Our home planet is a complex and dynamic machine.
Its land, ocean and atmosphere provides everything that we
humans need to thrive.
But now, human activity is throwing the planet's finely tuned
systems out of balance. But what are these systems?
How does the Earth work? And how can we live sustainably on Planet Earth?
APPLAUSE
Welcome to this year's Royal Institution Christmas Lectures.
This year has been a bit different,
so we're going to have to do things a bit differently.
That's right. For the first time
since 1825, when Michael Faraday created these lectures, we're not
going to have a live audience here in the theatre with us,
but Faraday would be amazed to know that we are joined by children
watching from their homes and their schools all over the UK and Ireland.
It's a virtual audience that will rotate as we go through
the lectures. So, hello and welcome. Give us a wave.
And that's not the only thing we're doing differently this year.
This year, we have combined our expertise so that between
the three of us, we can cover a subject as big as the Earth itself.
So, you'll next see me in lecture two,
where we'll be talking about the oceans.
And with me in lecture three, we'll be looking at the atmosphere.
I'm Chris Jackson and I'm a geologist and in my lecture,
I'm going to show you how the Earth's climate has changed over
billions of years in response to an amazing array of natural processes.
And by doing that, we can then maybe better understand how
the climate could change in the future.
So let's go back to the beginning.
4.5 billion years ago was literally hell on Earth.
200 degrees Celsius, that's four to five times hotter than
the hottest place on Earth today.
So how did we go from that to the place we now call home?
Well, to show you, I need you to join me on a 100 metre long journey
around the Royal Institution, where every step will be 50 million years.
We'd better get a move on.
Back then, there would have been no life-giving oxygen
in the atmosphere. Instead, it would have been
a poisonous soup of carbon dioxide, methane and ammonia.
This would have been a tough place to live.
But then, about 3.8 billion years ago...
..the oceans formed and life appeared.
Stromatolites were a trailblazer.
These tiny microbial critters not only coped with the boiling
temperatures and the toxic gases, but they were able to take
carbon dioxide and turn it into life-giving oxygen.
But for 2.25 billion years, until the end of this corridor,
there was still hardly any oxygen in the atmosphere...
..until the Great Oxygenation Event
when some sun-worshipping bacteria learned to take CO2 out
of the atmosphere, producing food with oxygen being the waste product.
But the Earth's climate was restless.
Sometimes, it was Snowball Earth,
other times literally Club Tropicana.
And then, at other times, almost nothing
during the so-called Boring Billion.
But one billion years ago, things got really exciting.
Sponges appeared and single-celled organisms gave way to complex
multi-cellular life that we now know as animals.
Life finds a way.
And then, 541 million years ago, the Cambrian explosion,
an eruption of life inside and outside the oceans.
Animals, plants, flowers.
But then, 252 million years ago, 75% of all species went extinct.
Life is never easy.
And out of the ashes, new and more complex life evolved.
Dinosaurs came...and went.
The flightless ones, anyway.
Primates appeared. And then, 200,000 years ago, Homo sapiens emerged.
And after our 100 metre long journey around the Royal Institution,
all of civilisation can fit on the width of a single human hair.
And we now occupy every corner of the globe and we've become
so dominant, we've started to influence the Earth's system
and the life on it.
We've defined a new geological epoch, the Anthropocene.
And in only 200 years,
the Earth's population has gone from around one billion to more
than seven billion, and this global presence has had a truly global
impact and we've actually started to change one of the most fundamental
things on the Earth, the atmosphere, driving changes in our very climate.
So we've talked already a lot about climate,
but how does that differ to the weather?
Well, the weather describes things like temperature and, say, rainfall.
Effectively, weather tells you what to take out of your wardrobe.
Now, you've been waiting very patiently,
so I would like to come and ask you -
what do you think the weather is going to be like tomorrow?
I'm just coming up to this screen here and I am going to ask Aasmah...
What do you think? Do you think it might be rainy or snowy, or...?
What do you think it's going to be like tomorrow?
I think it's going to rain.
You think it's going to rain, brilliant.
OK, let's go and see, because I happen to have a magic wardrobe.
Let's see if it's going to rain today. Or tomorrow, sorry.
Oh, my word, Aasmah! You got it right, look.
You are perfectly prepared.
You know, rain jacket, umbrella. Thank you so much.
OK, that's one out of one. Let's go back up here. Who have we got?
Constancia and Alanah, what do you think?
It will probably be relatively frosty in the morning
because it's December. Thank you, Constancia.
So, frosty because it's December, and that makes sense, doesn't it?
So, let's see what we've got in our magic wardrobe.
Oh, dear, Constancia and Alana!
I don't think this person is ready for the frosty December weather.
I don't think you'd make it to the end of the day.
Thank you so much.
So you can see why we as Brits love weather forecasts,
cos the weather's always changing. And climate is kind of like weather,
but think of it as the average of weather.
It doesn't tell you what to take out of your wardrobe,
it actually tells you what to have IN your wardrobe.
And that's important, cos in the UK, where it's quite mild,
I can get away like I'm dressing today.
You know, kind of jeans and T-shirt, nothing to worry about.
But the climate does change, more slowly, but it does change.
And if you want to think about that, it's useful, I think,
to think, well, OK, I'm going on a holiday to a beach next...
..let's say next year.
I might want to wear shorts, flip-flops, a sun hat.
