An emerging tropical cyclone–deadly heat compound hazard

Abstract

Word count (not including references or opening paragraph): 2,000 Climate change may bring new hazards through novel combinations of extreme weather (compound events) 1. Here we evaluate the possibility of dangerous heat following major tropical cyclones (TCs)-a combination with serious potential consequences given that mega-blackouts may follow powerful TCs 2 , and the heavy reliance on air conditioning 3. We show that "TC-heat" events are already possible along densely populated coastlines globally but, so far, only an estimated 1,000 people have been impacted. However, this number could rise markedly, with over two million at risk under a storyline of the observed TCs recurring in a 2°C warmer world than preindustrial. Using analogues as focussing events we show, for example, that if the catastrophic 1991 Bangladesh Cyclone occurred with 2°C global warming, there would be >70% chance of subsequent dangerous heat. This research highlights a gap in adaptation planning and a need to prepare for an emerging TC-heat compound hazard. Extreme heat is a major threat to public health and a risk that is projected to rise with global warming 4 , even if temperatures are held below the Paris targets of 1.5 or 2°C 5. With around 1.6 billion units in operation, air conditioning (AC) reduces vulnerability to extreme heat 3,6. However, populations dependent on AC may become highly exposed in the event of power failure 7. Significant electricity outages have already been caused by Tropical Cyclones (TCs), with the top three events (2013 Typhoon Haiyan, 2017 Hurricane Maria, and 2012 Typhoon Bopha) incurring between 3.2 to 6.1 billion customer-hours of lost supply over one or two months 8-11. Significant heat-related mortality was not reported during these mega-blackouts, but given the rapid rise in dangerous humid heat projected at low-latitudes 4 , we identify the growing threat of a catastrophic "TC-heat" compound hazard. In this storyline, a TC first cripples electrical infrastructure, then is followed by deadly heat as the population tries to recover. Here, we provide the first assessment of the present and evolving risk of the TC-heat

Understanding and managing connected extreme events

“…For extreme heat, diverse health hazards will very likely interact more frequently as the recovery time between heat waves shrinks, making it a prototypical instance of a connection between extreme events enhanced by climate change 65 . Other societal drivers such as power outages, whether resulting directly from physical drivers 66 or induced to prevent poorly maintained equipment from sparking wildfires during compound wind and low-humidity events (such as in the 2019 California fire season), can also feed back onto health outcomes. These examples underscore how human decisions made over decades modulate the health impacts of extreme events on much shorter timescales.…”

“…Well-designed infrastructure can exhibit strategic purposeful failures which nonetheless result in property damage or loss of life, as in the Mississippi River flood example discussed above. Emergency response and rebuilding efforts may be particularly vulnerable to sequences of extremes, such as a heat wave following a hurricane- 66 or wildfire-induced power outage. Infrastructure decisions (investment, maintenance and outreach) play a key role in connecting extremes, especially for the most exposed or vulnerable communities.…”

“…The need for skilful forward-looking assessments is underscored by the rapidity of projected twenty-first century warming, which will result in historical conditions always providing incomplete information on the contemporaneous range of possibilities 12 . Therefore, the coming decades will no doubt see previously unanticipated or newly important combinations of extremes 66 . Additionally, risk relationships may change in a qualitative way, such as the emergence of summertime drought-heat interactions in historically cool-summer regions 52 or the increased risk of compound flooding due to sea-level rise 45 .…”

Coincidence of increasingly volatile winters in China with Arctic sea-ice loss during 1980–2018

“…The proposed definition of temperature whiplash expands the current matrix for temperature extremes (Zhang et al 2011) not only in the number of indices but also in the complex nature of them. Essentially, whiplash events belong to the category of 'sequential extremes', which overlay and further amplify risks from temporally-aligned extremes (Bates 2018, Zscheischler et al 2018, Matthews et al 2019.…”

Nonstationary weather and water extremes: a review of methods for their detection, attribution, and management

“…For example, the risk from compound tropical cyclones and heatwaves is sensitive to the seasonal cycles in tropical cyclone probability (which peaks in late summer) and extreme heat (mid summer). A greater frequency of tropical cyclones earlier in summer, or more extreme heat late in summer, would increase the risk of compounding and attendant impacts (Matthews et al, 2019).…”