Historical records of the deadliest storms and heatwaves may be a poor indicator of the scale and impact future weather disasters could have, warn scientists at King's College London.
"History is almost guaranteed to make us underestimate future risk. The events that have shaped our sense of what extreme weather can do are not the worst that can happen.
Dr Tom Matthews, Senior Lecturer in Environmental Geography at King's College London
They argue that current planning tools have a blind spot when it comes to understanding how extreme the worst events could be. They say the what-if scenarios now widely used in risk assessment are not designed to identify, and therefore prevent, worst possible outcomes, such as greater death tolls, and more severe impacts on infrastructure and people's health
The warning comes after a summer in which thousands of excess deaths were recorded across Europe during the June heatwaves alone and amid current analysis on how the El Nino weather phenomenon could bring more extreme weather worldwide, with very significant impacts possible within the UK.
The peer-reviewed perspective paper, published in Nature Sustainability, analysed deaths from every recorded tropical cyclone and extreme heat event between 2000 and 2025 worldwide. The findings suggest that the vast majority of deaths occurred from a handful of enormous events and suggests that future incidences could be far worse than human intuition suggests.
The paper highlights that Cyclone Nargis, which killed almost 140,000 people in Myanmar in 2008, caused more than twice as many deaths as the other 675 deadly tropical cyclones of the 2000-2025 period combined.
Similarly, heatwave deaths were concentrated within just a few deadly events, the most lethal being in Europe in 2003, when around 70,000 people were killed-with almost half the deaths occurring within the first two weeks of August.
Focussing on extreme heat and cyclones to illustrate the scale of potential worst-case events, the analysis suggested that it was difficult to rule out very rare future events generating death tolls in the millions, though they stress that just because this might be possible does not necessarily mean it is likely.
Dr Tom Matthews, Senior Lecturer in Environmental Geography at King's College London and lead author said: "History is almost guaranteed to make us underestimate future risk. The events that have shaped our sense of what extreme weather can do are not the worst that can happen. They are the worst that have happened so far, in a short record, in a climate that no longer exists."
The authors also looked at possible scenarios that could lead to such devastating outcomes and found that, even in the present climate, a worst-case heatwave in Paris,
Current approaches to climate risk assessment are generally good at considering familiar hazards like hurricanes of unfamiliar intensity (for instance, having higher wind speeds) the authors say, but not for pre-empting events without any sort of precedent, for example, a devastating heatwave just before a strong hurricane - when many millions could be evacuating and not have the future protection of air conditioning.
Dr Matthews added: "We are asking the research community to treat the discovery of unknown catastrophic events as a scientific objective in its own right.
"That means working backwards from an outcome nobody wants and asking what could produce it, and it means bringing in people who are not usually in the room, such as those who can harness the power of human imagination, such as risk scholars and writers of climate fiction."
The authors have set out three main priorities to help pre-empt, and prevent, very severe impacts from extreme weather events: horizon scans conducted by participants with diverse expertise to help leverage the power of human imagination, including existential-risk scholars, frontline communities, insurers, climate-fiction writers, and climate modellers; better understanding of the thresholds beyond which impacts grow very steeply; and mapping the physical limits of weather in climates far hotter, and far colder, than today's.
