Welcome to Meteorology Matters. What if we told
you that humanity's really profound influence
on Earth's climate? You know, the very air around
us might have been detectable much, much earlier
than we previously imagined. Yeah, we're talking
about a time when, like, horse -drawn carriages
were still the main way to get around. Exactly.
Long before gas -powered cars were even a common
sight. It's a revelation that genuinely shifts
our understanding of climate history and, well,
our long -term impact. Today, we're embarking
on a truly captivating journey, sort of a scientific...
thought experiment really, to explore precisely
when the human impact on our atmosphere became,
you know, undeniably discernible. It really challenges
so many assumptions about the timeline, doesn't
it? It does, pushing that moment of clear detection
back over a century. That's right. Our mission
in this Meteorology Matters exploration is to
unravel how scientists kind of peering back through
time, but using today's advanced tools and sophisticated
climate models have pinpointed a precise moment.
A moment when a human fingerprint would have
emerged. Exactly. In the atmospheric temperature
record. And this isn't just, you know, a historical
curiosity for scientists. It fundamentally reshapes
our understanding of humanity's longstanding
and often overlooked connection to global atmospheric
changes. It really makes you consider just how
long we've truly been altering our planet on
a planetary scale. It really does. So, if we're
tracing this impact, where do we even begin?
Where do we see the earliest scientific glimmers
of understanding how our atmosphere actually
works? Yeah, what was the foundation? Right.
What set all this in motion long before anyone
even thought of a carbon footprint? That's a
great place to start because the groundwork was
laid surprisingly early. Picture the mid -19th
century, a time of incredible scientific curiosity
discovery. Even while the Industrial Revolution
was rapidly expanding, a handful of visionary
scientists were quietly unraveling the fundamental
physics of Earth's atmosphere. And who were these
pioneers? What did they actually uncover? Well,
the absolute foundation of our understanding
of the greenhouse effect comes from the late
1850s, early 1860s. This is when two really brilliant
individuals Eunice Foote and John Tyndall, working
independently, mind you, conducted these pivotal
experimental discoveries. Ah, Foote and Tyndall.
Yes. They were the first to really demonstrate
the heat -trapping properties of carbon dioxide
and other greenhouse gases, too. How did they
even do that back then? Well, you can imagine
they're labs. They'd fill these glass tubes with
different gases, right? Then expose them to sunlight,
measuring how much heat each gas absorbs. Simple
but clever. Very. And Foote, who's actually a
self -taught scientist and a women's rights advocate,
she even hypothesized that an increase in atmospheric
CO2 would lead to a warmer planet. Wow, back
then. Absolutely, predicting something remarkable
for her time. Tyndall later confirmed and expanded
on her work, adding critical detail about the
specific wavelengths of heat that CO2 absorbed.
So these are like the seminal moments. Definitely.
Essentially identifying the very mechanism that
allows our planet to stay warm enough for life,
but also critically how it could be altered.
So they showed certain gases act like a blanket,
trapping heat. But did anyone before them have
inklings of this? Was the idea totally new? Good
question. No, not entirely new. But the experimental
proof was. Earlier thinkers, like the French
mathematician Jean -Baptiste Fourier back in
the 1820s, had already proposed that the Earth's
atmosphere played a crucial role in keeping it
warm. He compared it to a greenhouse, right?
Or a hotbox. Exactly. Then Claude Pouillet in
the 1830s refined these ideas, and even earlier,
the Swiss naturalist Horace -Benedict de Saussure,
like 1700s, he did experiments with something
called a heliothermometer. What now? Heliothermometer.
Basically an insulated black box designed to
trap solar radiation. So it hinted at how the
atmosphere might work. Okay, so the theory was
kind of brewing. The theoretical stage was set,
yeah. But it was the meticulous experimental
work of foot and Tyndall that really solidified
the understanding of specific gases as the heat
trappers. Got it. And this brings us to a name
many might recognize. Svante? Arrhenius. Ah yes,
Arrhenius. What was his big contribution to this?
