>>> Okay.
First, I would just like to invite you to take a deep
breath and relax, pretend you're at the ocean and you're
now ready to absorb paleoclimate information.
>>Carol, that's wonderful.
We are going to talk today about paleoclimate.
We know it's summer and people really might not want to be
here in July doing this, so we thought we'd try to make it a
little bit more fun.
We're calling the talk "Sherlock Holmes and the Case
of the Scientist-Detectives Sleuthing the Climate Past and
Projecting the Climate Future." That's a picture of us.
And Carol, do you want to talk first about us?
>> No, not about us.
>>I think Bruce already talked about us.
>> Yeah, he talked about us.
>>Okay.
So sleuthing the climate past, projecting the climate feature,
you might be wondering why, you know,
why do we want to do this.
And basically, to me, the most important thing is,
we can't know if the changes happening today are unusual
unless we know not just what earth's climate has been like
in the past, but how and why the climate has varied in the
past.
So what will we find?
And also, you know, why does past climate matter?
And I think this is a really important question.
In order to really understand what's happening now,
we have to be able to answer the question: Is the current
climate change unusual compared to earlier changes in earth's
history?
That's a question from the 2007 ICCPP report.
How many of you heard someone question whether current
climate changes are caused primarily by human activities
claims, "climate changes all the time"?
I don't know about you, but I hear that all the time.
They're right, earth's climate does change all the time and in
many different time scales and in many different directions.
But just saying that doesn't negate or explain anything
that's happening right now.
People who say that don't understand how and,
most important, why earth's climate has changed in the
past, and so they're missing the crucial point.
So the answer to the question -- Is the current climate
change unusual compared to earlier changes in earth's
history?
-- is a resounding yes.
And by the end of today's presentation,
we hope you will be able to explain why this is true to
your students, too.
>> Great.
And one thing we forgot to mention is that we have another
computer open, and there's two of us,
so if there are any questions that are burning questions that
you don't want to lose as we're talking,
feel free to ask it in the question area,
and one of us hopefully will be able to respond in a reasonable
fashion.
That's one of the benefits of having two presenters.
So, many of you are probably familiar with this diagram,
but I don't know if you know the evidence that was used to
obtain it.
That's what we're going to talk about next.
And so we're going to be looking at climate records and
we're going to be looking at the earth climate at long,
long time scales to hundreds of million years to 100-year time
scales.
We are going to look at the kinds of tools that
paleo-sleuths, such as Carol and myself have.
We're going to look at the concepts that we use,
some of the data sets that we can get and some of the
procedures that we take when we try and make these analyses.
And then we'll finally do some of our own sleuthing if we have
a little bit of time.
So, are you ready to match wits with Sherlock Holmes?
Okay.
Well, one thing is you got to think bigger than Sherlock.
It's not just London.
And we have to think on bigger scales than Sherlock Holmes,
in fact much bigger scales than Sherlock Holmes.
We have to think about the impact of sun and earth
geometries in space.
In fact -- and we won't talk about this much -- but if
you're talking about billion-year time sales,
we've got to think cosmically, very,
very big spatial scales and now time.
Let's talk about time for a minute.
We're not talking about just the late 1800s in London.
We're, in fact, talking about 4.5 billion years of earth
history.
And what you will see in this diagram of earth history,
we have a lot of detail towards the present,
which is the biggest part of this spiral,
and then the Cenozoic.
That's our most recent era.
And as we go further and further in time,
you see there's less and less data plotted on this diagram,
and so we don't have the resolution that we have in
modern times to reconstruct the past.
And this is something that we might be able to talk about a
little bit later at the end.
There is a lot more resolution in this recent time.
And you see in this picture that we have here -- Carol,
can you point right here to what's happening in modern
times?
You see that there is a lot of variability;
there's a lot of activity in those wiggles.
And paleoclimate people love wiggles.
One of the things that you see, if you look on the left side of
the scales, is that we don't have nearly the same amount of
information or detail, and that's because of the
resolution in those deep time.
So, let's move on and look at the next one.
But this is the hardest part.
We have to combine these unimaginable spans of time and
unimaginable spans of space and put them together.
And if we put them together, what we have is paleoclimate.
And we've set the stage for talking about paleoclimate.
So I'm going to review really quickly some of the mental
tools that we have.
You don't have to remember all of these things because we are
going to be talking about each one of these points,
but sometimes it is helpful to know where we're going.
So here are some of the mental tools,
some of the things that are in our detective kit.
We have to remember that the earth is a system.
I'm sure that's not an alien idea for any of you guys.
Just remember that everything is connected to anything else.
If you change one thing in the system,
something else is going to change.
The second thing that paleoclimate people use is we
do a lot of observation of modern systems.
We learn about the biota in the oceans.
We learn about algae, how they respond to changes and climate
in modern day.
We look at pollen grains and see how pollen changes over
time.
We do all these things.
So those are the data that we use.
We observe the record of past environments using what we call
paleoarchives -- and an archive is like a library -- and we
look at the sediments in oceans, the sediment in ice,
the lake deposits, ^^.
These are the libraries that have information for us about
past climate.
And in those different libraries we see fossil plants,
we see fossil animals, and we see evidence of biological,
geological and chemical processes.
And here is a shorthand word for you, biogeochemical.
That puts it all together, and if we slip out,
we might use that word again.
So here is our procedure.
Just like a guy like Sherlock Holmes, we are going to detect,
we're going to deduce and determine.
We have some assumptions that climate is constantly changing,
that we can detect it using our paleoarchives,
using principles of biology, biogeochemistry.
We deduce why these changes occurred,
what environmental conditions responsible.
And one thing that we won't have enough time to talk about
but is very important is we need to know the age of
material that we're dating.
And if -- and this is the big if -- if we have these patterns
at different geological context around the world and we see it
in more than one place and we see patterns,
then we can say this looks like it's global,
it looks like it's climate, and you've got your story.
Carol, you want to go next?
>> Okay.
So where do we find our evidence?
We find evidence in ice cores.
We find evidence in sediment cores.
