[Scott] On the next "Energy Switch," we'll look at extreme weather and climate.

- There's been huge declines in numbers of people that die from extreme weather events.

Basically all extreme weather events over time.

- In the U.S.

or globally?

- In the U.S.

and globally.

Yeah.

- So one of the reasons scientists are so concerned isn't so much about current events.

When you look at the cumulative increase in carbon dioxide levels in the atmosphere, and think about it in the context of like if you had a credit card that had a lot of debt on it, you're basically building momentum in the climate system toward a fundamentally different planet.

[Scott] Coming up, how much is climate change driving extreme weather events?

[Narrator] Major funding for this program was provided by Arizona State University.

Shaping global leaders, driving innovation, and transforming the future.

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[upbeat music] - I'm Scott Tinker, and I'm an energy scientist.

I work in the field, lead research, speak around the world, write articles, and make films about energy.

This show brings together leading experts on vital topics in energy and climate.

They may have different perspectives, but my goal is to learn, and illuminate, and bring diverging views together towards solutions.

Welcome to the "Energy Switch."

We often hear that climate change is driving extreme weather, hurricanes, floods, droughts, and wildfires.

To understand this better, our guests discuss the IPCC data and climate science looking at heat waves and cold spells, warmer air's ability to hold more moisture, dry soil's ability to accept more rain, historic rainfall, and current patterns, storm frequency and intensity.

The trends they reveal will surprise you.

Today's experts are Patrick Brown.

He's a climate scientist, the Head of Climate Analytics at Interactive Brokers, a lecturer at Johns Hopkins, and a former co-director of the Breakthrough Institute.

Andrew Revkin is an environmental journalist, a 20-year veteran of the New York Times, and Founding Director of the Initiative on Communication and Sustainability at Columbia University.

Next on "Energy Switch," Extreme Weather and its Relationship To Climate Change Part I. Well, Andy and Patrick, thrilled to have you here.

- It's great to be here.

- Great to be here.

- Real high level, why should our 110 million listeners care about extreme weather?

- Yeah, I mean, we should care about extreme weather 'cause it's very consequential.

So it costs about a percent of GDP annually.

Global GDP causes 20 million people to be forced to move annually, and, you know, still causes tens of thousands of deaths annually.

In terms of, you know, connection to climate, we should, if we're thinking about, you know, being forward-looking and how we're planning infrastructure and things, we should definitely be aware of which things are changing and how strongly they're changing.

- Right, right, so those linkages.

Well you mentioned it, weather and climate, what's the difference?

- Yeah, I mean, the shorthand is climate is average weather right?

And so all weather counts towards climate.

You only observe climate change by documenting changes in the weather.

And so, you know, when we talk about contemporary climate change, we're usually referring to what's the effect of elevated greenhouse gas concentrations on the weather.

- Sure.

- There's a climate scientist at the University of Georgia who says, "Climate is your personality, weather is your mood," and I think that works pretty well.

- Okay, if I'm hearing you right, you can't really look out your window and see climate, you're seeing weather right?

- Yeah.

You're seeing weather.

[Scott] Okay.

- And you can say, oh, this is a nice average day.

And when as soon as you do that, you're talking about climate meaning, this is the weather I grew up with.

And if it's like really weird, then you start to say, "Well, what?

Wow.

I never saw a storm like this."

And that's when you start to ask this question, is this a new thing or is it something that just hasn't occurred in my lifetime?

- So let's give a tangible example, a recent event.

Hurricane Helene came crashing in and lots of destruction.

I mean, looking at it, seeing it, it felt different to me.

Was it?

- The physical setup there was that in the days and weeks leading up to the event, there was a lot of rain in Western North Carolina.

So the ground was saturated, and then you had this very fast moving hurricane that brought, you know, a lot of its moisture with it up into the Appalachian mountains.

And so you had wide swaths of North Carolina, where there was 12 to 20 inches of rain led to a great deal of flooding.

You know, $60 billion of damage, 230 people died.

So obviously a devastating storm.

But when you look, you know, in the past, there was a pretty big flood in 2004, there was a, a major flood in 1916 that was a comparable magnitude.

And in 1791, it looks like there was a flood that was-- - In that region.