Arrhenius, a brilliant Swedish chemist, came
along in the late 1800s building directly on
foot and Tyndall's work. And he made what was,
for its time, just an utterly astounding and
prescient prediction. OK. He was one of the first
to really recognize that the burning of fossil
fuels, mostly coal, back then during that big
industrial push, was increasing the amount of
carbon dioxide in the atmosphere. Right, that
makes sense. But he didn't stop there. He went
a remarkable step further. He actually calculated,
estimated, that a doubling of atmospheric carbon
dioxide could lead to a surface temperature increase
of around 4 degrees Celsius. Wait, hold on. 4
degrees Celsius, it sounds... uncannily familiar,
isn't that close to modern estimates for climate
sensitivity? Bingo. He figured that out over
a century ago. Precisely. It was a profoundly
insightful calculation based on the best available
physics and observations of his time. Made more
than a century ago. He wasn't just guessing.
He was using scientific principles to anticipate
a key aspect of climate change with incredible
foresight. He understood the mechanism and even
estimated its magnitude long before anyone could
have imagined the scale of fossil fuel use we
see today. That's incredible. So the theory was
there, the understanding of how CO2 warms the
planet was emerging. But to actually detect a
human influence, you need data, right? Observations.
What was happening on that front? You're right.
Theory needs proof, needs observation. And in
parallel with this developing theoretical understanding,
the practical data needed to identify these human
fingerprints was kind of slowly but surely accumulating.
By the 1860s, systematic daily measurements of
surface temperature had begun, mostly in urban
areas across Europe and North America. So like
weather station data. Pretty much. This provided
a foundational record of localized temperature
changes, establishing a baseline of sorts. But
surface measurements alone, that wouldn't give
you the full atmospheric picture, would it? You
need to go higher up. Exactly. To truly understand
global climate and the vertical structure of
temperature, scientists needed to look beyond
the surface. They needed to venture into what
they called the free atmosphere. The air masses
above the ground. Right. And that was a significant
challenge for the technology of the time. However,
pioneering efforts started in 1892. A French
physicist, Gustave Hermite, And a journalist,
Georges Besançon, launched some of the first
unpiloted weather balloons. Unpiloted balloons
in 1892. Yep. And they weren't just balloons.
They carried these compact devices designed to
measure temperature and pressure high above the
ground. That's amazing. Just sending stuff up
and hoping for the best. Kind of. It's incredible
to think of them just sending up balloons, completely
unaware they were laying the groundwork for discovering
an entirely new atmospheric layer. What a leap
of faith and ingenuity. So they were essentially
sending up little weather stations on a string
almost. Precisely. And their work paved the way
for more systematic balloon -based measurements
toward the end of the 1800s, notably by Léon
Tesserin de Borde in France and Richard Assmann
in Germany. Okay, more systematic efforts. Yeah,
they used balloons made of paper, silk, rubber,
constantly refining their techniques. And what
they discovered was truly groundbreaking. What
was it? They found that temperature didn't just
keep dropping the higher you went, which was
the common belief. Great, colder, higher up.
Instead, they observed a distinct layer above
roughly 11 to 14 kilometers, where the temperature
either stabilized or even increased with height.
Increased. That's counterintuitive. Totally unexpected.
And that finding marked nothing less than the
discovery of the stratosphere. a whole new layer
of our atmosphere. Wow. The stratosphere, that's
a huge discovery. How did that early balloon
tech evolve into what we use today? Well, these
early experiments, where they often had to recover
the instruments manually. Right, flying the balloon.
Yeah. They rapidly led to the development of
what we now call radiosons. That was a massive
technological leap. Radiosons, okay. Imagine
a small weather balloon carrying a compact instrument
package. Maybe the size of a shoebox, measuring
temperature, pressure, humidity. But crucially,
unlike the earlier ones, radio suns could transmit
these measurements directly down to ground stations
via radio. Ah, real -time data. Exactly, real
-time data from much higher altitudes as they
went up. It revolutionized atmospheric observation.
