This is Jala g b with Oliver stimple. the history of complex
life on Earth has been punctuated by mass extinctions,
five of these extinctions, the so-called Big Five stand out as
being particularly lethal one, at the end of the ordovician,
one in the late devonian, and those at the end of the Permian,
Triassic and Cretaceous, But the sedimentary record also tells us
that there have been a total of 31 significant disruptions to
the Earth environment since the beginning of the phanerozoic,
542 million years ago. So why did only five of them
lead to catastrophic mass extinction?
And can we compare the disruptions to the environment
that we see in the geological record with the one being cause
now by human activities? Dan Rothman has tackled these
questions by studying, disruptions to the Earth's
carbon cycle as revealed by high-resolution, measurements of
carbon isotope ratios within carbonate, rocks.
His results indicate that the Earth system has a critical rate
of change. Over long timescales disruptions
occur when the rate of change in the amount of carbon injected
into the Earth system exceeds this rate.
And they also hypothesize has that it short time, scales
disruptions occur. If the amount of the carbon
injected exceeds a critical size, Dan.
Rothman, is Professor of geophysics at the Massachusetts
Institute of Technology. Dan Rothman.
Welcome to geology B. Thank you delighted to be here.
As I said in my introduction. You focused on the carbon cycle
as an indicator of disruption to the Earth system.
What exactly do you mean by the Earth's system here?
And can you remind us as to how the carbon cycle works?
I think of the earth system as a combination of the physical and
chemical. Ant with life, which you might
think of as the biological environment.
So, the Earth System Dynamics, which is what this work.
Addresses has to do with the interaction of life and physical
/ chemical environment. Your second question was about
the carbon cycle the carbon cycle to a significant extent is
where our System Dynamics happen.
The carbon cycle is kind of the locus of the interaction of life
in the environment. What it is precisely plants.
Take up CO2 out of the atmosphere.
Also out of the oceans and consuming organisms like us eat,
either the products of photosynthesis or the animals
that lived off of photosynthesis and in doing.
So, we return the original organic plant matter.
The matter that was fixed back to the atmosphere and oceans.
So CO2 goes to organic carbon via photosynthesis and consuming
organisms return it back. The process of consumption is
typically referred to as respiration.
So if we look at the carbon cycle, does that enable us to
infer what the physical environment was at the time,
things like the temperature and the composition of the
atmosphere. It allows us to identify when
disruptions to the environment occurred.
So one can think of the carbon cycle as a loop between
photosynthesis and respiration. Asian.
Typically, there are given the impression that the carbon cycle
is in balance, that is nature is thought to be in Balance.
However, as is well known at present because of fossil fuel
burning, we're stressing it out of balance, but there's a very
important question that asks, whether the carbon cycle has in
some sense, been unbalanced in the past.
And if one looks at the geologic record, the answer is pretty
much unequivocally. Yes, it has.
And then the question is, why, and how do we know this?
We know this because of chemical traces, that are stored in
sedimentary rocks in the form of the isotopic, composition a
carbonate minerals and also organic matter and these
isotopic compositions change and sometimes they change abruptly.
And most curiously, they change abruptly.
Every time there is a mass extinction, all the rocks that
contain these records formed from It's of inorganic origin or
of organic origin. And where does one find them
formed from carbonate? Which in some cases is, simply
the precipitation of carbonate minerals at the seafloor.
And in other cases, is the remains of calcifying organisms.
And that's a more recent case when I say more recent here.
I mean, since the tree Asik, when calcifying
photosynthesizers existed, the data I used study bulk
carbonate. They're not focused on any
particular. Ocular species.
I did that to maintain a uniformity in the record and
I've looked at data that come from a wide range of sources,
outcrops for the oldest data and deep-sea drill cores for the
much more recent data. The focus is not so much on the
long-term evolution of the carbon cycle.
But rather on its disruptions in a sense.
What I've done is a little bit, akin to a seismologist who
studies earthquakes only but not the long.
Tectonic changes associated with just the burp.
You know, the blast the disruption as I call it, and the
cycle itself and there's a distribution of sizes of
disruptions on the rates at which disruptions occur.
So I made a catalog of those. Okay, so you mentioned Isotopes.
So what exactly is measured in these carbonate, rocks that
enables you to track the disruptions in the carbon cycle?
What geocanvas do is to measure the ratio of The heavy stable,
isotope of carbon, the abundance of it, carbon-13 to the lighter
stable isotope, which is carbon 12.
