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Madness over sea level rise in North Carolina

Posted on 29 June 2012 by John Bruno

Sleepy North Carolina became an international topic of conversation (and ridicule) this month thanks to our state legislature's bills declaring sea level rise "illegal", or more accurately, insisting that state planning for future sea level be based only on "historical records", meaning tide gage measurments during the last century (translation; there is no acceleration of sea level rise here folks - now move along).

What does the science say?

Everything started with the publication of the North Carolina Sea-Level Rise Assessment Report, prepared by the  N.C. Coastal Resources Commission’s Science Panel on Coastal Hazards in March 2010. The panel included regional and international experts on sea level rise and coastal geophysics from many of the state’s most esteemed scientific institutions, including UNC-CH’s Institute of Marine Sciences, UNCW, NC State, the US Army Corps of Engineers, East Carolina University, and Western Carolina University. (read more about the charge given to the panel by the state here)

Past sea level rise: The report describes the empiral findings of several studies of past sea level rise in North Carolina (Horton et al. 2009, Kemp et al. 2009, Zervas 2004, see references here). In the 20th century, sea level rise increased from 1mm/year to about 3.2 mm/year (12.6 inches/century). Eight tide gage stations indicate the recent sea level rise has varied from ~ 2mm/year in the southern part of the state to nearly twice that rate in the north, e.g., 4.3 mm/year or 17 inches/century in Duck, near the Virginia border (see Table 1). (Note a recently widely discussed paper on NC sea level rise (Kemp et al 2011) was not included in the report since it was not publsihed when the panel met in 2009 and 2010, however, most of the data/findings in Kemp et al 2011 were included as they had been publsihed in earlier related outlets, including Kemp's 2009 PhD dissertation.)

The NC science panel's report is supported by a just published paper in Nature Climate Change (Sallenger et al 2012), that describes a global hot spot of sea level rise that begins at Cape Hatteras, NC. Between 1970 and 2009, average sea level rise in the hot spot (which includes Washington, New York City, and Boston) was 3.80 mm/yr (±1.06). The authors tentatively attributed the hot spot to another aspect of global warming; the expected slowdown of the Atlantic Meridional Overturning Current, although see a discussion of other potential explanations here.

Sea level rise measured with tide gauges for 60-yr time series at locations across North America. source Circles are colour-coded to reflect computed SLRDs; no colour fill indicates SLRDs that are not statistically different from zero. Confidence limits are ±1σ and account for serial correlation; 50- and 40-yr time series results are shown in Supplementary Fig. S3.

Future sea level rise: Next, as requested, the panel cautiously projected some of the possible scenarios of future sea level based on different degrees of sea level rise acceleration. Globally, sea level rise is known to be accelerating (also see here) and expected to accelerate further due to greenhouse gas emissions and global warming, and more directly to the loss of ice mass from Greenland and Antarctica.

..based on multiple indicators suggesting that global climate is warming, the Panel believes that an acceleration in the rate of SLR is likely.

Confidence levels and margins of error are not calculated for the individual rate curves because the curves are considered to be the upper and lower boundaries of sea level over the next 90 years. It is important to understand that the curves were generated using a constant acceleration rate to reach the selected endpoints derived from the literature, and are not projections of actual sea level at specific future dates. As a consequence, it is not accurate to interpolate quantities of sea level rise for specific years since we do not know whether RSL acceleration will be constant over the next 90 years. The curves are primarily intended to illustrate the expectation of increased acceleration.

The Science Panel does not believe, based on the data available at this time, that it is appropriate to attempt to quantify confidence intervals or margins of error beyond those inherent in the chosen scenarios, as informed by the published literature. Nevertheless, the Science Panel is confident that the curves presented constrain the plausible range of sea level by 2100 as accurately as is possible at this time.

