How much will global sea level rise this century?

By: Dr. Jeff Masters , 02:49 PM GMT am 13. Juli 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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Quoting WAHA:

When is their next update?

In 20-40 minutes
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Quoting Stormchaser2007:
Lets not get ahead of ourselves. There is still a good chance that this dissipates by tonight.


agree
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1432. WAHA
Quoting BurnedAfterPosting:
Let the jumping to conclusions begin lol, this is how it all starts

I understand the excitement of the potential of a system, but lets not classify it something it is not.

Wait for the NHC to recognize the area first

When is their next update?
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Quoting AussieStorm:
Night all


night aussie
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Quoting Stormchaser2007:


Winds were not near 50knots. Those were rain contaminated. This has some ways to go...dont rush it.
look at post 1359
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We had 2 over hyped blobs and we are soon to have a over hyped wave


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New TWO in a half hour. I doubt it'll be mentioned.
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Lets not get ahead of ourselves. There is still a good chance that this dissipates by tonight.
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Quoting IKE:


He's on here almost every day...was on earlier today...


Really guess i should log on more.
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1425. Ossqss
Quoting IKE:


JFV.....now WeatherStudent..


Don't forget PresidentialElection :)
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Night all
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Quoting BurnedAfterPosting:
Let the jumping to conclusions begin lol, this is how it all starts

I understand the excitement of the potential of a system, but lets not classify it something it is not.

Wait for the NHC to recognize the area first


Yes, this is why I was asking about the TWO. It's not even acknowledged yet.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting cyclonekid:
Does anybody think this could also be the next Bertha '08?

It's almost impossible to tell.
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Let the jumping to conclusions begin lol, this is how it all starts

I understand the excitement of the potential of a system, but lets not classify it something it is not.

Wait for the NHC to recognize the area first
Member Since: Posts: Comments:
1420. WAHA
Quoting cyclonekid:
Does anybody think this could also be the next Bertha '08?

Bertha was cat.3. The wave we are talking about could be at most cat.1, so don't count on it.
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Quoting CaneWarning:


Well it can't be a TD if there is no surface low.
yes i understand that i am just saying that a surface low is trying to develop, thats all.
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2 pages back
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1416. IKE
Quoting LPStormspotter:


That's right. Anyone see him on here anymore? I always felt sorry for him..


He's on here almost every day...was on earlier today...
Member Since: Juni 9, 2005 Posts: 23 Comments: 37860
Quoting LPStormspotter:


That's right. Anyone see him on here anymore? I always felt sorry for him..


He's always on under the name WeatherStudent.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
annular canes are defined by a very large eye, and a perfectly symetrical appearance... while Carlos is somewhat symetrical/well defined, it's eye was only 10 NM across last I checked.

Carlos has low shear, and as a result is circular in appearance.
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Quoting IKE:


JFV.....now WeatherStudent..


That's right. Anyone see him on here anymore? I always felt sorry for him..
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Quoting canesrule1:
yes, but as indicated in that QuikSCAT not only are the winds exceeding 50 knots but there seems like a surface low is trying to develop, imo.


Winds were not near 50knots. Those were rain contaminated. This has some ways to go...dont rush it.
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Quoting cyclonekid:
Does anybody think this could also be the next Bertha '08?


No.
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Quoting WAHA:

Did he even look at quikSCAT?
i looked at the quikscat but sometimes that can not be accurate because of the time period between when it was taken to know, you get me.
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Quoting canesrule1:
yes, but as indicated in that QuikSCAT not only are the winds exceeding 50 knots but there seems like a surface low is trying to develop, imo.


Well it can't be a TD if there is no surface low.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Does anybody think this could also be the next Bertha '08?
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Quoting LPStormspotter:
Hey IKE,Weathers,456.

What was the young man's name last year that was always in a panic. He was from Tampa i think. was it RJ..or jf cant remember? Do yall


weatherstudent?
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Quoting LPStormspotter:
Hey IKE,Weathers,456.

What was the young man's name last year that was always in a panic. He was from Tampa i think. was it RJ..or jf cant remember? Do yall


jfv - and I think he's Ft. Lauderdale.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
1404. IKE
Quoting LPStormspotter:
Hey IKE,Weathers,456.

What was the young man's name last year that was always in a panic. He was from Tampa i think. was it RJ..or jf cant remember? Do yall


JFV.....now WeatherStudent..
Member Since: Juni 9, 2005 Posts: 23 Comments: 37860
Quoting CaneWarning:


No, it lacks a surface low.
yes, but as indicated in that QuikSCAT not only are the winds exceeding 50 knots but there seems like a surface low is trying to develop, imo.
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the latest Carlos images show few feeder bands...almost annular in appearance. very cool, compact little storm...
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1401. WAHA
Quoting CaneWarning:


No, it lacks a surface low.

Did he even look at quikSCAT?
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Quoting Stormchaser2007:


Nothing to read.

000
ABNT20 KNHC 141133
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT TUE JUL 14 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER ROBERTS/BEVE


Thanks. I just wondered if they had even mentioned this wave at all. I guess maybe if it keeps its convection it may get a mention tomorrow.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
1399. IKE
Quoting CaneWarning:


The last TWO that was released. I'm at work and don't have my links. Has anyone read the TWO?


There was nothing listed.

New one comes out in 45 minutes or less.
Member Since: Juni 9, 2005 Posts: 23 Comments: 37860
Quoting WAHA:

I agree. That already looks like it's a cat.4!


LOL
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Hey IKE,Weathers,456.

What was the young man's name last year that was always in a panic. He was from Tampa i think. was it RJ..or jf cant remember? Do yall
Member Since: Posts: Comments:
Quoting CaneWarning:


The last TWO that was released. I'm at work and don't have my links. Has anyone read the TWO?


Nothing to read.

000
ABNT20 KNHC 141133
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT TUE JUL 14 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER ROBERTS/BEVE
Member Since: Posts: Comments:
Quoting WAHA:

In what two?


The last TWO that was released. I'm at work and don't have my links. Has anyone read the TWO?
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting canesrule1:
that has to be a TD, great inflow and outflow high cloud tops and it looks like there is a surface circulation because of that outflow.


No, it lacks a surface low.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
1393. WAHA
Quoting CaneWarning:
Has this been mentioned in the TWO?

In what two?
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Old AOI:

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Quoting Weather456:
Thanks SW, I figured. But actually I was reffering to the potential it has.

One of the best darn looking waves of the year

that has to be a TD, great inflow and outflow high cloud tops and it looks like there is a surface circulation because of that outflow.
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Quoting Weather456:
Thanks SW, I figured. But actually I was reffering to the potential it has.

One of the best darn looking waves of the year


I agree 456! WOW! This could be ANA in the before the weekend...wouldn't you think.
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Has this been mentioned in the TWO?
Member Since: April 26, 2009 Posts: 3 Comments: 3667
1388. WAHA
Quoting LPStormspotter:


LOL.. ????

Well, now it doesn't I think.
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Last 48 Hrs of E-ATL: Its really interesting... this wave came from almost nothing.

http://www.meteo.psu.edu/~gadomski/SAT_TROPATLEAST/animir.html
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Quoting IKE:


I think it's the blog that jumps the gun sometimes.

***Not necessarily directed to you***


I agree :P This blog gets soo crazy, you just have to lurk sometimes to keep safe.
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1385. WAHA
Quoting Stormchaser2007:


I had to delete the images due to the fact they both updated. It was a mistake on my part.

I forgive you.
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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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