The Earth's temperature has reached the critical warming threshold of 1.5 degrees set by the United Nations Conference on Climate Change for 12 months in a row.

And let's just say we're feeling the impacts on our weather.

Broadcaster: It's hell on earth as hurricane Ian slams into Florida.

Maiya: We know that greenhouse gases work like a blanket surrounding planet earth, and we're pumping them into the atmosphere at record rates.

But I want to know how warm the world will get and what the world will look like with all that extra heat energy supercharging our weather.

To do that, we'll need one of the most powerful supercomputers in the world, an idea of how greenhouse gases compare to the past...

I am holding 55,000-year-old ice.

and how our emissions of those gases are changing in a surprisingly hopeful way.

I'm Maiya May, and I'm fascinated by our dynamic planet, our weather, and our climate.

What began as a career in broadcast meteorology has become a mission to figure out where we are... Woman: Oh, my God!

and where we're going as we leave this long, stable climate period and enter the hockey stick era.

So in this episode, we're gonna see what the most advanced climate models say about each region in the U.S., and we're gonna witness a trend that's happening all over the world, and that's also reshaping those models' predictions for our climate.

Oh, what?

Wow.

[explosion] Oh, my God.

Whoa.

Oh, my God.

[thunder] There's a lot of scary and depressing news about climate right now, and so many people are experiencing extreme weather, heat waves, and flooding firsthand.

But I want to talk about why I think our collective understanding of the current situation is wrong.

First, I'm going to Oregon State University to try to get a sense of how much carbon dioxide we're emitting by looking at an ancient piece of atmosphere literally frozen in time.

Hi, Maiya.

Hi, Katie.

How you doing?

Welcome.

Nice to see you.

So here at Oregon State University, we study earth's climate history.

We have something like 9 miles of marine sediments that were cored from all over the world.

And so using these archives, we can go back in the past, sometimes tens of millions of years, to reconstruct how earth's climate has changed in the past and evolved over time.

You did this recent study.

I'm really curious to learn more about this particular study.

Can you tell me about it?

Yeah, we were interested to know how carbon dioxide concentrations in the atmosphere changed during the last ice age, right?

And so we did that by measuring ancient atmosphere that's trapped in ice cores.

Maiya: The cores were drilled in Antarctica and stored at -30 degrees.

So to see them, we wore the same suits they wear in the field.

All right, here we go.

Is this how Antarctica feels?

Oh, yeah.

Oh, my goodness.

So here's a chunk of an ice core.

This ice is 55,000 years old.

Wow!

This is how we know what goes into our climate models and what our climate was like in the past.

I mean, it's awesome.

It looks a lot different from the ice you find in your freezer.

Yeah.

It's got a bunch of little, tiny bubbles that are frozen in the ice, and they contain ancient atmosphere.

And so we can bring this into the lab, release that gas, and then measure it to see what the greenhouse gas concentrations were in the past.

OK, so we put the piece of ice in a steel container that's frozen, and then we vacuum out all of the modern air, and then we crush the ice with some steel pins.

We collect that gas to tell us the concentrations of CO2.

And what did you find in your study?

We found that during particular intervals throughout the last ice age, CO2 rose really abruptly.

In one interval, for example, it rose over 10 parts per million in just 50 years.

So how does that rate of change compare to today?

So even though it was the fastest natural rise in CO2 that we've observed in the paleo record over the last 100,000 years, it's still 10 times slower than the CO2 rise that we're observing to, yeah, today.

10 times slower.

So that means today, CO2 is rising 10 times faster than at any point in the past?

That's correct.

Maiya, voice-over: Over the last 100,000 years, we went into and came out of an ice age.

Sea levels dropped as the water was locked away in the ice, then rose dramatically as the ice melted.

Temperatures fluctuated by as much as 10 degrees Celsius, yet through all that major change, we've never seen CO2 levels rise anywhere near as rapidly as we're forcing them to rise now.