And this picture is showing a lot of different kinds of
sediments: Glacial sediments that outwash in the ends of
glaciers; alluvial sediments means sediments that were
deposited by running water from rivers and streams;
eolian sediments are the sediments that were carried and
deposited by wind; and then we have things like peat,
which are organic sediments that build up.
And we find fascinating stories inside sediments.
They are one of our best archives where we find climate
information stored and often, not always,
in organized ways so that we can know the sequence of the
events.
So this is showing you a hypothetical lake bottom.
I know for a long time, when I would tell people that I cored
lakes, they would sort of not really understand,
even though I was going to a frozen lake,
so there was ice up here and we were coring through the ice,
they didn't realize that what we were doing is we were going
to the bottom of the lake and then we were taking the core.
This is an example of the kind of things we might find in a
lake core and different kinds of layering that we can see in
the core that you might look at that and think, okay,
I don't know what's going on, where is the climate data that
is telling me if it was cooler or if it was warmer.
Well, what we're interested in is what we call proxy data.
Perhaps something in the sediments left fossil evidence
of an organism's response to temperature or perhaps the
sediments themselves contain minerals that might have been
formed only under specific conditions,
like when it's very, very salty or not salty.
Anything in the earth's system that sensitively records any
kind of environmental conditions, you know,
temperature, humidity, et cetera,
and is preserved over time, can provide proxy climate data that
we can construct past climate from.
And I think understanding proxy data is a really important
thing, and people often do it or have done it without
necessarily realizing.
So here's just a little proxy data sleuthing activity for
you.
I want you to imagine you're sitting in an office with no
windows and you've been there for hours working on a
presentation for your students.
Your source of data or evidence is other teachers coming in and
out of the room.
You can't see outside, but other teachers coming in and
out of the room.
So my question for you is based on this data or evidence,
can you interpret, can you determine what the weather is
like outside?
So I want you to just think for a moment about what proxy data
sources you can use to deduce the temperature outside when
you can't measure it directly with instruments.
So right now I want you to just think of anything that you can
and share it in the chat box.
Actually, I think they have to share in the question box.
>> In the question box?
>> In the question.
>> Where is the question box?
>> It's right there.
As you can see, we're neophytes to go to webinars,
so you're going to have to have a little bit of patience,
but I see people are already putting all kinds of great
stuff: Reports from observers, coats, quality of cloning,
umbrellas, jackets.
I think they got everything.
Some people are looking at coral data.
You guys are super sleuths.
I think that we are just going to just leave you in that room.
That's wonderful.
>> I just wanted you to get the idea.
And you can do a similar thing with students to get them to
understand that we use proxy data all the time,
whether we're thinking about it or not.
And the one that I thought of it might be very easy for them
to get what they think it means if other students come into the
classroom with wet umbrellas.
So even if you couldn't see out the windows,
the blinds are drawn, if other students come into class with
wet umbrellas, they are probably going to assume that
it's raining.
So what's important to realize is the umbrellas are not
measuring rainfall, but they are an indirect indicator of
rainfall.
And that's exactly what we mean by proxy data.
Other examples could be similar to some of the things people
were just mentioning.
You know, if you're wearing sandals or tank tops or parkas,
that's going to give you some indication of temperature.
Now, just one example of that wouldn't necessarily -- maybe
an eccentric person comes to class wearing a parka in July,
so you want a large number of examples.
If most of the people are wearing sandals,
that's going to indicate something to you.
>> So, once again, we're talking about the
reproducibility of data.
Really good.
Okay.
So now we're going to give a real simple and very fast
example of some of the kinds of proxy data, just one example.
I know that when you're reading things people mention pollen
grains; they mention coral.
That's fantastic.
And what we're going to look at today is a special kind of
proxy that we find in lake sediments called diatoms.
So diatoms are a common kind of algae.
They have a distinctive -- they call it a frustrule,
but it's basically it's coating.
And because it's made out of silica,
it persists through time.
If you know about pollen, pollen is covered by spore of
pollenin, and that also is like the hardest material known to
humans and scientists.
You can get boil it in hydrochloric acid.
The diatoms are equally as ^^resistant.
And importantly, we studied using this modern analogies.
We know these species have very specific ecological tolerances.
And if we find certain species, we know a little bit about that
water body.
Once again, we don't know about the climate,
but we know how those particular diatoms are
responding to the environment that they are in.
I took this from an exercise that I've listed at the end
from something called mud ed, which is from my home
laboratory at University of Minnesota.
They have a bunch of student activities that teachers can
use to teach about paleoclimate.
But here we have a bar core.
You have light and dark bands.
A light band and a dark band equals one year,
and so each one of those bands we have taken a sample of
diatoms, and you will that each one of those has a very
different assemblage.
And if you look at the top of this diagram,
you will see that there is listed six or seven different
kinds.
And what we know about those different diatoms -- the first
one on the left is a shallow, near shore clear water type.
The next one is a surface dweller.
It's nutrient rich.
What that means is that you begin to get too many nutrients
in the lake and it becomes eutrophic and kind of green and
slimy.
That's a really good environment for this particular
^^core.
That's really different than cyclotella, cyclotella,
which is here, because it's a surface dweller.
It likes clear water and low nutrients.
So you might see in the samples -- sample 1, sample 2,
sample 3 and sample 4 -- at the bottom that first you have a
lot of the cyclotella saying that you have low nutrients and
clear water.
And then the next sample you're beginning to see a lot more of
the ^^lapasira and the flagilaria.
Both of those are nutrient rich.
And so what we're seeing as we are going from clear water to
we're going to a eutrophic state of slimy green lake.
Let's just go to sample 4.
You see that sample 3 you're beginning to get some of those
shallow, near shore clear water species.
And by sample 4, you have a completely different kind of
environment where you have a lot of these staurosira,
and they're sand dwellers that you find in the bottom part of
the lake.
So this is not telling us anything about climate,
but it is telling us something about, for instance,
precipitation-evaporation ratios.
If you have a lot of clear water,
if you have a lot of water running into a lake because
it's raining a lot, you're going to have a lot more of the
cyclotella.