Yeah, get ready for that hot day.
But what about going to the same beach 60 million years ago?
You know, what would it be like then?
And as a geologist, this is where I get very, very excited
cos it's a chance to read the rock record and the fossil record.
What we have here are some cores of rock
and these are about a metre long, each core in here.
And these have been obtained by drilling down a couple
of kilometres below the seabed offshore Scotland.
These rocks span an age range of about 150 to 350 million years.
So let's take this core in here.
You can see these different changes in colour.
There's different layers of colour. And they're different types of
sediment, different grain sizes, different compositions.
And those changes in the grain sizes
and the composition of the rock tell us
about things like climate changing and tectonics, mountain building,
all of these geological processes are coded into these rocks.
But when we're thinking about climate, it's not the rocks
themselves we're really concerned with, it's what's inside the rocks.
And specifically, we're interested in their fossil content.
If we come over to this microscope on here, you can
see these are the sorts of fossils we sometimes find in rocks.
These little delicate things in here,
which are so small we're having to magnify them, are called
foraminifera and these foraminifera, you can see in here,
they not only existed in the ancient oceans,
but they also exist in the modern oceans.
And these animals, you know, they build this shell,
this hard shell, to protect themselves.
And in that shell are a number of different elements, you know,
they've got different chemistries,
but two of the really important elements...
..or one of the important elements that are in those shells is oxygen.
And oxygen comes in different types, different flavours.
We have here a white oxygen 16, which is
a lighter oxygen isotope, and we have a heavier blue oxygen 18 here.
How is that recorded in the shells of those creatures
we just looked at under the magnifying glass?
So to show you that science, we have spared no expense for you.
We have created this beautiful, ancient ocean,
which I'm just going to slide forward here.
And it looks just like an ocean, of course.
And in this ocean, we have both the lighter oxygen 16s,
the whites, and the heavier oxygen 18s, the blues.
And we're going to simulate heat here to see how these react
differently to the warming of the oceans in a relatively cool climate.
And you can see those isotopes are jiggling around and...
Whoops! There goes an 18. And there goes a 16.
You see, I'm doing quite a good job of keeping these naughty
isotopes together, bouncing around. And you see they're evaporating off.
Now, what we can see is out of there, what
we typically find evaporating out are these lighter white oxygen 16s.
And the critical thing that happens to them is they go to higher
latitudes, towards the poles, where they are trapped inside ice sheets.
So these oxygen 16s get trapped inside the ice sheets
and that means our ancient ocean, as you can see here,
is now relatively enriched in the heavier oxygen 18s.
Now, what does that mean for our foraminifera?
If it's growing in that sea, when it's relatively cool,
that means that foraminifera will be enriched in the blue oxygen,
heavier 18 isotopes, with less of those 16s.
Now, what happens if we warm the ocean?
So let's warm the whole planet. We melt the ice, OK?
So we can have the ocean still here and then we have...
Remember, we have this big ice sheet in here, containing all of that
trapped oxygen 16 and it all just gets dumped back into the ocean.
And you can see them all jiggling around in there.
So you can now see by doing that, we've changed the ratio,
the relative abundance, between those two isotopes,
meaning that the foraminifera that is growing at that
time in the ocean, when it's relatively warm,
will have relatively more of those lighter oxygen 16s,
so hopefully, you can
see there those two foraminifera will have coded into those
shells that different ratio of hose oxygen isotopes.
So although these shells are really tiny, and we had to magnify them,
they are these amazing messengers of temperature from deep time.
And if we study lots of rock layers with lots of those different
fossils and do that chemical analysis on those shells, we can
actually build up a relatively clear
and accurate picture of how climate has changed through time.
So I've come over to this graph here and what I'm showing you on this
lower axis, this is the X axis here. Let me just pull that out for you.
That's about 550 million years of time.
So 550 million here, going through to today.
And on the Y axis here, this is temperature.
And the temperature here goes from about 10 to 35 degrees at the top.
So that's the temperature range against time.
And the yellow is our trace of how that temperature's changed
through time. And when we draw out that temperature plot,
using the information from our forams,
we get this really amazing and complex curve.
This period here, a long time ago, where it was kind of warm.
There were periods here...
..when it was relatively cool.
And there's periods of these big swings,
these big and relatively abrupt, sharp changes in the temperature.
And this is the temperature now.
So the really clear thing, the picture that's
painted from that is the climate has changed through time.
It's quite a dynamic thing.
So now we've thought about the what, we now need to think about,
as a scientist, the why. What is driving these changes
in the temperature and the climate?
Well, one really obvious thing to think about would be the sun.
So the sun is the very thing that heats the Earth,
so if the changes in the sun's output of heat was varying
through geological time, maybe that could explain it,
but we know that the sun's heat output has overall just
increased steadily through time. So, with you, that is
our mystery to solve during the course of this lecture, the why.
So to start this investigation, I think
it's simplest to just think about what's around us.
What are we surrounded by?
We're surrounded by the atmosphere and to help us
understand the atmosphere, I would like to welcome Dr Tamsin Edwards.
APPLAUSE
Hello, Tamsin. How are you? I'm very good, Chris. Thank you.
Good, good. Well, I heard you know a little bit about the climate.
That's right. I'm a climate scientist,
so I use computer models to predict future climate change. OK.