So I can see why people are pessimistic.

Our situation is serious, but I think there's another reason people lose hope.

It's a relatively simple misunderstanding about how much greenhouse gas we're really going to emit in the future.

The emission scenarios that we use to run climate models are a little bit old at this point.

You know, many of them were developed in the early 2010s, when we were in a very different world.

Global emissions had increased 30% in the previous decade.

China was building a new cool plant every two days.

Maiya: And things felt dire.

Major coal mines and export terminals were proposed all over the country, and renewables seemed like they could never offer a meaningful solution.

Now, if you go back to 2014, for example, just before the world signed on to the Paris Agreement, the alternatives that the world had to fossil fuels were extremely, extremely expensive, far more expensive than fossil fuels.

So if you look at solar or wind or batteries or electric cars, they were so, so expensive that it seemed incredibly unlikely that any country, really, was going to move away from fossil fuels to those sources of energy.

Zeke Hausfather: And the idea that the 21st century could be dominated by coal didn't seem that far-fetched.

And so you had scenarios where global emissions tripled by the end of the century, global coal use increased fivefold, global temperatures hit, you know, between four and five degrees by 2100.

Maiya: So the highest greenhouse gas emission scenario used in the climate science community where the world's emissions skyrocket for most of the century was dubbed "business as usual."

This scenario is often cited in scientific journals, popular media, raising concerns that we're on the fast track towards doomsday.

But since those emission scenarios were created, things have changed.

For decades, activists, lawyers, and policy makers worked to limit the use of coal.

In the United Kingdom, a carbon tax made coal less competitive.

In the United States, coal plants were required to reduce pollution, but many opted to shut down instead.

Even coal export terminals were rejected by local communities.

And now coal plants have begun to shut down, but it's hard to believe that we've reached the end of the fuel that powered nearly all of human industrialization.

And I had to see for myself.

So I went to an area just south of Detroit, Michigan.

Here, the Trenton Channel Coal Plant went into operation a century ago.

All right, so this coal plant that we're going to was shut down a few years ago, and now at 6 A.M. on June 21, 2024, it will transition away from coal forever.

And it's not alone.

Half of the coal plants that operated at peak coal use in the U.S. will shut down by 2026.

We are about seven minutes out.

I kind of feel like this is like a New Year's Eve countdown situation.

I'm excited.

I mean, we've been hearing about the transition to renewables all over the world, and it's just really cool to be in the place where it's actually happening in less than, less than... Oh, less than a minute.

[Chuckles] So it's about showtime.

They said there would be three--one minute.

Man: One minute.

One minute, one minute.

There's gonna be three horn blasts right before it happens.

So that should be happening here very soon.

[music] Oh, what?

Wow.

[explosion] Oh, my God.

Whoa!

Oh, my God.

[music] I was not expecting that.

They said, "One minute," they said, "One minute," and then all of a sudden, it just exploded.

[music] Hannah Ritchie: So that very, very high-emission scenario, which leads to very, very severe and very, very alarming climate outcomes, is probably unlikely at this point.

The issue is that it's often referred to still as "business as usual," when the reality is that we're no longer on that pathway.

It's pretty clear that that world, even if it might've been possible back then, is not really possible today.

You know, clean energy is the cheapest new form of energy in most countries.

Maiya: Utilities are actively moving away from fossil fuels.

A new battery storage system will soon be built on the site of the demolished coal plant, and it'll be the largest standalone energy storage site in the Great Lakes region.

Coal plants are being demolished all over the U.S. ♪ [music] And this trend is happening across much of the world.

[music] Hannah: There is a reasonable chance that either this year or within the next few years, global coal use will peak.

Maiya: On our current path, the world is likely to double the warming we've already experienced, and that's pretty terrifying, because as the world warms, every fraction of a degree matters.

But I think we should be encouraged by the progress we've made in the last decade.