Now, truly global records of free atmosphere
temperature didn't really kick in until around
1946, or maybe more broadly with the International
Geophysical Year in 1958. IGY 58, right. But
statistical reconstructions using historical
upper air and surface data can even extend back
as early as 1918. So the observational network
was definitely growing. OK, so we're getting
temperature data from higher up. What about the
historical chemical record? How did they know
what CO2 levels were actually like way back then
before Arrhenius? That's where Earth itself acts
as a kind of historical archive. Oh, so. The
vast ice sheets of Antarctica and Greenland.
These ice cores act like frozen time capsules.
Right, the ice cores. As snow falls in compacts
over millennia, it traps tiny bubbles of ancient
air. Scientists can drill down, extract these
cores, sometimes hundreds or thousands of meters
deep, and analyze the air trapped in those bubbles.
A direct sample of past air. A direct sample
of Earth's past atmosphere. They've revealed
precise historical signals of carbon dioxide,
methane, other greenhouse gases, going back hundreds
of thousands of years, way before the Industrial
Revolution. So what did they show for the period
we're talking about, the late 1800s? From those
cores, we know that between 1860 and 1899, atmospheric
carbon dioxide was growing at a rate of approximately
2 .5 parts per million by volume per decade.
Okay, so a measurable increase even then. A measurable
increase. So you had the theoretical understanding
from Arrhenius, the developing observational
methods for the atmosphere, and now, thanks to
ice cores, a detailed historical chemical record.
The pieces were starting to come together. By
the late 1800s, early 1900s, the picture was
emerging. Burning fossil fuels released CO2.
CO2 enhanced the greenhouse effect that would
warm the surface. And the ability to measure
atmospheric temperatures was advancing fast.
But, and this seems like a big but, there was
still a crucial missing piece, wasn't there?
Something preventing them from getting the full
picture. You've hit on the critical point. Yes.
They knew broadly that CO2 would warm the surface,
but they didn't yet have a clear understanding
of exactly how these elevated CO2 levels would
specifically change the vertical structure of
atmospheric temperature. Meaning? Meaning they
didn't fully grasp the distinct and different
effects on the stratosphere versus the troposphere,
that lowest layer where we live where weather
happens. Ah, the cooling versus warming pattern.
Precisely. That critical understanding that detailed
modeling works that could show those precise
vertical changes wouldn't become a until much,
much later, specifically with groundbreaking
modeling work published in the 1960s. Wow, the
1960s, that's a significant gap. A huge gap between
the initial theory and the ability to detect
the specific pattern, the unique fingerprint
of human influence. And that missing piece, that
later development of sophisticated climate models,
brings us right to the core of this fascinating
research we're discussing. The central question
the scientists posed was, well, it was truly
audacious, wasn't it? It really was. When could
scientists first have definitively known that
fossil fuel burning was significantly altering
the global climate if they had access to today's
advanced tools and models? Yeah, the big what
if. And this contrasts sharply with a lot of
previous studies, right? which mostly looked
at surface temperature changes or maybe paleoclimate
reconstructions. Exactly. Those often suggested
a later detection time for human influence, sometimes
well into the 20th century. But this study took
a different angle. What's unique about this particular
research and why it's so compelling is its deliberate
focus on the stratosphere. Why the stratosphere?
Because that upper layer of the atmosphere is
expected to show a remarkably large human -caused
signal with very distinct patterns of change.
Think of it this way. The stratosphere is like
a quiet room. A small sound in a quiet room would
be much easier to hear than in a noisy concert
hall, right? Right. The concert hall being the
troposphere. Pretty much. The troposphere has
much more natural variability, more noise. So
the stratosphere makes the signal potentially
much clearer, easier to detect, especially early
on. It's a strategic move to find the earliest
possible evidence of our impact. So if we're
going back in time, hypothetically, with today's
tech, how did they actually construct this scenario?
It sounds like something out of science fiction,
this Gdankin world. It's an ingenious approach,
this Gdankin world, a thought experiment world.
To answer the big question, the researchers constructed
this simulated scenario with some key assumptions.
OK, what were they? First, they assumed that
global monitoring of atmospheric temperature
with the kind of accuracy we achieve today could
have existed as early as 1860. Wow. So imagine
super accurate sensors everywhere back in 1860.