And so you must be thinking about all of the different
components of Earth and, you know,
we're really interested in the atmosphere at the moment,
so how does that feed in to understanding the climate? Exactly.
The atmosphere is THE most important part of the planet
when it comes to climate change, as we're going to see. OK.
There's kind of all this amazing equipment here, but I can't quite
understand how this could ever tell us
anything about the atmosphere, so what are we looking at here? I know.
Well, this archaic bit of kit, I'm so happy to tell you,
is a really, really important and historic experiment
and it was built 161 years ago by a man called
John Tyndall in the basement laboratory of the Royal Institution.
And he was wanting to understand how gases of the atmosphere worked,
so we've got lots of different pieces here,
it's not set up as an experiment.
So, what about this kind of long thing here?
So, that's where he held the gas, so the gas that he was going to study.
He looked at oxygen, nitrogen, hydrogen, carbon dioxide,
water vapour, ozone, chlorine... Lots and lots of different things.
And he put the gas inside the tube.
We've got a cube here which is the heat source,
so he put boiling water in there as a nice constant heat source.
So then... There's this kind of peculiar thing facing towards me,
which looks like a double ended microphone or something.
OK, so all the pieces down your end are basically
at the time the state of the art of measuring temperature changes.
So he put that at the other end of the tube.
I think I would learn a huge amount if we could actually recreate
the experiment, but I think we'd get told off by the RI if we try and...
It's very fragile and very special, so instead,
we're going to create a modern version of this historic experiment,
which was one of the founding experiments of climate science.
Tyndall was a Director of the Royal Institution and actually,
he gave many of the Christmas lectures.
He first showed his results to the public just like we're doing
now, so we've got a nice big tube here, much bigger than his.
That's going to represent our atmosphere.
So at the moment, all it's got in there is just ordinary air.
We've also got a heat source. Ours is a little bit... Low tech.
A little bit more low tech than Tyndall.
So we've just got a candle here.
OK. OK, so you've got to imagine you're out in space... OK. OK.
So the heat source here is to represent the Earth
because the Earth's surface is always emitting heat
and when things are warm, they give off infrared radiation.
So what you've got there is an infrared camera for measuring
temperature changes.
OK, so what kind of temperature is it showing now?
So, the maximum temperature we've got in there is about 21 degrees.
It's fairly steady, yeah. OK.
All right. So what we're going to do is light the candle... OK.
..just to see how it looks with the ordinary air inside, OK?
It's already jumped up from when you lit it,
so it's climbed to around about 50 degrees.
It's kind of changing quite a bit. I guess the candle's flickering.
It's quite variable. In fact, probably not as constant
a heat source as Tyndall's actually. So it's kind of varying around...
And that infrared camera is telling you that maximum temperature
there of... What was it?
About 50 degrees, it's kind of climbing a little bit, yeah.
OK, so that's the ordinary atmosphere. What we're going to do
is we're going to test another gas that we're going to put into
the tube and we're going to see what effect that has,
because what your infrared camera is doing is it's measuring how
much heat is getting from the Earth through the atmosphere
and escaping out to space.
So we want to see what this gas does.
So I think we've filled up the tank, so we've changed...
We've changed the atmosphere, so what can you see?
So, we've seen a decrease in temperature.
We've kind of gone down, we've bobbed down to about 40 degrees
and it's kind of scooting around there. So we've seen about
ten degrees or so... It's made a big difference, exactly,
because what you're seeing is that
the gas in the tube is absorbing infrared radiation from the candle,
so less is getting out to space to you. Yeah.
And that basically means that on our planet, on the Earth, that is
heating up the atmosphere, it's heating up the planet
because less heat is getting out to space.
So we've just demonstrated what Tyndall first showed, is that
some types of gas have this really special effect on infrared radiation
and they absorb it and they stop it from getting out to space.
I mean, you're teasing me in this investigation, of course,
because we keep saying "mystery gas"... Mystery gas.
And I think it's time to reveal actually what
we put inside our atmosphere, so I'm just going to take this off.
And we have... Ta-da! ..methane. Exactly.
So, methane is a really important greenhouse gas.
It's produced naturally on the planet,
but human activities are increasing it in the atmosphere as well.
So methane is one of many different types of greenhouse gas
that we have in the atmosphere and it's important to
remember that we need them to live. They're really important to us
because if we didn't have any greenhouse
gases in the atmosphere, the average temperature of the planet
would actually be minus 18 degrees Celsius.
So, significantly colder than today. Way too cold.
So we need greenhouse gases, but what's happening at the moment
with climate change is basically a little bit too much of a good thing.
OK. So, thank you so much, Tamsin. Thanks, Chris.
APPLAUSE
So, thanks to Tamsin, we're getting somewhere with our investigation.
I feel like we've made a really big breakthrough in the case,
because it seems like greenhouse gases in the atmosphere
are a really important player in this.
They play a very important role in controlling the temperature and the
climate, but like Tamsin said,
there are quite a few greenhouse gases, but which one is it?
Which one is the big boss, driving everything?
So, to help me with that, I've hired some gas detectives
from Biddenham International School and Sports College.
You can see the kids here, they're hard at work,
trying to bring to life both the chemistry of these different
greenhouse gases, but also, you know,
some life to those gases as well.
And you can see there, maybe they've got some evidence for me
in this climate case and... Oh! OK! Thank you.
