There’s not much dispute these days, up and down the coast, about whether the ocean is rising. The question is: How high will it go here, and how fast?
North Carolinians must wait until 2016 for an official answer. That’s the law.
An article in Insurance Newsnet about sea-level-rise denial in North Carolina contains some delicious quotes:
A new documentary film, ” Shored Up,” shows anguished commission members imploring their science advisers to somehow “soften” the high-water warning.
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Jimmy Johnson oversees a plan to protect sensitive coastal habitat for a state-federal partnership called the Albemarle-Pamlico National Estuary Program. Biologists say that rising salt water has killed forest and wetlands around the fringe of the 2-million-acre estuary. Asked at a Harkers Island gathering how scientists and regulators might make use of the official sea-level prediction expected in 2016, Johnson blanched.
“I apologize for being rather evasive, because I have to be,” Johnson said.
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The 2012 law was championed by Eastern North Carolina Republicans who distrusted the 39-inch forecast. They said they wanted to make sure that state policy is grounded in solid science and common-sense analysis.
“You can believe whatever you want about global warming,” Rep. Pat McElraft, an Emerald Isle real estate agent who helped sponsor the measure, said in 2012. “But when you go to make planning policies here for our residents and protecting their property values and insurance rates … it’s a very serious thing to us on the coast.”
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I am especially impressed by that last one. You can believe whatever you want about global warming and Santy Claus and such, but coastal property values are serious business, right?
It sounds real easy. They measure the sea leve in the vacinity, don't they? They need to have a big meeting with the board. Bring a chart of the sea level rise - all the data going back as far as they have it. And take a look at it. You can lay a straight edge on it or if it appears to be a curve you can lay a curve on it and project out into the future. No one can be sure that the future will resemble the past but that will show any obvious issues to be concerned about.
Actually that is what they are doing. They are ignoring any evidence that the curve might accelerate.
I have a screen shot from page 69 of this NOAA document (I'm pretty sure I can't post it in a comment here). It shows sea levels going back at least 100 years from eight stations US (and Hawaii pre-statehood). It's extremely difficult to visually discern any increase in the slope of the sea level as a function of year corresponding to increasing atmospheric carbon dioxide, melting land ice in the Arctic or Antarctic, or increasing oceanic heat content. It's clear that sea levels are rising at these stations but my eyeball gauge makes a preliminary estimate that the rate of rise has been approximately constant for a century. What explains this?
By the way, the pedant in me wonders why we refer to "heat content" rather than internal energy. I've always read in thermodynamics texts and references that heat is the transfer of internal energy via a difference in temperature just as work is a transfer of potential or kinetic energy. Thus, "heat content of the ocean" wouldn't make any more sense than "work content of a raised weight." Is this just a convention or am I missing something (or being a pedantic jerk)?
About sea level rise, there is some sign of acceleration over the past century once you average enough records.
http://commons.wikimedia.org/wiki/File:Recent_Sea_Level_Rise.png
http://thewatchers.adorraeli.com/wp-content/uploads/2011/06/global-mean-sea-level-rise.jpg
Important, though, to look at the projections:
http://www.realclimate.org/images/sealevel_1.jpg
Hansen would claim that these projections are severely understated; natural sea level rise can be as rapid as several meters per century driven by glacial retreat
http://initforthegold.blogspot.com/2007/08/4-meter-sea-level-rise-precedent.html
And while surface temperature has been lagging the models, sea level has not:
http://www.ci.uri.edu/ciip/projects/RICC%20Content/SLRReady/SLRCazenave.png
About heat vs heat transfer, I see your point but I think it is indeed a semantic quibble in this context. If heat transfer goes into the ocean, causing the ocean to warm up, it is easy to go conceptually from the temperature change to the energy flux using the "heat capacity". So, close enough.
Related:
http://www.huffingtonpost.com/2014/03/17/congress-flood-insurance_n_4981226.html
Acceleration over the 20th Century in the global rate appears to be small if it happened. Gregory et al. 2013 is a good reference to look at the factors involved. Couple of highlights: The temporal spacing of large volcanic eruptions likely contributed an increase of thermal expansion in the first half of the century and a decrease in the second half. Essentially the large eruptions throughout the 19th Century cooled the ocean so during the quiet period between 1910-1963 the oceans would have warmed as a recovery. Then in the latter part of the 20th Century a string of large eruptions acted to dampen the overall ocean warming. Glacier melting also possibly contributed more SLR in the first half than second of the century, though uncertainties are large.
It's becoming increasingly clear that SLR over the past 2-3 decades has accelerated above the 20th Century rate, but there is large regionality to trends - see the map half way down this page. The Western US coast and Hawaii are in regions which have risen well below the global average over the past 20 years.
It's such a tricky business. This comes close to home - my home - as we are about 3 feet above an apogee moon storm tide of which I took pictures on January 3 this year. I've been visiting and living in the neighborhood (Fort Point in Boston) since the mid 70s and the Channel has always flooded. It's a difficult measurement but it's quite clear that what we have seen in the last few years is an acceleration. The amounts are tiny but the trend in regular and steadily larger overflows can be teased out without any scientific measurement.
I keep hammering away at this point: it is not necessary to be a scientist to observe the degradation in one's own neighborhood and connect it to global incidences in every kind of event that are on the increase. At the moment, they are small enough to be dismissable if one applies dedicated blinders, an absence of curiosity, and doesn't look much at data from everywhere on the globe.
I consider this attitude, and the lack of curiosity as well about what most scientists are doing and observing when their conclusions don't fit with the desired conclusion, to be disastrous. By the time this thing has gained further momentum, it will be truly difficult to reverse the tide.
Sea level rise can be non-uniform because it is superimposed on geological uplift or subsidence; or it can be because shifting sea level pressure has moved some of the surface water. Global averages may or may not be affected by global constraints.
Thinking top down is something of an oversimplification in some aspects of climate change, e.g., severe events. But when it comes to sea level, it's very clear physically that the sensible way to think of it is that there are local phenomena that are simply superimposed on a global ocean volume trend.
It makes no sense to speak of regional differences as if that somehow made the increase in water volume more obscure or uncertain. Any local decline with respect to the mean trend must be compensated by a local increase elsewhere. Yes, that follows from the very idea of a mean, but that's not the point. With temperature, one place can warm faster than the forced trend, and the argument that somewhere else must cool in compensation, while a useful rule of thumb and not without merit, is complicated and far from bulletproof. With events like floods or hurricanes, physics offers no global constraint whatsoever, and we really are looking at an aggregate of essentially decoupled local phenomena. On the other hand, with a local anomaly in sea level rise, the water simply has to go somewhere else or come from somewhere else.
One way to make the distinction is that aggregated global measures of globally constrained phenomena have a variance that is much less than would be expected from the variance of the component measures, even accounting for first order dependence between the data series. As a specific example, global temperature is far less variable than the variance of continental temperatures, even accounting for pairwise correlations among the continents. In the case of the sea level, it's unambiguous. If there's zero net heat exchange across the interface, there's no substantial change in global ocean volume, regardless of what sea level is doing in one or another location.
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