Sea level rise estimates upheld through peer review


Peer review is unlikely to substantially alter the range of state sea level rise predictions computed by a group of local scientists and engineers.

After the N.C. Coastal Resources Commission Science Panel spent months of meetings wading through historical data, local geologic and oceanographic effects and global sea level rise estimates, a draft report was sent to Dr. Robert Dean, professor emeritus in the University of Florida’s coastal and oceanographic engineering program, and Dr. James Houston, a retired U.S. Army Corps of Engineers research director, for peer review on Dec. 31, 2014.

The panel will correct a mathematical error made when computing confidence intervals in the report and better explain how and why ocean current trends are incorporated into the sea level rise estimates. However, after discussing the first round of peer review during a Jan. 26 meeting at N.C. State University in Raleigh, the panel declined to act on Dean and Houston’s recommendation to incorporate a different set of data into the formula used to calculate the state sea level rise.

The group of scientists and engineers used data collected at five tide gauges operated by the National Oceanographic and Atmospheric Administration (NOAA), along with land subsidence rates and changes in ocean currents — especially in the speed and position of the Gulf Stream — to calculate a range of sea level rise estimates for locations along the coast. Dean and Houston questioned the panel’s decision to factor ocean current trends into the report’s predictions, arguing the data — which resulted in higher sea level rise estimates for the coast north of Cape Hatteras — is cyclic and might even out over longer periods of time.

The panel acknowledged the exact impact of ocean trends over longer periods of time is unknown while discussing Dean and Houston’s suggestion, but also examined the consequences of relying only on global sea level rise rates coupled with local tide gauge and land subsidence data, a strategy that would shrink estimates for the northeastern coast by a few inches.

Longtime East Carolina University geologist and panel member Stan Riggs confirmed the effect of ocean currents on sea levels north of Cape Hatteras.

“I can tell you from spending a lifetime working on the water up there in the northeast that the oceanographic effects are dramatic. There might not be data to point it out, but I can guarantee that it’s there,” Riggs said.

The panel agreed to continue using ocean current trends to calculate local sea level rise rates, but pledged to better explain the decision in the report.

Dean and Houston also advised the panel to incorporate data on ocean water elevations collected by satellite altimeters in addition to tide gauge data — an approach the panel has already considered, said N.C. Sea Grant construction and erosion specialist and panel member Spencer Rogers, but abandoned because varying timespans of data collection and the assumptions inherent in the different methods are not easily reconciled.

The panel will explain their decision to forgo adding the satellite data in a response and updated report due to Dean and Houston by Feb. 15.

The back-and-forth between the panel and the peer review committee is an accepted part of the scientific process, Rogers noted, and not an indication of controversy.

“It’s important to keep in mind that all of this is draft discussion. The really important thing for the public is the bottom line of what we come up with, and we think we’re getting good comments and working along the way of normal scientific process,” Rogers said. “While it may have the appearance of some disagreements, it’s a healthy scientific discussion that we appreciate at this point.”

The final estimates in the working draft of the report, still considered preliminary and subject to change, are not likely to change much based on the peer review, Rogers said. The report suggests waters off the coast of Wilmington could rise 2-5 inches over the next 30 years, compared to a range of 6-12 inches near Duck, N.C. An earlier iteration of the report released in 2010 estimated a statewide swell as high as 39 inches by 2100, leading the N.C. General Assembly to stall creation of policy addressing sea level rise until an updated report is compiled and submitted to the state legislature by March 1, 2016.

The panel will meet again in March 2015 to respond to Houston and Dean’s final round of comments and make changes to the report as needed before sending the report to the Coastal Resources Commission by March 31. At that time the report will be available for public review and public comment.

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1 Comment

  1. These issues have become 100% political. I see PhDs lose their heads over party affiliation. From now on, studies have to be made by 50% democrats and 50% republicans in order to see some truths. Tired of political bullying instead of science.

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