- Did you know that wildfires can create their own weather?

Did you know that they can create their own tornadoes?

Can you even imagine something scarier than a firenado.

As the climate warms and more acres burn each year, it's clear that the risk from wildfires is real and growing.

Warmer, drier weather changes fire, but fire also changes weather.

And fire tornadoes are one of the most obvious examples.

In the last few years, there've been more sightings and even video of these than ever before, making experts wonder are these rare events becoming more common?

The most extreme was in Redding, California, where there was the equivalent to an EF3 tornado during a major wildfire.

The Carr Fire that spawned that fire tornado destroyed over 1,600 structures and claimed eight lives.

So we're visiting a lab where researchers create and study fire tornadoes to figure out what's going on.

Definitely watch to the end of this one, because it's not all doom and gloom.

We have some rare, but important good news about wildfire and climate.

But first, let's see a fire tornado.

(intense music) - Hey Maiya.

- How are you?

Yes, Jason right?

- That's right.

- I am still trying to wrap my mind around fire tornadoes.

- It's kind of like "Sharknado" or something like that.

It's pretty crazy and actually pretty scary, the real thing.

So it really is the two words combined.

It's basically a tornado.

I mean, at the worst case, it's a full-size tornado that occurs in a fire area.

And so it's actually caused by the fire.

- [Maiya] So are we gonna see that today here?

- Absolutely.

- [Maiya] Jason is able to observe the dynamics and the behavior of a fire whirl in the controlled environment of the lab.

- [Jason] You really need two main ingredients.

You need, what we call vorticity, which is just rotating air.

And then you need a way to stretch that rotating air.

(suspenseful music) You can see it's starting to spin up there.

- You don't have to do anything else?

Wow, whoa.

- It kind of self drives itself.

- Oh my gosh.

As we learned in season one of "Weathered," a normal tornado gets its rotation when there is wind shear with two wind currents flowing from different directions, then a supercell thunderstorm pushes the rotating air up, stretching the storm and increasing the speed of rotation.

(ominous music) - [Jason] And so the stretching mechanism in a fire tornado is actually the fire itself.

So the buoyant accelerating air that the fire is causing above the fire, that acceleration is what causes that stretching and that stretching, just like stretching a piece of Play-Doh, shrinks the diameter of that mass of air.

And that shrinking diameter causes it to spin faster.

- That's called the conservation of angular momentum.

When an ice skater moves their arms inward, the mass is moving closer to the center, and allows the skater to spin faster.

The fire whirl does the same thing, as the buoyant accelerating air from the fire pulls the world upward stretching and tightening the spiral.

To understand where the initial rotation comes from, Jason set up an experiment to show me how this might happen in the real world.

- We have some fire resistant pads that we're placing.

Then we're gonna roll on some alcohol, and then we're gonna light each of these.

And so what this is really representing is, is a way that a fire whirl can form out in the real world where you have several fires that are interacting.

Each fire is causing this hot buoyant gas to form above it when it burns.

That gas wants to go up.

This fire in the middle, the only place that air can come in to replace it is through these gaps.

So there's a gap here, a gap there, and a gap over there, and they cause this rotating air.

And in the end, it causes rotation, which spins up into a fire whirl in the middle.

And so this could happen out in the real world in the case where you have some embers that loft into the air and start what we call spot fires or a bunch of different fires.

And if they happen to form in certain configurations randomly, it can actually spin up to a fire whirl.

- It's easy to imagine how this could become more common as more acres burn in wildfires each year.

There are just more opportunities for topography or the arrangement of spot fires to create a similar formation and add the rotation needed for a tornado.

(torch blaring) Oh, there it is.

There's a fire tornado.

That is crazy.

While smaller fire whirls are more common, there's still a lot that scientists don't know about true fire tornadoes, including whether or not they're happening more frequently.

This makes Jason's research all the more critical.

What we do know is that the spinning motion delivers oxygen very efficiently, allowing fuel to burn dangerously fast.

And that's something that the fire lab has begun to include in firefighter trainings, after the tragic events of the Carr Fire.

So we know that fires can create their own weather, but fires are also driven by weather, right?

- Yeah, yeah.

It's kind of a two way thing.

- How important is weather in determining the severity of the fire?

- Weather's huge.

So we're developing some new fire behavior models, computer models, that predict how a fire spreads.

We use experiments in this lab to generate a lot of that information that goes into that model.

But weather is massive, especially wind, but dryness is huge too.

And firefighters do a lot of training classes to understand the weather and what the weather does to fire, and also to identify cues that they can look for that might tell them of like impending hazardous conditions.

- Okay so, we know that fires can create wind, lightning and even rain.

We also know that weather is the most important factor in fire severity.

High wind on a hot day with low humidity means that any fire that starts is gonna be extremely difficult or impossible to put out.

And as the climate warms, there are more hot, dry days and more fire.

Now here's the good news.

All that fire is not anywhere near as bad for the climate as we once thought.

It might look like the smoke coming out of a power plant when we see these big smoke columns stretching 20,000 feet into the sky.

But Dr. Lisa Ellsworth and her team did some fascinating research in a fire burned area in Oregon.

And her findings were surprising.

- We have a plot up there and we have one down there.

And then we have one kind of at the end there where it wraps around.

- [Maiya] We know trees store carbon through photosynthesis as they take it out of the air and use it as a building block to grow.

But Lisa's work sheds light on what happens to that carbon after a fire.

- We were out in these plots for two summers, and we measured every single piece of burnable material that's out here, every piece of carbon that's out here.

(calm music) You can tell there's a lot of large wood on the ground.

It's hard to find somewhere to step.

So most of the carbon, it's still stored here on this site, The fine fuels, the grasses and the needles would have burned up.

But the vast majority of the biomass is in these big chunks.

And these big chunks are still here.

They're still storing carbon.

So up here, we have a patch of this fire that burned with very low severity.

And we measured those patches as well in the exact same way, and found that there's really the same amount of carbon storage in the low severity parts as there were in the highest severity parts, because all of the parts of the tree are still here on site.

- And other researchers have found that wildfires release around 20% or less of the carbon stored in a forest, meaning that as long as they're left alone, burned forests continue to store carbon that otherwise might be a greenhouse gas in the atmosphere.

But I wanted to see this for myself.

Oh my goodness.

Look at this.

I mean, I can't imagine Lisa and her team actually like wading through all of this brush here to measure the tree trunks, the bush underneath.

Measuring all that carbon and finding that it is holding the same amount as this old growth forest to the left.

When I think of a burnt forest, I think of just, like everything's gone, everything's just burnt down.

There's just like dirt leftover.

So for me, it's kind of surprising to see you still have these trees still standing.

It makes sense that this tree would hold as much carbon as that tree because really it's just the branches that are gone, and you have this new growth here.

So that definitely makes sense.

That definitely makes sense to me.

(calm piano music) Still, the danger of fires posed to us is real.

Nearly half of the country was covered in thick smoke last summer.

And if you were in a smoky area, you probably remember that respirator mask and HVAC filters were suddenly sold out everywhere.

So before the fire comes, think of everything you wish you had, but couldn't get and go stock up as best as you can.

A great way to filter smoke in your house is to take an HVAC filter and put it on one side of a box fan.

Simple, cheap, and it works.