Fierce fighting on SLR in North CarolinaRichard Treadgold | June 28, 2012
Nature Climate Change just published a paper called “Hotspot of accelerated sea-level rise on the Atlantic coast of North America” written by Asbury H. Sallenger Jr, Kara S. Doran & Peter A. Howd, of the USGS. Hey, another climate scientist named Sallenger but not called Jim!
Is this paper a credible source? John Droz, jr, is spearheading support for proposed, unprecedented, “anti-green” legislation in North Carolina that would make it illegal for state agencies to use accelerated SLR projections as a basis for state rules and regulations. The bill is called HB-819.
Legislators are reeling from two months of a green backlash against the proposed legislation and now this “Hotspot” paper is giving them serious doubts about the wisdom of passing it. John’s asking for scientific or any other assistance. He writes:
Once the environmental movement heard about this threat to one of their key agendas, they were enraged. There have been hundreds of articles written attacking the legislators’ plan, worldwide. For those of us locally defending these efforts, it has been akin to being in caught up in a hurricane!
Two things that have struck me are that the message from these evangelists is so well-scripted — and also that it is almost entirely false.
If you want to see an accurate recounting of this situation, read this.
Anyway, where we are now is that: 1) the NC senate passed the proposed bill 35-12, and 2) the NC house is now debating a watered-down version.
The NC House leadership has evidently been shaken by the intensity of the backlash, and is concerned about the political fallout from going through with their initial plan.
Another stumbling block has been the (coincidental?) issuance of this report right in the middle of this whole matter. That report is being thrown in the legislators’ faces as an indication that what they are proposing flies in the face of scientific evidence.
As such, some legislators have asked me for commentary on that report — which I am asking for your help with.
Please let me know, ASAP, if you have done a critique of that report, or whether you are aware of any good ones being done elsewhere.
Thank you for your support.
Climate warming does not force sea-level rise (SLR) at the same rate everywhere. Rather, there are spatial variations of SLR superimposed on a global average rise. These variations are forced by dynamic processes, arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes, arising from mass redistributions changing gravity and the Earth’s rotation and shape. These sea-level variations form unique spatial patterns, yet there are very few observations verifying predicted patterns or fingerprints6. Here, we present evidence of recently accelerated SLR in a unique 1,000-km-long hotspot on the highly populated North American Atlantic coast north of Cape Hatteras and show that it is consistent with a modelled fingerprint of dynamic SLR. Between 1950–1979 and 1980–2009, SLR rate increases in this northeast hotspot were ~ 3–4 times higher than the global average. Modelled dynamic plus steric SLR by 2100 at New York City ranges with Intergovernmental Panel on Climate Change scenario from 36 to 51 cm (ref. 3); lower emission scenarios project 24–36 cm (ref. 7). Extrapolations from data herein range from 20 to 29 cm. SLR superimposed on storm surge, wave run-up and set-up will increase the vulnerability of coastal cities to flooding, and beaches and wetlands to deterioration.
The bottom line appears to be that, to the projected SLR rise by 2100 under any IPCC scenario, we must add from 20 to 2 cm, but I’ve asked Sallenger to confirm.
How good is it? The predictions are all from models. I can see some weaknesses, foremost among them being their assumption of continued warming throughout the 21st century. Future SLR is dependent on some pretty vague statements like “could rise”, “could also reduce”, “may indicate”, “could slow AMOC”, “ice melt could freshen surface water”, “NAO rate differences may indicate changes in strength of the gyre system”, (although) “NAO may not contribute to forcing the NEH”, “Aerosols may also play a role in explaining variations in NEH SLRDs” (SLRD is sea level rate difference).
What’s causing the acceleration? They won’t tell you, so take your pick. The paper mentions the North Atlantic Oscillation, so is it liable to be cyclic?
Reading this paper is raising all kinds of red flags for me, but being unable to follow the technical information means I cannot describe its faults.
I’d like to help John Droz. The paper could cause a backdown in the legislature against world-leading planning legislation.
Any thoughts on the paper’s specific faults would be much appreciated.
UPDATE SAT 30 JUN 2012 1240 hrs
On 27 June I wrote to Dr Sallenger:
I wonder if you might have time to help me understand this paper’s conclusions, please? The abstract states:
“Modelled dynamic plus steric SLR by 2100 at New York City ranges with Intergovernmental Panel on Climate Change scenario from 36 to 51 cm (ref. 3); lower emission scenarios project 24–36 cm (ref. 7). Extrapolations from data herein range from 20 to 29 cm.”
Does this mean the paper concludes that, to the projected SLR rise by 2100 under any IPCC scenario, we should add from 20 to 29 cm?
On 29 June he replied:
We would not say that for any scenario you would add 20-29 cm. That range was merely to illustrate that projections from the observations are in the same general range as those predicted by the models. We are closest in line with the lower emissions values.
My thanks to Dr Sallenger, although I still find it difficult to take his statement to some more obvious conclusion.
Does anyone have an interpretation?