Off the Charts Heat: Zombie Fires, Drought, and Heat Domes

Published Jul 20, 2021

Climate scientist Dr. Kristina Dahl checks in with the Got Science? team on this summer’s dangerously hot and dry weather.

In this episode

Colleen and Kristy talk about

  • the science behind increasingly hot summer days
  • what heat domes and zombie fires are
  • what science and technology we have now to combat the climate crisis
Timing and cues

Opener (0:00-0:30)
Intro (0:30-2:28)
Interview p1 (2:28-13:18)
Break (13:18-14:08)
Interview p2 (14:08-24:51)
Throw (24:51-25:23)
Segment (25:23-27:47)
Outro (27:47-29:00)

Related content

Segment: Taofik Oladipo
Editing: Colleen MacDonald
Additional editing and music: Brian Middleton
Research and writing: Pamela Worth
Executive producer: Rich Hayes
Host: Colleen MacDonald

Full transcript

Colleen: I hate to say this, but I’ve started to really dread summer.

Now, full disclosure, I’ve always been more of winter person, but I did grow up near the ocean and I’ve enjoyed many summer days reading a good book under a beach umbrella, the ocean breeze keeping the temps bearable, and the occasional dip into the frigid waters off the Massachusetts coast.

But now, even in New England, summer means heat waves that feel hotter, and happen more often than they did when I was growing up. And I don’t do well outdoors in the heat. I also don’t do well stuck inside, waiting for it to cool off so I can walk my dog.

I know I’m lucky that I don’t have to be outside when it’s over 95 degrees for days on end. But for me, these recurring heat waves—blistering hot temperatures when the sun is out, and nights that are too warm to provide any real relief—these are the most visceral reminders of the damage we’ve done to our climate. When your work addresses global warming… it’s hard not to feel bummed out every time you can viscerally feel the warming.

Adding to the bummer feelings, we’ve just been through one of the strangest extreme heat events to hit the United States, with highs well over 100 degrees in Pacific Northwest cities that usually don’t top 85. I reached out to my colleague Dr. Kristina Dahl, senior climate scientist at the Union of Concerned Scientists for some answers about how our changing climate is making these heat waves, plus wildfires and drought, more likely… and also for some reasons to stay hopeful… and to keep fighting for the deep cuts in emissions we need.

After talking to her, I realized… as bummed out as I may get as the temperature rises, I’m not giving up on a better future. I hope you’ll feel the same way as you listen. Colleen: Kristy, welcome back to the podcast.

Kristy: It's great to be here, Colleen. Thanks.

Colleen: So, we've more or less checked in the last couple of summers with regard to extreme heat. Talk to me a little bit about what you're seeing so far this summer.

Kristy: So, this summer, even before the official start of the season on the summer solstice, we were seeing extreme heat happening in different regions throughout the country. I've tended to think of it like the Eye of Sauron for "The Lord of the Rings" fans out there, where you've just got this intense eye that's drifting from one part of the country to the other. Because it seems like there's always some region this summer that's experiencing really intense heat. We saw it in early June in New England, where we saw schools in Massachusetts and New Hampshire, either closing for the day or dismissing students early because the heat was so intense and a lot of classrooms just aren't equipped for that. They're not used to experiencing extreme heat during the school year. The heat then moved to the Great Plains and we saw roads buckling outside of Omaha, Nebraska. And then, of course, it turned to the Pacific Northwest, a region that's just not at all used to dealing with extreme heat, but was dealing for an extended period of time with conditions more typical of, like, Phoenix or Dallas. Colleen: Right. Some of the temperatures, for example, in Portland, Oregon were completely off the charts, right?

Kristy: Yeah. I mean, they were seeing temperatures above 110. I think one day they hit something like 115, which is hot even for someplace like Phoenix, but is easily 30, 35 degrees above normal for that area.

Colleen: So, while we're talking about Oregon and the Pacific Northwest, there's a lot of discussion about the heat dome causing problems. And I wonder if you could explain to us what the heat dome is and its connection to climate change.

