WTW-自然灾害回顾2023年1月至6月（英文原版）.pdf

1 1 wtwco.com Natural Catastrophe Review: Expert insights, lessons learned, and outlook January–June 2023 1/ Foreword 03 2/ Recent Events 07 2.1 Worlds apart: Implications of the Türkiye earthquakes for California 08 2.2 Is the record number of convective storms in the first quarter a sign of things to come in the U.S.? 14 2.3 An unusually large number of Category 5 tropical cyclones 16 2.4 Building back better following Tropical Cyclone Gabrielle 18 2.5 Counting the costs of climate and land-use change after the Chilean Wildfires 22 2.6 Out of the woods: How far will Canada’s wildfires spread? 24 2.7 A view of catastrophic flooding from across the world 29 2.8 Emilia-Romagna floods: A product of urbanization and climate change 32 2.9 Why were there so few European winter windstorms in 2022/2023? 34 3/ Outlook 38 3.1 In the tropical Pacific, El Niño is in the wind 39 3.2 The 2023 North Atlantic hurricane season: Record hot Atlantic Ocean versus El Niño 43 4/ Contacts and Information 46 TABLE OF CONTENTS 2 2 3 3 Foreword We hope to provide new perspectives that will help with natural catastrophe risk management and resilience in sectors such as insurance, banking, government, and corporates across all industries. In this edition, we look at some of the physical, vulnerability, and socio-economic factors that contributed to natural disasters in the first half of 2023. We also consider what the rest of the year might hold with El Niño s return and the upcoming North Atlantic Hurricane season. The first six months of 2023 were dominated by the devastating Kahramanmaraş earthquakes in Türkiye and Syria and several weather-related catastrophes. A record-breaking start to the U.S. tornado season resulted in billions of dollars in damage, while the ongoing megadrought in Chile brought destructive wildfires. Canada is also experiencing its worst-ever wildfire season, with a record-breaking 8.33 million hectares destroyed after only two months of the May– September fire season. Cyclones Freddie, Gabriele, and Mocha had wide-ranging impacts in the Southern Welcome to the latest issue of WTW’s Natural Catastrophe Review, a bi-annual publication that brings insights from our experts — including our WTW Research Network — to examine recent natural disasters, lessons learned, and emerging trends. Hemisphere, and significant flooding affected a number of countries including Italy, Ethiopia, Somalia, Malaysia, Brazil, and New Zealand. Climate change will once again be at the forefront of business and government agendas as a result of these events. However, it is critical not to forget the role socio-economic factors play in determining the severity of extreme weather outcomes. Natural hazards only become disasters when they intersect with an inadequately prepared society. Katrina was a disaster because underlying social inequalities in New Orleans worsened storm damage and challenged disaster recovery. The wildfires that ravaged Chile in February this year were a disaster because of the intermixing of forestry plantations and communities (Section 2.5). In New Zealand, flooding Welcome 4 4 1 Smith, N. There s No Such Thing as a Natural Disaster. Understanding Katrina: perspectives from the social sciences 11, (2006). It is nearly 20 years since Neil Smith – who was a Distinguished Professor of Anthropology and Geography – published his seminal essay There’s No Such Thing as a Natural Disaster 1 . This was written in the aftermath of Hurricane Katrina and initiated a conversation on how we think about natural catastrophes. 5 5 following Cyclone Gabriele was exacerbated by debris from forestry activity that clogged rivers and destroyed buildings and infrastructure (Section 2.4). And the recent devastation in Italy’s Emilia-Romagna region from flooding was worsened by land-use change (Section 2.8). If we are to improve resilience in a warming world, we must therefore look not only at how the frequency and severity of extreme weather events are changing, but also at how interactions between hazards and society are changing too. In New Zealand, there is a concerted effort to “build back better” following the second wettest summer on record. This requires a holistic approach that considers the physical, social, and economic aspects of affected communities 2 , as well as investment in risk management research to inform decision-making. Lateral thinking on earthquake risk In February, the largest earthquake to hit Türkiye in nearly a century killed over 50,000 people and destroyed thousands of buildings. When a major disaster occurs, there are often lessons to be learned that will help us build back better. For example, following the 1999 Mw 7.6 Izmit earthquake in northern Türkiye, new building regulations and a national insurance pool were put in place to improve resilience. As lessons begin to emerge from the most recent event, we must remember to think laterally to improve risk management, particularly in