[A provocation from Danny Hillis:]
[It's time to start talking about engineering our climate]
What if there was a way to build a thermostat
that allowed you to turn down the temperature of the earth
anytime you wanted?
Now, you would think if somebody had a plausible idea about how to do that
everybody would be very excited about it
and there would be lots of research on how to do it.
But in fact, a lot of people do understand how to do that.
But there's not much support for research in this area.
And I think part of it
is because there's some real misunderstandings about it.
So, I'm not going to try to convince you today that this is a good idea.
But I am going to try to get your curiosity going about it.
And clear up some of the misunderstandings.
So, the basic idea of solar geoengineering
is that we can cool things down
just by reflecting a little bit more sunlight back into space.
And ideas about how to do this have been around literally for decades.
Clouds are a great way to do that, these low-lying clouds.
Everybody knows it's cooler under a cloud.
I like this cloud because it has exactly the same water content
as the transparent air around it.
And it just shows
that even a little bit of a change in the flow of the air
can cause a cloud to form.
We make artificial clouds all the time.
These are contrails, which are artificial water clouds
that are made by the passing of a jet engine.
And so, we're already changing the clouds on earth.
By accident.
Or, if you like to believe it, by supersecret government conspiracy.
(Laughter)
But we are already doing this quite a lot.
This is a NASA picture of shipping lines.
So passing ships actually cause clouds to from.
And this is a big enough effect
that it actually helps reduce global warming already by about a degree.
So, we already are doing solar engineering.
There's lots of ideas about how to do this.
People have looked at everything from building giant parasols,
on to space, to fizzing bubble waters in the ocean.
And some of these are actually very plausible ideas.
One that was published recently by David Keith at Harvard
is to take chalk and put dust up in the stratosphere
where it reflects off sunlight.
And that's a really neat idea,
because chalk is one of the most common minerals on earth
and it's very safe, it's so safe we put it in the baby food.
And basically, if you throw chalk up into the stratosphere
it comes down in a couple of years all by itself, dissolved in rainwater.
Now, before you start worrying about all this chalk in your rainwater,
let me explain to you how little of it it actually takes.
And that turns out to be very easy to calculate.
This is a back-of-the-envelope calculation I made.
(Laughter)
(Applause)
I assure you, people have done much more careful calculations
and it comes out with the same answer.
Which is that you have to put chalk up at the rate of about 10 teragrams a year
to undo the effects of the CO2 that we've already done.
Just in terms of temperature, not all the effects, but the temperature.
So, you know, what does that look like?
I can't visualize 10 teragrams per year.
So I asked the Cambridge bio department and Taylor Milsal
to lend me a hand.
And this is a hose pumping water at 10 teragrams a year.
And that is how much
you would have to pump into the stratosphere
to cool the earth back down to pre-industrial levels.
And it's amazingly little, it's like one hose for the entire earth.
Now, of course you wouldn't really use a hose,
you'd fly it up in airplanes or something like that.
But, it's so little, it would be like putting a handful of chalk
into every Olympic swimming pool full of rain.
It's almost nothing.
So, why don't people like this idea?
Why isn't it taken more seriously?
And there are some very good reasons for that.
A lot of people really don't think we should be talking about this at all.
And in fact, I have some very good friends in the audience,
who I respect a lot,
who really don't think I should be talking about this.
And the reason is that they're concerned
that if people imagine that there's some easy way out
that we won't give up our addiction to fossil fuels.
And I do worry about that.
And it's actually a serious problem.
But there's also, I think, a deeper problem.
Which is, nobody likes the idea of messing with the entire earth,
I certainly don't.
I love this planet, I really do.
And I don't want to mess with it.
But we're already changing our atmosphere,
we're already messing with it.
And so I think
it makes sense for us to look for ways to mitigate that impact.
And that we need to do research to do that.
We need to understand the science behind that.
I've noticed that there's a theme that's kind of developed at TED,
which is kind of, fear versus hope,
or creativity versus caution.
And of course, we need both of those.
So, there aren't any silver bullets,
you know, this is certainly not a silver bullet.
But we need science to tell us what our options are
and that informs both our creativity and our caution.
So, I am an optimist about our future selves
but I'm not an optimist because I think our problems are small.
I'm an optimist because I think our capacity to deal with our problems
is much greater than we imagine.
Thank you very much.
(Applause)
Chris Anderson: Danny, you know we do have a real-life expert on clouds with us.
Do you mind if I invite her up onstage?
Kate, do you mind if I invite you back onstage?
We can have a conversation about this.
(Applause)
So, Kate, what did you make of Danny's talk?
Kate Marvel: Denny, you seem so nice and I hope we can be friends
and you terrify me.
(Laughter)
I am very worried about geoingeneering solutions
for many different reasons.
I feel like if I went to the doctor and the doctor said, "You have a fever.
I know exactly why you have a fever.
We're not going to treat that, we're just going to give you ibuprofen,
and also your nose is going to fall off."
I would be really upset and I would want a new doctor.
And I feel like dealing with climate change
by reducing the amount of sunlight we get
is really problematic.
Because there are physical reasons to be frightened by that.
For example, it's not going to do anything about ocean acidification.
And I care very much about the health of the oceans.
But I think -- I'm a physicist, but I'm also a human being and a citizen.
And I'm frightened as a citizen.
Because, I feel like, when I want to do an experiment,
I have to go to my university
and if there are human subjects, I have to obtain informed consent
from every single human subject.
And I feel like what you are proposing to do
is involving all of us as your human subjects
and I'm not sure I consent to that.
(Applause)
Danny Hillis: I sympathize with all of that.
And I think it would be great if we lived in a world
where people had to get their consent before messing with it,
but you are already in the middle of an experiment.
KM: And I'm not happy about that one, either.
DH: Right, I'm not, either.
People are already messing with the atmosphere.
And we don't really understand the effects of it.
So, we are geoingeneering.
And so what I'm arguing for is we should understand it,
we should do the research to understand it.
I'm not claiming it's secure, but it may be...
It may be something that we need
to help us cool down while we fix the problem.
And I don't think we can throw away any options now.
I think we really need to get the knowledge.
If we're going to do geoingeneering -- which we are going to do,
even if it's a bad idea --
we need to understand it and we need to do a better job of it.
CA: OK, this is the start of an incredibly important conversation.
Thank you, both of you, we're going to continue this.
KM: I hope we can still be friends.
CA: Thank you, thanks Denny.
(Applause)