But if there is a lot of evaporation and the nutrients
are becoming more concentrated, then you're going to have a
concentration of this assemblage that has the ones
that like nutrient-rich environment,
like the lapasira and flagilara.
So, once again, this is how diatoms work.
It's a proxy.
It's not telling us what the climate is,
but it's telling us, through a couple mental steps,
a couple leaps of faith, what's happening.
Okay.
I just want to interject something here.
If you do diatoms, not in a lake,
but you can do them at a pool, you can look at saltwater ones
in the oceans, and if you were finding an abundance of diatoms
that were shallow and then they became deep,
you got deeper water ones, and then you ended up having no
diatoms at all and you have land-dwelling ones,
you can get information about the sea level rising and
falling, which is another in itself indirect indicator of
climate.
I just want to throw that bit in.
>> Wonderful.
Thank you, Carol.
Okay.
I'm going to move on here.
Next slide, please.
So, one of the challenges that we are facing here,
as we're talking about something a little bit more
complicated.
We're talking about paleoclimate.
And so in order to understand paleoclimate,
we have to refer to four principles.
And each one of these concepts are something that we could do
a whole webinar on and maybe as climate stewards you already
seen whole webinars on each one of these topics.
But we're going to look at each one of these briefly,
and if you don't know a lot of the details about these four
things, don't worry about it.
You could still understand paleoclimate.
You just might not get all of the detail about the
mechanisms.
But we are going to talk about energy balance,
about the greenhouse effect, the unequal heating of the
earth's surface and carbon cycles.
All four of these are things that are implicated in
long-term climate change.
So I can't give a climate talk without giving the five-word
answer to why climate changes, and that is energy in does not
equal energy out; you have climate change.
So if your inputs, solar energy coming in is greater than the
stuff coming out -- and that's what happens when you have
greenhouse gases holding energy in for a while -- you are going
to have warming.
But if the inputs are less than what's coming out,
you are going to have cooling.
And that principle is going to hold whether or not you're
talking about today or hundreds of millions of years ago.
The second thing is, looking at CO2,
because CO2 changes that energy
but using the greenhouse effect.
And here is a nice slide that shows how the greenhouse effect
works.
And we can just move on.
And then the last thing -- second to the last thing,
I guess, is the fact that weather and climate on earth is
created by unequal heating of the earth by the sun.
And so you get a lot more heat at the equator,
you get a lot less heat by the poles and so you have movement
of the heat by air and by water currents.
So here on the left you are seeing some heavy cells,
down at the bottom you see the thermohaline circulation
patterns.
Those are really important because if those change in
where they're going or how big they are,
you're going to have changes in the distribution of heat on
earth and you'll have a change in climate.
Last is the carbon cycle.
And you probably know, from all the work that you've done so
far, that putting greenhouse gases in the atmosphere from
fossil fuel emissions is one of the reasons why we're seeing
rapid climate change today.
And what you will see is that the carbon cycle also plays a
role on longer time scales.
So now we're in the meat of the talk.
And I apologize if this slide came out so light.
It didn't seem that light last time.
But hopefully you can see it.
We can change it before you get the final copy and download it.
But there are different natural processes.
And these are the cycles.
When people talk about natural climate cycles,
these are some of the things they're talking about.
we want to drive home is that the processes that change
energy balance, different natural processes have
different levels of impact at different time scales.
So if we're talking about the earliest earth origins -- and
we're really not going to do that today -- we see changes in
the cooling and consolidation of the crust,
the evolution of the biosphere, the evolution of oxygen in the
atmosphere.
There's some solar galactic things going on that we're not
going to talk about here.
But we're going to talk about three different time slices in
paleoclimate history.
And the first one is looking at hundreds of millions of years.
And what we're going to see is that for that scale of hundreds
of millions of years plate tectonics and mountain building
is really important.
The second time slice we are going to look at is looking at
hundreds of thousands of years, and there we are going to see
that changes in the earth's orbital geometry,
the earth and the sun, the orbital forcing, has a role.
And the last time slice we're looking at is looking at
100-year time scale, and there we see things like sunspots and
volcanism playing a role.
So, today's goal is to explain these different climate changes
on different time scales.
The important thing here, though,
that I want to talk about is that just like Sherlock,
we're only human.
You see there is a whole bunch of different forcings along the
apsis of this graph.
Some of you heard of ENSO or pacific decadal oscillation,
So, there are a lot of other things we're not going to be
talking about.
We're going to take these three most significant time slices to
understand paleoclimate.
And here's the thing, just like Sherlock, we are only human.
We are going to look at a few time slices,
but we have to put them all together at once,
and that's going to be something that maybe our
climate models can do better than humans can do and one of
the reasons why we resort to climate models.
We actually talk about climate in the present.
We have to consider some of these things,
but we consider them at very different scales.
On this slide here, I put a big box here,
which is human impact and CO2 that also we're seeing at a
100-year time scales.
But we're not talking about that today.
It's the most important thing for this time scale,
but we are only talking about those natural patterns.
So let's first look at plate tectronics.
This is a little bit of a funny diagram,
but the picture here that we see, it's conceptual.
It's not really quantitative.
And what we're doing, when you see the two blue blobs here,
this is how scientists view the relative importance of each one
of these forcing factors at different points in the
geological time scale.
So if you're talking about the deepest time scales on this
picture here, you're seeing that tectonic is the most
important.
So looking at these different tools,
you have to remember some of these mental tools we're going
not go over this every time, but this is the
first time.
Remember that the present is the key to the past.
That's a fundamental geological principle.
And the past is the key to projecting the future.
And that's why we need to study paleoclimate.
So we're going to be looking at energy balance,
whether or not energy in is equal to energy out and how
heat transfer by wind and water also changes because of
tectonics.
So what if the continents moved around,
what would happen to climate?
You probably heard about plate tectronics,
but what you see here is that over time you have a changing
land-ocean geography.
So look at 500 million years ago in the top left,
200 million years ago in the bottom right,
and that's a globe that you probably don't have from
National Geographic in your den.