Carbon 12 is 99% of the world's carbon carbon. 13, is nearly the
remaining 1% carbon 14, which everybody likes to think of as
the isotope of carbon is actually very minor and it
decays with a half-life of several thousand years.
So it's not in the picture and what we're looking at is ratios
of stable isotopes, the point that so Measurements, is that
these ratios change with time? And the reason they change is
because photosynthesis being a fast kinetic, reaction favors
the lighter, isotope of carbon. So the organic matter is
isotopically lighter than the CO2 from which it comes and by
about twenty eight parts per thousand.
And when carbon is buried in sediments, If or when there is
an imbalance in the carbon cycle, which is reflected in
makes of burial, then these isotopic ratios change.
And most of the time they're just changing modestly and
slowly but sometimes they change more abruptly and significantly.
So, as you said, a moment ago, you focus on those periods when
the change was abrupt. So, I guess it's a spike in the
ratio of carbon-13 to carbon-12. Is that right?
It's Spike, when you across the room.
So to speak, A Thousand Miles High, it may play out over tens
of thousands or hundreds of thousands of years, but it's a
spike in geologic time. Yes, so that's a nice way of
putting it, but do the geological records that you're
analyzing permit you to resolve detail within each Spike, or is
it just like one event, the two parameters that I focused on 10?
And to be the best resolve ability and those two parameters
are essentially the size of the disruption and that's basically
how much the ratio of C 13 to see 12 changes and the time
scale over which it changes it is the time scale over which the
carbon cycle is stressed out at equilibrium.
How long does it take to ramp up to its apogee?
So, to speak when the disruption is at its peak, okay?
So the size of that Peak, that you were able to measure, That
is the size of the change in the isotope ratio.
And so, you're connecting that to the mass say of the amount of
carbon that would have been injected into the system at that
time. Exactly.
So the underlying hypothesis, which is very, very reasonable.
It motivates. This is that when there's such a
change in the carbon cycle that represents an imbalance between
photosynthesis and respiration. And so this imbalance has its
own characteristic. Epic signature that known
isotopic change due to the imbalance.
We calculate how much mass was so to speak or reconfigured or
be mobilized within the carbon cycle during the course of the
event. That's a straightforward
geochemical calculation, okay? So before we talk about how
these events look, when you look at them over the whole of
phanerozoic time, what kind of physical mechanism would
underlie the injection? Enough carbon to create a spike
in your isotope ratios. Well, any of a great many.
So a popular one is excess anomalous.
Especially intensive, volcanic activity, massive volcanism.
Volcanic CO2 is isotopically light compared to our
atmospheric CO2. And so if you see the carbon
becoming significantly lighter, it's often a hypothesis that
volcanism may be the culprit of Very, very popular hypothesis.
Is the injection of methane into the atmosphere methane coming
from methane clathrates in the ocean.
Did you say methane clathrates? It's a solid form of methane,
buried beneath the seafloor. When temperatures rise, they can
be re mobilized within the carbon cycle, and this is
methane. Typically of biogenic origin,
but is Barry, but it has a way of coming back, that's an
attractive hype. Austin says, because methane is
very isotopically light compared to volcanic CO2 so you don't
need as much of it to account for the data.
Another very popular way of interpreting these things is by
changing the relative fluxes in the burial of organic carbon,
which is isotopically light. And the burial of carbonate
carbon which is isotopically heavy.
Compared to the average to change.
Those fluxes to sediment the so-called burial foxes, then the
isotopic. Ratios change.
Some of these mechanisms. I'm referring to can be thought
of as operating within the carbon cycle, such as methane,
clathrates burial is inside. Volcanism is on the other hand
outside the cycle. So, those are set of possible,
external, and intrinsic stressors.
And it's so far as the intrinsic ones go, I tend to think of them
simply as imbalances between respiration and production, you
have the planet wide ratio of carbon 12.
Carbon-13, if you like, then you said, the volcanic ratio is two
bit lighter than that more. C12 is life even more so, and
can you tease apart the various contributions?
Yeah. You can identify various sources
of light, and heavy inputs, but there are n sources of light,
inputs, and M sources of heavy inputs, and n.