Exactly. A network of highly advanced radiosondes
or even early satellite -like instruments beaming
back perfectly accurate data from every corner
of the globe right from 1860. That's a huge what
if. What else do they assume about these futuristic
historical instruments? They went further. Second,
They assumed that any instruments available back
then in this hypothetical world would have had
the same incredible accuracy as today's satellite
-borne microwave radiometers. The really precise
ones we use now. Yeah, these sensors measure
microwave radiation emitted by oxygen molecules,
allowing for very accurate temperature profiling.
So this assumption just eliminates any technological
limitations of the past. It lets them isolate
just the climate signal itself. And the input
data for their models, the CO2 levels and stuff.
Third, they ensured that the climate model simulations
they used for this historical analysis had access
to completely reliable estimates of carbon dioxide
changes. Using the ice core data and direct measurements
we talked about? Exactly. Drawn from those ice
core records, and later direct air measurements,
providing the models with a perfectly accurate
historical precedent, forcing the driver of the
change. So armed with this idealized historical
data and today's super accurate tools, what were
they actually hoping to achieve with this thought
experiment? What were the goals? This experiment
had dual ambitious goals. Primarily, it aimed
to estimate the detection times of human -caused
temperature fingerprints across different atmospheric
layers, stratosphere, troposphere, and across
various geographical regions. Okay, so when and
where could it have been detected? Right, but
it also aimed to understand how those detection
times would vary based on different choices of
the assumed start date for this hypothetical
monitoring. So starting in 1860 versus, say,
1900. Exactly. They explored a wide range of
start dates from that initial point in 1860 all
the way up to 1986. Why 1986? That's when truly
global satellite records of atmospheric temperature
change actually began in the real world. So this
allowed them to see not just when a signal could
be detected, but how that detection time itself
shifts depending on when you start observing.
Fascinating. And central to this whole thing,
you mentioned a technique called fingerprinting.
Can you explain that a bit more? How do you fingerprint
a human climate signal? Yeah, the fingerprinting
method is really the cornerstone here. It's a
powerful statistical technique used in climate
science. Its job is to distinguish human -caused
climate effects from natural variations. Like
picking out one voice in a noisy crowd. That's
a great analogy. Fingerprinting looks for unique
patterns, like the distinctive sound of a human
-caused climate signal amidst the background
noise of natural climate variability. And the
climate system has a lot of natural noise, right?
El Nino, volcanoes. Exactly. El Nino, volcanic
eruptions, solar cycles. This system is inherently
noisy. So you need a robust way to confidently
say, OK, this pattern we're seeing isn't just
natural noise. This is us. So they're looking
for a specific signature, a specific pattern.
Precisely. Specifically, this method searches
for particular model predicted patterns of atmospheric
temperature change that are characteristic of
combined human and natural influences. And for
the human fingerprint, that pattern is? It's
very distinct, characterized by stratospheric
cooling and simultaneously tropospheric warming.
Ah, that vertical structure again. Exactly. It's
not just a uniform change across the whole atmosphere.
Yeah. It's a specific vertically differentiated
structure of warming and cooling that models
predict our emissions would cause. It's like
a unique barcode for human influence. And how
do they know when that signal, that barcode,
is strong enough to be considered a definitive
detection, not just a random blip? Good question.
The confidence in detection relied heavily on
what scientists call signal -to -noise ratios.
Okay. Think of our crowded room analogy again.
If the specific voice you're listening for is
barely audible, the signal -to -noise ratio is
low. If the voice gets much louder, or the background
chatter quiets down, the ratio improves. Makes
sense. For detection to be considered robust
in this research, the human -caused signal had
to be significantly larger than the natural background
variability. Specifically, the signal -to -noise
ratio had to remain above a 1 % significance
level for a sustained period. 1 % significance?
That sounds pretty strict. It is. It means there's
less than a 1 % chance that the observed pattern
is just due to random chance or natural fluctuation.
It's a very high bar for certainty. Okay, here's
where it gets truly fascinating. the results
of this hypothetical experiment, they were absolutely
startling, weren't they? Especially for the stratosphere.