We have some evidence, that's been delivered from the hardworking
pupils, so let's see what they've... What they've got for us here. Ah!
OK. These look like some suspects. Methane.
And we looked earlier on at methane in the John Tyndall experiment
and methane is a real kind of major greenhouse gas, a real bruiser.
It's an enforcer. You know, if you've got a crime ring,
this would be the one you send out, but actually,
methane doesn't hang around in the atmosphere for that long.
A few tens of years.
And it actually gets broken down to carbon dioxide,
so I don't think methane is actually the kind of ringleader.
We've still got here on the board, you know,
some other kind of characters here, still working for the big boss.
Who else do we have?
OK. Water.
And yeah, we know, we talked about that with the experiment earlier on.
Water is a greenhouse gas. And that sort of makes sense, doesn't it?
Cos when it's a cloudy night, it's kind of warmer,
and when it's a clear night, it gets a lot colder.
But water's not always in a gas phase.
Sometimes when it's cold, it's a solid, it's ice,
and when it's warmer, it's a liquid phase.
So it's not always a gas, so I don't think water vapour is,
you know, the kind of main ringleader.
I think it just does what the big boss tells it to do.
Ah! This scary character here, ozone. And you've probably...
Some of you have heard of ozone?
But ozone's a tricky greenhouse gas because it works in two ways.
In the lower atmosphere, ozone is indeed a greenhouse gas,
but in the upper atmosphere, we need ozone because it actually
reflects back otherwise harmful UV radiation coming in from the sun.
So if you think about it in terms of a crime case,
this would be your informant, ozone.
You know, it's working for both sides.
So I don't think ozone's what we're after.
And then we have this scary character here,
carbon dioxide. You see with carbon dioxide here...
You know, carbon dioxide makes sense, remember,
because the stromatolites at the start of the lecture,
they said they saw you at the start of time, the very beginning.
And actually,
if you look at how carbon dioxide has changed in the Earth's
atmosphere over geological time,
we can see that it's kind of varied quite a lot.
There's been periods when it's been very low and periods
when it's been relatively high.
And that becomes really, really kind of important when we compare
the changes in carbon dioxide through time with
the changes in temperature
and we see the times of high carbon dioxide relate to these
times of relatively high temperature and these times of low carbon
dioxide relate to these times when the temperature was relatively low.
So, you can see that the...
..that correlation isn't perfect and that's probably
because of multiple reasons, one of which could be the sun,
the changes in the heat output of the sun,
cos it's the heat output of the sun that warms the Earth.
And like I talked to earlier with Tamsin,
there are other greenhouse gases as well,
so it's probably more complicated than simply carbon dioxide.
But it's clear there's quite a strong connection there,
so I think carbon dioxide could be
the big boss that we're after. Now, carbon is all around us.
Carbon is in the atmosphere, it's in the oceans
and it's in the earth beneath our feet.
So, how does carbon move around between all of those carbon stores?
How does it get from one place to another?
And therefore, how can it influence the climate?
Well, to show you, it's Christmas and when I was little,
I always wanted a marble run,
so I think I can combine my desire to find out why the climate
has changed in geological time with this fantastic creation here.
So, here we can see this marble run
and these white balls being brought up here, they are our carbon.
And we see a number of different locations on this marble run.
The first location up here is represented by these clouds
and this is the atmosphere and if I remove that, you can
see the carbon building up in the atmosphere.
We then move down into this location here, we see this water,
and this is the oceans.
And so we can see there's a store of carbon here in the atmosphere
and the oceans. It looks like quite a lot.
But actually, only 0.002% of the total amount of carbon on Earth,
about 44 gigatons, is above ground.
The rest of it, 99.998%, about 2 billion gigatons, is down here,
in the deep earth and you can see that huge store down deep in here.
So the question becomes,
how do we move carbon from the deep earth store up into the atmosphere,
such that it can influence the climate?
So, what is, geologically speaking, this lift?
Well, I'm really pleased to be able to point
the finger at something that I have been fortunate enough to be
able to work and play around for many years, volcanos.
And if we look up here,
this is a picture of me in a place called Nyiragongo in the Democratic
Republic of Congo in front of the world's largest lava lake.
It's truly spectacular.
And there's a lot to see around volcanos.
In addition to lava lakes, as you can see by this volcano here,
there's gas coming out of it, there can be ash,
there can also be lava coming down the front as well.
So there's lots and lots of geological processes
associated with volcanos.
But it's Christmas and this is no ordinary volcano.
This is a Royal Institution Christmas Lecture volcano
and we know one thing about those is they always erupt.
Ooh! Wow, so that was another spectacular eruption
here at the Royal Institution.
But there is a hidden piece in our climate puzzle.
So what you can see in the back over there, there's a special camera and
you're seeing an image of me now,
but what's really important here is, if you can see at the top,
I'm just pointing, you can see me very clearly.
It's like a dark colour coming out of the top of the volcano.
And that's because volcanos, between eruptions, keep puffing out gas.
They keep puffing out things like methane and carbon dioxide,
so these greenhouse gases. So it's not just the big
bang of the eruption we need to really think about.
It's kind of what's going on around that time.
But to understand why these volcanos are still tapping into this
carbon that's deep down, we need to be able to look underneath them and
that's normally impossible, but I have some great
friends at the Royal Institution who can make magic happen.
In fact, they can make volcanos fly.
