Reuters reporters set out to define a heat wave and uncovered something far bigger: "heat storms" that now blanket vast stretches of Earrh."Not spot areas that are hot for one or two days, very very large zones that have extreme temperatures for very very long periods of time."
Quotes of note
We saw these areas of extreme heat growing larger each decade and we knew we were seeing something bigger than expected. We needed a new vocabulary and the only name that seemed to stick through our reporting was heat storms.
in the 1960s, they averaged about five active heat storms at any given time; in the 2020s, it's 102.
A heat wave is 5 days or longer; a heat storm is an extended heat wave that covered at least 1% of the surface of Earth, about half the size of Canada.
VIDEO: Climate change is a global ‘emergence’ that’s threatening lives, foreclosing future! Oct 24, 2026 On this episode of On Assignment, the journalists behind the investigation, Maurice Tamman and Ben Welsh, explain how extreme heat became a constant feature of modern life, and why they needed a new language to describe it.
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0.00
Z It's rare that reporters and journalists get to name something. What I mean is we learn new things all the time. That's why we're reporters, but it's unusual that we find ourselves in need of a new vocabulary to describe precisely what it is we've learned.
A phenomenon of massive catastrophic heat storms that had once been rare had become not just regular but constant.
And a change that dramatic required a dramatic change in our language just to describe them.
Maurice Tamman is part of a Reuters team that won a Pulitzer Prize for its reporting on the global fentanyl crisis. Ben Welsh is a data journalist and computer programmer with more than 20 years experience; and they are the incredible crew behind the story we're talking about today. Mo, Ben, thanks for being here with me. [Yeah, thank you for having us. Thanks for having us.] And let's start with you, Mo. What is a heat storm?
We needed a new vocabulary and the only name that seemed to stick through our reporting was heatstorms. Goodness knows we tried to find other names for it that seemed more appropriate, but honestly, heatstorm was the only one that resonated throughout our reporting and so we stayed with it.
Z So Mo, how much bigger and how much hotter are we talking about?
M So, if we're just talking about heat storms, for example, in the 1960s, they average about five active heat storms at any given time., in the 2020s, it's 102.
And after that date, every day has had at least one heat storm active at some point anywhere in the planet. I mean, just to give some context on that, there are people who are going to go to the polls in the US this November who have never lived on a planet at a time when there wasn't at least one heat storm acting. And to me that just I found that one particular fact to be utterly staggering.
Z So they're far more common than they were half a century ago. And talk to me a little bit about the size. I mean, were these things are they- have they stayed big? They were big in the 60s and they're big now. There's just more of them. Or are they larger?
M Well, they're both larger and they stick around. so the largest heat storm in the 1960s covered about 6% of the planet's surface over the course of its entire lifespan. The one that we covered and wrote about in the first story of this series, Heat Storm Vera, lasted one year and one day. In that one year and one day it touched 85% of the planet's surface. There is virtually not a human being that was alive during that period who didn't experience that heat storm at least once and in many cases many more times than once, many more than was just one day.
5.30
Z Ben, before you could classify something as big as a heat storm, you actually had to come up with a definition for something more mundane and everyday, you had to define what a heat wave was. Why was that a challenge?
And it's because I think the idea of heat waves until very recently were kind of culturally determined by where people lived. Obviously, you have different climates in different places in the world. if you live very close to the equator versus, in northern Canada, your idea of what's hot, naturally varies. And but it turns out there really- no one has ever really kind of pinned down one common way to do it.
And so if we wanted to measure heat over time, which was our goal, we'd have to figure out how to do that. And so Mo and I interviewed dozens of climate scientists around the world. We collected a lot of the different ways that they're calculated in different spots; and we came up with we thought was kind of a good a good clear defensible conservative way to calculate what a heat wave would be that could be applied to the entire planet using one uniform measuring system.
So the standard we came up with is that a heat wave is defined as any streak of 5 days or longer of abnormally high temperatures which means ranking in the top 10% of what used to be normal in each location.
Now, a heat storm are those larger heat waves, and we defined those as any extended heat wave that at its peak covered at least 1% of the surface of Earth, which is roughly about half the size of Canada.
And when we did that, what we saw really surprised us. Even if you use a common ruler or measuring system for the whole planet to look at these heat waves, you see that they're often much much larger than what we talk about when we talk about heat, say on the news or in regular places.
It's not just little spotty areas that are hot for one or two days.
There's really these very very large zones that have extreme temperatures for very very long periods of time.
Z Did that catch you by surprise?
