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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People have to remember its only June.
Even in 2008 we didn't see a single storm form in June. Arthur formed in May and crossed over to June.
Bertha formed July 3rd and we had 3 systems in July, the most since 2005.
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Quoting canesrule1:
I now think that without the shear this AOI would be a hurricane by now but if the excessively strong shear continues i guarantee this will be dead very soon.


Oh great soothsayer, what will my fortune be?

"Guarantee" may be a bad choice of words, as we are speaking about weather, and it is nigh-impossible to rule anything out. (some people said the same thing about Ike when it hit the upper Texas coast. Some of those people haven't been found yet, either.)
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820. that's just wrong... I was just about to let that slide.
Member Since: September 22, 2005 Posts: 18 Comments: 2343
Quoting jeffs713:
820.

LOL.

Orca, I'm not sure if you will be forgiven... even though the blog is more concerned about the low that will never be in the caribbean.


Oh man... I will get even with squish28 :)
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the last time there was a cane in that area, in june???,not very likely,imo
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820.

LOL.

Orca, I'm not sure if you will be forgiven... even though the blog is more concerned about the low that will never be in the caribbean.
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nuetral,nuetral,nuetral,IMO....
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I now think that without the shear this AOI would be a hurricane by now but if the excessively strong shear continues i guarantee this will be dead very soon.
have a good expedition oz!!!!
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823. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 6209
Tropics are always a wait and see option to forecasting. We always look in the near term on the models and wait till we see a developing system before we jump on it. Right now..there is a broad circulation in the sw carribean... but until a low does form...its wait and see still.
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'morning all! :)

I'm off for an American Rockhound adventure!

NO TROPICS WHILE I'M GONE!
NO TROPICS!
NO TROPICS!

[/me knocks wood, throws salt over shoulder, and avoids mirrors!]

CycloneOz---
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Lets see, here we are at around post 800 and something and I keep seeing comments interjected about the doctors blog, global warming mumbo jumbo etc. I wonder who we have to thank for all of this.......



Quoting Orcasystems:
1705. Orcasystems 1:23 PM GMT on June 10, 2009

Quoting IKE:


LOL!


:(



We are in desperate need of a new Blog :(
Its getting so slow.. he might even mention GW just to Heat things up a bit (pun intended).


I should be taken out and shot :(
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The surface trof is amplifying per 850 vort increase
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Some wanted development but actually you have to monitor the tropics and never give anything 0% or 100%
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Quoting IKE:


There is defiantly some 850 MB Vort down there.
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816. IKE
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815. beell
Quoting tornadofan:
Beell - got some storms to your north I see. Maybe you'll get a few renegade storms today?


Eh...I'll say no. 700mb temps around 12-13C. We're kinda capped down here on the coast. Maybe an old boundary/sea breeze thing for a few lucky folks.
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Quoting Tazmanian:
EL Nino is comeing EL nino is comeing



El Nino is comeing EL Nino is comeing



yay yay yay yay


El Nino is comeing EL Nino is comeing !!!!!!!!


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BBC news online this morning:
http://news.bbc.co.uk/2/hi/science/nature/8094083.stm
Typhoons coincide with Slow earthquakes and MAY reduce frequency of larger quakes
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Quoting DaytonaBeachWatcher:
there is a low
there isnt a low
there is a low
there isnt a low
there might not be anything to watch in the tropics but at least someone is heating it up in here


The tropics are bipolar?
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Feisty wave now passing 40W. Not a lot of convection associated with it, though.

Member Since: September 22, 2005 Posts: 18 Comments: 2343
Quoting beell:
The smaller numbers all over the chart are the height of the echo tops. 370 = 37,000 feet and so on...
Ahhh... Thank's beell

Quoting Orcasystems:


Check the link again.. I put the wrong one up.
That one was about doing dual polorization to be able to take the debris (clutter) out of the equation.
Now this new link might take two cups of coffee. Thanks big fish, it is beginning to make sense. (Not that I can understand it all - but I now have a clue as to what is going on)
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809. IKE
Quoting stillwaiting:
morning everyone!!!,shear should be dropping quickly over the next 48hrs in the west carib,w/a ULL moving over the yucatan area and a t-wave moving thru the region south of jamaica,I believe their will be a tropical disturbance/invest after saturday,IMO


From....

MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
210 AM EDT THU JUN 11 2009

A RE-ENFORCING SHORTWAVE HAS DROPPED SE INTO THE
WESTERN UPPER TROUGH WITH EVIDENCE OF AN UPPER CYCLONE AT
22N78W. EXPECT THIS CYCLONE TO LIFT NE TODAY AND FRI REACHING
NEAR BERMUDA SAT WITH THE TROUGH FILLING TO ITS SW BUT CUTTING
OFF A SECOND UPPER CYCLONE OVER THE NW CARIBBEAN. GUIDANCE DOES
NOT SEEM TO HAVE A HANDLE ON THIS CUTOFF CYCLONE...AND THE
LATEST RUNS SUGGEST IT WILL INITIALLY TRACK SW AND THEN LATER W
OVER CENTRAL AMERICA...TOTALLY OPPOSITE TRACK OF GUIDANCE 2 DAYS
AGO.