So what did this thought experiment, this Kadankan
world, reveal first? The headline finding, the
one that really makes you pause, was that a human
-caused stratospheric cooling signal could have
been confidently identified by approximately
1885. 1885. Let that sink in. That's a century
before many people even started talking about
climate change seriously. Before cars were common,
before widespread electricity. How is that even
possible? It's astonishing, isn't it? That's
just 25 years after the hypothetical 1860 monitoring
start date. Just 25 years? And what's more, even
if this hypothetical monitoring in 1860 hadn't
been global, say we only had high quality stratospheric
temperature measurements in a limited region
like northern hemisphere mid -latitudes, detection
was still feasible by 1894, yearly 34 years after
the assumed start. Why that region specifically?
That region, the northern hemisphere mid -latitudes,
actually aided early detection because it generally
exhibits lower natural temperature variability
in the stratosphere compared to, say, the more
dynamic polar regions. Ah, so it was a quieter
place to listen for the signal. Exactly. Made
it easier to spot the emerging human signal.
And the scale of the emissions back then compared
to now, it must have been minuscule. Precisely.
What makes this even more profound is the scale
of the change at this early stage. The decadal
increase in atmospheric CO2 between 1860 and
1899 was roughly 10 parts per million total.
OK, 10 ppm over about 40 years. Right. Compare
that to the first 25 years of the 21st century,
2020 -25, where CO2 levels shot up by about 50
parts per million. Wow. So the increase in the
late 1800s was a factor of nine smaller than
what we've seen recently. Yet the signal was
apparently clear enough to be detected in the
stratosphere, hypothetically. So why the stratosphere
first? What makes that specific layer so sensitive
to our emissions, and why does it show this cooling
signature? It seems backward. Yeah, it seems
counterintuitive, but there are compelling physical
reasons. First, as we touched on, anthropogenic
increases in CO2 lead to a very pronounced cooling
of the mid to upper stratosphere. Right. Unlike
the troposphere, which warms. Exactly. Think
of it this way. CO2 in the troposphere acts like
a blanket, trapping outgoing heat from the Earth's
surface. But in the stratosphere, the increasing
CO2 means more heat is radiated away from the
stratosphere, directly out into space. So it
becomes a better radiator at that altitude. Precisely.
It becomes a more efficient radiator of energy
from that altitude. Okay, so it's like the CO2
is acting as a window for heat to escape from
that specific layer. That's a good way to put
it. Second, the pattern of this human -caused
cooling is remarkably distinct. It differs markedly
from the patterns of natural variability, making
it easier to pick out. The unique barcode. Right.
Third, this CO2 -induced stratospheric cooling
actually amplifies with increasing height. It
gets even stronger the higher you go into the
stratosphere. How much cooling are we talking
about? Over the entire simulated period. From
1860 to 2024, the multi -model average global
mean stratosphere cooling ranged from about 1
.1 degrees Celsius in the lower stratosphere
to a significant 6 .0 degrees Celsius in the
upper stratosphere. Six degrees. That's a huge
temperature shift over time. It is. And the primary
mechanisms for this cooling involve that increased
longwave emissivity from CO2 radiating more heat
away and also ozone losses, particularly later
in the 20th century. Ozone absorbs solar radiation,
so less ozone means less absorption, leading
to further cooling. So multiple factors reinforcing
that cooling signal. Yes. It's a very clear,
strong signature that doesn't get easily ground
out by natural noise, especially compared to
the troposphere. Okay, so while the stratosphere
provided this early striking signal, the troposphere...
the layer closer to home where weather happens
told a different story. What did the models reveal
about temperature trends down there? Right, down
below it's different. Unlike the stratosphere,
the two tropospheric layers looked at the lower
and the total troposphere have consistently warmed
in both the satellite data we have and in the
climate models. Which is what we generally associate
with global warming. Exactly. That's the warming
we feel on the surface, the warming that impacts
our daily lives. The multimodal average warming
simulated from 1860 to 2024 for these layers
was about 1 .2 to 1 .3 degrees Celsius. OK, so
it was warming down there, too. But. Why wasn't
the human signal detectable as early as in the
stratosphere? If it was warming, shouldn't that
be obvious? Ah, that's the crucial distinction.