These are really different configurations.
And what's important about this is the geometry of the land and
the ocean will actually impact climate because ice sheets can
only grow when continents are at the poles.
So that's one of the reasons why this is really important.
And why that's important, of course,
is Albedo because if you have polar ice that grows and you
have large ice expanses, you are going to be able to reflect
some of that solar energy back, and that's going to change the
earth energy balance.
Next, Carol, why don't you talk about this slide since this one
is yours.
>> Okay.
This just again shows two of the configurations from the
other slide so that we see 500 million years ago,
300 million years ago.
And I want you to notice that
500 million years ago you have lots and lots of ocean around
the equator with nothing impeding its flow and you don't
really have much land at the poles.
At 300 million years ago, you have land down here and you
have an ice sheet.
You know, you could have land at the poles and not have an
ice sheet, but you can never have an ice sheet without land
at the poles.
But I just wanted to point out how these correspond exactly to
evidence that we get from proxy data and records that have been
reconstructed.
So the 300 million year drop corresponds to this cold time
on the graph and this 500 million one corresponds on to
this very warm time on the graph.
>>Okay, great.
So another thing.
Remember we talked about how if you change the patterns of
current flow of wind and air, it's also going to change
climate.
There's a graph on the left, which is 90 million years ago.
There's one here today.
And what we see is a change from west to east orient
continents and east to west ocean circulation.
And by changing that to north and south,
we're having a gradual cooling that we've seen over the last
90 million years.
So that's really important.
Another thing that we need to know is that if you have
continents bashing into each other,
you're going to have mountain building,
and mountain building is going to make available fresh new
rock for weathering, and then that's going to be able to
react with water and with carbon dioxide.
sequestered in the atmosphere is going to be moved into the
ocean sediments where it is not available for the climate
system and that will then also cause a cooling,
so that's also really important.
So here's the summary.
It's all about 100 million year time scales and it's all about
moving continents, changes in the geometry of the land and
the ocean, the impact of the earth's ability to form polar
ice and albedo, the alteration of the transmission of heat
energy by currents of air and ocean currents and also
mountain building and the creation of making available
new rock weather and change the carbon cycle.
So, I have not seen any questions yet.
So if that's okay, we will just move right on.
Now we're going to look at this second time slice.
And the second time slice is looking at time changes that
are at a 100,000 year time scales.
And what we see here in this diagram is at most of the
climate variability that we see at 100 year time scales can be
explained by changes in the earth and sun geometries in the
solar system.
Okay.
This is a brief aside here.
I'm calling this the paleoclimate Rosetta Stone.
But basically I'm doing this because it's a record that
allows us to connect our instrumental observations.
So you will see a yellow line there,
that is CO2 that is measured at Mauno Loa since the 1950s.
And we have the CO2 measurements,
and you see that there's good concordance with the CO2
measurements and the heat of the global temperatures,
which is seen in the black line,
and that the Mauna Loa record is identical to the CO2 record
that we found in the ice cores that also run from the present
way back into the past.
So in this time slice you can see that it goes back to 1880,
but we can even go further and see that it goes back a long
long way.
Okay, Carol, do you want to do this one?
>> Okay.
So this is one of my favorite graphs,
although it might seem kind of nerdy.
>> It is nerdy, Carol.
>> Can you see a pattern in the data?
Now, I have sort of made it easy for you to see a pattern
in the data by putting all those red arrows there,
but it's really clear that there seems to be some
approximately 100-year cycle going on.
And note that the blue line is carbon dioxide concentrations
that we've gotten from ice core records.
The red line is the temperature record gotten from other proxy
data, and they correspond fairly closely.
So our question would be -- see this pattern -- what might have
caused it?
How do we know what caused it?
What could the evidence be?
What we're talking about here is we're sleuthing on the
100,000 year time scale, and we see the proxy data from ice
cores and sediment cores can provide evidence of ice mass,
temperature and past atmospheric CO2 concentrations.
So the first thing I want to mention is oxygen isotopes.
You know, if there's one thing I would want people to get
would be oxygen isotopes.
They're so incredibly useful.
So every element has different isotopes.
And with oxygen, the two really
important isotopes are 16 and 18,
which they're sometimes called the heavy and light oxygen
isotopes.
These can be measured directly from ice sheets,
and so the ice sheets that we have contain records of
hundreds of thousands of years of past climate,
and scientists drill into the ice sheets and Greenland in
Antarctica and get these cores of ice.
Now, I mention heavy and light.
Oxygen 18 is heavy.
Oxygen 16 is light.
I think that's sort of easy to get.
If it was pounds, 18 is heavier than 16.
Eighteen literally is heavier than 16.
And so the different masses, weight of oxygen isotopes cause
them to be unevenly distributed in the atmosphere and the
hydrosphere.
And I think an easy way of thinking about this,
like here is a picture that you could look at and says, okay,
sea water is rich and isotopically heavy.
H2O containing heavy oxygen.
Think about it this way: You're out here in the ocean.
You're a cloud.
You're out here in the ocean.
You've got a certain ratio of oxygen 18 and 16 in you.
The oxygen 18 is heavier, so it's going to rain out first.
So as your cloud continues to rain or snow,
it becomes depleted in the heavy isotope.
It becomes enriched in the lighter isotope.
So eventually, when it gets up to the north and it's snowing
up here in the north, it's isotopically light and you end
up with ice that's got more 16 than 18.
I hope that sort of makes sense.
Think of it basically in terms of weight and how that can
change the distribution in different
places.
>> And you always say, Carol, that oxygen 18 is heavier and
therefore it rains out first.
>> Right.
>> that's the way I remember it.
>> Okay.
So we can measure oxygen isotopes directly from oxygen
in the ice cores.
We can also measure oxygen isotopes in sediment cores.
Here we're not measuring them from the sediment directly but,
here again, we're using proxy data.
There are all kinds of little micro fossils in ocean cores
such as foraminifera and they build their shells out of
calcium carbonate.
Calcium carbonate contains oxygen.
So they are using oxygen from the ocean water at the time
they were alive.
