that IF it ended up developing and IF it made it that far and IF there was a trough coming, that the high would be too strong and it would do a jeanne.

I honestly dont care if im a person "who just cant stop thereselves lol" because if i want to learn about what a certain pattern would do to a storm i can and i dont have to stop myself for people like you.
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Quoting BenBIogger:
Might be the 2nd fish storm of the season.

if it even develops.


Not if it affects the Islands before it goes out to sea
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Quoting HaboobsRsweet:
With that said it will not form...nothing this month but August will be interesting.


agree
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Quoting BenBIogger:
Might be the 2nd fish storm of the season.

if it even develops.

You can't call it a fish for 2 reasons:

1.Long range forecasting has some flaws
2.There is Bermuda out there too

IMO
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With that said it will not form...nothing this month but August will be interesting.
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Quoting HaboobsRsweet:
Why dont you test your forecasting skills and see if you can predict it 7 days out. Improve on your long range forecasting. If you are wrong, make lessons learned. Why so afriad to look out 7 days? Gezz man I have to put together 2 week forecasts all the time. Try to grow as a forecaster.


Very true :P
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting reedzone:


Dissagreed, I believe the trough will stall and this system if it forms, will do a Frances track.


Yes, what you say is possible, and especially since the trough appears to be weaker in the 18z run. But if the GFS' is correct, then it will inevitably go out to sea. However if it were to move into the Caribbean, the recurvature will be postponed, because it would feel the weakness less caused by the trough. This is possible if it remains weak like the CMC and the UKMET seems to be showing or if the STR strengthens.
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or maybe they are great forecasters with lots of years behind their belts.
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Might be the 2nd fish storm of the season.

if it even develops.
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Quoting Weather456:
Still puzzles me how we know where this is going to end up in 7 days. Whatever crystal ball yall using, please lend me, becuz I was thinking of investing in IBM this winter.


I use no crystal balls.

However I find this device very handy when forecasting:

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Why dont you test your forecasting skills and see if you can predict it 7 days out. Improve on your long range forecasting. If you are wrong, make lessons learned. Why so afriad to look out 7 days? Gezz man I have to put together 2 week forecasts all the time. Try to grow as a forecaster.
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Endevour is scrubbed. They are going to discuss when they will try again.
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Quoting Weather456:
Still puzzles me how we know where this is going to end up in 7 days. Whatever crystal ball yall using, please lend me, becuz I was thinking of investing in IBM this winter.


They make a great line of crystal balls lol
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Quoting SavannahStorm:


The 00Z and 12Z runs, which are traditionally more reliable, both had a more westerly tack. The 06Z and this 18Z have a more easterly/northerly track. So I would expect the models to wobble back and forth between those solutions.


That said... I must emphasize that we are talking about conditions that are at least 144 hours out, and a difference in a couple of degrees of latitude where the low develops can have a profound effect on the outcome.
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Still puzzles me how we know where this is going to end up in 7 days. Whatever crystal ball yall using, please lend me, becuz I was thinking of investing in IBM this winter.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Like I have been saying since this morning, it will likely go out to sea. Albeit the GFS is showing a weaker trough compared to 12z, it is still adequate to induce recurvature. If the GFS continues to weaken the trough, a more westerly track plausible.
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Quoting HurricaneSwirl:


do you think it could do a jeanne? that storm sure was interesting.


Why are we even talking about what it may do 7 days down the road? Again no matter how many times it is said some just can't stop themselves lol
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Quoting reedzone:
Also we have a strong (2004) like High in the Atlantic, I don't see recurvatures unless a strong trough can digg in.. I basically see a WNW trend for the next few weeks.


do you think it could do a jeanne? that storm sure was interesting.
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The "Weather Channel":

However, a weak low pressure circulation, midway between Africa and northern South America in the central tropical Atlantic, is coupled with a cluster of persistent showers and thunderstorms.

Although small and currently poorly organized, a circulation this far south in mid July has some outside chance of developing into a tropical cyclone.

Conditions are currently a bit hostile for development, but a small system, such as this one, can develop fast if conditions become favorable.

Tis low will be monitored for potential development as it moves west to west-northwest at between 10 and 15 mph.
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We just got rocked in southern MS. I am looking to see if any tornados were reported but the warning sirens were flaring.
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Also we have a strong (2004) like High in the Atlantic, I don't see recurvatures unless a strong trough can digg in.. I basically see a WNW trend for the next few weeks.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
Quoting futuremet:


Yup, I think this what will actually happen. Most of the models agree with this too.


Dissagreed, I believe the trough will stall and this system if it forms, will do a Frances track.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
Anvil, field mill and lighting no go. Scrubbed!
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no go weather rule

best be safe then sorry
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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