World: Highest Mortality, Tropical Cyclone

References

Cerveny et al. 2017: WMO Assessment of Weather and Climate Mortality Extremes: Lightning, Tropical Cyclones, Tornadoes, and Hail, Climate Weather and Society,

Discussion

The Bangladesh (at time of incident, East Pakistan) Cyclone of 12-13 November, 1970. This notorious tropical cyclone is sometimes referred to as the ‘Great Bhola Cyclone’ with an estimated 300,000 (low end) to 500,000 (high end) storm-related fatalities (mostly the result of a large storm surge overwhelming the islands and tidal flats along the shores of the Bay of Bengal). Frank and Husain (1971) note that the origin of the Great Bhola Cyclone can be traced back to the remnant of a tropical storm that moved westward across the Malayan Peninsula on 5 November. This system spawned a depression over the south central Bay of Bengal on 8 November 1970. That depression strengthened and likely attained storm intensity on 9 November, while continuing to drift very slowly northward. An estimated maximum wind of 100 kt (51.4 ms-1) in the November 1970 cyclone corresponded to a central pressure between 950 and 960 hPa. Two major concerns were raised by the committee in the investigation of this proposed extreme. First, do the official records match the high range in death tolls (300,000 to 500,000) for this incident? Second, are there other tropical cyclones that could potentially have had a higher death toll? As with any disaster of this magnitude, exaggerated death tolls are frequently common and official values difficult to obtain (Paul 2011). For example, online sources and published sources often differ significantly in numbers associated with specific disasters (e.g., Terry et al. 2012). One of the first professional articles addressing the death toll of this 1970 tropical cyclone was by Frank and Husain (1971). They explicitly state, “On 12 November 1970, a severe tropical cyclone of moderate strength riding the crest of high tide lashed East Pakistan with a 20-ft storm surge and killed approximately 300,000 people. The official figures show 200,000 confirmed burials and another 50,000 to 100,000 missing.” Similarly, Sommer and Mosely (1972) state based on the two site surveys that the mean mortality was “16.5%, representing a minimum of 224,000 deaths.”

A recent official WMO source (WMO, 2012) also cites that mortality value of 300,000 as an official death toll. During the course of the investigation, members of the WMO evaluation committee have also uncovered many recent professional documents citing the 300,000 mortality values. For example, Ali (1979), Murthy (1984), Murthy et al. (1986), Dube et al. (2008) and Nott et al. (2014) consistently cite a mortality value of 300,000. However, less regulated sites such as Wikipedia consistently state 500,000 people dead. Unfortunately, these sites claiming a 500,000 death toll list as source weblinks which are dead or inactive or, as one committee member noted, “part of the ‘grey’ literature.” Consequently, given the consistency in the reviewed professional literature (particularly articles dating to times just after the catastrophe), the committee recommended acceptance of the estimated 300,000 value as best available estimate of the Great Bhola Cyclone mortality. However, the question remains as to whether other cyclones might have produced equal or larger death tolls. For example, in their review of the Great Bhola Cyclone, Frank and Husain (1971) directly state in the text that the “Bakerganj” cyclone in 1876 killed between 100,000 and 400,000 people. However, as one committee member noted, they listed only the lower estimate in their own table (Table 1 of Frank and Husain, 1971) by declaring a value of only 100,000 dead for the Bakerganj cyclone. Other claimants such as the potential 300,000 deaths in the typhoon of 1923 for Japan have difficulties in that many of those deaths were likely caused by the Great Kanto (Tokyo) Earthquake which occurred almost at the same time when the typhoon hit Japan. Similarly, although on-line sources cite the death toll due to the Haiphong Typhoon in Vietnam in 1881 as up to 300,000, a recent study by Terry et al. (2012) reported that this horrendous figure does not match with the population in Haiphong at the time and probably contains an error which mixes up the number of death and the cost of damages. Another contender which is also commonly mentioned in online sources is the Super Typhoon Nina in China in 1975. The torrential rain of the storm that caused the collapse of the Banqiao Dam, resulting in severe flooding in Henan province, China. While some online sources suggest the death toll of the event may have reached up to 230,000, more professional sources state that the flooding killed 26,000 people and another 100,000 died of subsequent disease and famine (Yang et al. 2016). Even fairly recent tropical cyclone mortality values are quite variable. Committee members identified mortality values for Cyclone Nargis in 2008 varying from “more than 100,000” (Webster 2008) to 146,000 people with a commonly quoted range of 130,000 to 140,000. However, those death toll of Cyclone Nargis is unlikely to affect the consensus on the Great Bhola Cyclone event with an estimated death toll of 300,000 people. Finally, there were some discussions among committee members regarding the uncertainty in the primary cause and mortality figure of the Great Bengal Cyclone of 1737 (e.g., Bilham 1994; Chakrabarti 2013). While some sources list that cyclone as having a death toll comparable to the Great Bhola Cyclone of 1970, committee members with particular expertise in tropical cyclones noted that death counts from large killer cyclones in historical times, particularly before modern records, are highly uncertain. This corresponds to the recommendation that only values after 1873 be accepted into the WMO Archive of Weather and Climate Extremes