FitzGerald et al 2008:
Sea-level rise (SLR) poses a particularly ominous threat because 10% of the world’s population (634 million people) lives in low-lying coastal regions within 10 m elevation of sea level (McGranahan et al. 2007). Much of this population resides in portions of 17 of the world’s 30 largest cities, including Mumbai, India; Shanghai, China; Jakarta, Indonesia; Bangkok, Thailand; London; and New York.
In the last article – Sinking Megacities – we saw that some of these cities are sinking due to ground water depletion. To those megacities, this is a much more serious threat than global sea level rise (probably why we see so many marches and protests about ground water depletion).
The paper continues:
..The potential loss of life in low-lying areas is even more graphically illustrated by the 1970 Bhola cyclone that traveled northward through the Bay of Bengal producing a 12-m-high wall of water that drowned a half million people in East Pakistan (now Bangladesh) (Garrison 2005).
In Bangladesh, storms and cyclones are much more of a threat than sea level rise. Here is Karim and Mimura (2008) listing the serious cyclones over the last 60 years:
Figure 1 – Click to expand
There is an interesting World Bank Report from 2011. First on floods:
In an average year, nearly one quarter of Bangladesh is inundated, with more than three-fifths of land area at risk of floods of varying intensity (Ahmed and Mirza 2000). Every four or five years, a severe flood occurs during the monsoon season, submerging more than three-fifths of the land..
The most recent exceptional flood, which occurred in 2007, inundated 62,300 km² or 42 percent of total land area, causing 1,110 deaths and affecting 14 million people; 2.1 million ha of standing crop land were submerged, 85,000 houses completely destroyed, and 31,533 km of roads damaged. Estimated asset losses from this one event totaled US$1.1 billion (BWDB 2007).
Flooding in Bangladesh results from a complex set of factors, key among which are extremely low and flat topography, uncertain transboundary flow, heavy monsoon rainfall, and high vulnerability to tidal waves and congested drainage channels. Two-thirds of Bangladesh’s land area is less than 5 m above sea level. Each year, an average flow of 1,350 billion m³ of water from the GBM [Ganges, Brahmaputra, and Meghna] basin drains through the country.
Figure 2
I recommend this World Bank report, very interesting, and you can see some idea of the costs of mitigating against floods. These problems are already present – floods are a regular occurrence, some mitigation has already taken place, and more mitigation continues.
I read the entire report and all I could find was that rising sea levels would exacerbate the problems already faced from storm surges: p.6:
Increase in ocean surface temperature and rising sea levels are likely to intensify cyclonic storm surges and further increase the depth and extent of storm surge induced coastal inundation.
However, the projections indicate that sea level rise is much less of a problem compared with possible increases in future storm surges and possible increases in future flooding. And compared with current storm surges and current flooding. We will look at floods and storm surges in future articles.
In the report it’s clear that floods and storms are already major problems. Sea level is harder to analyze. Trying to account for a sea level rise of 0.3m by 2050 when severe storm surges are already 5-10m is not going to make much of a difference. If we had accurate prediction of storm surges, to +/- 0.3m, then sea level rise of 0.3m should definitely be accounted for. But we don’t have anything like that kind of accuracy.
Well, they do some calculations of adaption against storm surges for projected changes up to 2050:
Under the baseline scenario, the adaptation costs total $2.46 billion. In a changing climate, the additional adaptation cost totals US$892 million.
In essence the question is “what is the storm surge for a once in a 10 year storm in 2050”? (I’m sure Bangladesh would really prefer to build protection against a once in 100 year storm). An extra $1bn for future problems, or a total of $3.5bn to cover existing and future problems, seems like money that would be very well spent, representing excellent value.
Nicholls and Cazenave (2010), in relation to the susceptible coastline of Asia and Africa, comment on adaption:
Many impact studies do not consider adaptation, and hence determine worst-case impacts. Yet, the history of the human relationship with the coast is one of an increasing capacity to adapt to adverse change. In addition, the world’s populated coasts became increasingly managed and engineered over the 20th century. The subsiding cities discussed above all remain protected to date, despite large relative SLR.
Analysis based on benefit-cost methods show that protection would be widespread as well-populated coastal areas have a high value and actual impacts would only be a small fraction of the potential impacts, even assuming high-SLR (>1 m/century) scenarios. This suggests that the common assumption of a widespread forced retreat from the shore in the face of SLR is not inevitable. In many densely populated coastal areas, communities advanced the coast seaward via land claim owing to the high value of land (e.g., Singapore).
Yet, protection often attracts new development in low lying areas, which may not be desirable, and coastal defense failures have occurred, such as New Orleans in 2005. Hence, we must choose between protection, accommodation, and planned retreat adaptation options. This choice is both technical and sociopolitical, addressing which measures are desirable, affordable, and sustainable in the long term. Adaptation remains a major uncertainty concerning the actual impacts of SLR.
In the World Bank 2011 report, in chapter 4, after their analysis on risks and costs of storm-induced inundations in 2050 resulting from projected higher cyclonic wind speeds and a projected increase in sea level of 0.27m, they comment, p.24:
As a cautionary note, it should be noted that this analysis did not address the out-migration from coastal zones that a rise in sea level and intensified cyclonic storm surges might induce.