- Yeah pretty comparable magnitude.

So, not unprecedented, but we do think the rainfall rates were enhanced by elevated greenhouse gas concentrations.

And you know the estimate from world weather attribution was, it was 10% more rain than you would've gotten otherwise.

- Yeah.

Interesting.

- This gets to your point of weather and climate, many of the impressions, including much of the media coverage that had some climate component to it, it was pretty quick to jump to the global warming as the framing for that storm.

But as Patrick said, there was a study in 1960 by the Tennessee Valley Authority, and that said that the development in the region, where people built their towns was constricting the streams and the floods in ways that made the storm even worse.

The outcome was worse than it would've been.

So that gets to this really important point for anyone, whether you're a journalist or the public of getting a understanding that the impacts or the flood is different than the rain.

The rain as Patrick was saying, can be exacerbated by global warming.

The flood can be exacerbated by all kinds of things.

- I mean, we shouldn't take for granted that, you know, the huge reduction in lives lost that we've seen from these types of tragedies.

So, you know, a big part of that is that we have so much better forecasting than we used to have.

And so we can have evacuation orders put in place that of course, like didn't exist, you know, before modern weather forecasting and modern communication technologies.

You know, all that was done with Hurricane Helene.

- Interesting.

- You know, we focus on the, on the failures, but all these things are things that they don't have in low income countries.

And they're things that we didn't used to have.

And so we should appreciate them and not take them for granted.

- Say that again.

You said the big drop in deaths.

What's the data on that?

- So there's been huge declines in numbers of people that die from extreme weather events.

Basically all extreme weather events, over time.

- In the U.S.

or globally?

- In the U.S.

and globally.

Yeah.

And yeah, I mean, a big function of that, or a big part of that is weather forecasting, but also just general economic development and infrastructure and sturdier buildings.

And if you can evacuate a region, if you can get outta there.

- Right.

- That's a huge part of that.

- Communications and preparedness.

- Yeah.

- This is saving lives.

Okay.

- The place I've written about that, where this is most striking is Bangladesh, where in the 19, around 1970, cyclone hit and hundreds of thousands of people were killed.

And you have the same ferocity of cyclones now in that region.

And the death rates, again, every death is a tragedy, but they're in the hundreds or dozens because of radio, satellites, integrated systems for getting people out of harm's way.

- So a hundred to a thousand times fewer deaths.

A hundred thousand and down to hundreds.

- Yeah.

- That's incredible.

Well, for our viewers who may not know, what is the IPCC?

What is that?

- The Intergovernmental Panel on Climate Change.

- Intergovernmental Panel on Climate.

- And it's a highly vetted, peer reviewed, kind of open discussion of the climate.

They don't do the research.

They look at the research every five or six or seven years-- - And it's global research.

So they're pulling in from universities, think tanks, governments-- - You name it, yeah.

So they come out with these basic conclusions and the summaries.

And we, journalists and policy makers and everybody else sort of ingests this.

- It sounds trustworthy.

Can we trust the science that comes outta the IPCC or the, it's not the science, the summary of the science.

- A point towards trust is that it's not some cabal, it's researchers and scientists at institutions all around the world that volunteer their time to synthesize the literature, you know, in their kind of subfield of study.

It's very much oriented around the negative impact of CO2 emissions and greenhouse gas emissions and how to, you know, avoid impacting the climate.

- Right.

- And so when it comes to trustworthiness, you know, I think that Working Group I, the physical science basis is very trustworthy.

And I read it a lot just for preparation for interviews like this.

I think Working Group II has a pretty strong negativity bias because it's kind of like that's the orientation of the whole report, is that the physical science, then the impacts, which then-- - Go find the problems.

- Which then motivate the reduction in emissions, often taking outcomes that are actually getting a lot better over time.

Like increasing crop yields or decreasing mortality from extreme events and kind of presenting them in a way that makes it seem like they're getting worse.

Which I think are confusing for a lot of people reading that.

- Absolutely.

Yeah, interesting.

- Some of the leadership of the IPCC, the people who are at the top, and not just the written summary, but the way someone would explain it to, in a press conference, they would also tend to focus on the worst case outcomes and not present the full contexts.