Despite this warming, robust, anthropogenic fingerprint
identification in the troposphere was not feasible
with an 1860 monitoring start date and only 40
years of hypothetical data. Not feasible. Why
not? The human signal simply wasn't strong enough
yet to clearly stand out from the natural background
variability in that layer. The noise was too
high relative to the signal. So when did it become
clear in the troposphere according to the models?
Consistent detection of human fingerprints in
tropospheric temperature only occurred for assumed
monitoring start dates on or after 1960. 1960,
that's a significant delay compared to the 1885
potential in the stratosphere. A very significant
delay. So the noisy concert hall analogy really
holds true here then. The human signal, the warming
was there, but it was just harder to pick out
from all the other sounds. Exactly. And the reason
for this delay is multifaceted. Firstly, as we
said, the global mean anthropogenic signals are
generally smaller in magnitude in the troposphere
compared to the dramatic cooling in the stratosphere.
OK, smaller signal. Secondly, And this is critical
for the fingerprinting method. The signal patterns
from human influence and the noise patterns from
natural variability are more similar in the troposphere.
Ah, so they look more alike. Yes, they tend to
blend more, making it inherently harder to distinguish
the human influence from natural ups and downs
early on. Okay. Any other factors? Furthermore,
the rate of warming in the troposphere only saw
a really significant increase after approximately
1980. Why after 1980? This acceleration was partly
due to controls introduced on anthropogenic sulfur
emissions, mainly in the late 1970s and early
80s. Think acid rain regulations. Right, sulfur
pollution. Prior to those controls, sulfate aerosols
from human industrial activity actually had a
damping cooling effect on the troposphere. They
reflected sunlight. So they were masking some
of the greenhouse warming. Effectively, yes.
They were masking some of the underlying warming
trend from greenhouse gases. Once those aerosols
were reduced, the greenhouse gas warming signal
became much more apparent and accelerated. So,
natural forces and even other human pollutants
can act as a kind of cloak, temporarily obscuring
the main CO2 signal. Let's talk more about that
natural variability. It's not just CO2 driving
things. How does something like a massive volcanic
eruption impact this detection process? Volcanoes
are indeed powerful short -term disruptors. Large
explosive eruptions think Krakatoa in 1883, Pinatubo
in 1991. A gum. Right. Those inject vast amounts
of sulfur dioxide high into the stratosphere.
This SO2 converts into tiny sulfate aerosols
that reflect sunlight. Okay, and these cause
temperature changes. Oh yes. Very distinct short
-term signals. How do they affect the stratosphere
specifically? We know CO2 cools it. Right. Volcanoes
do the opposite, temporarily. In the stratosphere,
especially the lower stratosphere, where most
of the volcanic aerosol hangs out, these eruptions
cause a temporary warming signal. Warming? Why
warming there? The aerosols absorb some radiation
at that altitude. This warming typically lasts
one to three years. So it's the exact converse
of the long -term cooling signal from CO2. So
a volcano could temporarily cancel out or mask
the human cooling signal there. Exactly. It can
temporarily counteract the human fingerprint
in the stratosphere, making it harder to spot,
like someone briefly turning up background noise.
And what about down in the troposphere? We usually
hear volcanoes cause cooling. Correct. Down in
the troposphere, these same eruptions cause short
-term cooling signals. This generally lasts a
bit longer, maybe three to five years. Because
the aerosols block sunlight from reaching the
surface. Precisely. So what this means for our
detection timeline is that volcanic activity
can temporarily cause the human signal either
stratospheric cooling or tropospheric warming
to dip below the detection threshold. Briefly
delaying recognition. Yes. For instance, the
study notes that the massive Krakatoa eruption
caused a noticeable dip in the signal -to -noise
ratios around 1883 -1885, momentarily obscuring
the human fingerprint just as it was trying to
emerge in that hypothetical 1885 detection scenario.
Interesting. And the troposphere cooling lasts
longer? Tends to, yes. Volcanic temperature signals
generally persist longer in the troposphere than
the stratosphere, largely due to the huge thermal
inertia of the ocean. Ah, the ocean takes longer
to cool down and then warm back up. Exactly.