B I can't speak for Mo but for me personally. Yes. I knew that obviously the planet is getting warmer. There's so much evidence of that. I knew that from my own life, the summers feel hotter than they used to.
But to really see on the map, as you can see in our story, that for months or weeks at a time, the extreme heat where I live- or that I read about in Europe- is actually connected geographically to places quite distant from that as climate change and global warming take hold and the planet heats in general. Just the scale of it did surprise me. Yes.
Z As part of your reporting, you've applied names to these storms. Why did the decision to do that?
M There are two reasons and in part that goes back to talking to some researchers who study the issue of communicating science. And part of it is to create what they call to objectify this phenomenon.
And by giving them names, you are effectively telling the reader, telling people that this is a defined object. It has boundaries. It has shape. It has a lifespan. And in much the same way that hurricanes have similar things, they have lifespans. They have boundaries. They have affected areas.
And if you want to be able to communicate in a narrative form, for example, we can introduce Heatstorm Vera at the beginning of the story. Now, every time we come back to that and explain what happened to people who were affected by Vera, we can just say Vera and everyone will understand it.
When somebody's trying to understand what's happening in their community and you tell them well Heatstorm Vera is affecting you, now they have some definition, they have boundaries around that much easier to understand what the consequences are when you've created boundaries around it,
10.03
And part of creating boundaries around it is giving it a name that you can reference and reference back to when you want to talk about it in the future or or storms that are approaching now that might be getting names too.
b If we can't name it, how can we talk about it at all?
Z One of the strengths of any work of explanatory journalism involves revealing connections to people that may have been invisible beforehand. So, last summer we saw the headlines that Europe was cooking from Brussels to Budapest, people were experiencing just terrible terrible heat scenarios. People were dying, forests were burning.
And then if you spin the globe on the border of Nepal and China, this glacier just suddenly collapsed and flooded a huge area and entire towns were destroyed. Was that one storm that cooked Europe and then blanketed Nepal?
B Yes, it was.
Z Mo, in some of the biography you write about the storm that's called Vera that cooked so much of our planet in 2023 and 2024, you did this remarkable thing where you sort of took us on a world tour of one storm., you took us to Texas, you took us to the Amazon rainforest, you took us to the places of Spain's olive oil growing region.
And everywhere you took us, you told us a different anecdote of just how dramatically life there had changed. Could you take us to Texas and tell us what you learned about what Vera did on one Friday night there when some kids were playing a football game?
M Yeah. So, briefly, Friday football in Texas is something that I think approaches religion; and Friday night football is a big cultural touchstone needless to say.
In this particular case, Austin had been suffering through a long period of heat waves and heat storms including Vera during the period leading up to the game, it was hot. And there was one player who in particular, I think there were others that suffered, but there was one player in particular who suffered from the heat, ended up throwing up on the sidelines, continuing to play, ended up in the hospital.
It was rather touch and go for a period. And there was even a debate whether or not they should drill a hole in his head to relieve the pressure caused by brain swelling. And that's just one example.
And there are other more dramatic examples of heat causing deaths from sports practices because people aren't accommodating the fact that we live in these in hotter circumstances now, and in Texas in particular, I think now they're talking about moving and building a bunch of interior practice spaces that can be cooled so that they don't have to deal with the heat; that is directly as a result of of the warming of the planet and and the fact that these heat waves and heat storms are becoming far more common, especially in this in the lower latitudes that would include Texas.
Z Take us too quickly to the Amazon; you described a marine biologist- there's famously a species of dolphin that can sometimes appear pink colored and they're somewhat revered culturally as icons of the local environment. What happened there?
M They cooked effectively. Yeah. the water got so hot that they could no longer survive and they died by the hundreds. We saw scenes of these iconic pink dolphins and they kind of have a cartoonish look to them when you see them in the water- almost a very charismatic species of dolphin.
And to see them effectively cooked in their own water- be like us cooking in the air.
I mean maybe arguably that's what's happening to the football players who are playing on Friday nights.
But to see these iconic pink creatures just by the hundreds just laying on the side of the lake that had been under heat storms and heat waves and Vera for very very many days and months and that was the result you see. When a shallow body of water like that heats up and creatures depend on it to live, they're going to die and that's what you saw.
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Z Dan, I think it's pretty rare that in journalism you get to name something. A work of explanatory journalism often involves uncovering things that we hadn't seen before, but it wasn't like Woodward and Bernstein named the Watergate Hotel. It was already there.
But you guys have had the chance in this story to frame something, to put a boundary around it. At what point in your reporting did you feel that you were sort of in your own uncharted waters? You had to put a new boundary around what you guys were doing. This was unlik previous prior reporting you'd done.