So we're going to take a dive down beneath this volcano
to around about 5km, so quite deep down below it, you can
see the rocks in here and what we have in here in this
kind of goldy colour here is the magma.
Some of you will have heard of that.
This is a magma chamber, so this is an area of semi-molten rock
and it's one of the ways, in these magma chambers and these pipes
that magma gets fed up to eventually be erupted out of the volcano.
But that's just a temporary stop off point for what is going on much,
much deeper down.
And we're diving now down to, you know, a few
tens of kilometres beneath the volcano, right down
in here into an area known as the mantle.
And down at mantle depths,
we have lots of rocks which are rich in carbon
and it is the melting of those carbon-rich rocks and the ascent
of the magma that allows us to erupt carbon
and carbon dioxide out of the top of the volcano,
so the story for volcanic carbon is quite a deep, rich one.
So now we've established this link between volcanos
and the carbon cycle
and we've seen that volcanos are one of the really key ways to bring
carbon from the deep earth store down here up into the atmosphere.
So the question is, do volcanos just erupt randomly,
or is there something in the Earth's engine that causes these
intense periods of volcanic activity?
And about 57 million years ago, so not too far away from where
I'm standing now, North America
and Europe were actually stuck together,
as part of a giant continent known as Pangaea,
but processes, forces deep within the Earth, caused them to drift
apart, as we're seeing in this video here, forming the North Atlantic.
And as they drifted apart, magma rose up and fed thousands
and thousands of submarine volcanos.
And because we had these submarine volcanos
forming in the North Atlantic,
they pumped vast quantities of carbon dioxide into the atmosphere.
And that carbon dioxide triggered a major geological event,
known as the Paleocene-Eocene Thermal Maximum or the PETM.
That was truly a time of Hothouse Earth.
But what do we mean by "hothouse"?
We are talking temperatures which were five to eight degrees
higher than at present and that happened in only a few tens
of thousands of years and it lasted for around about 200,000 years.
And this event is what we call geologically a hypothermal
and what's a hypothermal like?
Well, if you wanted to take a bath at the Paleocene-Eocene
boundary, you could have gone to the equator and walked into the sea.
The water was that warm.
But we're geologists. You know, we're looking back in time.
We need evidence to really prove that some of these events happened.
So how do we know that the Earth became really warm at this time?
Well, to help me look at some of the evidence,
I'd like to welcome to the stage Dr Peta Hayes.
APPLAUSE
Hello. How are you? Hello. I'm fine, thank you. Good to see you.
So, you have a rather unusual job title.
Yes, I am the Senior Curator of Palaeobotany
at the Natural History Museum.
Palaeobotany. What does a palaeobotanist do?
Palaeobotanists study ancient plants
and how they have evolved over geological time.
So you're telling me that plants and flowers, you know,
they've been around a long time?
Yes, we have evidence of plants living on the land going back
more than 425 million years. Wow, OK!
And I have brought some to show you. Great, thank you.
So, these specimens are about 50 to 60 million years old.
They look very similar to modern plants,
so this is Osmunda, the royal fern. OK.
And I've also brought some Metasequoia, which is
the dawn redwood. OK. So you're saying these specimens
here were found in a place which currently has ice kind of on it.
Yes, so the Earth was so much warmer that in the High Arctic,
there were forests flourishing near the poles. Wow, OK!
So let's head over to the blackboard
and kind of look where that is on our temperature versus time graph.
So the Paleocene-Eocene kind of boundary is here
and Metasequoia I think was one of the terms you used,
so let's pin that to our evidence board and connect it to this point
in Earth history. So it's pretty clear, I think, palaeobotany,
there's a lot of important information in there, isn't there?
Yes. Palaeobotany is a key piece of the climate scientists' toolkit.
Thank you so much, Peta. Thank you.
APPLAUSE
So the Paleocene-Eocene Thermal Maximum didn't only just warm
the Earth, it also caused the oceans to become very acidic
and relatively poor in oxygen.
But fortunately, you can see here on the graph,
Hothouse Earth didn't last forever.
Eventually, the Earth cooled and that's because the warming triggered
a process that drew down carbon dioxide from the atmosphere
and took it down into the deep earth store and that process was rain.
THUNDERCLAP
So, I'm going to show you that process here.
What have we got? There's a lot going on here, so at the front here,
I've got some water, so that's going to be my rain.
And I have a landscape. There's some trees
and there's rivers cutting across that landscape as well.
And on that landscape, at the top here, we have exposed rock.
And at the end of the rivers,
where they empty into this water here, this fluid in here,
this is the ocean, so this is going to
be our ocean down here at the front of this experiment.
And one thing that happens with rainwater is it falls through
the atmosphere, it dissolves carbon dioxide
and it forms a weak acid called carbonic acid.
And although that wouldn't harm us or any other living creatures,
it's actually strong enough to dissolve rocks.
So I'm going to make myself here by adding some frozen carbon
dioxide to this water. I'm going to make myself an acid.
Can you see it bubbling away in there?
Nobody would want to see rainwater like that,
would they, bubbling away?
So I'm going to pour it on. So I'm going to replicate rain
onto rock on a landscape, so I'm going to pour it on top here.
A lot's going to happen.
And you can see the water runs down through the rivers
and comes into the sea
and, hopefully, if I scoot round here, look in the ocean here.