other parts of the world where recent observations are lacking. In Section 2.1, Temblor s Ross Stein examines the lessons from Türkiye that can be applied to California, including the possibility of large events on secondary faults, interacting mainshocks that attack buildings twice, and the likelihood of extreme shaking near the rupture and in deep basins. Property market tipping points In recent years, there has been an increased focus on socio-economic tipping points, where gradual changes in the climate system could result in abrupt changes to socio-economic systems 3 . An example is Hawke s Bay, a region on the east coast of New Zealand s North Island, which is one of the country s most desirable locations for coastal living. In February, Cyclone Gabrielle brought destruction to the North Island, with record- breaking winds and flooding that destroyed houses, infrastructure, and crops. In Section 2.4, Neil Gunn discusses the impacts of Gabrielle and looks at recent research that suggests Hawke s Bay is approaching a socio-economic tipping point, where losses from the gradual increase in extreme weather events could lead to the collapse of property prices. 2 Mannakkara, S., Wilkinson, S. instead, they are often part of a chain reaction. Examples abound of mainshocks striking within hours to months of each other, including the 1811-1812 Mw 7.2, 7.0, 7.4 New Madrid, Missouri, quakes several months apart; the 1992 Mw 7.3 Landers and Mw 6.5 Big Bear, California, shocks 3 hours apart; the 2002 Mw 6.6 and Mw 7.9 Denali, Alaska, quakes 10 days apart, and the 2019 Mw 6.4 and Mw 7.1 Ridgecrest, California, quakes 31 hours apart 1 . In fact progressive or compound mainshocks are not restricted to any region or tectonic setting. 1 Toda, S. in others, it drops. This is what Temblor’s Realtime Risk technology (whose development was supported by the WTW Research Network), does: once a large quake strikes, the hazard changes, which models need to capture so that next year s risk is reflected in models. This is in contrast to conventional earthquake risk models, which do not take stress interaction into consideration. The bad news is that buildings damaged in the first shock can collapse in the second, which the ‘hours clause’ in insurance contracts does a poor job of accounting for. Think of the many horrifying building collapse videos of the Türkiye quake we saw, filmed in daylight. The first quake struck in the dark, at 4 am local time, and so most of the videoed collapses occurred during the second shock, with the buildings succumbing to a ‘one-two punch.’ Trying to account for this dynamic accumulation of damage in fragility and vulnerability models is an active area of research 3 . 10 10 Figure 2. There are about 25 observations (red) of Peak Ground Acceleration (PGA) exceeding 0.5 g. At this level of shaking, all but the most resilient buildings generally suffer structural damage. The Temblor Ground Motion Model (blue) does a good job of capturing this shaking at distances of 10-400 km from the fault rupture. Source: Temblor 4 Erdik, M., Tümsa, M. B. D., Pınar, A., Altunel, E., and Zülfikar, A. C. A preliminary report on the February 6, 2023 earthquakes in Türkiye. Temblor. http://doi.org/10.32858/temblor.297 (2023). 5 Yeginsu, C., Ruiz, R. both have experienced Mw 7.8 shocks in the past 170 years 8 . The East Anatolian Fault resembles the Hayward-Rodgers Creek Fault in northern California, the San Gregorio along the central coast, the Owens Valley-Inyo Fault in eastern California, and the San Jacinto in southern California. So, those faults should have Mw 7.8 shocks in any stochastic event set one is using. The Cardak-Sürgü Fault closely resembles the Garlock Fault in southern California. Both are so misaligned for the tectonic stresses that they must be very slippery to move at all. But despite that misalignment, we should assume that the Garlock Fault, which abuts the San Andreas, is capable of a Mw≥7.5 event. The most important lesson is that the Türkiye quakes did not strike on the equivalent of the mighty San Andreas Fault, but instead on shorter, low-slip-rate faults that are often deemed incapable of quakes of this great size. The East Anatolian Fault is 600 km long with a slip rate of ~10 mm/yr, and the Cardak-Sürgü Fault is 200 km long with a slip rate of ~3 mm/yr; both can be considered part of the broad East Anatolian Fault Zone. The Mw 7.8 earthquake nucleated on the minor, 20-km-long Narlı Fault, and then jumped onto the East Anatolian Fault, propagating in both directions (SW and NE), ultimately attaining a rupture length of 300 km with ~4.5 m average slip. The Mw 7.5 shock nucleated on the Cardak Fault, and also ruptured in both directions. To the east, it jumped onto the Source: Temblor 8 Emre, Ö., Duman, T.Y., Özalp, S., Elmacı, H., Olgun, Ş. and Şaroğlu, F. Active Fault Map of Turkey with and Explanatory Text, General Directorate of Mineral Research and Exploration, Special Publication Series-30. Ankara-Turkey. https://www.mta.gov.tr/en/maps/active-fault-1250000 (2013). 