Kristy: Sure. So, a heat dome is an area in the atmosphere of very high pressure, and it tends to push air down toward the surface of the earth. And as the air moves downwards, it heats up and you essentially get areas that are kind of trapped under this dome of heat. Part of what's doing that trapping is a wavy pattern in the jet stream. So, the jet stream is this broad current of air that brings us most of our weather in the United States, it moves from west to east across the country. But rather than being just, you know, a straight line west to east, it has sort of waves and sometimes it's a little farther north, sometimes a little further south. And what we've observed over the last few decades with climate change is that the waviness of the jet stream is getting stronger. So, we're having bigger, ups and downs north and south in the jet stream.

And what that is causing is weather patterns to become kind of stuck. We see this not just with heat in the summertime, but we've also seen it with things like hurricanes, you can get weather patterns getting stuck in place, and you essentially during a hurricane end up dumping tons and tons of rain in one place because it's not just moving quickly along as it used to. So, that's part of what's been happening with this heat dome that everyone's been experiencing is that, it's trapped in one of those waves of the jet stream.

Colleen: And how do you know that's connected to climate change?

Kristy: It's not entirely clear yet how that is connected to climate change. It's a really active area of research in the scientific community. So, we've observed this increase in the waviness of the jet stream that at the same time it's happening, , we also see the climate warming as a result of human activities. So, there is likely a connection there, but it's not entirely clear what it is or what it will be like going forward. So, hopefully, research in the next few years will help to clarify that so we can better understand it.

Colleen: So, you live out in the Bay Area in California, let's talk about wildfire season for a moment. What's happening on that front?

Kristy: So the West has been in a state of very severe drought, particularly over the last few months. In much of California, we received between 30% and 40% of the amount of rain we usually experience during the wet season. So, it's been very dry. We've got reservoir levels really low. We've got the moisture of vegetation, which is something that's carefully monitored for wildfire purposes is very low. The vegetation's very dry. And so, as a result of all that, they are expecting an above-average wildfire season out West, not just in California, but much of Oregon, Washington, even as far East as Northern Minnesota in the latest forecast. They're showing enhanced risk of wildfires this summer.

Colleen: So Kristy, I think many people are wondering, if the drought, the wildfires, intense heatwaves, if they just continue to keep ratcheting up, what will things look like in 10 or 20 years?

Kristy: Yeah. I mean, we're looking at a future that's somewhat constrained, right? We're used to being able to go outside in the summer, go to the beach, go to the park, go to the swimming pool. But we've seen, especially with the recent Pacific Northwest heatwave, a lot of those options no longer are on the table when it's extremely hot. You know, it's dangerous to take a walk outside. We've seen community pools having to close because the decks around them are too hot. Playground surfaces become too hot to touch and unsafe for kids. And so, we're looking at summers essentially becoming a time when we have to spend more time indoors than we're accustomed to doing. When it comes to wildfires, California has always experienced...and the West has always experienced wildfires as part of natural ecosystem out here, but people are starting to think more about wildfire season and to plan for it.

We've had so much wildfire smoke out here in the fall season for the last few years that I do hear people starting to take that into account when they're making travel plans, for example, or having family come to visit. You know, all of that said, we're going to have to find a way to live with these kinds of conditions. And that may mean that you can't go to the playground in the summer because it's too hot. That may mean that you can't go hiking in the fall in parts of California because the smoke is too intense. But I think a lot of people will start to question where they're living as they find their lives increasingly constrained by climate change.

Colleen: I've been reading a lot about different pieces of infrastructure failing, like roads buckling.

Kristy: Yeah. There's a lot of infrastructure that's affected by extreme heat. in Seattle recently, they had to slow down their light rail trains because the rails can bend and deform in the heat. And also, the power lines above the trains, when it's really hot, start to sag. And so that can cause problems as well. So, just your typical daily commute on the light rail would be affected by extreme heat.

Colleen: I've heard the term zombie fires used, which, of course, anything with zombie in it sounds terrifying. But as I understand it, this is a place that's already been ravaged by a wildfire, but somehow this fire can come back in the same place. Is that right?