Suddenly we're getting little particles in the ocean.
You can see them raining down from the top of the ocean
and settling on the bottom of the ocean.
Let me do that again.
So there's a flood. We dissolved a lot of rock there.
And again, you can see this kind of snow, almost.
It's raining these particles down
onto the bottom of our model ocean.
This is what's known as the carbonate silicate weathering cycle.
So we're dissolving these rocks and we're getting calcium, magnesium
and bicarbonate ions. They're being taken down into the ocean,
and it is there where we get a helping hand from sea creatures.
Sea creatures who need to make protective shells, and they make
those protective shells from calcium carbonate.
So they're actually taking the carbon dioxide
which is in the atmosphere to build their shells.
But they don't live for ever.
As you saw in our little demo here, they die after a while.
When they die, they fall to the bottom of the sea
and they actually form part of the Sedimentary Record.
We still haven't got rid of our carbon dioxide though yet, right,
because it's at the bottom of the ocean.
It could still get back into the atmosphere.
We need a way to get rid of that, and we do that with plate tectonics.
So if I stand back here, the Earth's plates can move around
and there's these places called subduction zones.
You can see the red kind of layer there,
and that red layer is going down below the brown layer.
That contact where we see mountains being built
is a subduction zone.
And those animals, which have all the calcium carbonate,
the carbon dioxide in their shells,
get dragged down on that red plate,
deep into the Earth, charging that Deep Earth carbon store.
Now, what's on the landscape
on the continental plate and the brown plate?
There's volcanoes. Those rocks melt deep beneath the volcanoes.
It's those volcanoes which are the way, then, to get the carbon
back up into the atmosphere to make carbon dioxide.
So this diagram really beautifully shows us the carbon cycle.
The way we... This experiment, as well, it's showed us how we
draw down CO2, move it into the oceans,
take it back into the Deep Earth
and then put it back up into the atmosphere via volcanoes.
And like I said, this process was really, really critical
at the end of the Paleocene-Eocene Thermal Maximum.
It allowed the Earth to return to cooler conditions.
But what happens if too much CO2 is removed from the atmosphere?
Well, the Earth will cool,
and I can replicate that here again at the marble run.
If we look at the atmosphere store,
we can see that carbon dioxide is building up in this store,
which we then can release,
simulating that rapid cooling of the Earth.
And you can see all of that carbon is going down into the ocean store
and ultimately into the Deep Earth store.
So, come back to the blackboard here,
we can see that these kind of cold conditions, these icehouse
conditions are seen at a number of points on the graph.
We can see the most recent cold conditions were about 10,000 years
ago during a time that you've probably heard of - the Ice Age.
And that's the time when the Earth was, you know,
a few degrees cooler than it is now.
But that's not the only time we've had icehouse conditions
on Earth. Way back in geological time, here,
320 million years ago, during a time known as the Carboniferous,
there was also evidence for glaciers
at places which are now quite warm.
So the Earth hasn't just been cold once.
It's been cold quite a lot of times.
But what geological evidence is there, or what are geologists
looking for in the rock record
to prove to people and actually work out that this ever happened?
Let's go over here and look at the clues which are contained
within the rocks.
We see here, just for scale, this is a hammer in here.
So the hammer is about 30cm long.
And we see these layers of rock, and these rocks
are relatively fine-grained.
They're made of sand and mud.
But what's really odd is this giant boulder that's just sitting
in the middle of these much finer-grained rocks.
So the question is, how did this rock get in the middle
of all of these fine-grained sediments?
And to show you that, I need some ice. Now, ice forms glaciers,
and glaciers break down to make icebergs.
And I have my super high-tech iceberg here.
But what's as important for us is what happens when icebergs melt.
So, audience, are you with me?
Can you count down from five... ALL: Four, three, two, one...
Whoa!
So that was all - thank you - that was all very, very dramatic.
And I'm going to come back over to the tray, and here
we have that large boulder which fell from the iceberg
down into these fine-grained layers of sand.
And that looks very much like the dropstone we looked at in the photo.
And it's probably no surprise it's called a dropstone,
because of the demonstration we saw.
But it's not just the rocks we're looking at for evidence
of ice activity on Earth in colder climates.
We can actually look at the physical landscape itself.
So look up here. In Iceland, we can see this giant glacier
which has carved out this big
U-shaped valley, and that's because the ice is dense
and it can grind its way across the rocks.
And as it reaches the sea, it breaks up into icebergs,
and it's the melting of the icebergs that we just looked at
in the demonstration that gave us the dropstone.
But we don't need to go all the way to Iceland
to see the action of glaciers.
We can go not too far up the road here, towards the Lake District.
A beautiful U-shaped valley formed about 10,000 years ago,
but it doesn't have the ice in it now because it's a lot warmer
than it was then when this landscape formed.
So now we've seen some good evidence for these times of cold climates
on Earth. And we looked a bit, as well, at the role that volcanoes
played in that, so kind of in... in here.
But what does this all mean for something really important -
life on Earth? Because life is very sensitive to changes
in temperature and the overall climate.
And to understand that, we need to go and look at the rocks again.
So, if we look up at the screen here,
there's some beautiful flowers on some rocks here.
We're not interested in the flowers.
We're interested on the right-hand side with the whitish-coloured
rocks. In those rocks, palaeontologists -
these are, you know, fossil-hunters -
they found lots of fossils.
