In this video
We're going to talk about a highly controversial
Subject the idea that we can deliberately change the world's climate to combat the effects of global warming and this idea is called geoengineering
And in addition to this video which is going to focus more on the physics of how geoengineering works
I highly recommend that you check out my friend feathers video series on the subject
he's been doing a whole bunch of different videos on different techniques that we could use to this end and
Go check them out because they're pretty awesome. And I've been doing a little bit of work on them fact-checking samba Suns so
Yeah, they're pretty cool
Last time we
Extensively looked at global warming and climate change and found that the observed warming over the past century or so is directly linked to co2
levels in the atmosphere now
The more carbon dioxide there is in the atmosphere
The less energy that the earth emits into space
causing an energy imbalance which results in the earth
Warming now that description of global warming suggests two different solutions to the problem
So let's look at those one at a time solution 1 the energy imbalance
Which is causing the warming is itself caused by carbon dioxide in the atmosphere
So to reduce the amount of warming, let's remove carbon dioxide from the atmosphere
solution to
The earth is emitting less energy into space than it used to while the amount of energy that it receives from the Sun has remained
constant
Ish, so to remove the energy imbalance
Let's reduce the amount of energy that the earth is absorbing from the Sun now both of these solutions
Probably ranked on the plausibility scale whew somewhere between impractical and absolutely insane
But a huge amount of research has been done on the subject and it's more possible than you're probably thinking
Now one of the people doing the research on the subject is my colleague Angus Ferraro
Who's an associate research fellow here at the University of Exeter?
And I interviewed him all about the topic so over trying this to talk about the first of these solutions
So that's the easiest thing to do that's probably what people would say is like well, why can't we just create a giant
Some kind of catalytic thing that will just you know blow air through and suck carbon dioxide out
Of the air and in in theory that's quite possible and it can be done right now. In fact, it's being done right now
There's there are some companies that
Construct these kind of weird wonderful machines that do this
It's a really cool one
it basically looks like a giant Bank of jet engines and all its doing is blowing air over this stuff which chemically removes
Co2 from the atmosphere
The main problem with that is that the energy requirements for something like that are very very large and that makes it very expensive
Some of the more weird wind wonderful proposals for this kind of thing would be okay
So we need somewhere with abundant cheap energy
But it doesn't really matter where it is
other than that because co2 is well mixed around the atmosphere as long as it has access to air then it can remove co2 so
People propose. Ok, we'll just have these entirely automated
installations and deserts with huge solar panel arrays all around them to satisfy the power requirements, but
Anything on this scale is going to be very very expensive
So if we think about the sheer mass of co2 that we need to draw down Giga tons and Giga tons of co2 that
Would be very expensive no matter how you set up your energy supply system
So at the moment co2 moving in the atmosphere just isn't feasible on the scale that we're talking about
but it's definitely definitely worth researching and hopefully sometime in the near future new technologies will allow it to play a
Significant role in cooling the climate, but what about solution number two?
Right, so we should think about what's going on with the energy balance of the earth at the moment
What's happening is carbon dioxide is reducing the amount of radiation that the earth is emitting to space
So that means we've got a imbalance of energy at the top of the atmosphere and at that's causing the plant to warm up
So we need to bring that energy balance back into balance
And one way to do that is just to reduce the amount of energy coming in so that then produced amount going out
There's balance by a reduced amount coming in and so to do that we to try and essentially dim the Sun
A couple of ways we might be able to do that one, which is extremely expensive and probably not going to happen in them
well in this century is
To launch a constellation of satellites and space basically just stick it in between the earth and the Sun
And so what this would do is basically reflect a small percentage of the sun's radiation
the only use needs to be about 1/2 percent to achieve the kind of
Cooling's of a tenth of a degree or something that we'd want to achieve
so
You could stick some satellites in space and do it that way but sticking everything in space is really expensive
So that probably isn't going to work
Most of the ideas grouped under solar radiation management use what we refer to as aerosols
Yes, so when people think aerosols they think the spray can stuff, right?
What you use?
forever
and that's not 100% far from the truth because when we talk about aerosols and atmospheric physics
We talk about tiny tiny particles in the air, but we made up a better thing so they could be
small amounts of
Software AG acid droplets of sulfuric acid or they could be bits of carbon bits of SERPs
There could be various organic compounds emitted by plants the things that these
Aerosols have in common is that they interfere with the flow of radiation and the energy?
going in out of the
System. So these aerosols then act me the earth more reflective
Reducing the amount of energy that we absorb from the Sun and so reading the energy balance and this happens in nature already
So let's move a can actual processes only makes sense just on a bigger scale to produce a significant effect
so there were 1 we could mimic volcanic eruptions which basically emits in fact
They basically produce sulfuric acid aerosol. And yes in the stratosphere in this opera cassada aerosol acts like a cooling haze
Which reflects some sunlight?