And M are large numbers. Then you how can you know, which
ones did it more? Particularly the isotopic
composition of volcanic CO2, it's lighter than An atmospheric
CO2. But it represents the planetary
average because it's basically the CO2 is deeply buried within
your Earth or the carbon is deeply buried in the earth that
comes out as CO2 and it represents the isotopic
composition of carbon in the mountain.
But what happens is it because the carbon cycle photosynthesis
in particular favors, photosynthesis favors the light
isotope, it creates fractionation the difference in
the isotopic. Between light organic carbon and
heavy inorganic carbon. So what did you see when you
plotted these events on a diagram spanning?
The phanerozoic, the most interesting plot takes all of
these events and asks, how do they appear in a plot of the
size of the event versus the time scale at which they occur
timescale being distinct from time?
That is from the date by which they occur.
Heard it's did it occur over a million years over?
100,000 over 10,000 years. When you make such a plot
something interesting is already evident basically see the data
all fall one half of the plot in the other half of the plot is
empty, and divisions of the plot is a diagonal line.
And the diagonal line, you can think of is the rate of change
of the isotope ratios, as a function of the time scale at
which they occur. So, it's a kind of Flux so to
speak and isotopic flux. And what that says and this is
without any kind of interpretation, it's just say,
let's take the data and put it on this plot.
It says that there's this kind of like a speed limit stuff,
can't happen that fast. And the reason the speed limit
is there as because you don't see enormous events and small
amounts of time. What you see, instead is small
events and small amounts of times, the big events take
longer to occur. So I thought that was
interesting And so what I did is try to do something further,
which is to transform this plot and to physical axes.
So that people like us can discuss it and everybody will
understand what's there. And now, the two axes in this
plot, one is still time scale but the other is mass instead of
isotope change. So what is the mass here in
mass? Is the amount of carbon that was
taking part in this isotopic change.
So you integrate the flux, the In flux of carbon, which I think
of as a respiration flocks integrate, that respiration
flock over the time scale and you're going to mass.
And when you make that plot, the something, what in physics?
We will call it data collapse. It's actually quite remarkable
roughly half the data end up falling on a line.
What is that line? That's really interesting.
I called outlying a characteristic rate because it's
the rate of a constant ratio of Mass to timer characteristic
flux so there's this characteristic flux in the
carbon cycle. So that's one interesting thing.
Second interesting thing is that four of the five mass extinction
events, basically, not much else have flux greater than the
characteristic flux. So there are associated with
changes in the carbon cycle that occur at faster than the
characters degree and the extinction event at the end of
the Permian has by far the fastest rate and it stands out
as an extreme outlier this And on the other side of the line
are all the slow events that only Specialists have ever heard
of. And they represent small changes
occurring, longest time scales to be more precise.
They represent low flux offense. I spent quite a bit of time,
trying to figure out what this division of the space means.
Okay? So let's talk about that.
All these events that you analyze during the phanerozoic.
And I believe there were 31 of them.
Most of them actually. Fell near or on this straight
line, which represents a critical rate of change or
critical carbon flux. The criticality of that line is
an interpretation and I'll tell you how I came to that
interpretation as a matter of pure phenomenology, there's a
characteristic flocks or characteristic rate of change.
What could that mean? Well, we talked a little bit
earlier about all the ways in which the isotopic Action of the
carbon cycle could change. And that translates to all the
ways in which the carbon cycle could end up being disrupted.
And we listed a bunch burial changes, methane burps, and
volcanoes becoming anomalously active, and there's a host of
others. If all these things were going
on, some one time another, another time, why would there be
a characteristic rate? Well, I mean there could be but
it doesn't really make sense that so many diverse.
Officers would yield the same characteristic, right?
So the alternative hypothesis is that.
It's the carbon cycle that is changing and it's not really
something outside the carbon cycle.
That's making a change. There may be something outside
the carbon cycle, it instigates the change but then the carbon
cycle then carries on on its own and That's a classic way and
nonlinear physics or nonlinear Dynamics for systems to behave.
You stress them a little bit and then they become come in one
manner or another unstable. And the instability has a
characteristic signature. Maybe the simplest of the
results of such instabilities are non-linear oscillations, in
which there's a system, which goes from being inactive to
oscillating as you often see, when things start to vibrate
because of them. Very stresses that have been
placed on them. And those vibrations have a
typical amplitude and a typical frequency And the hypothesis, I
eventually came to is that what we're seeing for this
characteristic rate is a kind of shadow of that characteristic
oscillation but it's only half a cycle of the oscillation as it
goes up and it comes down and it comes back to where it came
before. And so the question is, how
could that happen? Then the theory of dynamical
systems. This is a well-known scenario
and such systems are called excitable.
