How much will global sea level rise this century?

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

Share this Blog
4
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 485 - 435

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Quoting tennisgirl08:
Weather 456 - I am curious of your opinion of the CATL disturbance.


Basically, an area of interest that is being watch. My thoughts are here at my blog and are mainly unchange from this morning. The wave has gain latitude and has some cyclonic turning evident, which is interesting to note. Wind shear and SST remain favorable ahead of the system so the only inhibiting factor remains the dust north of it. I think the wave will head of towards the WNW, probaly not getting too far north since we don't know how deep it might get. After reaching the islands or at the edge of the dust airmass, development maybe monitored even more closely. I cannot tell whether it will be a fish or not since we don't have all the answers yet. Just a watch and see case here.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Here's our future invest... and I think i'll leave until later tonight now.

Link
Member Since: July 29, 2006 Posts: 28 Comments: 1802
Quoting SavannahStorm:



"Wait, so it wasn't just tropical... it was extra tropical?!"

\

LOL!
Member Since: Posts: Comments:
Quoting SavannahStorm:


The quotation marks denote sarcasm.



I picked up on that but still... wow
Member Since: Posts: Comments:
481. WAHA
I
Quoting Drakoen:


wow

I think you know a lot about Cyclone Aldonca of march 2004, what was the sea surface temperatures it was over?
Quoting Drakoen:


wow


The quotation marks denote sarcasm.
Member Since: Posts: Comments:
Quoting SavannahStorm:



"Wait, so it wasn't just tropical... it was extra tropical?!"



wow
Member Since: Posts: Comments:
Quoting tennisgirl08:
NHC discussion: Can someone elaborate?

..TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 27W S OF 16N MOVING W NEAR 15 KT. A
BROAD AREA OF LOW-LEVEL CYCLONIC TURNING IS APPARENT IN VISIBLE
SATELLITE IMAGERY AS WELL IN THE 600-800 MB LAYER ACCORDING TO
SATELLITE DERIVED WINDS. THE WAVE ALSO COINCIDES WITH A LOW
AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 7N-13N BETWEEN 24W-30W. DEEP CONVECTION NEAR
THE WAVE IS LIKELY BEING MAINLY SUPPORTED BY LOW LEVEL
CONVERGENCE NEAR THE ITCZ.

A TROPICAL WAVE IS E OF THE LESSER ANTILLES EXTENDING FROM
18N53W TO 5N49W MOVING W 15-20 KT. THIS WAVE HAS BECOME
INCREASINGLY TILTED NW-SE BY THE NE WIND SURGE E OF THE AXIS
OVER THE N PORTIONS OF THE WAVE AXIS. A WELL DEFINED INVERTED V
PATTERN IS EVIDENT IN THE LOW-LEVEL CLOUDS SEEN ON VISIBLE
SATELLITE IMAGERY. THE WAVE ALSO COINCIDES WITH A WELL AMPLIFIED
MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. A
SMALL AREA OF SCATTERED MODERATE CONVECTION IS FROM 9N-12N
BETWEEN 50W-53W. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE
ALSO N OF THE WAVE AXIS FROM 19N-26N BETWEEN 52W-55W. THIS
SHOWER ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE
NEAR A SHORTWAVE UPPER LEVEL TROUGH. GFS APPEARS TO HAVE A GOOD
HANDLE ON THIS FEATURE AND SHOWS IT MOVING INTO THE LESSER
ANTILLES TOMORROW WITH THE N PART LIKELY FRACTURING.




The wave closest the island will likely move into the Lesser Antilles with the northern part weakening. In relation to our area of interest, none.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting StormJunkie:
Afternoon all

Been lurking for the past few weeks saving my energy for Aug, Sept, Oct...But post 410 brought me out of lurk...That comment deserves a ban imvho...May be the most edgy and unwarranted comment of the year!

:~)


What? It was only a reaction to a loss and a death. Ban the poster i was replying to if anything.
Member Since: July 29, 2006 Posts: 28 Comments: 1802
Weather 456 - I am curious of your opinion of the CATL disturbance.
Member Since: Posts: Comments:
474. WAHA
Quoting Weather456:
But it's winter in the South Atlantic, if they barely get development during their summer why would they get development during thier winter?