In fact the cost data assumes population growth in the vulnerable regions.
Likewise, here is Hinkel et al (2014):
Coastal flood damages are expected to increase significantly during the 21st century as sea levels rise and socioeconomic development increases the number of people and value of assets in the coastal floodplain.
[Emphasis added].
This assumption bias creates an interpretation challenge. It would be useful to see notes to the effect: “If the population migrates away from this area due to the higher risk, instead the cost will be $X assuming a reduction of Y% in population in this region by 2050“. This extra item of data would create a useful contrast and I’m guessing that we would see impact assessments reduce by a factor of 5 or 10.
It is difficult to see realistic global sea level changes, even to the end of the century, having a big impact on Bangladesh compared with their current problems of annual flooding and frequent large storm surges. Of course, adding an extra 0.5m to the sea level doesn’t improve the situation, but it is an order of magnitude smaller than storm surges.
The adaption costs estimated by the World Bank to protect against storm surges (already required but at least a work in progress) seem moderate in value.
Lastly, I wasn’t able to find a detailed elevation map (with, say, 0.5m resolution), instead the ones I found graded the elevation with respect to sea level in fairly coarse steps. I’m sure the information exists but may be proprietary (in GIS data for example):
Figure 2 – Click to expand
I have to admit that I believed something like 25% of the Bangladesh population were around 1.0m or less above current sea level. This map says that the 0-3m area is quite small. If anyone does have a better resolution map I will post it up.
Articles in this Series
Impacts – II – GHG Emissions Projections: SRES and RCP
Impacts – III – Population in 2100
Impacts – IV – Temperature Projections and Probabilities
Impacts – V – Climate change is already causing worsening storms, floods and droughts
Impacts – VI – Sea Level Rise 1
Impacts – VII – Sea Level 2 – Uncertainty
Impacts – VIII – Sea level 3 – USA
Impacts – IX – Sea Level 4 – Sinking Megacities
References
Coastal Impacts Due to Sea-Level Rise, Duncan M. FitzGerald et al, Annual Rev. Earth Planet. Sci. (2008)
Impacts of climate change and sea-level rise on cyclonic storm surge floods in Bangladesh, Mohammed Fazlul Karim & Nobuo Mimura, Global Environmental Change (2008) – free paper
The Cost of Adapting to Extreme Weather Events in a Changing Climate – Bangladesh, World Bank (2011) – free report
Sea-Level Rise and Its Impact on Coastal Zones, Robert J Nicholls & Anny Cazenave, Science (2010) – free paper
Coastal flood damage and adaptation costs under 21st century sea-level rise, Jochen Hinkel et al, PNAS (2014) – free paper
I am a little surprized that you dont have Brammer 2013 http://www.sciencedirect.com/science/article/pii/S221209631300003X; in your reference list which also supports your argument.
“It is difficult to see realistic global sea level changes, even to the end of the century, having a big impact on Bangladesh compared with their current problems of annual flooding and frequent large storm surges. Of course, adding an extra 0.5m to the sea level doesn’t improve the situation, but it is an order of magnitude smaller than storm surges.”
Seriously?
So you add on the SLR to the storm and the additional impact is really small?
Nathan,
“Seriously?”
Yes. All my posts are serious.
Yes, I add SLR onto the storm and the additional impact is really small. I apologize for my confusing method. It’s called “trying to make sense of the data with zero concern for the zeitgeist”.
Imagine for a minute that I’m not an agent of darkness (or an ignorant dupe of an agent of darkness). Explain the impact of the projected 2050 0.3m SLR in the light of frequent 5m+ storm surges in Bangladesh. Or the projected 2100 0.5m SLR.
Nathan wrote: “So you add on the SLR to the storm and the additional impact is really small?”
The way I look at it is that mitigation of storm surges is needed with or without sea level rise and that allowing for sea level rise makes the mitigation just a little harder.
Mike M.,
Strictly speaking, building sea walls against storm surges is adaptation, not mitigation in climatespeak. I don’t know of any way to mitigate storm surges. The alarmists think that higher temperatures from CO2 will lead to more severe storms, but the jury is still out on that. If that were true then reduction in CO2 would mitigate against an increase in the magnitude of storm surges.
DeWitt,
My understanding, albeit from limited research, is that increasing sea surface temperatures (SST) was thought to be the driver for generating more tropical cyclones and more extreme tropical cyclones, but that is under question.
Here is IPCC SREX (Special Report on Extreme Climate or as it is really titled: “Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation”) from 2012, p.160:
Here is Ramsay and Sobel 2011 (one of the papers cited):
then they put forward the alternative hypothesis about the SST difference and go on:
And in their conclusion:
Here’s what the 2013 AR5 IPCC report said on tropical cyclones, in chapter 2:
Current datasets indicate no significant observed trends in global tropical cyclone frequency over the past century and it remains uncertain whether any reported long-term increases in tropical cyclone frequency are robust, after accounting for past changes in observing capabilities (Knutson et al., 2010)…
In summary, this assessment does not revise the SREX conclusion of low confidence that any reported long-term (centennial) increases in tropical cyclone activity are robust, after accounting for past changes in observing capabilities.