Thank you very much.

When I was a boy,

my parents would sometimes take me camping in California.

We would camp in the beaches, in the forests, in the deserts.

Some people think the deserts are empty of life,

but my parents taught me to see the wildlife all around us,

the hawks, the eagles, the tortoises.

One time when we were setting up camp,

we found a baby scorpion with its stinger out,

and I remember thinking how cool it was

that something could be both so cute and also so dangerous.

After college, I moved to California,

and I started working on a number of environmental campaigns.

I got involved in helping to save the state's last ancient redwood forest

and blocking a proposed radioactive waste repository

set for the desert.

Shortly after I turned 30,

I decided I wanted to dedicate a significant amount of my life

to solving climate change.

I was worried that global warming would end up destroying

many of the natural environments that people had worked so hard to protect.

I thought the technical solutions were pretty straightforward -

solar panels on every roof, electric car in the driveway -

that the main obstacles were political.

And so I helped to organize a coalition

of the country's biggest labor unions and biggest environmental groups.

Our proposal was for a 300-billion-dollar investment in renewables.

And the idea was not only would we prevent climate change,

but we would also create millions of new jobs

in a very fast-growing high-tech sector.

Our efforts really paid off in 2007,

when then-presidential candidate Barack Obama embraced our vision.

And between 2009 and 2015, the US invested 150 billion dollars

in renewables and other kinds of clean tech.

But right away, we started to encounter some problems.

So first of all, the electricity from solar rooftops

ends up costing about twice as much as the electricity from solar farms.

And both solar farms and wind farms

require covering a pretty significant amount of land

with solar panels and wind turbines

and also building very big transmission lines

to bring all that electricity from the countryside into the city.

Both of those things were often very strongly resisted by local communities,

as well as by conservation biologists

who were concerned about the impacts on wild-bird species and other animals.

Now, there was a lot of other people

working on technical solutions at the time.

One of the big challenges, of course, is the intermittency of solar and wind.

They only generate electricity about 10 to 30 percent of the time

during most of year.

But some of the solutions being proposed

were to convert hydroelectric dams into gigantic batteries.

The idea was that when the sun was shining and the wind was blowing,

you would pump the water uphill, store it for later,

and then when you needed electricity, run it over the turbines.

In terms of wildlife, some of these problems

just didn't seem like a significant concern.

So when I learned that house cats kill billions of birds every year,

it put into perspective the hundreds of thousands of birds

that are killed by wind turbines.

It basically seemed to me at the time

that most, if not all, of the problems of scaling up solar and wind

could be solved through more technological innovation.

But as the years went by,

these problems persisted and, in many cases, grew worse.

So California is a state that's really committed to renewable energy,

but we still haven't converted many of our hydroelectric dams

into big batteries.

Some of the problems are just geographic;

it's just you have to have a very particular kind of formation

to be able to do that,

and even in those cases,

it's quite expensive to make those conversions.

Other challenges are just that there's other uses for water,

like irrigation,

and maybe the most significant problem

is just that in California the water in our rivers and reservoirs

is growing increasingly scarce and unreliable

due to climate change.

In terms of this issue of reliability, as a consequence of it,

we've actually had to stop the electricity

coming from the solar farms into the cities

because there's just been too much of it at times.

Or we've been starting to pay our neighboring states, like Arizona,

to take that solar electricity.

The alternative is to suffer from blowouts of the grid.

And it turns out that when it comes to birds and cats -

cats don't kill eagles; eagles kill cats.

What cats kill are the small common sparrows and jays and robins,

birds that are not endangered and not at risk of going extinct.

What do kill eagles and other big birds,

like this kite as well as owls and condors

and other threatened and endangered species,

are wind turbines;

in fact, they're one of the most significant threats

to those big bird species that we have.

We just haven't been introducing the airspace with many other objects

like we have wind turbines over the last several years.

And in terms of solar,

you know, building a solar farm is a lot like building any other kind of farm:

you have to clear the whole area of wildlife.

So this is a picture of one third of one of the biggest solar farms in California,

called Ivanpah.

In order to build this,

they had to clear the whole area of desert tortoises,

literally pulling desert tortoises and their babies out of burrows,

putting them on the back of pickup trucks, and transporting them to captivity,

where many of them ended up dying.

And the current estimates are that about 6,000 birds are killed every year,

actually catching on fire above the solar farm

and plunging to their deaths.

Over time, it gradually struck me

that there was really no amount of technological innovation

that was going to make the sun shine more regularly

or wind blow more reliably;

in fact, you could make solar panels cheaper,

and you could make wind turbines bigger,

but sunlight and wind are just really dilute fuels,

and in order to produce significant amounts of electricity,

you just have to cover a very large land mass with them.

In other words, all of the major problems with renewables aren't technical,

they're natural.

Well, dealing with all of this unreliability

and the big environmental impacts

obviously comes at a pretty high economic cost.

