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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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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Quoting WAHA:

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


LOL.. ????
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1383. WAHA
Quoting CaneWarning:


Tampa. Why?

I used to live near tampa.
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Quoting CaneWarning:


Tampa. Why?


no reason.. Seen your pic and just wondering.. No biggie
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Quoting WAHA:

Then maybe stormchaser2007 did it wrong. either way this is a strong wave.


I had to delete the images due to the fact they both updated. It was a mistake on my part.
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1380. WAHA
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. That already looks like it's a cat.4!
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Quoting LPStormspotter:


Cane where are you from?


Tampa. Why?
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Tropical Update
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Quoting CaneWarning:


I know what a time lapse is, but he said before and after.


Cane where are you from?
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Quoting WAHA:

The system west of that is starting to get dissorganized, I will pay more attention to the system close to Africa.


850Vort has increased today with this particular wave. SAL is still plaguing the convection however, the SAL is moving out ahead of this feature at a pretty good clip. SAL to the north appears to have decreased substantially. I wouldn't toss it out just yet as it will be nearing the islands by the weekend.
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1375. WAHA
Quoting CaneWarning:


I know what a time lapse is, but he said before and after.

Then maybe stormchaser2007 did it wrong. either way this is a strong wave.
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Thanks SW, I figured. But actually I was reffering to the potential it has.

One of the best darn looking waves of the year

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Quoting WAHA:

Wow, you didn't even know what time lapse of two pictures were? no offense, just LOL.


I know what a time lapse is, but he said before and after.
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1372. IKE
Quoting reedzone:


Trust me if this was near the Islands or USA, it would be tagged today, but it's near Africa, so they will probably wait till tonight or tomorrow morning. However, the NHC in the past has been known to jump the gun sometimes on these little critters.


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

***Not necessarily directed to you***
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Well the big difference between this wave and other this year, look where the location is... north of 10N. This actually has a good chance at becoming a little something.
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Quoting Weather456:


I think is the other way around.


The images updated as soon as I posted them. Sorry
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1369. WAHA
Quoting CaneWarning:
1360. Before what and after what?

Wow, you didn't even know what time lapse of two pictures were? no offense, just LOL.
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Quoting Weather456:


Hey StormW,

What do you think of the wave gaining convection as oppose to losing it once it emerged? Frankly, I was expecting the wave to decouple like past ones.


Yeah, Most don't come off convection guns blazin.. usually they are used to fireing during the day and dying off at night on land then once over the sea they can't do that and have to start gathering their own moisture (usually means LLC)to support themselves 24 hrs... This one's done that.

I think i got that right. Please correct me if i'm wrong.
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It's not even a invest.
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Quoting Stormchaser2007:
No EWRC. Carlos is just tightening up.


http://www.ssd.noaa.gov/goes/flt/t7/loop-rb.html

I don't know... IR shows a well formed eye prior to it clouding over/becoming intermittent, and reforming as a differently sized/proportioned eye. Yes, I know it happens most often in major canes, but that looks like an ewrc to me, in frames 6-7-8.
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Quoting Stormchaser2007:
Before:



After:



I think is the other way around.
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Quoting robbieNDBC:


You are exactly right. They will not tag this today. Maybe tomorrow. They're just going to write it as a wave on the surface analysis.


Trust me if this was near the Islands or USA, it would be tagged today, but it's near Africa, so they will probably wait till tonight or tomorrow morning. However, the NHC in the past has been known to jump the gun sometimes on these little critters.
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1360. Before what and after what?
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1361. WAHA
Quoting CaneWarning:
Wow, that's a nice CV blob. What do you all think about it? The conditions don't seem to unfavorable.

Maybe that is what it seems like, except it doesn't entirely have a closed center of circulation yet. It might have a closed center of circulation by tomorrow.
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Updated IR:

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Quoting Weather456:
It has gain convection since leaving the coast, opposite to other waves this season and also indicate the potential the system has. However, I would like to see a bit more persistence since these features are fragile in the EATL. Also only the UKMET develops it. But there is always the difference between the models show and what actually occurs.


Agreed!

The quikscat of this area (admittedly from earlier) shows great convergence...though the eastern half of the circulation is incomplete. Typically we have to look for westerly winds to define a closed circulation...now we need southerlies on the eastern half of the circulation.

This may come though fairly easily...as the low separates itself from the climatological elongated west-east trough extending out of western Africa!
Embedded in a temporarily moist environment.

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Quoting Stormchaser2007:


There is no way that this will be tagged an invest today. It will have to persist until tomorrow morning. It would also have to look the same or better to be tagged tomorrow morning. Not so great chance of that happening as these AEWs are rather fragile.


You are exactly right. They will not tag this today. Maybe tomorrow. They're just going to write it as a wave on the surface analysis.
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1354. WAHA
Quoting WeatherStudent:


Good afternoon Senior Chief! Might the Atlantic be finally awakening from it's temporary sleep thus far this season? :)

It could, but then might dissipate while it gets closer to north america.
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Quoting AussieStorm:

me troll... no way


Not what I meant... I realized that it wouldn't be seen the way I intended right after I posted it. I know you aren't a troll. :)

I was just talking about our continual downcaster who doesn't provide much in the way of backup.
Member Since: August 3, 2008 Posts: 16 Comments: 5925
Wow, that's a nice CV blob. What do you all think about it? The conditions don't seem to unfavorable.
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it appears carlos could be the first major of the season w/top winds over 135mph,IMO...
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Quoting StormW:
Greetings,

Here for a short, then back after lunch.


Hey StormW,

What do you think of the wave gaining convection as oppose to losing it once it emerged? Frankly, I was expecting the wave to decouple like past ones.
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Afternoon Storm.
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Quoting alaina1085:
Aussie, I think he was referring to Benblogger as a troll, not you. :)

i guessed that... i just want this user/troll to back up his statement with facts.
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Nice signature.

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1344. Ossqss
Can it make it through?

Member Since: June 12, 2005 Posts: 6 Comments: 8192
1342. WAHA
Quoting Stormchaser2007:
Updated RAMSDIS visible.


The system west of that is starting to get dissorganized, I will pay more attention to the system close to Africa.
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Quoting StormW:
Greetings,

Here for a short, then back after lunch.


Nice to see ya storm.. How's it going?

Brandy
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Aussie, I think he was referring to Benblogger as a troll, not you. :)
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Well shear appears to be 5-10 knots, SSTs 26-28C and moist enviroment, it has what it needs. As with Carlos, not all take advantage.
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Updated RAMSDIS visible.

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I just want this user to back up his opinion
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1336. WAHA
Quoting Patrap:
Everything is monitored rolling off Africa,..always.
The first thing one looks for is sustainability,..then it will bear closer scrutiny.

Many a impressive wave rolls off the Continent ,only to dissolve into "poofness" over the Eastern Atlantic after a Day or two..


Or, it could make a comeback in the East Pacific. So far in 2009 all storms did this.
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Quoting jeffs713:


I would like a troll for 500 please, Alex.

me troll... no way
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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