So the ocean water at the time they were alive is going to
have a certain ratio of oxygen 16 to 18,
and that can give us information about temperature
and also ice volume.
>> Let me just interrupt here just for a second, Carol.
Remember those diatoms?
Diatoms do the same thing when they build their bodies.
And so in lakes we don't have brands,
we don't have foraminifera but we have diatoms and we can do
the same thing: We can do stable isotope measurements on
those bodies and come up with the same kind of data and get a
terrestrial record that way.
>> So the long-term variations in the ratio of the isotopes of
oxygen 16 and 18 don't just tell us temperature but are a
direct indicator of ice sheet volume and therefore indirectly
sea level.
This is one of my favorites things.
So I just want you to imagine that there is only a certain
amount of
water on the earth and that's because there is only a certain
amount of water on the earth.
And so imagine that if you take a bunch of that water and you
freeze it into ice sheets and less of that water is available
for the ocean and the sea levels drop.
Okay.
I think we are sort of running short on time,
but I'm going to speed up a little bit of this.
I just want to point out right here that if we look at this
oxygen isotope record that we have,
this one is showing the past five million years.
If you start at five million and you're coming up this way,
there is a big change around three million where suddenly
the swings back and forth from warm to cold are much more
extreme.
And this corresponds to the alternation between glacial and
interglacial conditions, so having this much ice in the
northern hemisphere and that much ice.
And that's a curious kind of thing.
So if we think back to the continental drift thing,
we might wonder, why would we suddenly be getting ice ages.
If we look at the continents are in the same positions from
three million years ago to today,
it's the same conditions, but we have ice sheets.
So the mechanism that's causing glacial periods must be a
different kind of condition.
>> So again, like Rusty mentioned before,
it has to be something bigger, like look at the solar system.
And so this is -- sorry about that -- seemingly complicated
but I think it's the most wonderful thing if you can get
this.
We call them orbital variations.
Again, it's just changes in
earth-sun geometry.
There are three of them that change the distribution,
the amount and the distribution of solar radiation that comes
to the earth.
So the first variable is that the actual orbit of the earth
changes through time and cycles a hundred thousand years from
being more elongated to being slightly rounder.
The second one is you're all familiar with the earth is
tilted when you have a globe, but you might not realize that
the angle of tilt varied through time from slightly more
tilted to slightly less tilted on a cycle of 41,000 years.
And then we have something called the precession of the
equinoxes which is a little, I don't know, confusing.
But just think of it as, you know, what is an equinox.
We have spring equinoxes and fall equinoxes, right?
So just think of it as the seasons.
The seasons slide around the orbit so that sometimes spring
could be at this most extreme orbit.
Sometimes it could be winter; sometimes it could be fall.
So the thing is that when all of the variations in these
three cycles line up, ice sheets build up at the poles,
albedo increases, and an ice age was born,
and that's when you're supposed to see all this ice.
>> Congratulations, you're a mother.
Okay.
And I think we're not doing too bad on time.
>> Right.
You guys are okay on time.
I'm just wondering really quickly if you can go back to
that previous slide for one second because one thing that
we notice is that there is quite a bit of misconception
when it comes to aspects of the rotation
around the sun.
And so can you, with the eccentricity cycle,
can you just go back and explain the degree of
elongation because, for the most part,
most people look at this perspective,
their students do anyway, and they believe there is sort of
an oval traveling of the earth around the sun when, in fact,
the orbit of the earth around the sun is really primarily
circular.
>> Right.
If we showed it literally what it looked like,
you would not be able to see it.
>> That's why I didn't make that mistake in our textbook.
Everybody has this misconception.
>> Right.
It's definitely exaggerated in this diagram,
and so it leads to the misconception that it's being
farther away from the sun alone,
but that's a really important thing.
And really it's only being farther away from the sun in
combination with the other things.
And one of the things I wanted to say but I thought there
wasn't time for because it's one of my favorite things that
I would say to students is I want you to imagine that the
earth is at its most elongate orbit and it's also tilted as
far as possible away from the sun.
Okay.
So our longest tilt that we could have -- and it's winter;
it's a northern hemisphere winter,
so you have the northern hemisphere titled as far away
from possible as the sun during the longest orbit.
And they can imagine that would be the time when it would be
the coolest in the northern hemisphere and that would be a
good time for an ice age to happen.
that, too.
But it's actually not.
It's actually a counter-intuitive thing.
But what matters is to have summer happening in the
farthest away, longest tilt because then you can have cool
summers that allow ice sheets not to melt and last until the
next year and keep growing.
So it's like simple and complicated at the same time.
Does that help or not?
>> I think so.
We will see how simple or complicated it is from the
questions you get.
>> Okay.
>> Moving on.
>> All right.
So now we're going to get back to this last time slice that
we're going to talk about today,
which is looking at variation at 1,000-year time scales,
and what you see on this wonderful melograph is that
annual solar forcing explains a lot of the variability that we
see naturally over time scales of a thousand years or less.
So, let's talk a little bit about sunspots.
Now, the thing that's kind of cool about sunspots is that --
and let's just move on.
We all know what a sunspot looks like.
>> But I want to interrupt and say I want you to point out to
them why you titled it "But what about sunspots." >>Oh,
okay.
I said what about sunspots because if you go to some of
these climate skeptic blogs, people talk about the solar
cycles and sunspot cycles as being maybe the reason why
we're seeing global warming.
Yeah, they're always saying but what about sunspots.
>> What about sunspots.
But in fact that doesn't answer
everything.
And here, let's take a look here.
One thing that we do have in common with our beloved
Sherlock is that back in Victorian days and even back
into the 1600s, scientists were largely gentlemen of their time
were looking out at the sun and recording sunspots,
so we got actually 400 years of great data, observational data,
primarily from Europe but also from China and India.
And what we see is that around 1650 to 1700 we had a very
significant drop in the amount of sunspots.
This was first seen by score and now it's called the maunder
minimum, and this was the minimum number of sunspots.
And once again, this is kind of counterintuitive because a
sunspot is a place where you don't see the sun.
