Sea level rise: what has happened so far

By: Dr. Jeff Masters , 2:05 PM GMT on June 10, 2009

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Sea level has been rising globally since the late 1700s. This rise has accelerated in recent decades, thanks to increased melting of glaciers and ice sheets due to a warmer climate, plus the fact that warmer oceans are less dense and expand, further increasing sea level. Though sea level rise appears to have slowed over the past five years, it will significantly accelerate if the climate warms the 2 - 3°C it is expected to this century. If these forecasts of a warmer world prove accurate, higher sea levels will be a formidable challenge for millions of people world-wide during the last half of this century. Sea level rise represents one of my personal top two climate change concerns (drought is the other). I'll present a series of blog posts over the coming months focusing on at-risk areas in the U.S., Caribbean, and world-wide. Today, I focus on the observed sea level rise since the Ice Age.

What's at stake
Higher sea levels mean increased storm surge inundation, coastal erosion, loss of low-lying land areas, and salt water contamination of underground drinking water supplies. About 44% of the Earth's 6.7 billion people live within 150 km (93 miles) of the coast, and 600 million people live at an elevation less than ten meters (33 feet). Eight of the ten largest cities in the world are sited on the ocean coast. In the U.S., the coastal population has doubled over the past 50 years. Fourteen of the twenty largest urban centers are located within 100 km of the coast, and are less than ten meters above sea level (McGranahan et al., 2007). The population of many vulnerable coastal regions are expected to double by 2050, according to the U.S. Census Bureau.

Sea level rise since the Ice Age
Before the most recent Ice Age, sea level was about 4 - 6 meters (13 - 20 feet) higher than at present. Then, during the Ice Age, sea level dropped 120 meters (395 ft) as water evaporated from the oceans precipitated out onto the great land-based ice sheets. The former ocean water remained frozen in those ice sheets during the Ice Age, but began being released 12,000 - 15,000 years ago as the Ice Age ended and the climate warmed. Sea level increased about 115 meters over a several thousand year period, rising 40 mm/year (1.6"/yr) during one 500-year pulse of melting 14,600 years ago. The rate of sea level rise slowed to 11 mm/year (0.43"/yr) during the period 7,000 - 14,000 years ago (Bard et al., 1996), then further slowed to 0.5 mm/yr 6,000 - 3,000 years ago. About 2,000 - 3,000 years ago, the sea level stopped rising, and remained fairly steady until the late 1700s (IPCC 2007). One exception to this occurred during the Medieval Warm Period of 1100 - 1200 A.D., when warm conditions similar to today's climate caused the sea level to rise 5 - 8" (12 - 21 cm) higher than present (Grinsted et al., 2008). This was probably the highest the sea has been since the beginning of the Ice Age, 110,000 years ago. There is a fair bit of uncertainty in all these estimates, since we don't have direct measurements of the sea level.


Figure 1. Global sea level from 200 A.D. to 2000, as reconstructed from proxy records of sea level by Moberg et al. 2005. The thick black line is reconstructed sea level using tide gauges (Jevrejeva, 2006). The lightest gray shading shows the 5 - 95% uncertainty in the estimates, and the medium gray shading denotes the one standard deviation error estimate. The highest global sea level of the past 110,000 years likely occurred during the Medieval Warm Period of 1100 - 1200 A.D., when warm conditions similar to today's climate caused the sea level to rise 5 - 8" (12 - 21 cm) higher than present. Image credit: 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.

Sea level rise over the past 300 years
Direct measurements of sea level using tide gauges began in Amsterdam in 1700. Additional tide gauges began recording data in Liverpool, England in 1768 and in Stockholm, Sweden in 1774. These gauges suggest that a steady acceleration of sea rise of 0.01 mm per year squared began in the late 1700s, resulting in a rise in sea level of 2.4" (6 cm, 0.6 mm/yr) during the 19th century and 7.5" (19 cm, 1.9 mm/yr) during the 20th century (Jevrejeva et al., 2008). There is considerable uncertainty in just how much sea level rise has occurred over the past few centuries, though. Measuring global average sea level rise is a very tricky business. For starters, one must account for the tides, which depend on the positions of the Earth and Moon on a cycle that repeats itself once every 18.6 years. Tide gauges are scattered, with varying lengths of record. The data must be corrected since land is sinking in some regions, due to pumping of ground water, oil and gas extraction, and natural compaction of sediments. Also, the land is rising in other regions, such as Northern Europe, where it is rebounding from the lost weight of the melted glaciers that covered the region during the last Ice Age. Ocean currents, precipitation, and evaporation can cause a 20 inch (50 cm) difference in sea level in different portions of the ocean. As a result of all this uncertainty, the 1996 Intergovernmental Panel on Climate Change (IPCC) report gave a range of 4 - 10" (10 - 25 cm) for the observed sea level rise of the 20th century. The 2007 IPCC report narrowed this range a bit, to 5 - 9" (12 - 22 cm), or 1.2 - 2.2 mm/year. Rates of sea level rise are much higher in many regions. In the U.S., the highest rates of sea-level rise are along the Mississippi Delta region--over 10 mm/yr, or 1 inch/2.5 years (USGS, 2006). This large relative rise is due, in large part, to the fact that the land is sinking.