It holds onto that volcanic chill for longer.
Okay, so volcanoes are big short shocks. What
other natural forces create this noise or maybe
ripples in the signal? I'm thinking about the
sun itself. Does solar activity play a role?
Excellent point. Yes, beyond volcanoes, solar
variability also plays an important role, primarily
through its roughly 11 -year cycle. The sunspot
cycle. Right. The total solar irradiance, or
TSI, the total amount of solar energy Earth receives
fluctuates slightly on this rhythm. It varies
by a small percentage. And that affects temperature.
It does. This fluctuation causes coherent stratospheric
warming during periods of high TSI when the Sun
is more active and corresponding cooling during
periods of low TSI. Okay, so the Sun's activity
can either help or hinder us in spotting the
human CO2 signal in the stratosphere. Precisely.
This natural solar forcing can either reinforce
the human -caused CO2 cooling if the sun is in
a cooling phase, or partially offset it if the
sun is in a warming phase. Making the human signal
easier or harder to detect. Exactly. It influences
the strength and clarity of the human signal,
especially for those early monitoring start dates
when the anthropogenic signal was relatively
smaller. It's like another instrument in our
orchestra, either playing in harmony or slightly
out of tune with our target CO2 sound. And it's
not just the regular 11 -year cycle itself, is
it? There are longer -term variations. That's
right. It's not just the cycle. Longer term,
lower frequency changes in the amplitude of this
11 -year solar cycle can also cause what the
researchers call ripples in the human signal
strength and the detection times. Ripples, meaning?
Meaning, the time required for detection doesn't
always just get shorter and shorter as you start
monitoring later. Sometimes, because of these
solar variations, it might take slightly longer
to reach detection for a later start date compared
to an earlier one. Can you give an example? Sure.
The study found that for a hypothetical 1920
start date, It actually took a bit longer to
detect the signal compared to a 1900 start tape.
Part of the reason was that the period following
1920 sampled larger amplitude solar cycles, meaning
more pronounced solar warming periods that counteracted
the CO2 cooling. Another ripple occurred for
analysis periods ending near a solar maximum
in the late 1930s. This caused the signal -to
-noise ratios to temporarily diff below that
significance threshold, thereby delaying fingerprint
detection for start dates around that time. So
it illustrates how these natural solar forces,
even though they're smaller in magnitude over
the long haul compared to greenhouse gases, can
still influence the precise timing of when a
human signal becomes statistically undeniable.
Exactly. They add complexity to the detection
timeline. Okay, so given the hypothetical nature
of this Gdankin world and all these complexities
with natural variability, how much confidence
can we really place in these findings, especially
those really early detection times like 1885?
The reliability seems to hinge on how accurately
the climate models estimate that natural internal
variability, the noise. That's absolutely right.
If the models underestimate the noise, wouldn't
that make the signal look clearer earlier than
it really would have been? How do we know the
models are getting the noise right? That's a
critical question for any modeling study like
this. You have to validate the model's background
variability. So how did they check? Well, for
tropospheric temperature, there have been quite
a few studies using multiple climate models,
and they generally suggest that systematic underestimates
of decadal internal variability are not a major
concern. Okay. When we compare observed variability
in the troposphere using our satellite data,
it generally aligns quite well within the range
of variability the models produce in their control
runs. Control runs being simulations without
human influence. Exactly. They just run the model
with natural factors to see its inherent variability.
The fact that the model's natural variability
matches what we actually observe in the troposphere
gives us pretty good confidence in the tropospheric
findings and detection times. OK, confidence
is good for the troposphere. What about the stratosphere,
though? That's where the really early detection
happened. Is the confidence as high there? The
stratosphere, however, presents a bit more nuance.
There are simply fewer direct long -term comparisons
available for stratospheric temperature variability
between models and observations. Less data to
compare against. Essentially, yes. We just haven't
been observing the stratosphere globally for
as long or as comprehensively. Now, while some
studies show models sometimes have smaller variability
in their control runs compared to observations.