And some people think, oh, that means we're getting less solar
energy.
But actually the sunspots are a dynamic indicator that you have
a very active magnetic field and you have a lot more solar
players and a lot more solar activity.
And so when you have a minimum, you actually have cooler
conditions on earth.
And it's very small.
It's only about .
7/10th of a percent less sun, but it can be significant.
And if it lasts for a long time,
it can actually cause climate change.
That's really definitive and noticeable.
And this picture that we put up in the left is a painting by
Bruegel showing people that are skating on the canals in the
Netherlands, which never freeze over today,
and that's what happened during what we call the Little Ice
Age.
So that happened during that time.
So we know that sunspots can really impact climate.
I think we should go back to the other slide just because
we're not quite here yet.
The last thing that I wanted to mention about sunspots is that,
you know, the sunspots are a cycle,
and the cycle is what we call quasiperiodic.
So it's not exactly a cycle.
It's a cycle, but it's not a periodic cycle.
And so sunspot cycle, they say it's about 11 years,
but we never know for sure.
It might be nine years.
It's as short as nine, as much as 14.
But it happens in about that amount of time.
And this was a surprise for us because we always talk about
the solar constant.
And when we began to put instruments in the atmosphere,
when NASA began putting instruments in the atmosphere,
we began to see that there actually was this seven one
hundredths of a percent of change, and it is significant.
So here is a summary slide showing what we've just talked
about.
We talked about hundreds of millions of years.
We looked at the time slice of hundreds of thousands of years,
and then we look at hundreds of years,
hundreds to thousands of years, and we identified for each of
those time slices what the important mechanism is,
what the data source is and the underlying geological concepts.
The longest time scale we're talking about plate tectonics.
We're talking about hundreds of thousands of years.
We're talking about the Milankovich cycles.
We also call that the sun and earth geometry or the sun and
earth orbital forcing.
On the hundreds of years, we're
talking about the sunspot cycles.
And, of course, if we get down into looking at tens of year to
hundreds of years, we are talking about human impact
having the most effect.
But we're not talking about that in this talk,
so it's not in our picture.
Carol has her favorite diagrams.
And I find I'm not as smart as her because I really like these
really simple diagrams more than her wiggly diagrams.
But this is a diagram from more than 30 years ago.
It was, I think, one of the very first papers on climate
modeling by Jim Hansen, who just recently retired from
NASA.
And I want to explain this to you.
On the left side of the diagram,
you have a simple climate model.
The ocean has just one layer and then you have a terrestrial
layer.
So it's a very simple climate model.
On the right-hand side, the ocean has two layers.
And what this means is that the climate model is more complex.
The greater the complexity, the more grid cells you have that
you can put equations in and a greater approximation to
reality.
If you look, there are three lines in each one of these
boxes.
And the first line -- let's look at top left, Carol,
A -- you'll see a line which is CO2.
And that line is the line that was created by that early
climate model, and all they did was they ran the model and then
changed the CO2.
And lo and behold, there is some semblance of similarity,
but it's not very close between the model and the observed
data.
If you go down to the second level,
forcing.
And we didn't talk about that because that's not a cycle,
but you know that volcanoes occasionally erupt and it
changes the atmosphere and all the dust that goes in there,
plus a lot of the sulphur oxides,
create a certain amount of cooling.
So we have to consider the volcanic record as well,
which we can determine, using proxy data,
finding tetra and ash in our cores.
We can determine that as well.
And you see much better similarity between the observed
data and the model run.
It's looking pretty good.
And then, when you run all three, you look at CO2,
you look at volcanoes and you look at those sunspots I just
talked about, the solar quasiperiodicity,
it's getting even closer.
Now, let's just drop down to the bottom right of this graph
in a little bit more complex climate model and you can see
it's even closer.
And so now, remember all that and now we're going to take a
look at one more graph.
Carol, this is your graph.
>> Okay.
So this is just a modern version of that same thing.
This is from the IPCC in 2007.
And down here there's three different graphs,
but you can just look at one of them; it doesn't matter.
We got global and global and land and global and ocean.
The important thing is the difference between the blue and
the pink lines and the black line.
So the blue line is a model that was run using data only
from natural forcings.
The pink are models that were run using both natural and
human forcings.
The black is the observed temperature.
So I hope
that you can see in every single case the black is what
we observed to happen over this past hundred years.
The blue is what we would expect based on natural
variability.
We can only produce a graph that looks like our
observations if we include both natural and human impacts.
I think that's really significant.
It's actually showing the same thing as this;
it's just the up-to-date version.
>> That's super.
Thanks, Carol.
So now we have this summary and synthesis.
That was about 55 minutes.
I think we're right on time.
So why don't you just keep going.
>>Okay.
This is just a quick thing to like stress some of the
important things.
And since we can't hear you and you don't have time to answer
these questions, we're just going to zip through them,
okay.
So if we look at our data sources,
where do we find our evidence?
We find our evidence in natural history archives in the earth
system.
How do we get our data?
We select proxy data sets that are sensitive recorders of
changes in the climate system.
And what is a proxy data source?
We decided to call it the umbrella,
a source of data that provides indirect evidence of a climate
change, so not by measuring temperature itself but the
temperature effects on an organism.
>> Okay.
So, here we are.
We've told the story, a story I think that's every bit as
compelling as those fantastic Sherlock Holmes stories that my
husband read to me aloud when I was pregnant with our first
child a few years ago.
>> Was it 30 years ago?
>> He read the entire Sherlock Holmes during that time.
But anyway, the more precisely we understand the timing and
changes that occurred in our earth system,
if we understand precisely the movement of the plates when
that happened, the changes in atmosphere of gas
concentrations over time, the solar cycles and the solar
variability, if we look at all these things -- and we didn't
put on there, of course, which we should have put on there
also the orbital forcing -- the better we understand the
climate past.
Okay.
So by understanding the climate patterns of the past,
we have the context to know that the rate,
trajectory and mode of climate change we see today is
unprecedented in earth's history and we understand
today's climate change.