I think the cold core low that i thought was tropical was over 26 degrees celsius (last time i said farenheit epic FAIL) was about the same as Cyclone Aldonca was over. Aldonca was in the south atlantic, you know like in march 2004?
Conditions at 42001 as of
(3:50 pm CDT)
2050 GMT on 07/13/2009:



Wind Direction (WDIR): NNE ( 30 deg true )
Wind Speed (WSPD): 1.9 kts
Wind Gust (GST): 3.9 kts
Wave Height (WVHT): 1.3 ft
Dominant Wave Period (DPD): 8 sec
Average Period (APD): 4.9 sec
Atmospheric Pressure (PRES): 30.02 in
Pressure Tendency (PTDY): -0.02 in ( Falling )
Air Temperature (ATMP): 86.9 °F
Water Temperature (WTMP): 90.9 °F
Member Since: Posts: Comments:
12Z ECMWF +72hrs

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting tennisgirl08:
got this info. from hurricane city website:

"UPDATE BY: Jim Williams...The waves coming off of Africa are getting stronger and as usual for July they are dragging the African dust along with them into the Atlantic. This is why we usually have to wait until August to see development in the East Atlantic. The more waves that move across Africa the less dust they drag out ,so we need to see a few more strong waves before one actually develops with less dust attached. With each wave that emerges off of the coast of Africa the chances will be better for development."

Any thoughts on this? He doesn't see any development with these waves until August.


Sounds about right. The ICTZ is still fairly far south to supress the dust, and the best way to supress dust is to rain on it.
Member Since: Posts: Comments:
And just like that Im back into lurking. Have a great afternoon everyone.
Member Since: Posts: Comments:
NHC discussion: Can someone elaborate?

..TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 27W S OF 16N MOVING W NEAR 15 KT. A
BROAD AREA OF LOW-LEVEL CYCLONIC TURNING IS APPARENT IN VISIBLE
SATELLITE IMAGERY AS WELL IN THE 600-800 MB LAYER ACCORDING TO
SATELLITE DERIVED WINDS. THE WAVE ALSO COINCIDES WITH A LOW
AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 7N-13N BETWEEN 24W-30W. DEEP CONVECTION NEAR
THE WAVE IS LIKELY BEING MAINLY SUPPORTED BY LOW LEVEL
CONVERGENCE NEAR THE ITCZ.

A TROPICAL WAVE IS E OF THE LESSER ANTILLES EXTENDING FROM
18N53W TO 5N49W MOVING W 15-20 KT. THIS WAVE HAS BECOME
INCREASINGLY TILTED NW-SE BY THE NE WIND SURGE E OF THE AXIS
OVER THE N PORTIONS OF THE WAVE AXIS. A WELL DEFINED INVERTED V
PATTERN IS EVIDENT IN THE LOW-LEVEL CLOUDS SEEN ON VISIBLE
SATELLITE IMAGERY. THE WAVE ALSO COINCIDES WITH A WELL AMPLIFIED
MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. A
SMALL AREA OF SCATTERED MODERATE CONVECTION IS FROM 9N-12N
BETWEEN 50W-53W. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE
ALSO N OF THE WAVE AXIS FROM 19N-26N BETWEEN 52W-55W. THIS
SHOWER ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE
NEAR A SHORTWAVE UPPER LEVEL TROUGH. GFS APPEARS TO HAVE A GOOD
HANDLE ON THIS FEATURE AND SHOWS IT MOVING INTO THE LESSER
ANTILLES TOMORROW WITH THE N PART LIKELY FRACTURING.


Member Since: Posts: Comments:
But it's winter in the South Atlantic, if they barely get development during their summer why would they get development during thier winter?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
467. WAHA
Quoting Stormchaser2007:


A simple 'Link please' would have sufficed.

Link

Thanks for the link. I just faved it.
Quoting SavannahStorm:



"Wait, so it wasn't just tropical... it was extra tropical?!"



LOL
Member Since: Posts: Comments:
The Broad area of Low Pressure in the Atlantic has ways to go until it becomes a problem, what I was stating earlier was basically based on the information I was seeing. The B/A currently is more like 2004 where the tail end of it ends next to the East Coast. If the trough is strong enough, it might be able to recurve it but not until it passes Bermuda and the 2 models (GFS/EURO) prove my point on that. Notic how the GFS stalls the storm next to the USA, that's not a harmless recurvature. ;)
Member Since: July 1, 2008 Posts: 13 Comments: 7423
Quoting Stormchaser2007:
Cold core extra tropical. End of discussion.
Link



"Wait, so it wasn't just tropical... it was extra tropical?!"

Member Since: Posts: Comments:
Link
Member Since: Posts: Comments:
Quoting seminolesfan:

There it is...but that won't be good enough.

Have a good afternoon, Chaser. I'm out.

Everyone have fun tonight.


Have a good afternoon seminoles.
Member Since: Posts: Comments:
Quoting WAHA:

Hey, where the heck did you get THAT at?