For all of human history, producing energy has been synonymous with burning stuff-- campfires for cooking, burning coal in the early days in the Industrial Revolution, burning oil and gasoline in our gas tanks.

And so what we're talking about when we're talking about a clean energy transition is fundamentally moving away from that toward a world of producing electricity without burning stuff.

Maiya: Solar really transformed what our energy future could look like and has really defied all expectations.

So the International Energy Agency publishes yearly forecasts of what solar uptake will be, and they've been historically exceedingly bad at predicting this.

This is another reason that all of the climate doom people are feeling makes sense.

Every year, the world's foremost energy authority told us that solar adoption would plateau, real-world adoption would jump, and, again, they would project a flat line, but it didn't plateau.

Solar adoption has increased exponentially, and the reason for this growth can be explained by something called the learning rate.

For solar, the learning rate is 20%.

So if you double the amount of solar panel globally installed, that means that solar panels become 20% cheaper.

And that happens each doubling.

The declining cost for every doubling of capacity has happened for 40 years.

Maiya: It's so widely accepted that humans don't easily identify this type of change that there is a name for this idea, the exponential growth bias.

Hannah: They've vastly underestimated how quickly the prices would fall, and they've vastly underestimated how quickly these technologies could be deployed.

Solar has fallen by around 90%, onshore wind by around 70%, batteries by around 90%, such that they're now undercutting the cost of fossil fuels.

And now they are so cheap that even people who don't care about climate change as an issue are going to be adopting clean energy because it is cheaper than coal.

And that fundamentally changes the trajectory of where we're headed.

[music] Maiya: Still, our planet is warming fast, and the impacts are hard to ignore.

Coal use is probably near its peak, but the use of oil and gas is still growing, and CO2 levels in our atmosphere are breaking new records every year.

Low carbon energy sources are being deployed faster than fossil fuels, but we're nowhere near net zero greenhouse gas emissions.

So what we're experiencing today is a race between the impacts of climate change and the adoption of renewable energy.

Dr. Marshall Shepherd.

How are you?

Oh, good.

It's good to see you again.

Good to see you again.

Ha ha!

We go way back.

Yes.

Can you put 2023 in terms of climate change into perspective for us?

Yeah.

Well, record year.

We know it was the warmest year on record, and not just in terms of air temperature as well-- the sea surface temperatures, the hurricanes, just all of the signals that we would expect from climate change.

So how warm are we talking?

How warm was 2023?

It's a great question, and to give you some context, the Paris Agreement is trying to limit warming at 1.5 degrees Celsius.

For several weeks to months, we exceeded that threshold.

What worries me is that we're warming, and I fear that we'll see a continued trajectory and a rapid increase over time.

2023 brought us some of the warmest air and ocean temperatures on record, and it wasn't even close.

Maiya: And in 2024, that trend continued.

In 2015, nearly every country in the world agreed to the goal of limiting warming to 1.5 degrees in the Paris Agreement.

Now, for the first time in modern history, global warming has been above 1.5 degrees for more than 12 months.

So, I visited one of the most powerful supercomputers in the world to find out what climate models say about the impacts on our weather.

♪ Climate models, in a nutshell, are these systems of mathematical equations describing the physics and chemistry of, really, how the world works.

Maiya: But crunching those numbers on the scale of the entire Earth's climate requires some serious hardware.

And in here is Derecho.

Maiya: Oh, wow!

This machine is a 19.8 petaflops machine.

It'll do 19.8 quadrillion calculations per second.

We put all of our climate data into the machine, and it will take months to render some of these projects.

It's a lot of computing power.

So many of the scientists I've talked to for this series use this computer to run their projections into the future.

Man: You create hundreds of simulations of the future climate, and that gives you then probabilities and uncertainties of what the future climate look like.

Zeke: But even those climate models have some pretty big uncertainties.

And those uncertainties are really in two categories.

One is how sensitive the climate is to our emissions.