>> And I think that that's a really,
really important point when you talk about rate,
trajectory and mode.
When you saw those diagrams and you see the wiggles -- and
remember how I showed in the very early parts of those
graphs we're looking at very, very deep geological time,
we don't see a lot of the mode of change.
But when we get into the most recent records,
you see a lot of variability.
So the rate is how fast it goes.
The trajectory is the direction it goes and the mode is what
those wiggles look like.
I just want to clarify that.
>>Okay.
So we know that the only way the climate can change is that
the earth's energy ^^butt changes and inputs are unequal
to
outputs and that many different factors can force changes in
this balance.
And we know that the past paleoclimate record has no
analogue for the rate of change trajectory and mode of change
we see today.
And we cannot explain contemporary climate change
without human behavior.
I didn't point this out last time, did I?
>> No, you didn't.
>> The blue is carbon dioxide concentrations.
The red is temperature concentrations.
These blue-dotted lines are showing the boundary of the
natural range of CO2 over the last 800,000 years,
really long time period.
So the lowest it's gotten is 180 parts per million of carbon
dioxide, and that's when we're in an ice age.
When we're in an interglacial, like now,
it's normally never higher than 280 parts per million.
>> And where did they say it is as of a couple months ago?
>> Right.
Here it says 380, but we hit the scary number.
We're at 400 parts per million.
This is definitely outside the range of variability.
We're on earth in this continental configuration.
Okay, Bruce, this is where I was going to have you do the
poll questions.
>> Okay, let's fire 'em up.
>> What we could also do is anybody who wants to could also
type in any questions in the question area.
>> We have a number of those.
I know we're running long, but I think people are very into
this.
I think we should hit the polls.
If you can answer the questions briefly, that would be great.
So folks can go and start answering those polls.
Go right
ahead.
Polls in progress.
I will let you know when we have the maximum number and we
can continue.
50 percent voted.
>> Okay.
We're just going to kick it up a little.
Just had 70 percent.
Just a few more seconds.
True or false.
Okay, we're going to close the poll now.
That's the voting results.
>> That's wonderful.
So as compared to your earlier things that you showed,
I think we're around 76 percent,
unlike the whole group.
So this group that's watching the webinar is 94 percent is
seeing that carbon dioxide is causing global temperatures to
increase.
>> And if you've forgotten where we talked about that,
we talked about the plate tectonics and the long carbon
cycle.
We remove carbon dioxide from the reservoir in the sky to the
reservoir in the ocean, which then can cause cooling.
The reverse thing can also take place.
And I think we didn't make that clear.
So those of you with 6 percent, we didn't present it.
You're not wrong.
>> But it's also impressive that most people answered the
question correctly, even though Bruce misspelled it.
So that's really good.
>>Carol, you're such a you know what.
>>No, no, don't let my wife, the editor, see this.
>> I'll keep it secret.
>>The next one.
Polls are open.
Vote away.
We got 73 percent.
76 now.
Okay.
Here are the results.
>> Okay.
This is interesting.
So 52 percent say true; 47 per percent say false.
Bruce, I have a question for you: Can people still see my
power point
slide or do they only see the poll window?
>> I will put it back to the -- I'm hiding it so now they can
see the power point slide.
>> Okay, because I'm realizing instead of doing all the
questions at once, I would like to go over the right answers a
question at a time.
>>> Oh, of course, yes.
>> Okay.
So we already said that most people have gotten the last one
correct about increased carbon dioxide causing global
temperatures to increase, and that is something we clearly
see on this graph.
Some people would look at this really quickly and think those
curves look like they are at the same place.
But I just want to point out that you could take a ruler,
if you wanted, and see that the blue is the carbon dioxide.
You could see that the carbon dioxide starts to go up and
temperature is still low, then temperature goes up.
That is something that we see consistently in most cases.
People got that one correct.
Now, the next one, this is very interesting: Is the earth
currently warmer than it has ever been?
No, it is not.
I want you to look at these two graphs that we've got put
together here so that we can cover that long span of time
and see where we are today over here.
You can't actually totally see where I'm pointing the arrow
because the webinar panel is covering that.
But you can see that over the earth's history there is no way
that this is the warmest that it's ever been.
Even in, you know, let's say just the last 60
million years, there was something called the Eocene
Optimum where it was much warmer than it is today.
A lot of climate skeptics will point to that.
They'll say, oh, look, it was much warmer than it is today.
But that was a completely different geography of
continents and high sea levels and totally different things
going on.
You know, if we want to have sea levels 30 feet higher than
they are right now, you know, maybe we'd be perfectly happy
with that.
But the earth is not warmer than it's ever been.
It only warmer than it's been for the last 800,000 years.
Okay.
Now, we can do the next poll question.
>> Okay.
Thank you for correcting me with that.
Polls are open.
There's a few more people waiting to vote.
Okay.
And here are the results.
>> Okay.
Earth's climate has always shifted gradually between warm
and cold periods.
This is another of my favorite ones.
And I don't want anyone to feel bad for not getting this
because scientists didn't even get this until, I don't know,
the last fifteen years or so, maybe 20 years.
The answer to this is no and/or it depends.
Okay.
But it's sort of false.
It's false if we're talking about anything resembling the
human time scale.
Now, it's complicated because weather change appears abrupt
or gradual is partly a reflection of the lack of data
resolution and partly a reflection of scale.
So in a human time scale, much change really is abrupt.
There are places on some of these where it might look sort
of gradual, but then
if you get it zoomed in on the specifics, you see that it's,
in fact, changing a lot, too.
So I try to orient these so that they're going to increase
in detail and increase in resolution.
But I just want to point out one thing to you: There is this
time period called the Younger Dryas where it became cold we
know from ice cores in less than 15 years, ice age cold,
in less than 15 years.
And then a thousand years later,
it became warm equally as quickly.
And the idea of gradual changes is just a misconception based
on the fact that in the past we didn't have the really good
data and people would draw these lalala curves.
>> Lalala curves.
So, and here's a good point, too,
as a pedagogen you might want to consider, too.