Well, they're actually from a dynamical point of view always
stable, but if you stress them sufficiently but not that much.
They act as if they're going unstable and they do that only
for the equivalent of one cycle. And then they return back to the
stable equilibrium excitable systems were first studied in
Neuroscience, because this is how neurons work or sometimes
it's called Action. Potentials you inject a small?
I went into a neuron and if it goes above a threshold, in a
fire's appals, his pulse is called a spike.
This is how the brain works. For example, that's fascinating.
So they could be this dynamical system that maybe underlies the
carbon cycle, you stress it and it gets excited and does one
Excursion, which then is one of the things you pick up with your
spike in the isotope ratio and then it goes back more or less
to where it was before, right? Looks just like an excitation.
Ation. And so this is an example of
what people these days refer to as tipping phenomenon or a
Tipping Point. This is a particularly
interesting kind of Tipping Point in which we're not
Crossing change of state boundary phase transitions.
Instead, what we're doing is changing a parameter in such a
way that it acts as if across the boundary but then it comes
back to where it was. And with all these events that
you looked at you said, four The five big five extinctions, well,
above this line, which you interpret is a critical rate.
So is there something different there, that pushes them even
beyond what the carbon cycle would go to?
The idea is that most of us represent some type of modest
dress, which that is expressed by the internal dynamics of the
carbon cycle. That's a hypothesis.
That explains the characteristic.
Great. Now why are Sections above it.
I would qualify your statement a little bit more and say one is
unequivocally above the characteristic, right?
That's the end-permian extinction, three of them,
probably about it and what makes them special?
This is a great question. I say that they represent
excitations that have been stressed, well, beyond the
threshold, the excitation parameter is rate of change of
CO2. If we put CO2 into this system,
Them sufficiently fast than the carbon cycle.
Fires a kind of acidification pulse, which is a change in the
CO2 content of the oceans. If we do that in a way, that is
well beyond threshold, or the carbon cycle has some special
Dynamics to take into another region.
Then the result can be something that's effectively greater than
or worse than the typical spiking event.
It's a kind of grow since Ability as opposed to the
generic one, I don't really have a new theory of mass extinction
instead. What I am suggesting is that the
carbon cycle acts in association with mass extinctions, I can't
show that it causes the mass extinction.
I can't show that mass extinction caused the changes in
the carbon cycle. Instead, what I can clearly
point to is that there's an association that are and that
This is Association is particularly pronounced and the
cases of the worst mass extinctions, the four of the big
five. The curiosity is that there's a
whole bunch of other events, the ones I've studied, which you
might call them paleo climate events but not times of great
biotic. Turnover.
And there are significant disruptions by themselves.
And there's a very interesting question is to what makes them
different. Why aren't they mass extinction
grade? Wait, well, this study I did.
I basically undertook to try to address that question so I can
separate them in this space. I can answer your question by
saying extinctions or Worse, their excite-ation is pushed,
well beyond the threshold but there's a lot of questions that
remain unanswered just to come back to the underlying
mechanisms again. So when you have one of these
events that put you on this excursion, if you like to the
spike and then back again, do we have hypotheses as to what the
underlying chemistry? Oh, Biochemistry.
Is that first allows the Excursion at the characteristic
great and then brings it back down to where it was, that's a
good question. Any system that undergoes some
type of instability, can't stay unstable forever.
It is essentially my say, it Peters out.
Why does it do that? Is because there is always some
mechanism of dissipation. Something that slows it down and
insofar as carbon cycle disruptions go.
There's a A well-studied mechanism that slows down and
dampens out any kind of acidification Spike or Symbian
injection of CO2 into the oceans.
And that mechanism is sometimes referred to as carbonate,
compensation or sometimes referred to as the homeostatic
response of the oceans carbonate system.
At least, since the Triassic there, have been lots of shells,
littering the seafloor, which contain Minerals these carbonate
minerals, when they are dissolved by the acidic Waters
act to lower the ph. It's sometimes said that the
carbonate minerals at the bottom of the sea floor, sort of like
the oceans and acid pills that you might take when you have an
acidic stomach, they act to neutralize the pH because
they're being dissolved and that is thought to play out today.