And that made it, that's where criticism started to come in.

The process is biased.

- Right.

- And you add that to the newsroom bias.

Of course what do we write about?

We write about things that are bad.

And, that's been true for climate reporting.

So often when you dig into the actual reports there, they have all the nuance Patrick was talking about.

But the presentations get ever more distilled, da da da.

And the drama is what kind of drives this into our lives or not.

- Right.

We respond strongly to fear, certainly, humans do.

- Yeah.

- So given all that, how can we be confident that the climate is warming?

- Well, we have a consensus of measurements, basically.

And so we can measure that the atmosphere is warming.

We can measure that with a network of meteorological stations globally.

We can measure that with weather balloons.

We can measure that with satellites.

We can measure that the ocean is warming.

We can measure that the ice is melting the major ice sheets both with gravity satellites as well as satellite altimetry.

And we can measure that the sea level is rising, both because it's warming and because ice is melting.

So all of our global networks show that it's warming.

And you know, fundamental physics of the Greenhouse Effect has been known since 1700s, 1800s.

[Scott] How do we know how much today is human cause with?

- The main natural drivers of climate change on decade to centennial time scales are changes in volcanic activity and changes in the radiation coming from the sun.

And those two things should have basically caused no climate change since the Industrial Revolution, if not perhaps a slight cooling since the Industrial Revolution.

And so that leads us to believe that a hundred percent of the warming, since the Industrial Revolution, is due to enhanced greenhouse gas concentrations.

It's not a situation where it's like, well, humans contribute to it, but it would've been happening anyway.

But I mean, really modern global warming didn't really pick up till around 1975.

And that's when the forcing from enhanced greenhouse gas concentrations really became much larger.

- So the last 50 years.

- Yeah.

Yeah.

- And we weren't able to measure many things prior to 50 years ago either.

- Yeah well, temperature though is one of the easiest ones.

- Gotcha.

- So we have a pretty reasonable estimate of global average temperature dating back to the 1800s.

- So in the last 50 years, humans have forced how much warming into the system?

- Well, so we're now at 1.5 degrees above pre-industrial levels.

- C - Yes C.

- 1.5.

- And most of that, you know, a degree of that probably is the last 50 years.

- And one of the novelties here is the pace of the emissions.

You look back in climate history and way back the cycles of ice ages, warmings, you know, on that long time scale, CO2 carbon dioxide change appears to not be in the driver's seat.

- Right.

- It's kind of a reaction.

- Right.

- The world's changing.

And this, now we're talking about carbon dioxide being in the driver's seat.

- Interesting, well, let's hit these weather impacts, precipitation patterns and amounts.

Is warming impacting these?

- This is an arena where the timescale you're looking across really matters.

I became kind of chastened as a reporter when I went out in Jamaica Bay with a scientist named Jeff Donnelly.

And he takes a coring tube and puts it down into the marshy areas.

- Right.

- Sediment there going back actually a few thousand years.

- Right.

- And you have mud, mud, mud, mud, mud, sand, mud, mud, mud, mud, mud, sand, and the sand is when there was a hurricane.

That washed sediment off the beach into the mud.

And I wrote a feature about that going, this is really interesting 'cause it says the hurricanes have hit the East Coast in that region more than we might think just based on our experience.

- Yeah.

So precipitation patterns amounts, your perspective on that.

- So the theory for annual average precipitation is that that should increase by about two percent per degree Celsius of warming.

And it's not something that we've observed yet.

So our observation systems do not detect that there's basically no trend in annual average precipitation.

- So there's no observable trend.

You would expect something and it's not happening.

- Well, not necessarily because we know that this signal that we're looking for is small relative to just natural variability.

So it's not something we would expect to see emerge yet.

- Okay.

- Necessarily.

- Okay.

- For the most extreme precipitation, we expect that to increase by seven percent per degree Celsius of warming.

So that we should be up.

And that's just because the atmosphere can hold seven percent more water vapor per degree Celsius of warming.

So, we should be at about 10% more than we used to be.

So we have a network of stations that have long enough records back to about 1950 that we can look at this.

And so 89% of those stations show no change, but nine percent show an increase in extreme daily precipitation and two percent show a decrease.