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Some would argue that we were late in 1988 when Michael Oppenheimer and Jim Hansen went before Congress and said, "This is what's going to happen if we don't do something now."
Well, we, they were clear.
They were largely right in what they said.
And yet, we didn't do anything then collectively.
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B Well, when we came up with our formal definition of a heatwave, after talking to all the scientists and trying to adopt a really mainline, mainstream, defensible, super scientific approach to making them, we didn't really know what we would see when we mapped it out over the last 80 years of available data.
But then when we did, boom, we just saw on the map these areas of extreme heat growing larger and larger each decade as the Earth warmed. And we knew we were seeing something bigger than we expected and that was bigger than what we talk about in the news day-to-day.
And we we kind of felt, I don't want to speak for Mo, but I felt that to help our audience and the public and other people understand what we're seeing, to start a conversation about that, we needed to invite people to take a step back and look at the Earth from a- zoom out a little and look at the Earth from a greater distance and see these bigger changes that are happening in our planet.
Z I think a lot Mo about what you said about looking back at that point in 2008 when without anybody seemingly noticing we went from a period where heat storms could emerge, they could expand, they could cover part of the Earth and then retreat and then we as residents here could enjoy some time without a heat storm before the next one rose up.
And then in 2008 they just became so frequent that there's never been a moment where one is not churning somewhere. We weren't aware of that at the time. And so I wonder whether or not to a certain extent your reporting feels- are we in a way that we feel like maybe we're late to climate change in too many ways. We are maybe not responding as quickly to the facts of it. We are not responding as quickly as to what we might be able to do to arrest or at least slow some of its developments. And only now almost 20 years after that significant change happened are we even aware of it.
18.00
M Are we late? Well, I think one of the great challenges that researchers and scientists have had since climate change and global warming became part of our vernacular is to connect the real experience, the experience that you and I and anyone else might have had with heat to climate change. I think it's it's really difficult.
I get up every morning and I ask myself how hot it's going to be or in this time of year how cold it's going to be and I dress accordingly. I act accordingly.
And this was a genuine attempt to connect the lay person with the researchers and find a way of communicating how our world has changed. Are we late? I think some would argue that we were late in 1988 when Michael Oppenheimer and Jim Hansen went before Congress and said, "This is what's going to happen if we don't do something now."
Well, we, they were clear.
They were largely right in what they said.
And yet, we didn't do anything then collectively.
I mean, there have been fits and starts over time to try and manage these things, but we don't seem to have been able to arrest the rise in carbon dioxide in the atmosphere. It continues to go up every single year. The science is clear that even small amounts of carbon dioxide in the atmosphere are capable of trapping vast amounts of energy.
And let's not kid ourselves here. The planet itself is all about redistributing energy. That's how it works. That's why there are swirling weather patterns. That's why there are swirling currents in the ocean. It's all about just redistributing energy to find some kind of balance.
So we have known about this for a long time and we are now 30 years on from- 35 years on from Jim and Michael talking before Congress; and here we are still talking about how do we communicate to the public so something is done.
Are we late? maybe, but we're also not too late, I hope.
Z I want to talk about where the reporting is going to take you guys next. This is a series. Mo, you've traced around the globe looking at the effects that heat storms have had on people and places and you're watching this thing from the monitor that you've built. Talk me through some of the stories that are coming up next. What are we going to learn? What are we going to see?
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A very charismatic species of dolphin- to see them effectively cooked in their own water. That's what you saw.
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M Okay. so without giving away too much cuz I'd have to kill you if I told you too much, we will be examining in much more precise ways the health consequences of these events in various parts of the world. We will be examining how death might be caused by this and and and we will be looking at some ecological consequences of how plant life is affected and how natural disasters are influenced by these events.
So, but it will all be in the context of how heat waves and heat storms are interacting with those elements to create a situation that is in almost all cases worse for humanity and worse for the planet.
B And to us, that's really the heart and soul of data journalism; the numbers are just the beginning of the story. our job is to turn numbers into news. We are big- time nerds. We love making charts and graphs, but they are far from enough, right? And so what Mo and and many many other photographers and reporters and literally a cast of dozens here at Reuters are doing is using our data and these maps as their road map to to go out into the world, the places the the data shows are being impacted and to to find out what's really going on out there.
And so we're going to have a lot more to share before long.
Z A big thank you to Ben and Mo for all their time and reporting. For daily news around the world, check out our sister podcast, Reuters World News, 7 days a week. We'll be back next week on Assignment.
