How much will global sea level rise this century?
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
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Absolutely 100% agree! :P
I think the wave has potential to develop and I don't see it recurving before 50W. It is highly uncertain beyond that point.
I think it will loop 3 times in the Atlantic and then move south and cross the equator, put on its cloaking device and disappear for 4 days; eventually reappearing as a CAT 4 storm making landfall in Ecuador
and there isnt even an invest yet lol
Even if it were to hit Florida, I think you would be back home before it did
No idea. We have absolutley no idea.
If you are right I will give you a billion dollars i swear
NEVER trust the models past 96 hours. Heck...never trust than past 24 hours.
IF anything developes it looks like a trough will be in place...the question is will it re-curve over Florida or over the West Atlantic.
Ok Thanks, what are your percentages of this thing developing?
On a side note, some people are just way too sensitive to participate in an open forum. If you were here five or six years ago, like a lot of us, you'd have lost your minds with some our participants, ahem, Stormtop. I don't have anyone on my ignore list, I just enjoy everyone's comments for what they are and asking people not to quote others is just plain wrong. If I can give any advice on participating here, it is just to simply enjoy all of it and don't take anything personally.
Anyone remember when Stormtop used to post his own weather advisories in the guise of actual NHC advisories?
Oh boy... I hope this isn't correct!
Luckily, long range forecasts are seldom absolutely correct. Might get some rain out of it, if anything.
AOI
AOI
Good to see ya, dude.
Oh and ya'll...give the whole stormtop situation a rest. My goodness...
Yeah rx7, ain't nothing like it used to be.
No the plan has been foiled! It would have succeeded if not for you meddling bloggers!
I am sure there is a good analogy to show this, but I cant think of one right now lol
Still enjoy the foolishness here sometimes, the younger folks get so serious and you can tell when an older person comes in and just breaks everyone up into laughter...
(BAP that includes you!)
QS
Reed, I do not necessarily disagree with you.
However the most sensible case scenario at the moment is for little to no SE U.S. impact. Ever since yesterday, the models have been harmonizing toward a more westerly track, and then recurvature very close to the U.S. Things may change in the future, and the computer models may very well trend to a more westerly track. There complications that you must consider: strength, A/B high, and the trough.
The stronger the system, the more it will be influenced by upper level systems, and will be more susceptible to recurvature induced by the trough. Now SSTs should not be much of an inhibitor for tropical cyclogenesis since the temperatures are mostly marginally favorable. Wind shear will be a vital factor, because shear is high just to the west of it. Wind shear is expected to decrease near the Northern Antilles and the NE caribbean next week, providing a less hostile environment. This would reasonably lead to a stronger system, and therefore more of a chance to be caught by the weakness.
If the ridge stays strong, and continue to delay eastward propagation of the trough, then a more westerly track is likely. In addition to that, if the trough delays, shear should be weaker near Florida. This is why the 00z CMC expected this system to bomb out.
Overall, this all a matter of IF. But at the moment, a recurvature out to sea with no or little impact in the U.S. seems to be the scenario.
yes
Wonder how many people stopped lurking after you said that lol. Well said
All rotation in the mid levels for now
30-50%
In the Atlantic, there is a chance we'll see some development out of the deep tropics. The feature is a bundle of moisture and energy associated with a tropical wave, or two, and the ITCZ or Intertropical Convergence Zone. Several of the global computer models are indicating that an organized area of low pressure will eventually take shape in the region between Africa and the Lesser Antilles. It will probably be slow going since it is not climatologically a favorable area just yet. None the less, conditions are not terrible for development and thus we'll see how things transpire over the coming days. It would be interesting to see development out of the deep tropics if for no other reason than the forecast negative conditions for that region. Should something pop now, it would at least mean that perhaps, just perhaps, the region won't be as hostile as some of the long range models suggest. Still, we're about a month away from really eyeing that area of the Basin so for now, it is just wait and see.
I've stated ways back.
456,your not going unnoticed,..we saw ya earlier post.
Relax and enjoy a Fresca.
But a avatar update would really help yas in da Long run.
I feel Like were conversing with a cartoon half the time
No prob. Just came on and pulled up quikscat. Nothing at all going on at the surface other than rain.
oh my, can't breathe...
Carlos looks pretty strong, maybe next advisory it will be a major hurricane, am I correct?
And a very young one at that.
I think He is past his glory days,..as the Intensity forecast calls for gradual weakening from here out.
RAMMB on CARLOS
Thanks...that would indicate a Orange Circle on the NHC website. :) Good enough for me. Anything to get an Ana around here.
First West, then a curve to the North, then a RECURVE to the East LOL
In the sense of tropical met, a recurving cyclone is one that changes from a westerly component to an easterly one.
Allan's Tropical Model and Weather Data Page
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