Climate scientists are watching anxiously as some state legislatures seek to restrict how state agencies and planners prepare for potential sea-level rise.
In North Carolina, a battle is currently brewing over a bill that would “rewrite state law to spell out who would be authorized to predict the impact of sea level rise on the state’s coastal counties.” An initial version of the bill stated that the “Division of Coastal Management shall be the only State agency authorized to develop rates of sea-level rise … These rates shall only be determined using historical data, and these data shall be limited to the time period following the year 1900. Rates of sea-level rise may be extrapolated linearly to estimate future rates of rise but shall not include scenarios of accelerated rates of sea-level rise.” (Emphasis added.)
Quipped Scott Huler at Scientific American:
After that effort attracted opprobrium, including ridicule on the Colbert report, an amended version, passed by the State Senate on Tuesday, stated that “rates [of sea-level rise] shall be determined using statistically significant, peer-reviewed historical data generated using generally accepted scientific and statistical techniques.” Which sounds great, were it not for the subsequent qualifier that, “Historic rates of sea-level rise may be extrapolated to estimate future rates of rise 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 problem with all of this, of course, is that predictions of future sea-level rise are neither linear nor consistent with historic trends, as John Bruno of the University of North Carolina at Chapel Hill points out in a post on his blog, Sea Monster. Bruno notes that “sea level fluctuates naturally by 10s to 100s of meters but has been relatively stable for the last few thousand years,” that “greenhouse gas emissions are causing sea level to rise via ‘thermal expansion’ (warming a liquid increases its volume) and by melting mountain glaciers,” and that “the rate of sea level rise appears to be accelerating, i.e., non-linear”.
There is, Bruno continues, a great deal of variation: due to a combination of natural and anthropogenic factors, sea level will rise substantially more in some places than others, and in some locations may even decline. As for how much sea level rise, on average, to expect: that, of course, to a large extent depends on how much greenhouse gas emissions continue to increase, at what levels (if ever) atmospheric levels stabilize, and when (if ever) emissions decrease. But, says Bruno, along the plot lines of various emissions scenarios, “We have a pretty good sense of how much sea level rise to expect from … thermal expansion and the melting of mountain glaciers, but a third important mechanism is a lot harder to deal with: the melting and calving of ice from the massive glaciers covering Greenland and Antarctica.” (Satellite measurements are presently tracking at the upper level of IPCC projections; various researchers estimate average sea levels will rise by anywhere between 8 inches and 6.6 feet globally by 2100.)
At least scientists, while acknowledging the uncertainty that exists around the fringes, are seeking to refine the models and observations to provide greater clarity. Legislators in North Carolina are attempting to wish the whole issue away – and not surprisingly, they are doing so, it appears, at the behest of industry lobbyists and specifically NC-20, which Raleigh/Durham/Chapel Hill CBS affiliate WRAL dubs “a federation of coastal counties that would have a great deal to lose if the average American began to believe sea-level rise might obliterate NC coastal real estate.” As NC-20 chair Tom Thompson wrote in a memo obtained by WRAL: “Bottom line: we got everything we asked for … we got a commitment to totally abandon any reference to accelerated SLR. Instead, the State will use historic, linear sea level measurements to create future projections (about 8 inches by 2100 instead of the 56 inches once being considered).” (sic)
As that Miami Herald editorial notes, present sea-level rise projections are “not good news for coastal developers looking for loans and flood insurance. But developers have clout. And scientists don’t.”
A man prepares to use his kayak to get around town after the Pamlico Sound floods Cape Hatteras Island during Hurricane Earl in September 2010. (Mike Theiss, Corbis)
Flood waters from Hurricane Irene sliced through portions of Highway 12 on North Carolina’s Hatteras Island. This aerial photo, acquired by the National Oceanic and Atmospheric Administration (NOAA) on August 28, 2011, is part of a larger project to assess damage from Hurricane Irene along the U.S. East Coast. (NOAA/NASA/Corbis)
Beach erosion threatens Cape Hattaras Lighthouse in 1995. (Shepard Sherbell, Corbis)
After 130 years on the North Carolina beach, the Cape Hatteras lighthouse was moved a half mile inland in 1999. (Karen Kasmauski, Corbis)
Heavy construction equipment removes tons of sand in Cape Hatteras, North Carolina following the landfall of hurricane Isabel on Sept. 18, 2003. (Jim Reed, Corbis)
A Coast Guard C-130 Hercules fixed-winged aircraft from Coast Guard Air Station Elizabeth City provides an overflight of areas affected by Hurricane Irene in the area of Oregon Inlet, Aug. 29, 2011. (U.S. Coast Guard Petty Officer 3rd Class Stephen Lehmann, Corbis)