Remember how Bruce pointed out that because we're looking at a
side view of an orbit, it kind of looks really elongated.
And if we'd look at them top down, it would look round.
And lots of students don't see their earth's orbit as being
round because they been looking at textbooks for the last 15
years that say something different.
And the same case is here, too.
A lot of these graphs that we have shown you have a log scale
or a log scale, and that's the reason why you see a lot more
variability towards the end of the graph.
So, it really is a question of resolution of the data and the
resolution of the graphs that we're seeing.
There is resolution issues in both areas.
>>So the change is not gradual, and that's what scares people
sometimes.
>>That scares
me the most actually.
>>Okay, next question.
You can give me the next poll question, Bruce.
>> Next poll question.
Polls are open.
Okay.
>> Looking good, looking good.
>> All right.
So let's look at your answers now.
>> I'm pleased to see that 94 percent of you got this
correct.
>> You hear some banging on your end, guys?
>> No, not on our end at all.
We hear it somewhere else.
>> Okay.
I'll check.
Thank you.
>> Okay.
So, the climate change recorded over the last 150 years is
unusual compared to earlier changes in earth's history.
If we had past climate plotted at the same resolution,
we could see that the rate of increase in carbon dioxide is
presently over 10,000 times as fast as any increase in the
past.
So, remember what Rusty said before about you got, you know,
like how high the change is, but also what's really
important is the incredible speed with which this change
has happened, which means that people and plants and
environments are simply not going to have time to adapt.
Changes that look large in the past happened over 20,
000 years, a hundred thousand years,
a million years and things had time to adapt.
I guess you can go the next question, the last question.
>> You missed your calling.
>> I'm not going to quit my day job right now.
Okay.
So looks like everybody has voted.
So we share now.
>> Okay.
So this is interesting.
This is not a
strict yes or no answer.
So it's not terrible that everybody didn't get the best
answer, okay.
I would say that the best answer to this question is
changes in earth-sun geometry because that is the most
important forcing at that time scale.
Some people said plate tectronics.
Plate tectronics can impact things on a time scale of
10,000 to 100,000 years but little tiny little bits of it.
Okay.
It's a minor forcing.
It's not strictly wrong to consider that it could be.
It's just that the best answer is the orbital time scales.
>> And let's also point out, too, that that answer,
plate tectronics, can have a significant role if you change
the spatial scale, if you're looking at smaller areas.
But if we're talking globally once again,
the sun-earth geometry is the better answer.
So it's kind of a faulty question.
>> And I also want to point out that these orbital patterns are
important to understand for explaining to people things
about the different cycles in the past and how they explain
warm and cool periods, but they are not relevant today, okay.
These are not impacting our climate today at all.
Okay.
I stuck one more in here because I just love chronology,
and we didn't have time to talk about chronology.
So to the question time, how do we know when these things
happen, Sherlock said -- >> That, my dear Watson,
is a story for another day as I am afraid we have run out of
time to discuss time.
>> So that's the end of the
presentation and I know that this was probably -- a couple
of people mentioned this was a little bit quit,
and we do apologize.
We try to make it as simple as possible and try to yet deal
with these very complicated ideas in just an hour.
But I hope you will download this presentation because we
put in a lot of resources for you that you could use to talk
about some of these ideas with your classroom.
The student activities that use paleoarchives from lakes and
proxy data I got from the muded website at the Limnological
Research Center at the University of Minnesota.
We have quick-to-find diagrams and videos about climate are
really easy to find on climate.net.gov.
That's not a research portal; that's a communications portal.
Really, really readable information,
and that's important because a lot of this stuff is so
technical if you pick up a scientific paper,
but NOAA does the best with the paleoclimate section they have
on the web.
I have to put a plug-in for the stuff that I have been doing
this year.
This year we put together a brand new digital archive of
lessons for students and teaching resources at NASA.
It's called NASA Wavelink, and there's some really good
resources there.
And last, we also mentioned teachers domain.
A lot of you are familiar with that.
It's a great place to go to find some resources.
They do a great job with plate tectonics, in particular.
Also, if you're interested in either one of these two topics
of solar cycles
or Milankovich cycles, which is the earth-sun geometry,
you will see that there are some tutorials that have been
designed specifically for teachers,
and they use the five E method: Engage, explain,
explore -- Carol and I, you know,
she lives next door and we had a raccoon in the henhouse and
we both are a little bit sleep deprived.
But anyway, PBS and NASA got together.
And I was involved in the development of these resources,
and you can go through these resources and they will
actually show you the data.
You can play with the data a little bit.
There is a part that talks about how you actually can
teach this to your class.
Like I said, it's not for students.
It is for you.
So take a look at "The Climate Skeptic's Argument: Natural
Cycles or Human Activity or Earth's Orbit and Climate
Change.
Those are the two things we just talked about.
And last, for those of you who are not familiar with some of
these basic topics that we introduced in the beginning
that we just couldn't talk about,
we've listed some of these that we think are really,
really good as well that deal with these different topics.
So, if you've done okay on the polls,
we invite you to download your Super Sleuth Paleoclimate
badge.
You see our emails there.
We're really happy to take individual questions
afterwards.
Give us 24 hours to answer.
We're having little problems with internet here, too.
So hopefully you've learned a little bit and you're as
excited about paleoclimate and proxy
data as Carol and I are or at least maybe just a little bit
interested.
>> And if anybody wants to ask any questions now.
>> Yeah, I would say this: W have run now 20 minutes over,
but that's okay because you guys have given a terrific
presentation.
I am still recording this for an archive.
I would say, if anyone has to go,
then thank you for spending the time and joining us for this
more than an hour of professional development with
NOAA climate stewards.
I hope you have a wonderful evening.
For those of you who are interested and remaining and
listening to Rusty and Carol provide answers to a number of
some very, you know, thoughtful and good questions in the
question pane, please stick around.
We will be answering those questions.
If you have a question that you would like answered later,
please enter them into the question pane before you leave.
We will include them into the meeting notes in a couple of
days.
So, thanks very much.
We are staying on the line to answer some of those questions.