Sunday, October 30, 2011

Dealing With Sea Level Rise Skepticism

William Nuttle, Organizer for CERF 2011 Synthesis Sessions

Miami-Dade County embraces science-based sea level projections.

Ecologists use the term “shifting baseline” to call attention to a tendency in people to discount the magnitude of change occurring in ecosystems. In this context, a “baseline” is the conditions people use as a point of reference in assessing the degree of change. Daniel Pauly first used the term in 1995 to discuss problems fisheries managers face in estimating the target size of a fish stock that will be sustainable. Coastal managers face a similar problem in setting goals that will ensure the future sustainability of coastal communities and coastal ecosystems faced with climate change and accelerated sea level rise.

The source of the shifting baselines problem with fisheries is that there has not been a clear way for scientists to estimate how large fish stocks were before being reduced by wholesale exploitation. Pauly cites examples counter examples from astronomy and oceanography where the interpretation of historical records, often centuries old, provide an objective measure of long-term changes. By contrast, “each generation of fisheries scientists accepts as a baseline the stock size and species composition that occurred at the beginning of their careers, and uses this to evaluate changes.” The result is a general tendency for scientists to discount the magnitude of change that has occurred in fish populations over a period of several generations.

Coastal scientists and managers must deal with a similar tendency to discount the magnitude of future change in coastal ecosystems as the result of climate change and sea level rise. It is already difficult enough simply to predict how coastal ecosystems will evolve in response to global climate change, higher concentrations of carbon dioxide in the air and in the water, and accelerated rates of sea level rise. And this gets layered on top of the politically-charged question of whether or not global climate change is occurring in the way that science says.

Aside from these sources of uncertainty, the magnitude of change anticipated from accelerated sea level rise in vulnerable areas of the coast itself invites disbelief. For example, county governments in South Florida now accept that a 2 foot rise in sea level over the next 50 years is well within the realm of possibility. This translates into inland migration of the coast at rates of 1000s of feet per year in the low-lying region south of Miami. In similarly vulnerable areas of North Carolina, towns and county officials are resisting efforts by the state to spur them to take actions to defend against rising sea level.

Personal experience, or the lack of it, lies at the heart of the tendency to discount change. The objective analysis and predictions that coastal science can offer will always be, for most people, a poor substitute for experience. But, this is the best that can be offered for now, at least until the passage of time provides a store of experience for us to learn from. Session SCI-082 will hear presentations from specialists in a number of sea-level related topics, including experts on satellite records, glaciers and ice sheets, and coastal marshes. There will be a summary of sea level issues at the beginning of the session and an open discussion at the end.

CERF Session SCI-082: “Sea-level Change: Patterns, Processes and Impacts”
Monday afternoon
Moderators Thomas M. Cronin USGS, Torbjorn Tornqvist Tulane University

“Sea-level rise is among the most important societal issues related to climate change, yet it is also one of the most misunderstood in both scientific and public circles. This session would draw on experts in glaciology, oceanography, geology, geomorphology, climate modeling, coastal ecosystems, and coastal management with the goal of providing a realistic, state-of-the-art assessment of what we know and don't know about sea-level change. Potential topics include ice dynamics, rates of sea-level rise during past and present climatic warming, vulnerable coastal systems, non-eustatic processes (isostatic adjustment, subsidence, sediment flux, etc) and regional sea-level changes.”

This post relates to Topic 4: Baseline change to be discussed during the Synthesis Sessions at CERF 2011.

SoutheastFlorida Regional Climate Change Compact Counties, 2011.  A Unified Sea Level Rise Projection for Southeast Florida. Report prepared by the Technical Ad Hoc Work Group, April 2011.

1 comment:

  1. Miami-Dade County is at the forefront of understanding sealevel rise and its effects because most of the county is below 20 ft of elevation. Furthermore, Miami Beach residents need to sand bag their front entrances during extreme high tides. As sealevel rises, so do fresh groundwater levels, causing freshwater flooding in the interior of the county, underscoring that this is not just a coastal problem.