Living as I do in San Francisco, along the coast, I remain deeply curious how high the sea rise is likely to be, between now and 2100. I have a cousin who recently bought a house in our Marina district. I kid that he may have to move to higher ground before too many years pass. Reading a new book by Peter Ward, Biology and Earth and Space Science Professor at the University of Washington in Seattle (The Flooded Earth: Our Future in a World Without Ice Caps ), I learned, for the first time, that there is already in place a Bay Area Planning Commission which set out goals, in 2008, to plan for a likely three foot sea level rise. Unlike in Venice, Bangkok and other threatened cities, the planning commission has set in place plans to manage the rising waters. It readily acknowledges how unpleasant, sometimes dicey, such planning can be.
The bay area commission calls for plans to engage, if necessary, in triage: what to save and what to surrender. As the 2008 plan reads: “The plan should determine the measures needed to adapt to projected sea level rise by identifying: (a) the most significant structural, environmental, aesthetic, social, cultural and historic resources that must be protected from inundation; (b) those areas that are inappropriate for protection from inundation; (c)strategies and techniques that will make future conservation and development projects more resilient to climate change.
As many know, The International Panel on Climate Change in its 2007 report—much to the delight of some observers—predicted sea rises of from 18mm to 59mm in the twenty-first century. The 59 mm maximum the IPCC predicted (around 2 feet) is lower than the Bay Area’s Commission’s projected 3 feet or cognate projections of the Dutch Delta Commission, which is investing $144 billion on its plan to protect below sea-level areas of the Netherlands from sea level rises. The Dutch commission reckoned on a 4.25 foot rise by 2100 and, perhaps, a rise of 6.5 feet by 2200. Even the IPCC’ s more conservative estimate of .59 meters would devastate parts of Bangladesh, where a sea level rise of 400 mm at the Bay of Bengal would put 11% (some 10 million) Bangladeshi citizens in peril. A sea level rise of 200 mm would cause 740,000 environmental refugees or homeless in Nigeria.
The question o how high the sea is likely to rise in the next ninety or so years is, partially, a question of scientific predictions; it is, equally, a question of planning and investment for the future. Clearly, even the more conservative estimates of sea rise might imperil (at the great cost in billions of re-building the airports elsewhere) the airports of San Francisco and Seattle. Even when the IPCC’s predicted sea level rise of a maximum of .59 meters appeared, many scientists raised serious questions about the accuracy of its model. James Hansen, the NASA climatologist, in his recent book, Storms of My Grandchildren set his estimate of a minimum of 5 feet rise by the end of this century. Stefan Rahmstorf in a blog post  on the influential scientific web site, Realclimate.org, suggests that there were faulty assumptions in the IPCC’s predictive model for sea rise. He predicts a possible meter rise in sea levels.
The IPCC model assumed that the ice sheet melt rates of 1993-2000 would continue, along the same average measure, throughout the rest of the century. Even members of the IPCC (including Rahmsfort, representing Germany) thought that assumption was much too optimistic, especially since the rates of 1993-2000 already showed a significant increase (a rise of sea level from 1.8 mm per year to 2.8 to 3.1 mm per year) over sea rise rates before 1993. Much depends, in projections about sea level rise, on two variables: how fast will the ice sheets around Greenland and Antarctica melt. Another important variable is global warming’s impact on ocean warming. Warmer water expands the oceans. An important article in Science (Sept., 2008) by W.T. Pfefer et.al. "‘Kinematic Constraints on Glacier Contributions to 21st Century Sea Level Rise," projects rises of from 0.8 to 2 meters in this century. A one meter rise would have a major impact on 100 million people. In point of fact, based on IPCC projections, the recent ice melts are faster and more extensive than predicted.
There are, of course, uncertainties in every model of future global warming. In part, we have not experienced such impacts for a long time. No sane person or planner, however, would discount that global warming is happening and will increase and so, also, will sea level rise, due to melting ice sheets. It pays to read a book such as, The Flooded Earth, or connect with the Web site, Realclimate.org , to get a tutored sense of what is uncertain and what is beyond doubt.
Some of the uncertainties about global warming involve how high it can go to be tolerable (yet, inevitably, at some true financial costs to contain its negative consequences): can we sustain 450 ppm of C02 or will that take us too close to a tipping point of feedbacks (such as the melting of the tundras and the belching release of buried methane) so that, following the advice of James Hansen and Bill McKibben, we should aim more toward stabilizing parts per million of CO2 at 350 (it presently stands at 390)?
How much more warming of the oceans can we sustain? Already, in 1957, scientists Roger Reville and Hans Seus noted that “the oceans could not absorb CO2 as rapidly as humanity was releasing it.” With the ocean "sinks" filling up with CO2, the oceans have also become more acidic, threatening all coral reefs worldwide and encrusted sea fish. Warmer oceans also further erode ice sheets.
Another set of uncertainties have to do with how fast the warming will occur and, thus, how much time we have. Some have already despaired that it is too late. Others think we still have a margin of opportunity. Again, there are both “forcings” toward climate change (not all of them man-made) and feedback mechanisms. The more the glacial ice or ice sheets melt, the less the albedo effect (being able to reflect the sunlight back into space rather than absorbing it). That feedback exacerbates global warming.
Sea rise also threatens to involve coastal flooding and even deep contamination of fresh water sources. The Flooded Earth brought issues closer to home, for me, as it discussed The California Federal Bay Delta System. Deltas can be wonderful agricultural areas. A delta involves the inter-section of inflowing rivers where salt water meets fresh. In California, a major effort has been made to export the fresh water from the Sacramento River as it flows into the San Francisco bay to down-state San Joaquin Valley farmers. But as Ward notes in his book, “When freshwater is withdrawn at a faster rate than it can be replenished, the water table lowers with a decrease in overall hydrostatic pressure. When this happens near an ocean coastal area, salt water from the ocean intrudes into the freshwater aquifers.” So sea level rise can have important ramifications for fresh water supplies for drinking water. Salt contaminated fresh water supplies devastates farming.
Much money has been spent by fossil fuel-fueled lobbyists to raise skepticism about global warming (cf. James Hoggan’s Climate Cover-Up). But insurers, national security planners or coastal planning commissions can not take such a nonchalantly skeptical view. Too much is at stake for them—and for us too!
John Coleman, S.J.