And because there's lots of fossils,
it meant there was lots of life on Earth.
There was lots of biodiversity.
To the left of the flowers,
we find less fossils.
OK? So there's less evidence for life on Earth there.
So clearly something quite dramatic happened where those flowers are,
in this example here. This photo is from Italy.
So something really dramatic happened to life on Earth.
This kind of boundary here is at a time period, the end
of the Cretaceous, so about 65 million years ago.
And if we go and look at rocks of that age, all around the Earth
we see this similar kind of event,
this extinction event, where lots of life died.
But we have to be careful when reading the fossil record.
You know, if we're reading a book, imagine we've got faded letters.
We might not get the full story.
And Miranda Lowe from the Natural History Museum will explain why.
Well, we're in the basement of the Natural History Museum
in the amazing tank room,
and all around you, you can see jars of fish -
huge jars of fish, in fact.
And there's actually a giant squid in the middle.
There's a Komodo dragon, and lots of really exciting stuff.
So the specimens that you can see here now are three beautiful
examples of different forms of jellyfish.
The longer parts of the animal are the tentacles,
which often contain stinging cells.
And right in the centre of most forms of jellyfish
is the mouth and the anus.
So jellyfish actually eat and poo through the same hole.
So when animals are becoming fossilised, they need the right
climatic conditions for that to happen.
In general, the soft tissue will decay and dissolve away
and what you're left with is the hard skeleton.
Jellyfish have a gelatinous, soft body, extremely soft.
There are no hard parts to this actual organism,
and most of the time you won't find jellyfish within the fossil record
because it's too difficult to preserve.
Wow! So there are some amazingly terrifying beasts lurking
in the basement of the Natural History Museum.
And Miranda talked us through something called preservation bias.
That means we preserve some of the harder-shelled animals,
but we don't preserve the ones which lack those harder shells -
those soft, squishy ones.
But there are other biases.
There's other reasons why we don't find all the fossils
we might want to find.
So to help me further investigate the mysterious case
of the missing fossil, I would like to welcome Dr Chris Dean.
Hi, Chris. How are you? Good to see you.
I'm good, Chris. How are you? I'm good, I'm good.
You've got a job I deeply envy.
I'm a palaeontologist.
You are a palaeontologist. That is a very, very cool job to have.
But you're a rather strange palaeontologist, aren't you?
Yeah, I kind of am.
So, I'm not interested in individual fossils,
but more the fossil record as a whole.
So I'm kind of interested in what we see in the fossil record,
but almost more interested in what we don't see
and why we don't see it.
So you're looking for things we don't see. OK.
It's very complicated.
We're getting to the end of the lecture, so it's hard for me.
I think we need to kind of play a game to try and illustrate
what you're really interested in.
Sure. So let's come in here.
So hopefully you can see - down in front of me and Chris here,
there's 16 squares and they've got letters on each of them
and little handles.
And Chris has got his area to prospect for fossils,
so Chris is going to dig in his little area. Very exciting.
He's very excited. And I've got my area to dig in as well,
and I need to find more fossils than Chris.
I think I should be able to do this.
But there's so much to dig,
I don't... Do you think we can do this all ourselves?
I don't think so. I think we can get some help.
Does anybody... Would anybody like to help dig for fossils?
Do you think you could help us?
OK, awesome, there's some hands in the audience.
Right, I'm going to come up
and ask some of you to help us dig for fossils.
Chris is going to stay there. OK.
OK, let's start with Miriam.
What letter would you like us to take away?
You can hold it up or shout it out.
M. M. OK. Let's scoot down here, Chris.
We take away our M's. Are you ready? Yep.
OK! Thank you, Miriam. We both got a bone.
That's good. We're off to a good start. One all.
But let's keep digging. OK, whose hand is up?
I think we've got Katherine down there.
Katherine's got an I. Beautiful! Thank you, Katherine.
I'm ready and up we come. Oh, OK. What did you get?
I got nothing. No fossils for me. OK, but I got, like, a forest
so what's that?
So we can actually have problems with finding things
in the fossil record when things are covered up.
So if you have forests covering the land,
there aren't any rocks exposed, so we can't look for fossils,
even if there are fossils in the rocks underneath them.
OK, so that forest has stopped us. A natural kind of bias there
that's stopping us. So let's come up in here.
Isla, there we go. Isla, your hand is up.
Scoot it across. N. OK. Going for the corner here.
Let's have a look.
Oh, brilliant!
It's two to one! But I've got a clock,
so what does the clock mean?
So that could mean you've just run out of time to look for fossils.
It's really, really hard to go out and find as many fossils as possible
and you might have just not been lucky this time.
So there could have been fossils there
but we just didn't have time to get them? Exactly.
OK. Let's see. You palaeontologists are brilliant!
Seth and Jonah. F.
F. F, let's come back down again.
Ah, OK, nothing for Chris,
and I have a "no entry" sign. What does that mean?
Well, obviously, land is owned by different people, and sometimes
people won't let you onto their land to look for fossils.
So there could be a whole place with a whole abundance of rocks
but you just can't get access to it in the first place.
OK. So, you know, what we might draw the conclusion
from this kind of this game is that Chris has kind of got
more biodiversity, would you say?
Yeah, but it's a bit more complicated than that.
OK. So if we crouch down here and actually look at what's truly
buried in our area without...
