As large parts of California and the Pacific Northwest are beset by wildfires, the issue of climate change has taken on prominence in the national political conversation. Scientists increasingly point to rising temperatures and extreme dryness as exacerbating wildfires, but what other factors are involved? Science correspondent Miles O’Brien joins William Brangham to discuss.

TRANSCRIPT

William Brangham:

As we heard earlier, the impact of climate change was very much in the news today. It came up during President Trump’s visit to California. And the Democratic nominee Joe, Biden, lambasted the president’s policies regarding climate change.

So, our science correspondent, Miles O’Brien, is here to look at what we know and what we don’t and the other factors that might be contributing to these wildfires out West.

Miles, great to see you, as always.

So, we know the science is quite clear that climate change certainly contributes to, exacerbates the problems that these wildfires are demonstrating.

Can you remind us a little about the science of that?

Miles O’Brien:

Yes, William, exacerbate is a good word.

Climate change isn’t starting these fires, but it is creating the dry conditions that make it easier to have these fires ignite in the first place, spread faster, become bigger, so-called mega-fires, whether they’re caused by humans or by lightning, as has happened in many cases in California this year.

If you look at the annual number of burned acres in the West, it has increased just in lockstep with the change in climate. From year to year, the area burned up correlates almost directly to temperature variations.

And if you look over a 30-to-50-year period, the numbers and the amount of fires and the acreage burned correlates exactly with a 2.5-degree Fahrenheit increase in the temperature of the climate overall, which is what we have experienced.

Park Williams is a hydro-climatologist at Columbia University’s Lamont-Doherty Observatory.

Park Williams:

As you warm up the atmosphere, it can hold more moisture. And so it can pull more moisture out of forest ecosystems, therefore drying them out faster.

And so then, as long as you get spark and wind, and you have got enough to burn, then you’re going to burn it.

William Brangham OK, so we know climate change is playing a role, potentially major role, in this. But what else can explain this incredible devastation caused by these fires?

Miles O’Brien:

Yes, it’s worth reminding everybody that fire is just a natural part of the ecosystem in the West.

And what has really changed is the number of people who are living in close proximity to it. There are more and more people building in the woods, in areas that burn. Researchers have kind of a wonky term for it. They call it the wildland-urban interface, or WUI for short.

Researchers from the University of Colorado Boulder, found, between 1992 and 2015, Americans built 32 million new homes in the WUI. And when you have more people living in the forests, you have more people starting forest fires. Sounds like common sense.

But, as it turns out, 97 percent of the fires that actually destroy a home are started by people in the first place.

And here’s the thing. There’s no end in sight to this building boom in the woods.

Geographer and fire ecologist Jennifer Balch is with the University of Colorado, Boulder.

Jennifer Balch:

Eighty percent of the potential landscapes that could be built into have yet to be built into. And so more and more people are going to want to move into landscapes that are flammable.

And we currently have about 1.8 million homes that are threatened at high risk of threat from wildfire in the WUI. And that’s about $300 billion worth of value.

William Brangham:

So, if more and more of us are moving into the wilderness, are there things that we can do to manage those wildernesses better, so that we can reduce the risk of fire?

I mean, this is certainly something President Trump keeps stressing as a major issue.

Miles O’Brien:

Yes, the president talked about raking the forest, and there was a lot of controversy about that.

But there do need to be some changes in the way we manage the forests, if people are going to live in them. Each time we successfully put out a fire over the past 100 years, and they — we were very aggressive about it, the Forest Service and other enterprises doing that, we sort of kicked the can down the road, because it just allowed more underbrush and fuel for the fire to grow, creating more difficult problems.

So, at the U.S. Forest Service’s Fire Lab in Missoula, Montana, researchers had been spending a lot of time looking at alternatives. And one of the ideas is to thin the forests out, tend them a little bit, and do controlled, managed, prescribed burns, burns that won’t get carried away and damage the homes, making the forest afterward less of a tinderbox.

There was a 30-acre plot of ponderosa pine there that had not burned for 100 years. They let it be. And then, nearby, they thinned and burned to see what would happen. And that forest, in every measurable way, is healthier, resistant to bark beetles, and less likely to burn in mega-fire fashion, as we’re seeing right now in the West.

William Brangham:

OK, I want to make a huge change of topic here, given the you are also our expert, our resident expert when it comes to all things space-related.

People might have seen these headlines today that scientists believe they have found signs of life on Venus. What happened there? What should we take away from all this?

Miles O’Brien:

Well, above Venus would be a little more accurate.

But, yes, Venus isn’t the kind of place to raise your kids, to paraphrase Elton John, right?

(LAUGHTER)

Venus is — the temperature is 900 degrees Fahrenheit, on average, the pressure 90 times greater than that of Earth.

To think of life as we know it existing there is pretty hard to imagine. But researchers, using telescopes at — in Hawaii and Chile, have found signs of a gas called phosphine in the clouds above Venus, which are a little more temperate, albeit acidic.

Now, phosphine, what do we know about that? Actually, we don’t know a ton about it, except that it’s always associated with anaerobic life here on Earth, which is to say swamps and bogs and sewage. And there’s a lot of it, believe it or not, in penguin poop, believe it or not.

So, what could it be? Could there be some sort of life-form connected to the phosphine on Venus? The researchers looked at potential chemical and geologic processes, volcanoes, meteors, lightning. None of it supports the amount of phosphine they found.

And so it raises a huge question. We have been looking for so long for signs of life on Mars. Could it be our closest neighbor Venus has been overlooked in all this?

NASA is thinking about sending some missions to Venus or looking at four possible missions on the horizon. Two of them would be to Venus. And maybe this will give a little more credence for those teams to win those proposals.

And maybe we can go to Venus. And who knows? Maybe that will surprise us and we will find Venusian penguins. I don’t know.

(LAUGHTER)

William Brangham:

Venusian penguins. I love it.

Miles O’Brien, always good to see you. Thank you so much for your intel.

Miles O’Brien:

You’re welcome.