The panel's projections were based on the current science about sea level rise and climate change and are very much in line with the broad and deep consensus within the scientific community. The panel did not argue that any of the scenarios were more or less likely than others; they simply reported the probable range of sea level rise by 2100. They did not rule out lower sea level rise or far higher sea level rise, both of which are possible. Finally, the panels sea level rise forecast for North Carolina is concordant with what has been forecasted globally.   

Enter the politics

The report immediately attracted the attention of real estate investors and coastal development lobbying groups like "NC 20" that responded with anti-science propaganda like this (PDF). These groups successfully lobbied the state legislature to declare that coastal communities should only prepare for sea level rise this century of eight inches, which is lower than the rate most of North Carolina is already experiencing.

Thankfully, sanity and science prevailed (for the momemt) when last week, the NC house of representatives voted 144 to 0 against the Senate bill "outlawing" accelerated sea level rise. This is a radical change of heart by a house that only the week before had voted in favor an even more anti-science bill

This battle surely isn't over. But there are already several of lessons that could apply to similar battles going on in other states in the US and also in Australia. The most striking is how easily a small handful of advocates for junk sea level rise science were able to persuade the state legislature to write and initially vote in favor of a pretty crazy bill. They spout the same denier swill that SkS has been debunking for years. And they threw in some unique arguments for good measure, e.g.:

Moreover, although thermal expansion does cause satellite-measured mid-ocean sea level to rise, it does not necessarily cause coastal sea level to rise. If deep-ocean water were to expand, it would, indeed, affect coastal sea levels. But when surface water warms, it rises in place, like ice, and its displacement is unaffected, so it does not affect coastal sea levels.

The second lesson for me was how effectlve the widespred public shaming of the legislature and the debunking of NC20's propaganda was in changes votes (if not changing minds). 

Note: for more information on North Carolina coastal sea level rise, see John Bruno's SeaMonster blog.

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Comments 1 to 32:

  1. 29th century?
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  2. "Moreover, although thermal expansion does cause satellite-measured mid-ocean sea level to rise, it does not necessarily cause coastal sea level to rise. If deep-ocean water were to expand, it would, indeed, affect coastal sea levels. But when surface water warms, it rises in place, like ice, and its displacement is unaffected, so it does not affect coastal sea levels."

    WTF!

    I want some of their Kool-Aid!
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  3. The stories of King Cnut trying to control nature and the sea are probably a myth. He probably wasn't mad.

    Yet now we have an American state government trying stop the sea by doing a 'big brother' and re-writing history. Yep, in comparison Cnut had all his marbles.
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  4. ahhh. Just noticed Rob Paintings reference to Canute in a similar post. Plagarism wasn't intended :-)
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  5. The argument is flawed but makes some kind of sense. If surface water only warmed away from the coasts, then, indeed, the immediate effect would be the same as if that water expanded through freezing. It wouldn't tend to displace water underneath. But the flaw in the reasoning, of course, is that this water wouldn't remain there. Unlike floating ice, some of the raised volume of warmer water would tend to flow towards the coasts. If one delicately poured warm water on top of cold water in in the middle of a container, it wouldn't remain in the middle to form a stable reversed-bowl-shaped liquid surface.
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  6. heijdensejan, no that should be 20th century. The increase to 3.2mm/yr took place in the 1990s.
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  7. Just as an aside: The King Canute story is so ofttimes mistold, it's now risen to a level of mythical urban...myth! Canute was not trying to control the sea: he was trying to show the limits of kingly power. His sitting by the sea (perhaps apocryphal) was to show his minions that a king's powers had limits.

    Back to our regularly-scheduled science...;)
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  8. "Globally, sea level rise is known to be accelerating..."

    Not according to the satellite record.
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  9. Steve Case, 8,

    When you say "not according to the satellite record" do you mean "not if you ignore the data that doesn't show what you'd like it to show, while further putting undue weight on short-term trends that are heavily influenced by short-term factors?"
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  10. Steve,

    You may find this helpful in correcting your misunderstanding.
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  11. sigh. First NC legislated straight marriage as the only acceptable relationship. Now they're legislating straight lines as the only acceptable graph.