Poke these ones through the back and get them all off...
What we find is, what, Chris?
Well, actually, we actually have the same number of bones
or the same number of species under both squares
but I was just more lucky in the fact that I didn't have
any biases blocking my way.
So it's fair to say, if we want to read the fossil record,
we hopefully...you know, it's not scratched
and we don't miss a beat!
Very good! Thank you, Chris. Thank you so much.
No worries. Thank you, Chris.
So, even when we account for preservation bias and
sampling bias in the fossil record, we still have good evidence for
big changes in biodiversity at quite distinct periods in geological time.
And in fact, we see five mass extinctions.
And these mass extinctions occur throughout geological time.
And, at first, are seemingly kind of random,
but when you look more closely at where they're positioned,
relative to the changes in temperature
and the changes in the global climate, you see
the mass extinctions are where we have the big changes,
big kind of warming events and cooling events.
And one of the most dramatic examples of that, one of the most
dramatic extinctions in Earth history was here
at the end of the Permian.
So, around about 250 million years ago.
So how bad was it on Earth during the, you know,
the Permian Triassic boundary 250 million years ago?
Well, about 70% of all species on Earth went extinct.
Not only that, about 90% of all of the marine species -
so they're the animals living in the sea - they went extinct.
So this was a really, really kind of bad time to be around.
And as you see in here, one of the reasons so many species went
extinct at the end of the Permian
is because of lots of volcanic activity.
And earlier on in the lecture,
we talked about how volcanic activity was one
of the key ways of bringing carbon up into the atmosphere and causing
the increase in carbon dioxide.
So now we've looked at the geological past, and we've kind of
taken this wander through and built up lots of evidence to
kind of defend this curve, and we've looked where this curve came from.
But what about the climate and life in our present,
in our future as well?
And to really kind of answer that question, we need to come in
right to here on the graph.
And you can see there's a little inc... Well, seemingly quite
a small increase in temperature there, after all these big swings.
But, you know, I can't really get into the details there.
I really need to be able to zoom in.
So has anybody got something that could help me zoom in to this...
Oh, thank you!
MAGNIFYING GLASS CLATTERS
That magnifying glass will never do!
I think I can do so much better.
So here's my giant magnifying glass,
going in on the last 10,000 years of Earth history.
So we've gone from 50 million years on the axes to 10,000 years,
so we've really zoomed into the details at the end.
So here's that 10,000 years across here.
This is about two degrees' temperature change
along this Y axis, and the purple line is showing you how
the temperature has changed.
And what's kind of clear from this graph is, you know,
we've benefitted, I guess you could say, from a relatively stable
climate over the last kind of, you know, last 10,000 years.
But there is this really kind of dramatic increase at the end here
in global temperature of around about one degree,
and that's happened in just that last 100 years.
And the primary driver, the thing causing that rise in temperature
is our emission of greenhouse gases
and, in particular, carbon dioxide. So that one-degree rise.
So, to put it in context for you, how much carbon dioxide
are we putting out? We are putting out 40 to 100 times
more carbon dioxide than all of the global volcanoes combined.
So if you took all the volcanoes, added up how much carbon was
coming out of there each year,
we're putting out considerably more than that.
The only time carbon dioxide has been added to the atmosphere
at the same rate to increase the global temperatures
was 65 million years ago when an asteroid hit Earth,
and that was actually the asteroid which led to the death
of the flightless dinosaurs.
And clearly, by looking at the mass extinctions in the past,
we can see that these big changes in carbon dioxide and temperature
have huge consequences for life on Earth
and, therefore, we need to be mindful that, potentially,
such changes could have consequences for us.
And we're seeing the effects of climate change all around us.
We're seeing rising seas, we're seeing floods,
we're seeing droughts, we're seeing increased storminess on the planet.
And going back to the last 100 years, where we've seen
all of this action, we've seen all of these changes,
these planetary changes,
you know, can we zoom in and break this down further?
This graph just looks like a vertical line.
And maybe, to help us really visualise what's
going on in that really key part of OUR history,
maybe we can we can hear the changes in climate.
So, to bring the climate to life for me,
I would like to welcome musicians
from the Cardinal Vaughan Memorial School.
APPLAUSE
Wow! So I am very lucky to have my own string quartet!
So, Gabriella, who have you brought with you today?
We've got Alex on the cello...
..Tommy on the viola...
..Giancarlo on the violin...
..and I'm also on the violin.
Beautiful.
So I invite you to bring the last 133 years of climate change
to life with music.
So the cellos are playing music here at the low latitudes,
so around the equator through here.
The viola is playing the mid-latitudes through here,
so kind of around where I'm standing, in London.
And the violins are playing the high latitudes,
so up in the Arctic.
If you listen really closely, you'll notice, as the piece goes on,
both the pitch and the volume increases, and that is reflecting
the increasing temperature that the Earth has experienced
over the last 133 years.
APPLAUSE
Wow.
So, what does this mean for us, what we just heard -
that dramatic increase in temperature
over the last 100 years or so?
You know, can we change our ways to limit the consequences
and adapt fast enough to what is becoming a new hothouse Earth?
And these are some of the questions that we will be investigating
over the next two lectures.
And in the next lecture, Dr Helen Czerski will take a deep
dive into the alien world
that plays such a key and dynamic role in our planet - the oceans.
APPLAUSE