Maiya: As we add greenhouse gases into the atmosphere, the world warms, but how much depends on things like the amount of sea ice, the amount of snow on land that bounces heat back into space, and how our warming climate affects cloud cover.

And those have a lot of uncertainty in them.

And then the final element that comes into play when we're trying to figure out how much the world is gonna warm in the future is how the carbon cycle responds to our emissions, or what we call carbon cycle feedbacks.

Maiya: Right now, the ocean and the biosphere absorb about half of the CO2 that we emit from burning fossil fuels.

And that's really important because it reduces global warming.

But as the climate warms, they're expected to absorb less of that CO2, but we don't know how much less.

And so this combination of uncertainties in climate sensitivity and uncertainties in carbon cycle feedback means that even if we know precisely how much humans are gonna emit in the future, there's still a pretty big range of possible temperature outcomes.

Maiya: Although it's unlikely that we're headed towards the most extreme scenario, we'll almost certainly pass the 1.5-degree goal laid out in the Paris Agreement.

And to stay well below two degrees of warming, we would have to reach net zero emissions by 2050 and be almost halfway there by 2030.

But we're not on track to stop burning fossil fuels that quickly.

Hannah: Temperatures will continue to rise, and they'll continue to rise until we get emissions to net zero.

Maiya: But there is some more good news.

Most scientists now agree that the world will stop warming relatively quickly once we stop emitting greenhouse gases.

The earth will find balance as oceans, trees, plants, and even rocks absorb enough carbon to stabilize our climate.

♪ So, I wanted to know what climate models say about how our weather will change.

What's our nation going to look like as the climate warms?

♪ All right.

We're here in Atlanta, my hometown, and we're getting ready to talk to one of my favorite climate scientists about what areas in the United States are most vulnerable to climate change, and this is one of them.

Dr. Marshall Shepherd and his colleague, Dr. Binita KC, created a risk map of the United States that combines three big variables-- hazards, exposure, and vulnerability.

The hazards they modeled include heat waves, cold spells, extreme precipitation, and drought.

Maiya: So how do you define exposure?

So, exposure is what people, or infrastructure, or resources are actually being impacted by an extreme heat event or a drought or an extreme rainfall event.

If your eye homes in on this map, you see urban spaces.

Maiya: We're in Atlanta, and, I mean, this is metro Atlanta.

Clearly.

Miami, southern Florida, parts of the Southwest and L.A. and so forth.

So what that conveys-- that these are places that have a lot of stuff and have a lot of people.

And the last variable is vulnerability.

Yes.

So how do you define vulnerability?

One of the things that we know is that the most vulnerable parts of our community are communities of color, elderly, children under five, and the poor, irrespective of color.

And so that's what this captures.

So one of the things that immediately jumps out to me is this region in the south of purple-- high vulnerability.

That's the well-known Black Belt of the South.

You also see areas of vulnerability in Florida that are likely tied to the elderly community that tends to retire in Florida.

Before we dive into the results of this map and learn what areas are most vulnerable to climate hazards, I wanted to explore how the models predict these extreme events will change as the climate warms.

One of the most obvious changes--temperature.

So, with global warming, we're seeing not only increases in average temperatures, or baseline temperatures, but also in extreme temperatures.

So we're seeing unprecedented instances of record-breaking heat.

Maiya: The Southeast and Southwest already experience extreme heat, but that heat is gonna get a lot worse in the next 30 years, with parts of Louisiana, Texas, and Florida experiencing over 100 days reaching over 100 degrees a year, and days over 125 degrees used to be virtually non-existent, but by 2053, large areas of the country are expected to have at least one day a year reaching that incredible extreme.

And at that temperature, a prolonged power outage could cause mass mortality.

J. Marshall Shepherd: We should not be surprised by the warmest summers on record, the warmest winters on record, or warmest year on record.

I think we'll see that story over and over and over again.