    We're not all loonies here, I promise :/
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  12. Sphaerica - Steve Case is correct - sea level has increased in a near-linear manner over the last two decades. But as discussed in this post David Evans: All at Sea about Ocean Warming and Sea Level Rise), that's not greatly surprising considering the trend in aerosols and ENSO. However, El Nino seems to be forming, and we're likely to see a return to an El Nino-dominant period sometime soon. Sea level is therefore likely to spike upwards for a time. Indeed, globally-averaged sea level has already risen over 10mm in the last year:



    The longer-term problem is that ice mass loss from the Greenland & Antarctic Ice Sheets is accelerating and this, coupled with the Earth's current energy imbalance (that dictates further warming is effectively dialed in), suggests an acceleration of sea level rise is likely at some point in the future. This will be influenced by how the trend in human-made and natural volcanic reflective aerosols develop too.
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  13. OK, maybe I was being overly optimistic. According to the Daily Tar Heel (UNC school newspaper):

    Rep. Pat McElraft, R-Carteret, who is the primary sponsor of the bill the original study was flawed because it only used one model and ignores historical data, even though she said the panel was asked to incorporate multiple models and historical data. She said the bill will commission another study into the matter.

    “We needed to direct the state agencies not to use the 39 inches that the science panel came up with, because we don’t feel that was good science,” she said.

    McElraft, who said she doesn’t believe climate change is caused by humans, said it was difficult to use the study to predict climate change.

    “In 1974, the alarmists were talking about the ice age coming in,” she said. “What has happened, has the ice age come in?”
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  14. As Rob Painting reminds us @ 12, thermal expansion is but the usher. Wait 'till the WAIS really gets going. It's only just starting.
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  15. I'm honestly and ernestly asking this. Because I really don't know. I don't even have an associate degree.
    Don't they behave like bodies of water? What I mean is that like high or low pressure systems in the atmosphere move as bodies of air. They do mix when they meet but it only happens at the front? Most time one system moves others away.
    So depending on how far away or other factors, the expansion of water in the middle of the ocean wouldn't neccesary or imediately affect coast line?
    And why does the east coast have higher sea levels than other areas then? Don't all oceans connected?
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  16. CRV9 - Some reasonable questions!

    The oceans, as liquids, will move around with expansion in mid-ocean affecting coastlines in pretty short order (almost instantly in terms of the speed of expansion). There are multiple influences in play, though:

    - Persistent winds (trade winds) pushing and piling water downwind, lowering it upwind.
    - Gravity has an effect, with water pulling up slightly near continents.
    - Continents themselves move (rising and falling), mostly due to "Glacial Isostatic Adjustment" (GIA): the redistribution of weight from the ice that melted in the last ice age (several kilometers thick) means many continental areas are still rebounding from that mass, while others (balancing the the rising sections) are sinking. The East Coast of the USA is notably dropping due to this effect, as the northern Canadian sections of the continent are rapidly rising.


    [Source]

    This is why evaluations of sea level change need to take GIA into account, and use measurements from widely spread tidal gauges and satellites. Otherwise you may get thrown off by local effects.
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  17. KR:

    Doesn't the centrifugal force caused by the Earth's spinning on its axis tend to concentrate SLR along the equator, especially in the Pacific?
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  18. Thank for your quick reply, KR.
    I thought that the pure sea level rising at the East Coast line is higher than other areas, because of ocean currents, gravitational differences and other factors except local ones. So this is actual physical sea levels at local areas with local variables.
    Is it safe for me to think that the pure sea level risings around the globe are about the same? I mean without global and local variables, would water from melting ice from both poles move quickly enough to spread out throughout around? I wish I don't sound dumb.
    I thought water mixes kind of slow like air in the atmosphere, like a bunch of large volume of bodies of water here and there, or differences in different oceans. Yes, I did watch videos of ocean currents and winds around the glob from NASA.
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  19. North Carolina politicians demonstrate that global warming is a social/cognitive problem that resides with humans not science.
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  20. CRV9 - As John Hartz pointed out, redistribution of ice melt to the liquid at the equator is also a factor.