Figure 2. Absolute sea level rise between 1955 and 2003 as computed from tide gauges and satellite imagery data. The data has been corrected for the rising or sinking of land due to crustal motions or subsidence of the land, so the relative sea level rise along the coast will be different than this. The total rise (in inches) for the 48-year period is given in the top scale, and the rate in mm/year is given in the bottom scale. The regional sea level variations shown here resulted not only from the input of additional water from melting of glaciers and ice caps, but also from changes in ocean temperature and density, as well as changes in precipitation, ocean currents, and river discharge. Image credit: IPCC, 2007

Sea level rise over the past 15 years
According to the Intergovernmental Panel on Climate Change (IPCC) 2007 report, sea level accelerated from the 1.2 - 2.2 mm/yr observed during the 20th century to 3.1 mm/year during the period 1993 - 2003. These estimates come from high resolution measurements from satellite radar altimeters, which began in 1992. Tide gauges showed a similar level of sea level rise during that ten-year period. The IPCC attributed more than half of this rise (1.6 mm/yr) to the fact that the ocean expanded in size due to increased temperatures. Another 1.2 mm/yr rise came from melting of Greenland, West Antarctica, and other land-based ice, and about 10% of the rise was unaccounted for. However, during the period 2003 - 2008, sea level rise slowed to 2.5 mm/year, according to measurements of Earth's gravity from the GRACE satellites (Cazenave et al., 2008). This reduction in sea level rise probably occurred because ocean sea surface temperatures have not warmed since 2003 (Figure 3). The authors concluded that sea level rise due to ocean warming decreased more than a factor of five from 2003 - 2008, compared to 1993 - 2003, contributing only 0.3 mm/yr vs. the 1.6 mm/yr previously.


Figure 3. Global average sea surface temperatures (SSTs) from 1990-2008. SSTs have not increased in the past seven years. Image credit: NASA/GISS.

For more information
The best source of information I found while compiling my sea level pages was the Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region report by the U.S. Climate Science Program. It has a huge number of references to all the latest science being done on sea level rise.

References
Bard, E., et al., 1996, "Sea level record from Tahiti corals and the timing of deglacial meltwater discharge", Nature 382, pp241-244, doi:10.1038/382241a0.

Cazenave et al., 2008, "Sea level budget over 2003-2008: A reevaluation from satellite altimetry and Argo", Global and Planetary Change, 2008; DOI:10.1016/j.gloplacha.2008.10.004

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.

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.

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.

McGranahan, G., D. Balk, and B. Anderson, 2007, "The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones", Environment & Urbanization, 19(1), 17-37.

Moberg, A., et al., 2005, "Highly variable northern hemisphere temperature reconstructed from low- and high-resolution proxy data", Nature 433, pp613-617, doi:10.1038/nature03265.

United States Geological Survey (USGS), 2006, National Assessment of Coastal Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast, U.S. Geological Survey Open-File Report 00-179.

Tropical update
The tropical Atlantic is quiet, and the only region worth watching is the Western Caribbean, which could see formation of a tropical disturbance with heavy thunderstorm activity this weekend.

Jeff Masters

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1682. KEEPEROFTHEGATE (Mod)
i don't know anymore orca the past couple of years been gettin rough here in the city just yesterday a group of 3 mugged an 80 year old woman behind my building they used such force they broke her hip spineless cowards there has been at least three or four gunplay incidents and sept of last year one of my tentants got shot in the back lost a kidney only 18 most of it is gang related i guess

so the anwser is at the moment it may not be a bad idea to have something just in case
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Unfornately people act totally differnet when disaster occurs....seen it in Homestead myself and yes even the purest of people that live in Canada, some would become animals also....Hard to believe for some im sure!
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1674. Orcasystems

hey, i didn't say YOU were ignorant...i said I was ignorant. the images of armed robbers marauding through the streets of New Orleans was enough to convince me to take care of my family. Police forces for all their greatness have never *prevented* a crime, only responded to it afterward. i completely hope that i have in my possession an AR-15 with 1,000 rounds that i NEVER have to use...otherwise, it's a REALLY BAD DAY IN PEARLAND,TX!!
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Quoting Orcasystems:


KOG.. do you think you would actually need a weapon to protect yourself in the event of a natural disaster.. even in Toronto?

