So here's a thought.

The fossil fuel industry knows how to stop causing global warming,

but they're waiting for somebody else to pay,

and no one is calling them out on it.

I was one of the authors of the 2018 IPCC report

on 1.5 degrees Celsius.

And after the report was published,

I gave a lot of talks, including one to a meeting of young engineers

of one of the world's major oil and gas companies.

And at the end of the talk, I got the inevitable question,

"Do you personally believe there's any chance

of us limiting global warming to 1.5 degrees?"

IPCC reports are not really about personal opinions,

so I turned the question around and said,

"Well, if you had to fully decarbonize your product,

that is, dispose safely and permanently of one ton of carbon dioxide

for every ton generated by the oil and gas you sell,

by 2050, which is what it would take,

would you be able to do so?"

"Would the same rules apply to everybody?" somebody asked,

meaning, of course, their competition.

I said, "OK, yeah, maybe they would."

Now, the management just looked at their shoes;

they didn't want to answer the question.

But the young engineers just shrugged and said,

"Yes, of course we would, like it's even a question."

So I want to talk to you

about what those young engineers know how to do:

decarbonize fossil fuels.

Not decarbonize the economy,

or even decarbonize their own company,

but decarbonize the fuels themselves,

and this matters

because it turns out to be essential to stopping global warming.

At a global level, climate change turns out to be surprisingly simple:

To stop global warming

we need to stop dumping carbon dioxide into the atmosphere.

And since about 85 percent of the carbon dioxide we currently emit

comes from fossil fuels and industry,

we need to stop fossil fuels from causing further global warming.

So how do we do that?

Well, it turns out there's really only two options.

The first option is, in effect, to ban fossil fuels.

That's what "absolute zero" means.

No one allowed to extract, sell, or use fossil fuels

anywhere in the world on pain of a massive fine.

If that sounds unlikely, it's because it is.

And even if a global ban were possible,

do you or I in wealthy countries in 2020

have any right to tell the citizens

of poor and emerging economies in the 2060s

not to touch their fossil fuels?

Some people argue that if we work hard enough

we can drive down the cost of renewable energy so far

that we won't need to ban fossil fuels,

the people will stop using them of their own accord.

This kind of thinking is dangerously optimistic.

For one thing, renewable energy costs might not go down as fast as they hope.

I mean, remember,

nuclear energy was meant to be too cheap to meter in the 1970s,

but even more importantly,

we've no idea how low fossil fuel prices might fall

in response to that competition.

There are so many uses of fossil carbon,

from aviation fuel to cement production,

it's not enough for carbon-free alternatives to outcompete the big ones,

to stop fossil fuels from causing further global warming,

carbon-free alternatives would need to outcompete them all.

So the only real alternative to stop fossil fuels causing global warming

is to decarbonize them.

I know that sounds odd,

decarbonize fossil fuels.

What it means is,

one ton of carbon dioxide has to be safely and permanently disposed of

for every ton generated by the continued use of fossil fuels.

Now, consumers can't do this,

so the responsibility has to lie with the companies

that are producing and selling the fossil fuels themselves.

Their engineers know how to do it.

In fact, they've known for decades.

The simplest option is to capture the carbon dioxide as it's generated

from the chimney of a power station, or blast furnace, or refinery.

You purify it, compress it, and re-inject it back underground.

If you inject it deep enough and into the right rock formations,

it stays there, just like the hydrocarbons it came from.

To stop further global warming,

permanent storage has to mean tens of thousands of years at least,

which is why trying to mop up our fossil carbon emissions

by planting trees can help,

but it can only be a temporary stopgap.

For some applications like aviation fuel, for example,

we can't capture the carbon dioxide at source,

so we have to recapture it, take it back out of the atmosphere.

That can be done; there's companies already doing it,

but it's more expensive.

And this points to the single most important reason

why recapturing and safe disposal of carbon dioxide

is not already standard practice:

cost.

It's infinitely cheaper just to dump carbon dioxide into the atmosphere

than it is to capture it and dispose of it safely back underground.

But the good news is,

we don't need to dispose of 100 percent

of the carbon dioxide we generate from burning fossil fuels right away.

Economists talk about cost-effective pathways,

by which they mean ways of achieving a result

without unfairly dumping too much of the cost

onto the next generation.

And a cost-effective pathway,

which gets us to decarbonizing fossil fuels,

100 percent carbon capture and storage by 2050,

which is what net-zero means,

takes us through 10 percent carbon capture in 2030,

50 percent in 2040,

100 percent in 2050.

To put that in context,

we are currently capturing and storing less than 0.1 percent.

So don't get me wrong,

decarbonizing fossil fuels is not going to be easy.

It's going to mean building a carbon dioxide disposal industry

comparable in size to today's oil and gas industry.

The only entities in the world

that have the engineering capability

and the deep pockets to do this

are the companies that produce the fossil fuels themselves.

We can all help by slowing down our use of fossil carbon

to buy them time to decarbonize it,

but they still have to get on with it.

Now, adding the cost of carbon dioxide disposal

will make fossil fuel-based products more expensive,

and a 10 percent storage requirement by 2030, for example,

might add a few pence to the cost of a liter of petrol.

But, unlike a tax,

that money is clearly being spent on solving the problem,

and of course, consumers will respond,

perhaps by switching to electric cars, for example,

but they won't need to be told to do so.

And crucially, if developing countries agreed to use fossil fuels

that have been progressively decarbonized in this way,

then they never need accept limits on the absolute amount that they consume,

which they fear might constrain their growth.

Over the past couple of years,

more and more people have been talking

about the importance of carbon dioxide disposal.

But they're still talking about it

as if it's to be paid for by philanthropy or tax breaks.

But why should foundations or the taxpayer pay to clean up

after a still-profitable industry?

No. We can decarbonize fossil fuels.

And if we do decarbonize fossil fuels,

as well as getting things like deforestation under control,

we will stop global warming.

And if we don't, we won't.

It's as simple as that.

But it's going to take a movement to make this happen.

So how can you help?

Well, it depends on who you are.

If you work or invest in the fossil fuel industry,

don't walk away from the problem by selling off your fossil fuel assets

to someone else who cares less than you do.

You own this problem.

You need to fix it.

Decarbonizing your portfolio helps no one but your conscience.

You must decarbonize your product.

If you're a politician or a civil servant,

you need to look at your favorite climate policy and ask:

How is it helping to decarbonize fossil fuels?

How is it helping to increase the fraction

of carbon dioxide we generate from fossil fuels

that is safely and permanently disposed of?

If it isn't, then it may be helping to slow global warming,

which is useful,

but unless you believe in that ban, it isn't going to stop it.

Finally, if you're an environmentalist,

you probably find the idea of the fossil fuel industry itself

playing such a central role in solving the climate change problem disturbing.

"Won't those carbon dioxide reservoirs leak?"

you'll worry,

"Or won't some in the industry cheat?"

Over the coming decades, there probably will be leaks,

and there may be cheats,

but those leaks and those cheats

will make decarbonizing fossil fuels harder,

they don't make it optional.

Global warming won't wait for the fossil fuel industry to die.

And just calling for it to die

is letting it off the hook from solving its own problem.

In these divided times, we need to look for help

and maybe even friends in unexpected places.

It's time to call on the fossil fuel industry

to help solve the problem their product has created.

Their engineers know how,

we just need to get the management to look up from their shoes.

Thank you.