Kristy: Yeah. So, zombie fire is a relatively new term. They are also called holdover fires if you don't want to go the scary route. But essentially, these are fires that have burned in the summertime and there's still kind of embers smoldering, and they're able to continue smoldering below the surface of the ground over the wintertime period. So, we even see them in places like Siberia, where you have extreme snowfall on top of the ground, but underneath, you have fires feeding off of the kind of dry organic material that's in the soil. So, it is difficult sometimes to tell whether a fire that breaks out is a zombie fire or just another fire in the same place, but just the prevalence of these types of fires breaking out and where they're breaking out has led many to say, "Okay, these are likely holdover fires from the previous season." So, it is pretty scary to think that even once we have those fires fully contained and the danger to homes and the smoke-related danger starts to ease up, that there could be, you know, those kind of seeds of next season's fire already planted in the ground.

Colleen: I recently had dinner with some friends and one of their kids was really despondent about how climate change will affect their future. And these are kids in their 20s and 30s, and several of them were checked out. I wonder if there is there anything you could say to them about what can we should be doing?

Kristy: Yeah. When I talk to our colleagues who work in the clean energy space, there's just a consistent set of wins regarding clean energy. You know, just this summer we saw Oregon become one of the many states that's adopted 100% clean energy or clean electricity laws on the books. So that within the next 20 years, we should see many more states getting all of their electricity from clean sources. So, there is a lot happening and this is just a long fight, but the worst thing we could do right now is give up because there's an entire entrenched fossil fuel industry that would like nothing more than for us to do that so that they could continue to ravage the planet with their products. So, we're up against a powerful adversary in the fossil fuel industry, and we just have to keep fighting.

Colleen: So, Kristy, you are co-author on a report that detailed just how off the charts literally extreme temperatures will become if we don't act on climate change. Can you describe how the heat index will change?

Kristy: Sure. So, a couple of years ago, we released a report called "Killer Heat" that looked at the frequency of days with a high heat index in the future. So, the heat index is often called the “feels-like” temperature. It's what the National Weather Service usually uses as the basis for issuing heat advisories and heat warnings to the general public. And the reason they use it is that our bodies don't just respond to the temperature around us, but also to the humidity. And the heat index is a combination of temperature and humidity that's intended to reflect what the conditions around us feel like to our bodies. So, we use the heat index to look at how often communities across the country would experience really dangerously hot days under different global warming futures.

Colleen: If we continue with business as usual, what's in store for us?

Kristy: So, what we found with that analysis is that by the middle of this century, the number of days that have a heat index above 105 degrees Fahrenheit would roughly quadruple compared to the historical baseline of the end of the 20th century. And so, what that means that for over 150 cities across the country, they'd be seeing an average of 30 or more days per year with a heat index above 105. So, we're talking about millions of people experiencing the type of heat that we typically find uncomfortable and that for many people is actually very dangerous. But we don't have to be on that worst-case scenario emissions pathway. And one of the hopeful things that we found in our report is that if we reduce our emissions swiftly and dramatically so that we limit future global warming to 2 degrees Celsius, which is about 3.5 degrees Fahrenheit or less, we can really hold the line against the grievous impacts of extreme heat and preserve a future that's more or less recognizable for today's kids.

Colleen: So, we were at a standstill with the previous administration, and now we have a new administration and Biden has come out with a climate plan. What are the most positive things you're seeing in that plan and any particular milestones in the next three years, five years that will really say to you, "Okay, we're on the right path, we're moving in the right direction?"

Kristy: Yeah. So, we're incredibly hopeful about Biden's climate plans. Right from the start, we saw him staffing up with some of the best people around. People like Gina McCarthy and John Kerry who have been in this climate space for a long time. They know exactly what the science says and have long been champions for climate action. So, right off the bat, we were feeling really hopeful about what this administration could accomplish. In the announcements that Biden has made since then, again, we're seeing a reflection of what the science has been saying for a long time in the words that he's using. So, when he announced our country's Nationally Determined Contribution, that's the contribution that we plan to make as part of the Paris Climate Agreement that's international and every country makes their own NDC, it's called. His announcement of the NDC was right in line with what the scientific consensus says we need in order to limit future warming to 1.5 to 2 degrees Celsius.

