In the last 20 years the world has suffered seventeen of the twenty most costly hurricanes in history and nine of the ten most costly typhoons. These weather phenomena are actually different names for the same type of storm: tropical cyclones. These storms are primarily formed by a difference in temperature between the surface of the sea and the sky above it. A water temperature of at least 26.5°C is usually necessary for the formation of a cyclone. Annual global temperatures have increased by 1 degree in the last 40 years which leads to sustained higher temperatures in the oceanic basins in which tropical cyclones form; therefore increasing the chance of storm formation and storm intensity.
The world has experienced many costly storms in recent years, however the cost of rebuilding and repairs is almost always overlooked. In a series of tweets in mid-September the President of the United States of America drew attention to the death toll of Hurricane Maria, the worst natural disaster on record to have affected Puerto Rico. The governor of Puerto Rico’s official death toll stood at 64 following a statement in December 2017, this was increased massively at the end of August 2018, following a study by George Washington University, to 2975. The findings of this study have since been mischaracterised for political reasons, but its methodology provides an interesting insight into the way that governments and non-governmental agencies discover the effect of natural disasters on the health of their populations.
The authors of the study began by analysing the patterns in the mortality rate – the rate at which deaths occur in a population – in Puerto Rico using population census data and information obtained through death registration across the territory. The researchers then used a series of statistical tools called Generalised Linear Models; which allowed the researchers to input the data they had gathered on the location, time and reason for death. A code then turns this collection of data into a model which tracks the mortality rate in Puerto Rico and provides a function which can be used to estimate the number of deaths in any normal given month if the population is known at the beginning.
The results of the research were then compared to the number of actual deaths that occurred in the period between when the hurricane struck on the 20th of September 2017 to the 28th of February 2018, the end point of the study. The difference in these figures could then be used to find the number of deaths caused by the storm. The study also had to take into account the large number of people who fled the island in the aftermath of the storm to escape the destruction and poor living conditions which followed the disaster.
The study was commissioned following the storm in September 2017 and released its results on the 28th of August 2018 almost one year later. This is a long time in the frame of world events: the Winter Olympics; Trumps North Korea summit; the World Cup; the Commonwealth Games and the eighth amendment referendum in Ireland all happened in the time between the study being commissioned and the results being published. In science, however, where it can take years for research to come to a conclusion and even longer for it to be published, this study was a whirlwind.
While the methodology may change, this is often how mortality is calculated after widespread natural disasters, while it takes time it also provides reliably accurate information. Estimates of mortality can then be used by authorities to send resources to where they are most needed.
All evidence points to storms becoming more costly, stronger and more frequent in recent years. Improvements in the science behind tracking the effects of these storms mean that the responses of governments can be streamlined. As global temperatures continue to rise, the value of this kind of post disaster research will undoubedtly continue to grow.