A new look at the impact of extreme weather

The World Meteorological Organisation (WMO), an agency within the United Nations, has recently published a global atlas of mortality and economic losses from meteorological extreme events (WMO, 2021). In brief, from 1970 to 2019, 11,072 weather, climate- and water-related disasters caused 2.06 million deaths.

This second iteration of the WMO Atlas reports increased exposure, increased economic losses – but significant reduction in mortality due to the implementation of multi-hazard early warning systems (MHEWSs). The Sendai Framework for Disaster Risk Reduction 2015–2030 (Sendai Framework) recognised the benefits of MHEWSs by incorporating them into one of its seven global targets but, it was reported, only half of the 193 WMO member nations have MHEWSs.

The report also recognises that, under a changed climate, the number of weather, climate and water extremes will become more frequent and severe in many parts of the world.

The analysis is based on Centre for Research on the Epidemiology of Disasters’ Emergency Events Database (EM-DAT), which contains data on natural and technological disasters from 1900. For an event to be included in EM-DAT, at least one of the following criteria must be satisfied:

• • 10 or more people reported killed
  • 100 or more people reported affected
  • Declaration of a state of emergency
  • Call for international assistance.

Results

The WMO Atlas opens with a discussion of the attribution of extreme events to climate change. It noted that, while few studies have found any anthropogenic climate signal in small-scale severe weather events such as thunderstorms, there has been progress in attributing individual extreme events that occur over larger scales. For example, 62 of the 77 events reported to the Bulletin of the American Meteorological Society over the period 2015 to 2017 show a significant anthropogenic influence on the event’s occurrence. Almost every study of significant heatwaves since 2015 has found that probability has been significantly increased by anthropogenic climate change. Also, an increasing number of studies are also finding human influence on extreme rainfall events, sometimes in conjunction with other major climate influences such as the El Niño Southern Oscillation.

The past few decades have seen rapid growth in global populations living in flood- and cyclone-exposed areas, particularly in cities in developing countries. The WMO Atlas notes that, together, these trends will increase the risk of weather, climate and water hazards to human health.

Of those events contained in EM-DAT 1970 to 2019, 50% of events (11,072), 45% of deaths (2.06 million) and 74% of economic losses (US$3.64 trillion) were due to weather, climate and water hazards. Table 2 sets out the top ten disasters by number of fatalities.

Considering the top ten deadliest global weather-related hazard events, drought has been responsible for the greatest number of deaths (650,000), closely followed by storms¹ (577,232) and then floods (58,700) and extreme temperature (55,736) (Table 1 (a)). It should be noted that, as the WMO analysis excludes geological hazards, Table 1 may well change if events such as, for example, the 2004 Boxing Day tsunami were included.

Table 1: Top ten global weather-related disasters ranked according to reported deaths, 1970–20191 (source: WMO Atlas)

From 1970-2019, PerilAUS has recorded a total of 2698 deaths from natural hazards².

In contrast to the EM-DAT global results, the Australian experience (for the top ten deadliest disasters, 1970-2019) has extreme temperature events as the number one killer (748; 30.36%), followed by bushfires (293; 11.89%) and then storms (including floods resulting from storms, which includes cyclones) (138; 5.60%) (Table 2 (a)). As reported below (Figure 2), heatwaves have been responsible for 40% of weather-related fatalities from 1970-2019.

Table 2: Top ten Australian weather-related disasters ranked according to reported deaths, 1970–2019 (source: PerilAUS³, as at August 2021)

Trends

The WMO Atlas investigated trends by decade, and noted that, while the number of global weather, climate and water disasters increased by a factor of five over the period of study, deaths decreased almost threefold: from over 50 thousand deaths in the 1970s to less than 20 thousand in the 2010s (Figure 1). Important advances in early warning systems worldwide have been credited with reducing the deaths from weather, climate and water hazards (Intergovernmental Panel on Climate Change (IPCC) (2012)).

Statistics from the PerilAUS database (see Figure 2) show no particular trend, with very similar death totals for both the 1970s and the 2010s. The 2000s included the disastrous extreme heat and bushfire events of 2009. In the 50 years since 1970, heatwaves have been responsible for 40% of weather-related fatalities. (As an aside, these figures do not change significantly when geological hazards are included: Australia, as a relatively stable land mass, has had very few earthquake deaths and none from volcano or tsunami.)

PerilAUS

Risk Frontiers’ PerilAUS is a series of event-based databases on the occurrence and consequences of natural hazards in Australia, providing hard evidence, with the required breadth and depth, to inform risk management, understand past hazard impacts and examine trends over time and space. It is distinguished from many other databases by its length of record (with best confidence from 1900 but, for example, the PerilAUS lightning database is the longest continual national record in the world, dating from 1788), wealth of descriptive detail around hazard impact and deaths and a unique building damage “housing equivalent” calculator, enabling comparison of the impacts of hazard events of different types and at different times.

References

IPCC, 2021, Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)].

United Nations, 2015, Sendai Framework for Disaster Risk Reduction 2015–2030, United Nations Office for Disaster Risk Reduction, 32pp.

Risk Frontiers, 2021, Webinar Series: Our warming world. Implications of the IPCC 6th Assessment Report for Australia – Andy Pitman. https://vimeo.com/riskfrontiers/2021-webinar1

WMO (World Meteorological Organisation), 2021, WMO Atlas of mortality and economic losses from weather, climate and water extremes (1970–2019). WMO-No. 1267, https://library.wmo.int/doc_num.php?explnum_id=10902 accessed 2/9/2021