We've been hearing a lot

about how solar panels and wind turbines have come down in cost in recent years,

but that cost has been significantly outweighed

by just the challenges of integrating all of that unreliable power onto the grid.

Just take, for instance, what's happened in California.

At the period in which solar panels have come down in price

very significantly, same with wind,

we've seen our electricity prices go up

five times more than the rest of the country.

And it's not unique to us.

You can see the same phenomenon happened in Germany,

which is really the world's leader

in solar, wind and other renewable technologies.

Their prices increased 50 percent during their big renewable-energy push.

Now you might think, well, dealing with climate change

is just going to require that we all pay more for energy.

That's what I used to think.

But consider the case of France.

France actually gets twice as much of its electricity

from clean zero-emission sources than does Germany,

and yet France pays almost half as much for its electricity.

How can that be?

You might have already anticipated the answer.

France gets most of its electricity from nuclear power, about 75% in total.

And nuclear just ends up being a lot more reliable,

generating power 24 hours a day, seven days a week,

for about 90% of the year.

We see this phenomenon show up at a global level.

So, for example, there's been a natural experiment

over the last 40 years,

even more than that,

in terms of the deployment of nuclear and the deployment of solar.

You can see that at a little bit higher cost,

we got about half as much electricity from solar and wind

than we did from nuclear.

Well, what does all this mean for going forward?

I think one of the most significant findings to date is this one.

Had Germany spent 580 billion dollars on nuclear instead of renewables,

it would already be getting a hundred percent of its electricity

from clean energy sources, and all of its transportation energy.

Now I think you might be wondering, and it's quite reasonable to ask:

Is nuclear power safe? And what do you do with the waste?

Well, those are very reasonable questions.

Turns out that there's been scientific studies on this

going over 40 years.

This is just the most recent study,

that was done by the prestigious British medical journal Lancet,

finds that nuclear power is the safest.

It's easy to understand why.

According to the WHO,

about 7 million people die annually from air pollution.

And nuclear plants don't emit that.

As a result, the climate scientist James Hansen looked at it.

He calculated that nuclear power has already saved

almost two million lives to date.

It turns out that even wind energy is more deadly than nuclear.

This is a photograph taken of two maintenance workers

in the Netherlands,

shortly before one of them fell to his death to avoid the fire,

and the other one was engulfed in flames.

Now, what about environmental impact?

I think a really easy way to think about it

is that uranium fuel, which is what we used to power nuclear plants,

is just really energy dense.

About the same amount of uranium as this Rubik's Cube

can power all of the energy you need in your entire life.

As a consequence,

you just don't need that much land

in order to produce a significant amount of electricity.

Here you can compare the solar farm I just described, Ivanpah,

to California's last nuclear plant,

Diablo Canyon.

It takes 450 times more land to generate the same amount of electricity

as it does from nuclear.

You would need 17 more solar farms like Ivanpah

in order to generate the same output as Diablo Canyon,

and of course, it would then be unreliable.

Well, what about the mining and the waste and the material throughput.

This has been studied pretty closely as well,

and it just turns out

that solar panels require 17 times more materials than nuclear plants do,

in the form of cement, glass, concrete, steel -

and that includes all the fuel used for those nuclear plants.

The consequence is that what comes out at the end, since its material throughput,

is just not a lot of waste from nuclear.

All of the waste from the Swiss nuclear program fits into this room.

Nuclear waste is actually the only waste from electricity production

that's safely contained and internalized.

Every other way of making electricity

emits that waste into the natural environment,

either as pollution or as material waste.

We tend to think of solar panels as clean,

but the truth is that there is no plan

to deal with solar panels at the end of their 20 or 25-year life.

A lot of experts are actually very concerned that solar panels

are just going to be shipped to poor countries in Africa or Asia,

with the rest of our electronic-waste stream,

to be disassembled,

often exposing people to really high level of toxic elements,

including lead, cadmium and chromium,

elements that because they're elements, their toxicity never declines over time.

I think we have an intuitive sense

that nuclear is a really powerful strong energy source

and that sunlight is really dilute and diffuse and weak,

which is why you have to spread solar collectors or wind collectors

over such a large amount of land.

Maybe that's why nobody was surprised

when in the recent science-fiction remake of Blade Runner,

the film opens with a very dark dystopian scene

where California's deserts have been entirely paved with solar farms.

All of which, I think, raises a really uncomfortable question:

In the effort to try to save the climate, are we destroying the environment?

The interesting thing is that over the last several hundred years,

human beings have actually been trying to move away

from what you would consider matter-dense fuels

towards energy-dense ones.

That means, really, from wood and dung towards coal, oil, natural gas, uranium.

This is a phenomenon that's been going on for a long time.

Poor countries around the world are in the process still

of moving away from wood and dung as primary energies.

And for the most part, this is a positive thing.

As you stop using wood as your major source of fuel,

it allows the forests to grow back and the wildlife to return.

As