didn't change by more than 1 degree Celsius.

But then humans started burning fossil fuels,

around here.

Today, global temperatures have risen about 1 degree Celsius since pre-industrial times.

This is what that looks like so far:

Storms have gotten more intense,

wildfires are more common,

and ancient glaciers are melting faster and faster.

And that's just one degree of warming.

Without global action, the world is on track to warm at least 3 degrees Celsius by 2100.

This would be catastrophic.

That's why most scientists agree that we need to limit global warming to this range,

between 1.5 and 2 degrees Celsius.

Carbon dioxide, which is emitted when we burn fossil fuels,

accounts for most of the world's greenhouse gas emissions.

It's the main culprit behind climate change.

And to limit global warming to the degree that scientists are calling for,

we have to stop releasing it.

We have to “decarbonize.”

The US doesn't currently emit the most carbon dioxide of any country.

But as one of the oldest industrial powers, it's emitted more carbon dioxide in total

than any other country or region.

So America has a big role to play in decarbonizing.

But how is the US supposed to do that?

And is it actually possible?

If you want to get halfway there by 2030, you have to start now.

Now. Going fast.

There is literally zero more time to waste.

Dave writes about energy and climate for Vox.

And he says the 2020 US election comes with fairly clear stakes.

If Trump is reelected, that's it. Like there's no chance for 1.5.

And probably all chances for 2 degrees are gone.

“The United States will withdraw from the Paris climate accord.”

“...open up the coal mines.”

“...new offshore oil and gas leasing program.”

President Trump doesn't have a climate policy.

And his reelection will most likely continue policies designed to boost the fossil fuel industry.

They'd increase carbon emissions instead of decreasing them.

And the effects would be felt globally.

You just can't have the world's second biggest economy opting out,

moving kin the opposite direction, and expect the world to get there.

The other major candidate in the election does have a plan to address climate change.

And this part of it in particular is ambitious:

Biden has been convinced and pushed to the point that he's got a great climate plan.

What Biden's plan doesn't get into are the details on exactly how the US would actually do that.

But there are people who have thought about what it might look like to decarbonize by 2050.

And to understand that, it helps to get a picture of where America's energy comes from,

and where it goes.

[Scream]

Sorry, my son nearly stepped on a snake.

Do you want to say hi?

This is Saul Griffith. He's a physicist, and an engineer, but this is how Dave describes him:

Probably the person who knows more about energy as it's used in the United States

than any other human being.

A few years ago, Saul decided to make a model of America's energy use.

He ended up reading basically every available piece of data, from...

...the Energy Information Administration,

Department of Transportation,

the National Highway Transit Authority,

the Census Bureau,

Bureau of Labor Statistics,

and NOAA.

And so we pulled all of those together to build a very comprehensive picture of the US energy economy.

That picture of the US energy economy?

It looks like this:

If you're just looking at the whole thing at once, it just looks like a big pile of spaghetti.

It's hard to make sense of, but it just traces energy, every unit of energy.

How does it enter the economy? How is it used throughout the economy?

This kind of chart is called a Sankey diagram. And it's easier to understand in 3 sections.

These columns here on the left are the sources of all the energy used in the US,

like natural gas, coal, solar, wind, nuclear, and oil.

This column in the middle is what those energy sources get converted into.

So a lot of it becomes electricity. Most oil becomes the fuel we use for transportation.

And here, you can see how much natural gas energy is being used to generate electricity,

versus being used directly to power things like cooking stoves.

And over here on the right? This is where all the energy is used,

broken down into incredible detail.

Like how much energy is used to light shopping malls in the US.

Or how much energy is used by vehicles driven for work.

So you start to get this incredibly detailed picture of all of the interconnections,

which is really, really important when you do the next exercise:

what happens if we decarbonize?

Remember that carbon emissions come from the burning of fossil fuels. This stuff.

And Saul says that means that to decarbonize, we just need to follow their path.

The first place that leads you is here, with electricity and the energy we use to generate it —

the majority of which, in the US, comes from two kinds of fossil fuel: natural gas and coal.

If the US wants to decarbonize, it needs to stop getting electricity this way,

and replace it with other decarbonized energy sources.

That means coal power plants - gone.

Gas power — gone.

All electricity would come from renewable sources —

wind, solar, geothermal, hydroelectric, and biomass. Or, nuclear energy.

Decarbonizing the way we get electricity would be a huge investment.

But it would also only eliminate 20% of emissions.

And that's because electricity and energy are not exactly the same thing.

That doesn't solve vehicles' emissions.

It doesn't solve your heating emissions from using natural gas or fuel oil in your basement.

All these other parts of the economy draw their energy directly from fossil fuels.

Like transportation: We use oil for fuel.

And commercial and residential buildings, where we use gas and oil for heat.

But Saul says there's a kind of elegant solution to this:

you decarbonize these sectors by switching their energy source

from here, to here.

Make all of it electric.

Because we already have almost all of the technology we need to do it.

Heat pumps, batteries, electric vehicles, wind turbines, nuclear power plants.

We know that that can work. We know we can do electric cars.

We know we can do electric heat for nearly everything.

It's all in the end just about machines, right?

We've got a bunch of machines that use fossil fuel energy.

We need to replace them with machines that use clean electricity.

And so it really just comes down to a matter of industrial capacity:

How fast can you build machines?

There are some things we'd have a harder time decarbonizing.

Air travel will rely on fossil fuels until alternative technologies get better.

And things like steel and concrete are really hard to manufacture without fossil fuels.

But if we decarbonized as much as possible with the technology that we have now,

it would end most of the US's carbon emissions.

This chart shows the country's carbon emissions broken down by economic sector.

If electricity, residential, commercial, and transportation were mostly decarbonized,

you'd have solved a lot of the problem.

All of this would be a huge undertaking. And it needs to happen fast.

Saul's research modeled different scenarios

for the transition from fossil fuel-based machines to electric ones:

From a market-driven transition, to carbon taxes,

to a much more direct and heavy-handed approach that would replace our machines with

their electric counterparts very quickly.

And he found that because we've delayed action for so long,

none of these slower approaches will be enough.

If you went back to 2000 and started then, you could just put like a modest carbon tax in place

and it would have just eased us down over the course of 30 years or whatever.

But emissions kept rising and rising and rising.

So now to get where we need to go, they got to fall off a cliff.

And that means zero delay.

We're just talking about a level of industrial mobilization that none of us alive have seen.

It would look like what FDR did to prepare us to prepare the US for war.

Literally, every single solitary fossil fuel machine that goes out of service

is replaced by a clean energy alternative.

Every furnace, car, factory, you name it.

Nearly everyone is buying an electric vehicle,

nearly everyone is buying rooftop solar, nearly every new power plant that comes online is

industrial scale solar, or industrial wind.

We need that level of effort to do a lot better than two degrees.

All of recorded human history has happened within an era of relative climate stability.

An era that's about to end.

But we still have control over what comes next.

And the global effort that'll require hinges in part on what the US decides to do.

America can decarbonize. We have the technology to do it. We have the resources.

The only question is whether we want to do it.

I have a six year old and an eleven year old, and I have to believe that's going to happen. Otherwise..

And I have to try to make that happen,

as long as possible,

because it's their future we're stealing by not doing it.

Thanks for watching this episode of our 2020 election series.

We're focusing on the issues that matter most to you. And we got this topic requested by a lot of people.

We want to know what you think the candidates should be talking about.

Tell us at Vox.com/ElectionVideos.