Roughly 10,000 year, timescale, that time scale was Probably
longer in the past. And would that be because of
evolution of these calcareous microorganisms, precisely, the
invention of calcifying photosynthesizers, which created
was sometimes referred to as a deep-sea carbonate sink acts as
a stabilizing mechanism and the carbon cycle, the more carbonate
shells, there are in the sea floor, the easier it is to
dissolve these anti-acid pills on the bottom of the sea.
The easier it is to neutralize the event.
Shorter the time scale. It's a very interesting way in
which nature and maintains or tries to maintain equilibrium
and the carbon cycle, the final element of the story is that
there's always dissolved calcium carbonate coming into this
oceans via rivers and it's going out by a burial and rocks and
simply by flushing out the system at long timescales.
You also tend to dampen it out. So you talked about the
homeostatic timescale being about 10,000 years for the
modern ocean. So that's the time scale, if you
Like it takes for these non equilibrium processes to Peak
and damp out. Yes.
Because first approximation the damping time scale is also the
time scale, it takes to reach Peak disturbance.
So now I'd like to see if your way of approaching this problem
enables us to connect the events that you see in the geological
record for which, you know, the size and the duration to Events
that disrupt the carbon cycle on a much shorter time scale.
We have these events in geologic history that a current long
time. Scales tens of thousands,
hundreds of thousands sometimes millions of years and we have an
event today, which is basically is crying at a century time
scale, fossil fuel burning injection of CO2 in the
atmosphere and so it's reasonable to think that one has
nothing to do with the other, but that can't really be true.
There are Things you can learn from how the Earth system, the
carbon cycle behave in the past. So what I tried to do here show
what can be done in a quantitative way.
What we see in the data is this characteristic rate, this
characteristic rate provides a very interesting quantities says
that if things long time scales are stressed, if carbon is
injected into the system faster than the characteristic rate,
then we Serious disruption events at the same time as you
already indicated in your question.
There's also a damping mechanism.
So it was a damping mechanism and a characteristic rate and so
characteristic rate times a damping mechanism gives you a
mass or critical rate I should say because we take the
characters to create as an upper bound on the critical rate, it
gives you a critical mass. Now, why is that?
And for that, I mostly appeal to a Observation, this podcast has
been going on. Now, I'm not quite sure what it
will be after you edit it, but, you know, order, 30 minutes,
most people are probably listening to it inside and
outside let's say the CO2 levels went up 1 or 2 PPM during the
podcast. Nobody there's not a single
organism on the planet that will notice all right.
But it's rate of change will have been effectively infinite
or at least very, very large impulse or Delta function.
So You see right away that this idea of rates matter is kind of
limited in its applicability because you know here we have an
infinite right nothing's going on.
So what that means is that at the short time scale it's the
amount by which the system changes but it's the long time
scale. It's the rate at which it
changes and the way you can get the critical mass from the
critical rate is to multiply the critical rate by the damping
time scale and the product of those two because of the type of
relaxation mechanisms that talked about will give you the
critical mass and that then gives rise to a prediction we
can calculate this critical mass.
It's basically the mass that you would inject into the carbon
cycle over the typical damping time scale in this case today is
10,000 years. So we know that the critical
radius It is a few hundreds of a giga ton of carbon per year.
You multiply it by 100 years and you get a number that's on your
order of three or four hundred gigatons of carbon into the
oceans. And I believe we've put in about
200 Giga, tons. If you look at projections from
things like the ipcc report, what you can see is we will have
three or four hundred gigatons of carbon into the system, you
know, probably sometime before the end of this century is three
or 400 gigaton. Runs into the surface ocean and
so that suggests that if we stay on the present path but if it
gets over a certain amount then an instability might begin and
that instability is not instantaneous and so far as my
own work goes it would predicted a plays out over time scale
which is equivalent to the damping time scale, which is
10,000 years. So it's not something that
necessarily need to worry about the moment.
What this is They saying is that there's a very logical rational
way of looking at past carbon cycle events, and from them
being able to infer how much CO2 is too much and so far as the
future of life on Earth cars and result of this analysis, is that
anything that we can do to slow the injection of CO2 in the
atmosphere May pay out at a very long time, scale.
It's really intriguing. How you managed to connect a
short impulses? If you like that's driven by
anthropogenic fossil fuel burning with the geological
events that we see in the record.
So you mentioned a critical mass of something on the order of 300
gigatons. Are you able to figure out how
much carbon was injected into the system?