Or we could mimic things like ship tracks which enhance the brightness of clouds
Way down near the surface
when you look at a satellite image of the ocean and you can
Okay, so if you look at a satellite image of the ocean and then you track where the ships go you can see these kind
of white
Whiter regions where they go through the clouds and the particulates they produce from their chimneys
Basically brighten the clouds there. So we end up with brighter marine clouds, and this would also reflect
Space most research has concentrated on the first of these two ideas and more specifically has looked at the effects of
injecting additional aerosols into the stratosphere
Now as well as being dynamically more stable than the troposphere below it
The stratosphere has the advantage of being almost completely dry
So aerosols injected there would stay airborne much longer than they would in the troposphere where they would just get rained out now somewhat
unbelievably
This is where this comes in because we're not just limited to injecting sulfuric acid as an aerosol
we could inject anything into the stratosphere that produces a similar effect and what our soul has received a lot of attention in particular is
titanium oxide
Titanium titanium dioxide otherwise known as titania is
Another well, so you could make an aerosol out of it. It's not an aerosol
We find in great quantities around the atmosphere at the moment
Because it's basically a mineral it's called rutile mostly and it's actually surprisingly cheap
So everyone thinks titanium is like this really expensive stuff. Titanium is titanium. Dioxide. Is this dirty or that you find?
around the globe
The advantages it's incredibly reflective
So it's used in food a lot things like toothpaste
Things like aspirin and all your other white tablets to get that nice white shininess. They use titanium dioxide
so it's a 171 I think is the additive number and
yeah, in theory you could grind it up and spray it into the atmosphere and achieve a similar cooling effect to
sulfate, but with this solid particle that you can
Control a lot better and is obviously a lot more benign than cell Varick acid
Geoengineering has the potential to reverse some of the worst environmental damage that we're doing to the planet
But doesn't fundamentally address the root cause of the problem co2 in the atmosphere. And in addition to this it has some downsides
one of the fundamental downsides of
using geoengineering in this manner solar radiation management to
Counteract the global one from co2 concentrations is that if you even if you were to do it perfectly
Exactly cancel out the global average temperature change you would end up reducing
global precipitation
And that's something so there is there are some results in climate science that we're less sure of we're very sure of this reduction in
Precipitation it basically comes from the way that co2 affects the radiation balance of the atmosphere relative to the way
Solar radiation does basically solar radiation doesn't get absorbed by the atmosphere. Whereas co2 does this leads to a different differential
Atmospheric heating between the surface and the top of the troposphere
That affects the way rain is formed. Basically you end up with a reduction in global precipitation
Of course, no one ever experiences global mean precipitation. So it's very hard to say what will happen on a more regional scale
so we tend to run some climate model experiments of that and
The general consensus is among
The climate models is that probably there will be some regional changes in patterns of precipitation and bands of warm and cold
regions under geoengineering
But that actually the regional changes will probably be smaller than the ones that you would get under an unmitigated global warming scenario
So although there will be regional changes if you think about the regional changes that you might be seeing in the future anyway
And that might not be so bad
as for the big question of whether or not we will use
Geoengineering is not for me to say I am just a Finnish D student, and I don't know everything personally
I don't think that we're going to use solar radiation management anytime soon
There's just too many question marks associated with it at this point
But I hope that we can use co2 and weevil in the very near future
with new technologies now for more information about this and the ongoing debate about use
Geoengineering stay tuned to the channel because very soon there's gonna be video coming out about whether the cop21 climate meeting in Paris this December
Should consider the use of geoengineering. We're a bunch of world leading academics from X to chime in
So you didn't see much mean this video which is probably a good thing
Instead angus covered what geoengineering is deliberately changing the Earth's radiative properties
Co2 removal in the atmosphere which we'd like to do, but we can't really do it because it's not practical yet
solar radiation management which is practical but we're not quite sure if we'd like to do it yet and
the many issues involved in using these techniques
this was the last video in this crash course series on atmospheric physics and I very very much hope that you've enjoyed it and
If you've watched many or all of the episodes that you now feel you've got a firmer grasp of the basics of the field
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Thank you very much for watching
Okay. So here's my workbook. It's important. We're good. It's a book
I like books and it's got to work in that's my laptop, which has got the scripts with crash course videos
And that's my Japanese piece Lily always important to keep that around because it keeps the our oxygenated
This is not the time to change signees
Interesting thing but it's off believe, you know, when you're in a negotiation say you're buying a t-shirt or market store