So, it's really encouraging to see that. Also really encouraging to see him take up a platform called Justice40, which says that 40% or more of investments in climate causes should be going to communities who've traditionally been marginalized, who have been dealing with environmental harms for decades. So, it's exciting to see not just the adoption of the latest science in the things that the Biden administration is planning, but also the incorporation of these longstanding priorities of the environmental justice community. All of that said, that needs to translate into action. And that's where the rubber really hits the road, right? You know, we’re seeing it be difficult to incorporate climate change into the infrastructure plan. Hopefully, in the reconciliation package that goes along with that infrastructure plan, we'll start to see the climate component come through more. But we know that we're going to be facing a lot of opposition in Congress, and we really do need to see some of those pledges start to translate into regulations, laws, official policies, and dollars. You know, it's going to take a lot of investment to make a lot of these changes happen at the scale and speed that we need them to. So, we'll be looking for those concrete indicators of money invested, laws on the books to give us a sense that we will be able to accomplish the goals that the Biden administration has set out of reducing emissions by at least 50% by the year 2030.

Colleen: Do you think scientists are sounding the alarm bells loudly enough?

Kristy: You know, I think we need all kinds of science to be happening right now. And there are a lot of scientists in academia who prefer to focus on their own research problems, and they're not as concerned with raising the alarm. And some of that has to do with academic scientific culture and fears of being viewed as less objective by your colleagues. We do see a lot of scientists though starting to take up this cause and raise their voices. I participated in a session at the meeting of the American Geophysical Union just a couple of months before COVID hit, and one of the sessions I participated in was about just that, you know, scientists raising their voices and how to do it and how different scientists in different types of organizations have done it. And the session was standing-room-only. You know, it was planned for a relatively small room and people were just packed in and eager to hear about how they could do this kind of work. And I think that's one of the things that makes UCS, the Union of Concerned Scientists such a unique organization because it's an organization that has that scientific rigor and respects that and honors it while also saying, "Hey, it is okay to raise your voice when you see a problem that you think science should be addressing."

Colleen: That's really encouraging to hear. I think, ringing alarm bells, I think, it's an all hands on deck. If we make the maximum effort to curb global warming emissions, is there any going back to what we had before?

Kristy: It's difficult to see it going back to what we had before because that would require us not just to stop emitting greenhouse gases, things like CO2, but it would require us to be pulling carbon out of the atmosphere to get back to the sorts of concentrations we had when people were kids. So, we have the climate that we have and because carbon dioxide has such a long life in the atmosphere, the atmosphere and the Earth wouldn't naturally just cool themselves back down. We would have to take some of that CO2 out to make that happen. So, the good news though is that we have so many of the technologies that we need to deploy to markedly reduce our emissions. You know, we largely know how to get there, and it's a matter of political will both within the United States and other countries. And for the U.S. as a global leader, it's a matter of helping everyone to get to where we need to go in terms of the technology, in terms of building resilience to climate change, because historically, the United States has emitted the most in terms of greenhouse gases over the history of the last 150 years.

So, while we may not be the top emitter now, we were for a very long time, and we remain the country with the highest per capita emissions. So, we can't just be focusing on reducing the emissions in this country alone because that's really less than our fair share, to be honest. So, we need to be really stepping up helping other countries reduce emissions as well so that we can all be tackling this globally together.

Colleen: Well, I think that's a really good point. I mean, global warming knows no boundaries. We're responsible for so much of the emissions and other countries are bearing the brunt of the impacts. You know, Kristy, I didn't think we would be ending on a positive note, but, you know, hearing you say we have the technology to do this, we know how to do it, we just have to do it is encouraging.

Kristy: It is encouraging. I don't want to diminish what it's going to take to get us there, but this is a problem that humans have caused, and it's a problem that humans largely know how to fix. And so, the missing piece is the will to do it. And if we can get enough people marching in the same direction and agreeing that this is a cause we need to be aligning our will and desire toward, then I think we'd be able to make a significant amount of progress with the technologies that we have.

Colleen: Well, Kristy, thanks for joining me on the podcast. I'm happy that we could end on a little bit more positive note than we have in the past.

Kristy: Yeah, no, it's great. It's good to talk about all these things with you and, you know, I appreciate the continued focus you put on heat and wildfire in the podcast. It's great.

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