Say at the end of the Cretaceous, when the dinosaurs
died out the best work in that regard is done by some Geo
chronologiste at. Princeton that have Carefully
dated the magmatic deposits coming from massive, volcanism
in the Deccan traps in India, just before the and Cretaceous
event. Now, most people listening to
this will know the and Cretaceous event is the event
that was the demise of the dinosaurs, and everyone is
taught that, that's a result of an impact with an
extraterrestrial object, a bolide or meteor impact.
However, if you dig into it more deeply, it's also now well,
Guys, that was massive volcanism occurring at the same time and
the best geochronology shows unequivocally that the massive
volcanism was going on during this period.
Moreover, there's a significant pulse is not uniform in time,
but there's a pulse 10,000 years before the and Cretaceous event.
Now, no one's denying that the impact itself had some effect.
But now you've seen it, there's Pulse of volcanic CO2 going into
the system 10,000 years before. I know, is it this 10,000-year
number kind of interesting I thought alright because that's
the time it takes for the types of excitations.
I'm talking about to reach their worst or most severe limit and
so what you can do is put this data point on the type of plot
on talking about and on this plot we have the time scale of
the event and the side. Size of the event.
What such a plot shows is that both the magnetic flux pulse
which produces CO2 just before the and Cretaceous event and
current injection of CO2 in the atmosphere, basically exists
near the critical rate. Now, I should qualify that
because the critical rate is different in the case of the
Cretaceous event and modern disruption.
I spoke earlier of a critical mass but if we divide that
critical mass by the time scale which is injected into the
oceans, we get another rate. It turns out that because there
is a critical mass. The the shorter the time scale
of the injection, the larger is the critical rate a short time
scales. So there's basically what we
call scaling law that one can derive from this.
It says that it's short time scales.
There's not only critical mass but the critical No, Mass can be
reinterpreted as a critical rate that depends on the timescale.
The critical rate today is 100 times greater than the critical
rate in the Cretaceous and that's because this Cretaceous
event. I'm talking about plays out over
10,000 years. Or as today's event is
occurring, over a hundred years, there's a two orders of
magnitude and the rate. And it's interesting to note
that yes, of course, the current event.
Is a rate, which is 100 times faster and that's alarming by
itself, but it turns out that if you analyze it carefully, they
both fall on our rescaled critical rate line, in other
words in so far as the mass extinction risk is concerned,
both The Modern event and the and Cretaceous event appeared to
be near the critical rate. Even though the modern event as
a rate, which is 100 times faster.
So that's a pretty alarming conclusion.
That basically says that Whatever created the mass
extinction at the end of the Cretaceous was caused in some
way that you've now shown by an equivalent amount of disruption
to the carbon cycle in terms of its destructive potential.
How solid is the reasoning that led you to this conclusion?
Do you think the reasoning is solid within the data that we
have? But the most important thing
that's missing is an understanding of the negative
feedbacks that might occur. Are largely due to changes in
ecology or ocean ecology or ocean biology for that matter.
Over the course of the 10,000 years, which in the modern case,
if we disrupt it beyond the threshold, what's going to
happen? It may want to go off onto a
trajectory that would be unstable.
If the only thing that were governing the Dynamics, where
the long time scales, that is the Thousand Year.
Timescale controls on the dynamical, Adam, however, the
our system varies at a great deal of time scales, and it may
be that there are negative feedback so that occur at
Century timescales decade of time scales.
And so, on that act down this out, we don't know.
But the conclusion I'm drawing is absolutely solid on physical
grounds. Given the available data.
It's basically an attempt to say we have these observations.
What can we conclude from them? Using Elementary physical
intuition, and an understanding of what isotopic changes mean.
So what father worker observations, would you like to
see to test these ideas further and constrain the predictions a
little bit more? Any kind of data that allows us
to see stimuli distinct from responses?
Would help? And that's a difficult problem
because in geology, we usually have one window with which to
look at things and it contains both the record of the stimulus
and the response. So that would be something that
would maybe take us beyond the carbon cycle to look at other
Isotopes. Other Isotopes changes and
biomarkers organic changes the whole nine yards, so to speak
the whole periodic table. And you know, fossil changes
here basically what geochemists and paleontologist already do
but focused on the events themselves.
These periods of disruption. Dan Rothman.
Thank you very much, thank you. Oliver been a pleasure for more
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