Rising Sea Levels

By Bryan Walker 29/10/2012


Of all the consequences of human-caused global warming, sea level rise has always held special alarm for me in its inexorability, its extension into the future, and the enormous disruption it threatens to centres of high population and essential infrastructure. Scientist Scott Mandia (blog) and writer Hunt Janin have teamed to produce for the general reader an explanation of what it will mean for the world in coming decades and beyond. Their book Rising Sea Levels: An Introduction to Cause and Impact is patient and restrained in its survey, but no less sobering for that. Their coverage leaves no doubt as to the magnitude and extent of the measures that will have to be taken to try to cope with the effects of sea level rise as it gathers momentum and extent.

The authors don’t expect much in the way of mitigation of climate change by international agreement to limit emissions. Indeed, they take it for granted that emissions  are going  to continue to rise and that international agreement will continue to founder on obdurate differences between political blocks which negotiators appear unable to resolve even in the face of such a threat as global warming. Presumably one day the common danger will become so overwhelming as to force international agreement, but the authors see no such early likelihood and certainly not in time to forestall metres of sea level rise. The book is not about preventing sea level rise but about preparing for it and adjusting to it.

A short primer on global warming opens the book, in the course of which recent studies are referenced suggesting a potential one metre sea level rise this century, followed by possibly several metres within the next several centuries. The rise by 2100 may be appreciably higher than a metre, since the maximum level is still the subject of much responsible debate.

The momentum of sea level rise is now such that mitigation of greenhouse gases can hope to reduce its impacts only over the long term and only to a limited extent. Adaptation is unavoidable. Fortunately adaptation avoids the gridlock of international negotiation because it focuses on more narrowly-based national, regional and local efforts to cope with sea level rise. A whole range of adaptive measures can be addressed simply and quickly, albeit still with limited effect, and much of the book is devoted to highlighting some of these in the regions to which they are applicable. Mention is made of retreat as a strategy whereby a decision is made to pull back from the coast and surrender land to the sea, and there is wry reference to the easiest and often favoured  political option of “lots of talk, no action”.

The writers explain some of the ramifications of a higher sea level. Storm surges are likely to be more frequent and to cause serious damage to vulnerable coastal facilities. Insurance company Munich Re estimates, for example, that along the southern shores of Long Island even a half-metre sea level rise by 2080 will mean a 73 percent increase in property loss due to storm surges.

Coasts are never static. The book quotes Rachel Carson: “Always the edge of the sea remains an elusive and indefinable boundary.” But rapid sea level rise puts substantial additional strains on low-lying or erosion-subject land, on barrier islands, and on coastal wetlands and estuaries, along with causing saltwater intrusion in freshwater aquifers and surface waters.

New York’s task force on the subject “laboured mightily” and in 2010 “brought forth a mouse”

The generalities are brought vividly to life when the book moves to examine a selection of 25 cities and countries already facing or soon to be facing serious problems as the sea level rises. In the Atlantic ocean basin New Orleans faces much uncertainty as to how best to build protection, Miami suffers from “head in the sand” government mentality, and New York’s task force on the subject “laboured mightily” and in 2010 “brought forth a mouse”. Rotterdam and the Netherlands are well ahead of any other country in actually doing something about sea level rise on a highly organised national level, the Thames Barrier in London should provide protection for some decades yet, but “lovely and courageous” Venice probably cannot be rescued for very much longer. Alexandria will be 30 percent flooded by a sea level rise of between 0.5 and 1.0 metres unless effective remedial actions are taken and Lagos and the Nigerian coast will be severely affected, as will Recife and the Northeast coast of Brazil.

In the Pacific basin the book considers the complex threat to the San Francisco Bay Area before moving across to the highly vulnerable coastal cities of China, where the government recognises the adverse effects ahead. Vietnam also is aware of the danger to its coastal regions and is seeking to learn about possible adaptive strategies. Bangkok faces major flooding but the Thai government is tardy in recognising the need for remedial measures. Tuvalu and Kiribati are destined to disappear beneath the waves. The developed economies of Australia and New Zealand are mentioned as well placed to implement adaptation measures, but likely to encounter considerable costs and institutional constraints as they do so.

In the Indian Ocean basin Bangladesh stands out as a heavily populated country under severe threat. A one metre rise will see 50 percent of its land under water. What adaptation measures can cope with that are difficult to comprehend and the book understandably envisages drastic political upheavals if international assistance is not forthcoming. In neighbouring India, Mumbai and Kolkata face serious threats, as do Karachi in Pakistan and Jakarta in Indonesia. It is difficult to see the Maldives surviving.

It’s an overwhelming selection, all the more because it is just a selection. But there are measures that can be taken specific to each region and it is the purpose of the book to urge that adaptation issues be addressed as soon and as urgently as possible. The Netherlands is advanced as a case study of how much can be done to secure even a country of which 27 percent lies below sea level and two thirds of which is subject to flooding. The refreshing realism with which they plan for future sea level rise is well recounted.

The impacts of sea level rise are clearly going to be traumatic in many regions of the world, and the book does not need to underline that fact for any reader who follows its careful assessments. The sea is rising and national and local governments need to get down to the task of protecting their coastlines and populations to the greatest extent possible. If they want to prevent the sea rising to even more destructive levels than those already in prospect they will have to undertake urgent and drastic reduction of greenhouse gas emissions, but that’s a course they are collectively still unwilling to follow.