SOME UNCERTAINTY AT THE LOW LEVELS A WELL. A TROPICAL WAVE NOW
MOVING THROUGH THE GULF OF HONDURAS HAS LEFT A LOW LEVEL TROUGH
OVER THE CARIBBEAN ALONG 79W. ALTHOUGH MODEL GUIDANCE NOW SEEM
TO ALL FAVOR A LOW LEVEL TROUGH OVER THE W CARIBBEAN...EACH
DIFFERS ON PSN AND STRENGTH OF THE TROUGH...AND ASSOCIATED
DEVELOPMENT OF LOW PRES ALONG THE TROUGH...AND IF A LOW DOES
DEVELOP..ITS EVENTUAL TRACK. SO...FOR NOW WILL FORECAST BROAD
TROUGH OVER W CARIBBEAN THROUGH PERIOD WITH GRADIENT E OF THE
TROUGH SUPPORTING E TO SE WINDS 20 TO 25 KT.
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Beell - got some storms to your north I see. Maybe you'll get a few renegade storms today?
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STJS and shear relaxing discussed on stillwaitings blog(its from the 2nd)
I'll be updating when a invest seems likely!!

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Quoting IKE:


I agree.

This is not toward you, but it's been "3 to 5 days", for the last 3 to 5 days.

These same models that can't forecast reliably beyond so many hours, also can't forecast shear reliably beyond so many hours.

In other words, it's a guessing game.


Maybe several 3 to 5 days from now we'll have a major in the MDR to track.
805. beell
Not the boxes (I know what they are *grin*) The white numbers.

Sorry, KEH! LOL
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Quoting KEHCharleston:
Not the boxes (I know what they are *grin*) The white numbers.
Insects! We are talking insects?
Will pour myself a cupa joe, and read the article - thanks (I think) big fish.


Check the link again.. I put the wrong one up.
That one was about doing dual polorization to be able to take the debris (clutter) out of the equation.
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Looks like shear is beginning to relax in the tropical Atlantic, for the most part... It also looks like the SJS is beginning to pull off to the North. Probably won't be much longer before conditions become prime for hurricanes in the ATL
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morning everyone!!!,shear should be dropping quickly over the next 48hrs in the west carib,w/a ULL moving over the yucatan area and a t-wave moving thru the region south of jamaica,I believe their will be a tropical disturbance/invest after saturday,IMO
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801. beell
The smaller numbers all over the chart are the height of the echo tops. 370 = 37,000 feet and so on...
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Quoting beell:


On this particular graphic, these are Severe and Tornado Watch Boxes and the Time the watch expires in UTC

Hint, hint-check the graphic label at upper left.
Not the boxes (I know what they are *grin*) The white numbers.
Quoting Orcasystems:


The header on the graphic says [dBZ] which is a measurement of power or power lose, or more appropriately attenuation of power or received signal strength.

Read the link, it explains it, and what it is :)
Insects! We are talking insects?
Will pour myself a cupa joe, and read the article - thanks (I think) big fish.
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Hey there everyone! Back to watching and waiting for the season. I was surprised not to see a blog from Dr. M about what was going on in relation to activity. I know it's early, but usually there are invests and lows at least. Really hoping this trend lasts...
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798. beell
Quoting KEHCharleston:
Stupid question time:
What do the numbers mean on this graphic?
(click on image for full size)




On this particular graphic, these are Severe and Tornado Watch Boxes, watch number and the time the watch expires in UTC-the "Z" time.

Hint, hint-check the graphic label at upper left.
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Quoting KEHCharleston:
Thanks.. that does make sense... nothing above 360,
MODIFIED - oops... I see some numbers above 360


The header on the graphic says [dBZ] which is a measurement of power or power lose, or more appropriately attenuation of power or received signal strength.

Read the link, it explains it, and what it is :)
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Quoting DaytonaBeachWatcher:
havent got a clue
I still think you might be right. Most of the time, when I see a wind barb, the number would be right for wind direction. Maybe when wind shifts from northwest to northeast, you get the 360+east wind direction??
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havent got a clue
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EL Nino is comeing EL nino is comeing



El Nino is comeing EL Nino is comeing



yay yay yay yay


El Nino is comeing EL Nino is comeing !!!!!!!!
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Quoting DaytonaBeachWatcher:
wind direction, i would say
Thanks.. that does make sense... nothing above 360,
MODIFIED - oops... I see some numbers above 360
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wind direction, i would say
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Quoting Tazmanian:
well if it waits too march longer like AUG then we may not see any name storms out there this year
Sounds good to me.
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well if it waits too march longer like AUG then we may not see any name storms out there this year
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Stupid question time:
What do the numbers mean on this graphic?
(click on image for full size)


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Quoting kmanislander:


Very little chance through tomorrow. If the trough lifts out over the weekend that may change things, assuming we still have some activity in the area. Remember that June is not a traditionally active month so the odds of development are not high to begin with.

Let's see how it looks Saturday morning.
Thank you.
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This is the one thing I don't like about Wunderground, constant global warming blather that fails to ever prove any significant trace of real evidence. Temps outside of urban heat islands have fallen over the past few decades and the BS is constantly ramped up and changed to fit the desired results.
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Quoting IKE:


I agree.

This is not toward you, but it's been "3 to 5 days", for the last 3 to 5 days.

These same models that can't forecast reliably beyond so many hours, also can't forecast shear reliably beyond so many hours.

In other words, it's a guessing game.


It does seem like a record skipping (for the older folks reading the blog.)
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785. IKE
Quoting Weather456:
The best chances of development, if any, is 3-5 days from now per my blog.


I agree.

This is not toward you, but it's been "3 to 5 days", for the last 3 to 5 days.

These same models that can't forecast reliably beyond so many hours, also can't forecast shear reliably beyond so many hours.

In other words, it's a guessing game.
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Tropical Update
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Nothing will happen until after sunday, because thats when Dr. M. goes on vacation...lol
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Off to work now. Will check in later.
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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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