All I have to say is Katrina...people definitely needed to protect themselves...
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Quoting KEEPEROFTHEGATE:
i got two 3 foot swords from japan i payed 800 dollars for the pair of them along with two axes


KOG.. do you think you would actually need a weapon to protect yourself in the event of a natural disaster.. even in Toronto?
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Just stepped in. Can anyone update me on the Caribbean disturbance? Any chance for development? If so, when? Thanks
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1675. KEEPEROFTHEGATE (Mod)
i got two 3 foot swords from japan i payed 800 dollars for the pair of them along with two axes
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Quoting pearlandaggie:
1667. Orcasystems

Sir, with the utmost respect, you should have seen the area after Rita (although we didn't receive a direct hit) and Ike...law enforcement was paralyzed. You could only rely upon yourself for security. Personally, I'm actually quite ignorant of the let-others-defend-you and non-self-reliance attitude...maybe you could help me understand why my positions are ignorant.......


I didn't say it was ignorant?
I just don't understand it? I would bet that of the 29 houses in our Strata area.. maybe 5 of us have weapons.. and all 5 are ex/active military or RCMP.

The thought that I would have to defend myself, my family or my neighbours in the event of a natural disaster is just ludicrous up here. I am going to have to say its a completely different social mentality in Canada.

That being said.. KOG is in or close to Toronto.. again a different mentality over there also.
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1672. Vortex95

butcher knives are better than nothing! LOL

*i used to be a butcher! LOL*
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1671. KEEPEROFTHEGATE (Mod)
Quoting Orcasystems:


Why is it most people need a gun?
Self defence from your neighbours?
well ya need it if some ones got one and planning on robbing you because they have nothing and you do have something
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1667. Orcasystems

Sir, with the utmost respect, you should have seen the area after Rita (although we didn't receive a direct hit) and Ike...law enforcement was paralyzed. You could only rely upon yourself for security. Personally, I'm actually quite ignorant of the let-others-defend-you and non-self-reliance attitude...maybe you could help me understand why my positions are ignorant.......
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1666. SavannahStorm

ABSOLUTELY, my friend! or how about 5 blocks of dry ice, if you can get it :)
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Quoting SavannahStorm:


A block of dry ice.


Why is it most people need a gun?
Self defence from your neighbours?
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Quoting pearlandaggie:
if you really want to survive a major hurricane catastrophe, here is my recommendation (not all-inclusive):
1. dried food like Lipton Rice dishes and dried fruit
2. 100 gals. of purified water frozen as ice
3. 50 gals. of gasoline
4. 5 kW+ gasoline generator with several extension cords and timers to manage electrical loads
5. 300 feet of 3/8" rope for roof and other temporary repairs
6. 8000 Btu/hr window a/c for family comfort at night
7. Size C and D batteries
8. 3-5 large tarps (as large as you can find) for plugging roof holes
9. $1000 in small bill cash for consumables you can purchase
10. 12-gauge shotgun w/ 100 rounds or AR-15 w/ 200 rounds (to protect your family, food, fuel, and generator)

i'm sure there are other great things folks can recommend...this is just a starting point for discussion.

if you're offended by this post, please disregard..........


A block of dry ice.
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if you really want to survive a major hurricane catastrophe, here is my recommendation (not all-inclusive):
1. dried food like Lipton Rice dishes and dried fruit
2. 100 gals. of purified water frozen as ice
3. 50 gals. of gasoline
4. 5 kW+ gasoline generator with several extension cords and timers to manage electrical loads
5. 300 feet of 3/8" rope for roof and other temporary repairs
6. 8000 Btu/hr window a/c for family comfort at night
7. Size C and D batteries
8. 3-5 large tarps (as large as you can find) for plugging roof holes
9. $1000 in small bill cash for consumables you can purchase
10. 12-gauge shotgun w/ 100 rounds or AR-15 w/ 200 rounds (to protect your family, food, fuel, and generator)

i'm sure there are other great things folks can recommend...this is just a starting point for discussion.

if you're offended by this post, please disregard..........
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Quoting Orcasystems:


1. GulfScotsman 3:42 AM GMT on June 12, 2009 Hide this comment.

Action: Quote | Ignore User


What!? GS is lurking around here?!
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Quoting StSimonsIslandGAGuy:
Could y'all do me a favor? The blog list says there is a comment on my blog, but it wont show me what the comment says, or who posted it. Cam anyone check out the comment on my blog and say who made it and what was said?


