Sea Level Rise, Melting Glaciers, and North Carolina Law (USA)

North Carolina legislators are in danger of being drowned by a rising sea of scorn.
Last August, Hurricane Irene washed out several sections of Hwy 12 along North Carolina's Outer Banks. Accelerated sea level rise will make the North Carolina coast more vulnerable and so the state legislators are fixing to stop it. (NCDOT)
The State of North Carolina has got a good deal of attention of late for its apparent desire to mandate how much sea level will rise along its picturesque coast. Some in the state legislature may be feeling a good deal of self-satisfaction for concocting this little gambit, perhaps even high fiving each other and chanting things like “we don’t need no stinking climate scientists.” A lot of others are having a pretty healthy chortle at North Carolina’s expense. Even the Brits have gotten into it. For an especially good laugh check out this segment from Stephen Colbert.

It’s not often that a bill being considered in a state legislature makes the national news. But every once in a while one is so egregious you can’t help but shake your head. And North Carolina’s sea level bill is most definitely one of those.

Perhaps recognizing that laughing is good for people’s health and wanting to do their civic duty or perhaps out of a sincere belief that politicians understand climate better than scientists, North Carolina may move one step closer to making this a reality. The bill in question [pdf] described as Proposed Senate Committee Substitute H819-CSLH-38 [v.24] - "An Act to Study and Modify Certain Coastal Management Policies" came before the North Carolina Senate Committee on Agriculture, Environment, and Natural Resources this morning.

Relevant passages in the proposed bill include:

“The General Assembly does not intend to mandate the development of sea-level rise policy or rates of sea-level rise. The Coastal Resources Commission, in conjunction with the Division of Coastal Management, shall have the authority to define sea-level rise and develop rates of sea-level rise for the State.”

That sounds good, but then there’s this section:

“The Coastal Resources Commission shall be the only State agency authorized to define rates of sea-level rise for regulatory purposes and, if developed, shall do so in conjunction with the Division of Coastal Management…These rates shall be determined using statistically significant, peer-reviewed historical data generated using generally accepted scientific and statistical techniques. Historic rates of sea-level rise may be extrapolated to estimate future rates of rise [emphasis added] but shall not include scenarios of accelerated rates of sea-level rise unless such rates are from statistically significant, peer-reviewed data and are consistent with historic trends.”

The language is a bit murky, but seems to giveth and taketh away when it comes to accelerated rates: you can use them, but only if they are consistent with historic trends – sort of an oxymoron in the case of a rate that is accelerating.

So what’s wrong with this legislation? Here are a few paragraphs my colleague Prasad Kasibhatla and I penned for Rob Jackson, a Nicholas School professor who went to Raleigh to testify at the hearing:
  • The specific language regarding ‘accelerated rates of sea-level rising’ is confusing. However any legislative restriction on the use of accelerating rates of sea-level rise has no scientific basis. It is clear from the data that rates of sea level rise have accelerated over the past century and the reasons for that are largely understood - increasing ocean temperatures and glacial melt.
  • From a climate science perspective, it is highly likely that the underlying drivers of sea-level rise (increasing ocean temperatures and glacial melt) will continue to operate in the coming decades.
  • The March 2010 North Carolina Sea-Level Rise Assessment Report [pdf] prepared by the North Carolina Coastal Resource Commission’s Science Panel on Coastal Hazards presents a scientifically rigorous assessment of future sea-level rise for coastal North Carolina.
  • To mandate the use of historical rates of sea-level rise without acceleration is actually inconsistent with the historical record and with the scientific understanding of underlying drivers that has been developed from this historical record.
Surprise, surprise, the bill passed out of committee this morning. You can watch here. Incredibly, while the world waits with bated breath to see how much sea level rise the NC Senate will decide is lawfully allowable, the scientific community continues its work on sea level rise as if the legislation is irrelevant.

In point of fact, two papers on Greenland’s recent contribution to sea level rise were published in the last month.

Glacial Retreat Captured on Old Film

Anders Bjork of the University of Copenhagen and colleagues publishing in Nature Geoscience used old aerial photographs of glaciers in the southeast of Greenland from the 1930s to infer and compare rates of glacial retreat at six discreet intervals from 1933 to 2010. The 1930’s are of interest because that was also a period of rapid atmospheric warming in Greenland, although sea surface temperatures are much higher now. The authors found that while glaciers during the 1930s also had elevated rates of retreat they weren’t as large as current rates of retreat. The average rate during the 1930s was about 25 meters per year, whereas the average rate now is about 55 meters per year. Also back in the 1930s land terminating glaciers retreated faster, but now ice sheet and marine terminating glaciers are retreating much faster—a likely reflection of the current increase in both air and ocean temperatures.

Misreporting climate science is fairly common these days. So I guess we should not be surprised by misleading coverage of the Bjork et al study that appeared in The Register and elsewhere reporting that “photos taken in the 1930s by Danish explorers "show glaciers in Greenland retreating faster than they are today, according to researchers."”

Satellites Also Follow Glacial Retreat

Twila Moon of the University of Washington and colleagues publishing in Science reported on their analysis of satellite data measuring the velocity of Greenland’s outlet glaciers (those that drain the ice sheet to the sea) over the past decade. The bottom line was encouraging. While outlet glaciers in some areas are fast moving and continue to accelerate, other regions are characterized by glaciers with slower rates of acceleration or even relatively steady flows. The picture that emerges is that flow is variable across Greenland and while velocities are accelerating overall, the rate of acceleration slowed over the decade. Slowed to the point that it is below what was in line with sea level rise scenarios through 2100. They conclude that “sea level rise associated with Greenland glacier dynamics remains well below the low-end scenario* ... at present.”

Of course this latter result will need to remain in limbo until it is taken up by the North Carolina legislature.
End Note

Note this does not refer to total sea level rise, nor is it the sum of sea level rise expected from Greenland. It is a projection of just that portion of sea level rise from Greenland’s glaciers.


Mais visitados