African Cities and Sea Level Rise

This post is stimulated by a recent African Loft post on this same topic. David Wheeler and numerous coauthors with the Center for Global Development (CGD) have compiled the fundamental data. Alexandria in Egypt and Lagos in Nigeria are particularly at risk both because of their likely inundation by rising seas and because of their rapidly increasing populations.

As noted by Gupta and others (2009), "variations in coastal morphology will magnify the effects in some areas, while largely insulating others." Their complete paper projecting storm surge impacts for developing countries can be downloaded at the CGD webpage here. An appended spreadsheet (.xls 53k) further tabulates the data for 327 cities. Alexandria ranks second and Lagos third based upon the population projected to be exposed to storm surges by the year 2100.

Asian cities are also at serious risk, with Manila ranking at the top of the CGD compilation. Cities in Pakistan, India, Bangladesh, Myanmar (Burma), Indonesia, Thailand, and Vietnam are also among the top 20 in the CGD table. Impacts projected for Vietnam's Mekong delta by the CGD and many independent scientists were reported in a recent New York Times article by Seth Mydans.

Wheeler and his coauthors with the CGD are certainly qualified to compile these data and explain their implications for risk assessment and public policy. Wheeler himself stands out as a clear thinker who both comprehends the scientific literature and interprets it to the general public in simple language. Following the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), Wheeler (2007) penned a note about the sea level projections in which he correctly criticized their overly conservative use of glacial ice melting rates for Greenland and West Antarctica. As discussed in an earlier post on African Loft, a scenario in which these ice sheets continue melting at their present rates will in fact result in catastrophic submergence by the year 2099 along the coast of West Africa. Nigeria would be particularly affected because of the dense population in Lagos and other coastal cities.

Engineering the Pyramids?

Dr. Michael Barsoum of Drexel University heads a group which is asserting that blocks of artificially reconstituted limestone make up part of some Egyptian pyramids. My initial impression that their knowledge of limestone and sedimentary petrology is limited was only partially assuaged by reading their paper published in the Journal of the American Ceramic Society¹. In spite of detailed SEM examination and chemical analysis of numerous samples from neighboring natural outrcops and from the pyramids, only the novel hypothesis of an artificial block cemented with "geopolymer" is really fleshed out.

There are much simpler alternative hypotheses that would account for amorphous silica and microcrystalline dolomite as replacing cements either in the genesis of the limestone or in the weathering of the stone blocks after the pyramids were built. Dr. Barsoum is to be commended for creating a blog in which to promote his ideas and answer criticisms. His reponses to the criticisms that have been posted are quite strident and do not show much consideration of alternative hypotheses.

A similar sort of sensationalized "mystery" about the age of the Sphinx has been kept before the public eye by Dr. Robert Schoch of Boston University. Egyptology does attract advocates for extreme ideas and fanciful theories, although it must be acknowledged that Dr. Barsoum is himself Egyptian and has already had a successful career as an engineer and materials scientist. Barsoum does not appear to have a financial or professional interest in sensationalizing his findings, and he is promoting some novel applications of the geopolymer technology for building inexpensive housing in the developing world.

¹Barsoum, Michael W., Ganguly, A., and Hug, G., 2006, Microstructural Evidence of Reconstituted Limestone Blocks in the Great Pyramids of Egypt. Journal of the American Ceramic Society 89(12): 3788-3796.