So that's showing that this is starting to emerge and the fundamental theory behind that is very solid also.

And so it would be a big surprise if it didn't happen.

And so I think everything's kind of aligning with what we would expect.

- So let's do storms.

What are the trends in storms and hurricanes?

- Yeah.

I mean, we don't really see trends in the occurrence of hurricanes or in wind speed measures globally going back to 1980s when we have really good records.

And there's actually pretty good evidence, you know, trying to reconstruct that back further in time, that we've seen a decrease in occurrence of hurricanes-- - The number of.

- Since the 1800s.

- The frequency.

- And models actually project that too.

But when hurricanes do occur, we do think that they produce more rainfall because of this Clausius-Clapeyron seven percent more water vapor per degree Celsius of warming.

And we think that actually hurricanes are probably super Clausius-Clapeyron, meaning that it would be even more than that seven percent.

They also are riding on top of sea level that's risen nine inches since 1880.

So all the storm surges are higher than they would have been otherwise.

- So no global emergence in the frequency and maybe a decrease.

But when they do, there's more water in them and there's more storm surge 'cause sea level has come up.

And I don't want to dive into sea level so to speak, but part of that storm surge is this based on natural sea level rise, correct?

And some of it is being forced.

- I mean of those nine inches of sea level rise since 1880 and the vast majority of that is I think forcing from human emissions of greenhouse gases.

- One of the interesting research lines and storylines in recent years has been a focus on the variability of sea level rise in different parts of the world.

Different parts of the United States coast are seeing significantly more rapid sea level rise than, so it's not like one number across the world.

And another metric is the duration of a hurricane, how long it's alive.

And those statistics I think are still being hashed out, but... - Yeah.

I don't think there's trends in hurricane days.

There's not a change in accumulated cyclone energy.

And we don't, I mean, the expectation is that you get two point five percent more wind speed per degree Celsius of warming.

And that's very small compared to just natural variability.

So again, the models are saying that we think that signal is probably in there, but it's small and we wouldn't even expect to see it yet.

- And this is also an arena where aerosols get into the mix too.

The sooty, smoky, smoggy pollution.

There's a bunch of science that has accumulated in the recent years showing that the period from like 1990 through now through the 2020s, the Atlantic has seen a rise in hurricane activity.

But it's simplistic to say that's global warming because the pollution, the sooty, smoggy stuff has changed the dynamics of the circulation over the Atlantic.

We're sort of taking the lid off of a system that's letting hurricane activity come back up.

It was muffled by all that stuff.

- So there's mid latitude cyclones also.

So that would be what your weather person would call a low pressure system.

And so those, you know, don't get a lot of headlines.

But the, you know, the theory and the models and the observations project that those should get weaker as it gets warmer because their main source of energy is the difference in temperature between the tropics and the poles.

And that difference in temperature decreases as it gets warmer 'cause you have arctic amplification.

And so we see a decline in the strength of those in terms of wind speed and a lot of middle latitudes.

- So that's following what we would expect.

[Patrick] Yeah.

Yeah.

- That's not a, is that a bad thing then?

Is it?

- I don't think so.

- It's a benefit of climate warming.

- Well, yeah but it shows up in tornadoes statistics for example.

The strongest tornadoes, the ones in that sort of three to five category, the ones that killed the most people and caused billions of dollars of damage, look like they've been declining over the United States.

And again, it's inconvenient to someone trying to make the message about global warming.

Being everything you see that's weird and dramatic and destructive is because of global warming.

Well not for tornadoes.

- That's a little perk.

- Yeah and that's part of the science.

So you either accept the science or not.

[Scott] That's fascinating.

- It may make it a harder story to tell.

But it's part of what has to be in the story.

- Let's talk about the other side, the droughts then, this guy back here you know?

What do we see with droughts?

And contrary to that, the floods?

- We actually don't see a trend in global surface soil moisture.

And if you look at that in space, it's non-uniform.

You see some places with increases, some places with decreases.

You know, there's other metrics.

There's Palmer Drought Severity Index.

And that is something that we do see.

It seems like an uptick recently.

But these are not strong trends.

They're not, you know, like hockey sticks the way that some things that like global average temperature is, yeah.