13 13 Sürgü Fault, attaining a 150-km total length and ~7 m average slip. So, surprisingly, the slower, shorter fault had the highest slip. Even stranger, the Cardak-Sürgü Fault shouldn’t slip at all; it is misaligned for failure. It was formerly a ‘right-lateral’ fault (whichever side you are on, the other side moves to the right) that only recently became left-lateral (this switch is called ‘inversion’ by geologists). So, the key question is, are we prepared for Mw 7.8 and Mw 7.5 shocks on their California equivalent? The answer is probably no, because we’ve focused on events with repeat times of 500 years or less. Instead, Temblor’s event set yields an 1800-2000 year repeat time for quakes in this Zone. What’s essential is to harness these hard- won insights from Türkiye to better forecast seismic risk, and better prepare for its consequences in California and elsewhere, where much of what we have just witnessed can also occur. 14 14 2.2 Is the record number of convective storms in the first quarter a sign of things to come in the U.S.? by Cameron Rye Following a record-breaking first quarter for severe convective storms (SCS) in the United States, insurers and risk managers should consider whether their view of risk reflects the evolving patterns of SCS activity. Rank Tornado Count Year 1 *476 2023 2 398 2017 3 360 2008 4 292 1999 5 290 2012 6 282 2022 7 246 2007 8 231 1976 9 212 2020 10 207 2006 These high numbers were caused by a series of multi-day tornado outbreaks that can in part be attributed to the presence of La Niña (which often provides favorable conditions for springtime convective activity). The most notable outbreak occurred at the end of March, affecting states in the Midwest, Southern, and Eastern U.S. A total of 134 tornadoes were recorded between 7pm UTC on March 31st and 7pm UTC on April 1st, ranking third in the Table 1. Top 10 years with the highest Jan–March tornado counts. *Tornado count is preliminary and may change once the data is finalized by the Storm Prediction Centre. Data source: National Weather Service Storm Prediction Centre. 1 Verbout, S. M., Brooks, H. E., Leslie, L. M. in 2020, Chile s Centre for Climate and Resilience Sciences (CR)2 issued a report recommending increased regulation of the forestry industry in order for the country to become more resilient to the effects of climate change 2 . 1 Garreaud, R. D. et al. The Central Chile Mega Drought (2010–2018): A climate dynamics perspective. International Journal of Climatology 40, 421–439 (2020). 2 Center for Climate and Resilience Research - CR2. Forest fires in Chile: Causes, impacts and resilience. https://www.cr2.cl/eng/forest-fires-in-chile-causes-impacts-and-resilience/ (2020). Source: NASA s Earth Observatory 23 23 Forestry is big business in Chile, accounting for 3% of the country s GDP, and timber is the second- largest export commodity after minerals. Expansive plantations of fast-growing species (primarily pine and eucalyptus) have increased from 300,000 hectares in the 1970s to over 3 million hectares today. Previous governments encouraged this expansion by allowing the privatisation of large areas of public land and providing subsidies and tax breaks for plantations. The problem is that non-native pine and eucalyptus species contain oils and resins in their leaves that can easily ignite when dry. Research has also found that because plantations are often compositionally homogenous with few fire breaks, it promotes greater fire spread compared to native deciduous forests 3 . This, combined with the recent drought, has created a perfect storm that has proved difficult to control. However, climate change is expected to play an increased role in wildfire risk over the coming decades. Projections for the 21st-century indicate a rise in temperatures and a reduction in precipitation throughout Chile, which modelling studies suggest will lead to an increased occurrence of large fires 4 . Central-South Chile is particularly vulnerable because it contains nearly 90% of the country’s plantations, and 3 million people live within the wildland-urban interface 5 . (CR)2 says that if the government is to reduce the risk faced by its people, decision-makers need to move away from reactive measures focused on fire suppression, towards actions that target the source of the problem. This includes better landscape management, establishing safety perimeters around urban areas, and new laws to prevent unsafe practices such as the expansion of homes into forested regions 2 . 3 McWethy, D. B. et al. Landscape drivers of recent fire activity (2001-2017) in south-central Chile. PLOS ONE 13, e0201195 (2018). 4 Ciocca, I. et al. Increased wildfire hazard along South-Central Chile under the RCP8.5 scenario as revealed by high-resolution modeling. Environ. Res. Lett. 18, 034023 (2023). 5 Sarricolea, P. et al. Recent wildfires in Central Chile: Detecting links between bu