I mailed it to you
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Quoting StSimonsIslandGAGuy:
But on a more positive note, 6% of the way through the hurricane season and all is well!


Well.. We've already had 1 TD so Idk about that.
Member Since: July 8, 2005 Posts: 259 Comments: 24042
hows the SOI doing
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Quoting Vortex95:
DTV transition in less than an hour and twenty minutes.

Actually it happens at 1pm EST tomorrow ....Link
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Quoting Tazmanian:
Link



can any one make this out???


Once you fix the link...and then click on the English word at the top to convert it from Japanese... its the Japanese Met Agency


Use this link instead
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Quoting Tazmanian:
Link



can any one make this out???


Server not found
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Link



can any one make this out???
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AOI #1

AOI #2
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Quoting Tazmanian:
at last new toys added to the blog



and theirs some new "thingy" scrolling in the top right hand of my page:)....and good evening everyone!!!,shears dropping,there's a mjo pulse moving into the region,t-waves transitioning the ITCZ into the carib...chances of a TC before the end of the month are 70-80%,IMO....
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You guys talking generators should hear our 3 MW diesel at the office. Complaints pour in from up to a mile away when that baby fires up. Cannot stand within
100 feet of it without hearing potection...not policy, just hurts
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1648. Ossqss
Well, motor fuels are hazardous. Obviously, it's not recommended to circumvent your vehicles safety systems. ;)
GN
Member Since: October 13, 2005 Posts: 4 Comments: 2156
1648. Ossqss
Quoting HIEXPRESS:
1640. Ossqss
Owning a piece of hose (Georgia credit card) is against federal law?


Can't do it. The tanks have pressure and obstructions. Anti-syphon law

If you want it you will need to get it, post pump, from the cars fuel line.

Not something most need to try.
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1640. Ossqss
Owning a piece of hose (Georgia credit card) is against federal law?
Member Since: October 13, 2005 Posts: 4 Comments: 2156
1645. Ossqss
Quoting pearlandaggie:
1636. Ossqss

my dear friend, there are no laser grips for the AR-15! :) the lasers and tactical flashlights are mounted on the sides of the forward rails, leaving the top for red dot sights! LOL


Not on all of them :)
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alright, i'm out, too! have a good evening :)
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The last few storms I lost cable/broadband instantly, and the copper pair for phone & dialup about 3 days later as the phone company just let the batteries run down in the corner D/A box.
Member Since: October 13, 2005 Posts: 4 Comments: 2156
1642. KEEPEROFTHEGATE (Mod)
Quoting zoomiami:
Just hopped over to the blog entries for this same time last year. Although we had Arthur, it was basically a one day event.

Otherwise, the info was the same then as it is now, "tropics are quiet, still early".

So we are basically the same as last year.
enjoy it july and then august yet to come
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Quoting zoomiami:
Nice chatting, off to bed for me.
Night Zoo, time for me to walk the dogs. Nite all.
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1640. Ossqss
Quoting HIEXPRESS:
40 gal of gas in the boat, can plumb the boat to the generator. Chain the generator down. One dude thought he ran out of gas & when he went to check it, it was gone.


Interesting point to share. I appoached the car manufacturers about being able to tap the 50 gallons I have in my cars and they would not budge on letting me alter the access. They said it is Fed law.
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1635. HIEXPRESS

that's a good point...i TOTALLY forgot about the ~150 gals of gas i keep in my boat! thanks!
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If that blob ova test hit the GOM, we could have sum problems
1636. Ossqss
Quoting pearlandaggie:
1631. Ossqss

i heard that! that's when an AR-15 comes in handy :)


With a lazer grip and beta clip !
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40 gal of gas in the boat, can plumb the boat to the generator. Chain the generator down. One dude thought he ran out of gas & when he went to check it, it was gone.
Member Since: October 13, 2005 Posts: 4 Comments: 2156
Quoting GeoffreyWPB:
The local Publix in front of my house does not have a generator. And as they threw their bad food out in the back during Francis and Jeanne, so came the rats.

Oh I didn't get hit by Francis by I did get by Frances.Lol:)
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Nice chatting, off to bed for me.
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1631. Ossqss

i heard that! that's when an AR-15 comes in handy :)
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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.