A simple 'Link please' would have sufficed.

Link
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Cold core extra tropical.


There it is....

Have a good afternoon, Chaser. I'm out.

Everyone have fun tonight.
Member Since: Posts: Comments:
459. WAHA
Quoting Stormchaser2007:
Cold core extra tropical. End of discussion.


Hey, where the heck did you get THAT at?
got this info. from hurricane city website:

"UPDATE BY: Jim Williams...The waves coming off of Africa are getting stronger and as usual for July they are dragging the African dust along with them into the Atlantic. This is why we usually have to wait until August to see development in the East Atlantic. The more waves that move across Africa the less dust they drag out ,so we need to see a few more strong waves before one actually develops with less dust attached. With each wave that emerges off of the coast of Africa the chances will be better for development."

Any thoughts on this? He doesn't see any development with these waves until August.
Member Since: Posts: Comments:
I took a look at what WAHA was talking about, yes it is cold core

extra-tropical if you will lol
Cold core extra tropical. End of discussion.
Link
Member Since: Posts: Comments:
Quoting WAHA:

Yes it is, and there's a 50 percent chance that it really is (or was) tropical in nature.
No, not 50 percent. I'm not serving any more troll-tizers so this will be my last comment on this topic.
Member Since: Posts: Comments:
Will they launch if these storms get down range?

Member Since: Posts: Comments:
453. WAHA
Quoting Stormchaser2007:


Why are you intent on arguing with me? The SST's down there are way too cold.

From where it was before it dissipated it was under 26 degrees farenheit. Relatively favorable if you ask me.
We've gotten a go to close the white room out. They're alone now.
Member Since: July 8, 2005 Posts: 259 Comments: 24512
There are no thundershowers in the 20 nm area of the cape at this time. That could quickly change though.
Member Since: July 8, 2005 Posts: 259 Comments: 24512
Quoting seminolesfan:

Interesting exchange there, huh?


Yeah I dont know why its such a big deal.
Member Since: Posts: Comments:
449. WAHA
Quoting seminolesfan:

Interesting exchange there, huh?

Yes it is, and there's a 50 percent chance that it really is (or was) tropical in nature.
Quoting WAHA:
T
Just because it's winter down there doesn't mean a guarantee it isn't tropical. Tropical cyclones can happen all year round.


Why are you intent on arguing with me? The SST's down there are way too cold.
Member Since: Posts: Comments:
Quoting WAHA:
T
Just because it's winter down there doesn't mean a guarantee it isn't tropical. Tropical cyclones can happen all year round.

Chill man, go check out wikipedia or something about tropical cyclogenesis.
Member Since: Posts: Comments:
Member Since: July 3, 2005 Posts: 426 Comments: 129093
GO for GLS Mainline activation!
Member Since: July 8, 2005 Posts: 259 Comments: 24512
Quoting Stormchaser2007:


Its winter down there. If it was tropical we would have heard something about it. Those are pretty rare.

Interesting exchange there, huh?
Member Since: Posts: Comments:
443. WAHA
T
Quoting Stormchaser2007:


Its winter down there. If it was tropical we would have heard something about it. Those are pretty rare.

Just because it's winter down there doesn't mean a guarantee it isn't tropical. Tropical cyclones can happen all year round.


Hatch is closed! They're all seeled up.
Member Since: July 8, 2005 Posts: 259 Comments: 24512
Concerning the two AOI's off the coast of Africa, could the first help the developement of the second or vise versa with respect to dust and dry air? The SST's there are just at support levels. Just curious :)
Member Since: Posts: Comments:
Quoting WAHA:

how would you know?


Its winter down there. If it was tropical we would have heard something about it. Those are pretty rare.
Member Since: Posts: Comments:
Go Endeavour! Getting close to launch now,
we'll find out if the weather cooperates!
Member Since: July 8, 2005 Posts: 259 Comments: 24512
437. WAHA
Quoting Stormchaser2007:


Not tropical in nature.

how would you know?
Quoting WeatherStudent:


Futuristic prospects in reference to it, Drak?



Continue to monitor. Needs more model support but the ECMWF and GFS develop an area of low pressure. The GFS is more inclined to close off this low than the ECMWF.
Member Since: Posts: Comments:
435. WAHA
Quoting seminolesfan:

I didn't look, but its their winter now so I'm sure what you saw wasn't tropical in nature.

oh, sorry, it really looked like it broke off the front.

Viewing: 485 - 435

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Top of Page

About

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

Local Weather

Overcast
35 °F
Overcast