    Looking back at some of my references, thermal expansion is not uniformly distributed, nor are changes in salinity - I apologize for overstating the rate of redistribution. And combined with long term wind patterns, some areas such as the Western Pacific are showing sea level rise as much as 5X that of the global average. Meanwhile, the western coast of the US shows a sea level decline. Cazenave and Llovel 2010 has some excellent images of this distribution (see Fig. 3). The uniform global trend is ~3.4mm/year.

    Water does mix fairly slowly, especially below the top 100 meters where winds churn the "well-mixed" layer. Below that there are much slower thermohaline circulations, which help account for a 500-800 year oceanic CO2 adjustment period as seen in previous ice age cycles. That doesn't mean it's entirely stationary, though - and if a particular portion of the ocean expands or contracts the effects will ripple out from there ("Just a jump to your left... and a step to the right").

    Local effects, however, are very important in judging and predicting sea level rise!
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  21. CRV9 - The US is sinking. The US was levered up by the presence of the giant Laurentide Ice Sheet (imagine a see-saw, or teeter-totter) and, due to the elastic nature of the Earth's crust, has been slumping back down ever since the ice sheet began to melt away (much like a person hopping off the other end of a see-saw). The dark blue areas in KR's image are areas rebounding upwards much faster that anywhere else, because these were heavily loaded by ice mass at the height of the last Ice Age (Glacial Maximum).

    But that is but one mechanism which affects global sea levels - one operating over millenial timescales. On shorter time frames, changes in ocean currents and winds can piles water mass up in a region, increasing the rate of sea level rise there, despite the global average being smaller. Such is the case with islands in the Pacific, such as Tuvalu.

    Stop thinking of sea level as level, it isn't. If you were to hop on a boat and sail around the world, relative to a fixed distance from the centre of the Earth, you'd actually be sailing up and down hill as you went. This is because Earth's mass distribution and gravity is rather lumpy and, therefore, sea level varies from region to region. This will all be discussed in upcoming posts by the way.
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  22. Indeed. Ask any sailor worth his salts and they will quickly tell you (the scurvy lot of 'em) that sea levels vary due to wind, tide and phase of moon. For reference, a copy of Bowditch's American Practical Navigator is invaluable.

    (Full Disclosure: Published by my former employer)

    (Fuller Disclosure: I had no hand in the currently available edition nor do I profit by the sales of it. More's the pity...)
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  23. Thank you, thank you, KR, Daniel, Rob. You can't imagine how much I aprreciate your replies. That was what I thought but couldn't really express or properly articulate it, specially in details.
    (And it is almost impossible to find a place where I could ask simple questions and wouldn't wake up those and contaminate the place.)
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  24. CRV9 @18

    "Is it safe for me to think that the pure sea level risings around the globe are about the same?"


    CRV9, rises is sea level due to thermal expansion or changes in salinity do not involve direct changes in mass distribution, except that water from regions with higher sea level from these causes will tend to flow to regions with lower sea level. As the causes of long term temperature differences are (by definition) stable, the region of increased sea level will be stable as well, but the tendency of water to flow will redistribute heat elsewhere, and mitigate the sea level rise at the source of the heat while causing a rise elsewhere. It is, therefore, not a uniform rise, but not a localized rise either.

