In the summer of 2021, Canada’s all-time temperature record was smashed by almost 5℃. Its new record of 49.6℃ is hotter than anything ever recorded in Spain, Turkey or indeed anywhere in Europe.
The record was set in Lytton, a small village a few hours’ drive from Vancouver, in a part of the world that doesn’t really look like it should experience such temperatures.
Lytton was the peak of a heatwave that hit the Pacific Northwest of the US and Canada that summer and left many scientists shocked. From a purely statistical point of view, it should have been impossible.
I’m part of a team of climate scientists who wanted to find out if the Pacific Northwest heatwave was unique, or whether any other regions had experienced such statistically implausible events. And we wanted to assess which regions were most at risk in future. Our results are now published in the journal Nature Communications.
Tracking these outlier heatwaves is important not just because the heatwaves themselves are dangerous, but because countries tend to prepare to around the level of the most extreme event within collective memory. An unprecedented heatwave can therefore provoke policy responses to reduce the impact of future heat.
For instance, a severe heatwave in Europe in 2003 is estimated to have caused 50,000-70,000 excess deaths. Although there have been more intense heatwaves since, none have resulted in such a high death toll, due to management plans implemented in the wake of 2003.
One of the most important questions when studying these extreme heatwaves is “how long do we have to wait until we experience another similarly intense event?”. This is a challenging question but, fortunately, there is a branch of statistics, called extreme value theory, that provides ways in which we can answer that exact question using past events.
But the Pacific Northwest heatwave is one of several recent events that have challenged this method and should not have been possible according to extreme value theory. This “breakdown” of statistics is caused by conventional extreme value theory not taking into account the specific combination of physical mechanisms, which may not exist in the events contained in the historical record.
Implausible heat is everywhere
Looking at historical data from 1959 to 2021, we found that 31% of Earth’s land surface has already experienced such statistically implausible heat (though the Pacific Northwest heatwave is exceptional even among these events). These regions are spread all across the globe with no clear spatial pattern.
We also drew similar conclusions when we analysed “large ensemble” data produced by climate models, which involve computers simulating the global climate many times over. These simulations are extremely useful for us, since the effective length of this simulated “historical record” is far larger and thus they produce many more examples of rare events.
However, while this analysis of the most exceptional events is interesting, and cautions against using purely statistical approaches for assessing the limits to physical extremes, the most important conclusions of our work come from the other end of the spectrum – regions that have not experienced particularly extreme events before.
Some places have got lucky – so far
We identified a number of regions, again spread across the globe, that have not experienced especially extreme heat over the past six decades (relative to their “expected” climate). As a result, these regions are more likely to see a record-breaking event in the near future. And with no experience of such a huge outlier, and less incentive to prepare for one, they may be particularly harmed by a record heatwave.
Socioeconomic factors, including population size, population growth and level of development will exacerbate these impacts. As a result, we factor in population and economic development projections in our assessment of the regions that are most at risk globally.
Our at-risk regions include Afghanistan, several countries in Central America and far eastern Russia among others. These regions may be surprising, since they are not those people typically think of when considering extreme heat impacts of climate change like India or the Persian Gulf. But those countries have recently experienced severe heatwaves and so are already doing what they can to prepare.
Central Europe and several provinces in China, including the area around Beijing, also appear to be vulnerable when considering the extremeness of the record and population size, but as more developed areas they are likely to already have plans to mitigate severe impacts.
Overall, our work raises two important points:
The first is that statistically implausible heatwaves can occur anywhere on the Earth, and we must be very cautious about using the historical record in isolation to estimate the “maximum” heatwave possible. Policymakers across the globe should prepare for exceptional heatwaves that would be deemed implausible based on current records.
The second is that there are a number of regions whose historical record is not exceptional, and therefore is more likely to be broken. These regions have been lucky so far, but as a result, are likely to be less well prepared for an unprecedented heatwave in the near future. It is especially important that these regions prepare for more intense heatwaves than they have already experienced.
About The Author
Nicholas Leach, Postdoctoral Researcher, Climate Science, University of Oxford
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Related Books
Life After Carbon: The Next Global Transformation of Cities
by Peter Plastrik , John Cleveland
The future of our cities is not what it used to be. The modern-city model that took hold globally in the twentieth century has outlived its usefulness. It cannot solve the problems it helped to create—especially global warming. Fortunately, a new model for urban development is emerging in cities to aggressively tackle the realities of climate change. It transforms the way cities design and use physical space, generate economic wealth, consume and dispose of resources, exploit and sustain the natural ecosystems, and prepare for the future. Available On Amazon
The Sixth Extinction: An Unnatural History
by Elizabeth Kolbert
Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human. Available On Amazon
Climate Wars: The Fight for Survival as the World Overheats
by Gwynne Dyer
Waves of climate refugees. Dozens of failed states. All-out war. From one of the world’s great geopolitical analysts comes a terrifying glimpse of the strategic realities of the near future, when climate change drives the world’s powers towards the cut-throat politics of survival. Prescient and unflinching, Climate Wars will be one of the most important books of the coming years. Read it and find out what we’re heading for. Available On Amazon
From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.
