"A natural disaster is like a virus"

Debarati Guha-Sapir is an epidemiologist and health researcher. She grew up in Calcutta, where she witnessed how people suffered from heat waves and floods. Today she heads the Research Centre for Disaster Epidemiology (CRED) at the University of Louvain in Brussels. She also maintains the EM-DAT database, an ongoing archive of natural disasters of all kinds. Benjamin von Brackel talked to Guha-Sapir during the worskhop "Data Science for Human Wellbeing" at the Herrenhausen Conference "Extreme Events - Building Climate Resilient Socities" (Hannover, October 2019).

Portrait Debarati Guha-Sapir.
Debarati Guha-Sapir heads the Research Centre for Disaster Epidemiology (CRED) at the University of Louvain in Brussels. (Photo: David Carreno Hansen for Volkswagen Foundation)

Mrs. Guha-Sapir, you are a trained epidemiologist. How did you come to investigate natural disasters?

Debarati Guha-Sapir: A colleague in Brussels convinced me that, as an epidemiologist, I had precisely the right tools to analyze natural disasters. Such events unfold in the same way as a virus. When a virus breaks out, it affects people in different ways. So we are investigating why some people get sick and others do not, even though they are exposed to the same virus. I then looked at earthquakes and tsunamis, floods and hurricanes in the same way: Which people suffer first, which after some delay, and which not at all? Later on we also looked at heat waves.

Europe, too, has been experiencing deadly heat waves for some time now. How can data help us adapt to them?

With the help of the data, we can understand which parameters of a natural disaster are likely to pose a risk. In epidemiology, too, everything revolves around this question: How can we identify the risk? For example, we studied the heat wave which hit the Netherlands and Belgium in 2006, killing almost 1000 people. We wanted to find out more about the people who died and looked in detail at the profile of heat-related deaths. It turned out that that almost half of the cases were premature deaths. These are people who died well before their life expectancy, for example, people under the age of 65. That was a crucial discovery.

Interview: Disaster Epidemiologist Debarati Guha-Sapir
Gruppenfoto der 130 Teilnehmerinnen und Teilnehmer der Konferenz.
130 researchers from 30 countries took part in the conference in Herrenhausen Palace. (Photo: David Carreno Hansen for Volkswagen Foundation)

Why not?

The death certificate never says "death by cause of heat": Instead, doctors refer to a "heart attack" or "shortness of breath". So we had to search through huge amounts of data to find significant associations. When it became clear how many people had died as a result of the 2003  heat wave, enormous pressure was put on politicians to act.

What's changed?

Countries like Germany and Belgium have developed very good heat plans. When temperatures rise above 35 degrees Celsius, for instance, our university distributes free water and allows students to go home: little things. The problem is the implementation.

Zeit für Gespräche während des Workshops im Schloss Herrenhausen, Hannover. (
The workshop left room for group discussions. (Photo: David Carreno Hansen for Volkswagen Foundation)

In what way?

What is actually needed is accountability: Anyone who does not implement the heat plan must be held accountable. Climate researchers are already predicting another heat wave for northern Germany next summer – but nobody is preparing for it. What it really needs is for all hospitals, old people's homes and kindergartens to be informed right now, so that they can prepare appropriate measures in advance of the actual event. These are the places where the problems are most serious.

So following the heat wave of 2006 the authorities changed things, with the result that significantly fewer people died in the recent heat waves?

Yes, we are going in the right direction. But in the 21st century Europe, no premature deaths at all should be caused by a heat wave. Not with the money and the institutions we have. There can be no excuse for a 35-year-old dying because of a few hot days once in a while.

In our article "Deciphering Extreme Weather Events", Benjamin von Brackel focuses on the workshop "Data Science for Human Wellbeing" (Hannover, Oct. 2019) and shows, how the data scientists use huge data sets, so called Big Data, from which they construct statistical models to decipher extreme weather events and make predictions about the future.


At the Herrenhausen Conference "Extreme Events" international experts discussed the relations between climate extremes, sustainable development goals and resilient societies.