Maiya: If you Google "climate change," you get images of polar bears on melting sea ice, and you get images of drought.

A lot of people assume that a warming world means less water.

But as I've learned from talking to experts throughout the series, the future of precipitation is a lot more complicated.

In fact, for every degree of warming, the atmosphere holds 7% warm moisture.

With the exception of the Southwest, much of the country is expected to get wetter on average, but it's often the extremes that impact people in homes.

A 2024 study showed how extreme precipitation events are expected to get worse as the climate warms.

53 million people currently live in high-risk areas, but that number could double with two degrees of warming.

Daniel Swain: And so what we see is that the atmosphere not only can produce more extreme precipitation events but can also result in more intensive or faster evaporation when there's moisture available to evaporate.

Maiya: So that means both more rain and more drought, and while they are more difficult to model, hurricanes and wildfires are causing catastrophic damage in our warming world.

In the last decade, wildfires have caused hundreds of billions of dollars of damage across the West and parts of the Southeast, and hurricanes have devastated coastal communities.

And sea level rise will be a big threat along the whole Eastern Seaboard and the Gulf Coast.

But, of course, we don't all experience these hazards equally, and that's exactly what Marshall wanted to show in his climate-risk map.

The areas that are popping out to me--obviously, Florida.

Exactly.

California.

Yup.

The Gulf Coast.

Gulf Coast.

Let's talk about Florida first.

Very vulnerable to sea level rise, very vulnerable to heat, but also an elderly, aging population as well.

There's an envelope of temperature humidity that human beings are comfortable living in, and when we get outside of that, it causes heat risk and potential death.

We are seeing days or even weeks where temperatures and humidity combined are outside of that envelope of habitability for humans.

In addition, too-- Remember that exposure term we talked about, not only the people but the infrastructure.

This is sort of petrochemical alley, a lot of industry in here.

So when we bring that together, you get high risk.

Maiya, voice-over: We know that the deserts, Southwest and California, are vulnerable to drought, extreme rainfall, and water scarcity.

And extreme precipitation and flooding is also a big hazard in the densely populated northeast, but cities, Marshall found, were particularly vulnerable.

J. Marshall Shepherd: Let's use Atlanta.

Let's break this down.

Extreme flooding is not just the function of what falls from the sky as rainfall, but Atlanta also has a significant urban footprint in terms of impervious surfaces.

So what that does is when we get these more intense rainstorms, the rain falls, it doesn't infiltrate into the soil, it runs off rapidly into streams and creeks, and you get flooding.

And those surfaces are hot.

And so they absorb heat and reradiate that at night, and we get the urban heat island.

So in your opinion, what is the place that is most at risk?

This is a very skewed scale.

It goes from 0.5 to 20.

So South Florida, parts of the mouth of the Mississippi near New Orleans, and Los Angeles County, they're screaming at us for help.

I mean, I love this map.

It really drives home the fact that, I mean, adaptation and mitigation and resiliency is so important.

Absolutely.

And it's gonna continue to be important.

Because we're moving into the riskiest areas.

Yeah, we're there.

We're living this map.

[music] J. Marshall Shepherd: The map shows that climate variability and climate vulnerability is present in almost every county in the United States.

There's no safe haven to climate change, I would say.

Remember when we talked about the "business as usual" scenario, the one that could have been our reality if coal were still king?

Well, that's actually the scenario that Marshall based this risk map on, in part to give city planners a sense for what the worst-case scenario could be.

And that's important to consider when we look at these risk maps.

If we keep warming below two degrees, the extreme weather impacts will be so much less extreme than if we allow warming to reach four degrees.

Our number-one goal is to get to net zero carbon emissions.

And a lot of really smart people are working hard on making that happen.

So stay tuned for the next and final episode of the series, where we explore the most exciting solutions to get us out of this mess.

[music] ♪ You can watch the rest of Weathered: Earth's Extremes on the PBS app.

All six episodes are available to stream now.

♪