    Changes in sea level due to the melting of ice sheets, glaciers and ice shelves which rest on the sea floor do result in a substantial shift in mass. Ignoring gravity, the water will spread over the entire ocean surface, with a tendency to rise higher near the equator due to the Earth's rotation. However, because there is now less mass at the former ice sheet (or glacier etc), the ocean is less strongly attracted gravitationally to the former location of the water, and will move away. This will result in much larger sea level rises the further away from the source you are, and can even result in sea level fall close to the original source of the water. This is illustrated in the following graphic showing the effect of the loss of much of the West Antarctic Ice Sheet on Sea Level:



    To make things even more interesting, a significant change in mass at the Earth's poles will slightly change the Earth's rotation, which in turn effects ocean currents, tending to pile water higher on east coasts than west coasts (in the case of the loss of the WAIS). (discussion here)
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  25. Thank you, Tom Curtis.
    I just hope you don't expect me to understand those details fully(of course not, what I'm thinking). Detals are usually too technical and difficult for me with less education to understand fully. I'd guess "Devil is in details" to many scientists but to me personally it is the big picture. But of course, the details do help me to understand the big picture better and clearer to satisfy my personal curiosity. As long as I get the basic big picture, I'd rather let the experts sweat over the details.

    My personal big picture is this. I see AGW as the energy budget. That's it. Because once we got energy on the earth they have to go somewhere in some forms or shapes. Energy just doesn't disappear until dispate out to space.
    This temperature thing people are talking about seems to me is short sighted. To me it is one of forms of trapped energy apearances/symptoms(told you, I have a simplton's mind).
    For example latent heat which I've learned new here, the fact the stmosphere is holding more vapor now means holding more latent therman energy in the atmosphere. More ice are metling in water and land and not replenished is thermal energy was turned into water from ice.
    To me global climate is part of the earth's natural mechanism to even out or dispate or distribute thermal energy she catches from sunlight. More trapped thermal energy means to me is forcing the earth's mechnism/climate to adapt to new paradigm, thus climate changes. Of course, the earth is not standing still so it's dynamic. I think that it tries to reach equilibrium of natural cycles.
    Some poeple say the unusual warm temperature of 1998 of El Nino was an anomaly. I don't think so because extra heat was coming from the lower layer of oeasns where the heat was stored from the trapped heat above prior which I've learn new here too. So the trapped heat was finally coming out again. Energy doesn't just disappear, I beleive. So I'd foolishly belive we will see another record warm El Nino again someday.
    I'm probably making a fool of myself but I always wanted to say this somewhere. (and pardon me, english is my learned language)
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  26. The results of readings obtained on the basis of a satellite can not be ignored, however, during work tend to rely more on local readings, as far as I know.
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  27. Now it's moving to Australia:

    http://watchingthedeniers.wordpress.com/2012/07/13/false-prophets-queensland-lnp-votes-to-remove-climate-change-from-schools/
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  28. Hah.

    Just wait for the court challenge. We Queenslanders won't take this laying down.
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  29. Ttristan.

    The reasoned part of me thinks that surely even the LNP wouldn't go so far as to actually attempt to emulate North Carolina's attempt to legislate climate change from sight, but the facts that the LNP voted overwhlemingly to do so in their convention, and that one of Newman's first acts was to close the Office of Climate Change, makes me inclined to think twice.

    Their infatuation with Really Big Coal doesn't help to assauge one's doubts.

    Of course, the beauty of such a move is that it completely sidesteps the Conservatives' perceived necessity for folk such as David Wojick, Heartland's curriculum consultant.

    Reason, and the small issue of the sustainability of the planet's life-support systems, lead me to fervently hope that you and your fellow Queenslanders are successful should the LNP ever attempt to move on their resolution.
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  30. Richard Pearson is the Noosa LNP member who proposed that anti-science motion Bernard linked to.

    He just commented over at JoNova's blog. Not that I recommend the link. The fact that he's even there is a sad indictment of where Australian politics is at the moment.
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  31. Tristan.

    What's even more sad is that this political interference in science will likely grow much worse, and for many years yet, before it improves.

    That should be just enough to permanently stuff things up.
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  32. I feel it's my duty to point out that Tamino has a pretty good dressing-down of Dave Burton's sea level "analysis" over at Open Mind.
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