- And then you have these regional issues like, I'm kind of glad I don't live in California because they have this worst case climate.

Mega drought is kind of the norm.

And then you have these periodic super storms, fairly unpredictably.

These are monstrous fire hose systems coming across the Pacific gathering a lot of moisture.

So you're living in both, at both ends of-- [Scott] And this is back through time or-- - Oh, thousands of years yeah.

- Okay.

And floods?

- So the main metric for floods is annual maximum stream flow 'cause that's what we have pretty good data on.

And you look at that and there's not a trend in either direction.

And you look locally, it's non-uniform, but a lot of floods are caused by spring snow melt.

So a reduced snow pack reduces those types of floods.

And also this same mechanism of the atmosphere holding more water vapor means that it can evaporate more water vapor.

And so a lot of times the soil is actually drier and has higher capacity to take up that additional rainfall.

And so we think that those two countervailing factors in models anyway, offset that increase in precipitation such that the change in the future is not all that dramatic.

- You are really kinda bursting my climate drama bubble here, Patrick.

How about fires?

Certainly there's gotta be a trend in fires.

- Before we get to that, one of the really important things about this problem is that carbon dioxide in particular is a cumulative gas.

So one of the reasons scientists are so concerned isn't so much about current events.

When you look at the cumulative increase in carbon dioxide levels in the atmosphere, and think about it in the context of like if you had a credit card that had a lot of debt on it, you're basically building momentum in the climate system toward a fundamentally different planet.

So that's the thing that makes this really important.

I think most climate scientists, when they wake up at night worried, they're thinking about that long term change more than these.

- I'm glad we captured that.

And let's come back to that too.

- Yeah so the weather that encourages fires, we have seen an increase, but that hasn't translated into a global increase in wildfires.

So we've seen a decrease in wildfires globally since 2000 in terms of area burned as well as mass combusted.

So a big part of that is fire prone areas in the Savannah and Africa are now farmland or grazing land.

And so you've seen a big decline in-- - You've removed the fuel.

- Yeah in fires there.

- Okay.

- But you know, even in places of high concern like the Western U.S.

and California, we do think that wildfire now is much less in terms of area burned than it was in the 1600s, 1700s.

So basically land use and land management have a huge effect.

We didn't talk so much about heat waves, but you know, that's something that is, you know, very strong signal to noise ratio.

And is outside of historical-- - It is warmer and there are more heat waves.

- Right, right.

- Okay.

Yeah.

That's a direct forcing from... - Yeah and cold waves are getting less cold even around the Texas impacts.

[Scott] Yeah.

Yeah.

- The modeling shows that that even when you have a severe cold spell, it's less cold than it would've been otherwise.

- Yeah.

- And those are warming faster than heatwaves are warming.

- So all these things we've talked about, don't wanna oversimplify it here, mostly haven't emerged with rigorous statistical significance from the past yet.

Some are starting to show that and then things we're doing that are cumulative might drive that harder in the future.

Is that a reasonable summary of what we just talked about?

- Yeah.

- I guess it makes me feel a little calmer.

But let's take a break, and we'll come back to some of these topics.

[Patrick] Cool.

[Scott] Global data show that deaths from extreme weather are way down due to better alert systems and stronger buildings.

Heat and heat waves are up and directly related to the CO2 humans have released into the atmosphere.

Warm air holds more moisture, which has increased rainfall, but heat also dries soils which absorb more rain.

The result is that flooding has not increased and flooding is exacerbated by many factors besides rainfall, especially development and impervious cover like streets, parking lots and buildings.

Hurricanes also are not increasing in frequency, in fact may be decreasing, but when they do occur, they produce more rainfall.

Tornadoes are down and globally, wildfires are too.

The Scientific Working Group of the UN's Intergovernmental Panel on Climate Change, or IPCC agrees with all these findings.

However, our experts say the policy working group often paints a more negative picture.

We'll talk more about risks and impacts from extreme weather in part two.

[upbeat music] ♪ ♪ ♪ ♪ [Narrator] Major funding provided by Arizona State University.

Home to the Julie Ann Wrigley Global Futures Laboratory, addressing critical challenges toward a future in which all living things thrive.

Arizona State, The New American University.