Which would support the idea of maybe detecting
too early. Right. But it's also true that the
observed variability, the real world noise, can
sometimes be inflated by factors that aren't
fully included in the standard historical simulations
used for fingerprinting. Like what? For instance,
specific unusual volcanic eruptions, like the
huge Hungatanga event in January 2022. that injected
massive amounts of water vapor into the stratosphere,
causing unusual temperature effects not typically
simulated. Or, there might be small mismatches
in the assumed solar forcing used in the models
versus what actually happened, especially in
recent years after 2014. These things can make
the real world appear noisier. than the models
might otherwise predict based only on CO2 standard
volcanoes and solar cycles. So it's complex.
There might be slight underestimates of model
noise, but also factors making the real world
seem noisier than the model baseline. Exactly.
It's a nuanced picture. So despite these nuances,
how robust is the conclusion that a human fingerprint
could have been detected so early back in 1885
in the stratosphere? Does the uncertainty undermine
that finding? That's the key question. And the
answer, based on this research, is that the conclusion
remains incredibly robust. How so? Even if there
were some degree of underestimate of stratospheric
variability in the models, the observed and modeled
stratospheric cooling trends are just so substantial,
so large. The signal is huge. The signal is huge.
Model variability would need to be biased low
by an order of magnitude, a factor of 10, to
fully explain away those cooling trends as just
natural variability. A factor of 10 error? That
seems unlikely. Highly unlikely, based on everything
we know about atmospheric physics and model performance.
In fact, if you recalculate the signal -to -noise
ratios using the observed variability instead
of the model's internal variability, the ratios
remain incredibly strong. How strong? They reach
levels of certainty comparable to what scientists
call five sigma in physics. That's the level
often used to confirm the discovery of a new
particle, like the Higgs boson. Wow. So virtually
impossible for it to be just random chance. Essentially,
yes. Yeah. The signal is that clear in the stratosphere.
OK. And what about when global satellite records
actually began in the real world around 1986?
Did the signal become even clearer then across
the board? Absolutely. That's another striking
result. For monitoring, starting in 1986, when
we actually got comprehensive global satellite
data, The human fingerprint was detectable with
high confidence across all atmospheric layers
stratosphere and troposphere and across all geographical
regions Everywhere and every single one of the
32 different climate model simulations used in
the study every single model run showed it every
single one And this is true despite the significant
counteracting effects of the 1991 Mount Pinatubo
eruption, which, as we discussed, initially warmed
the stratosphere and cooled the troposphere.
So even with that huge volcanic disruption? Even
with Pinatubo's disruption, the underlying anthropogenic
signal was simply strong enough to emerge clearly
through that substantial natural noise by that
point. It provides overwhelming confidence in
the detection methods and the strength of the
human signal, especially from the 1980s onwards.
The message seems clear then. The human signal,
particularly in the stratosphere, is powerful,
it's distinct, and it has been for a very long
time. That sums it up well. This entire thought
experiment provides truly compelling evidence.
It suggests that with suitable high -quality
temperature measurements, the kind we hypothetically
gave the past a discernible human influence on
global climate could have been detected way back,
maybe by the end of the 19th century. And this
isn't just a hypothetical could have been, is
it? It underscores a profound reality. Significant
human interference with Earth's climate is not
some new phenomenon of the late 20th or 21st
century. Not at all. It has been present and
leaving its mark for over 130 years. It's a critical
reframing of the timeline, isn't it? And consider
the stark contrast. Those relatively small CO2
increases in the late 1800s were apparently enough
to leave a clear identifiable mark on the stratosphere.
Right. Whereas today, our increases are far more
rapid, far more extensive, and far more impactful
across the entire climate system. This historical
perspective really gives us pause. It forces
us to recognize the long -term cumulative consequences
of our industrial advancements and just how far
back our planetary influence truly extends. And
this leads us directly to the critical need for
continued observation, especially these upper
atmospheric layers that gave the earliest signals.
Why is it so crucial to keep monitoring given
this long history? Well, the findings powerfully
emphasize the indispensable importance of continuous,
high -quality monitoring of the upper atmosphere.
These atmospheric temperature changes, particularly
the stratosphere cooling and tropospheric warming
patterns, they aren't just indicators of our
current climate state. They also serve as early,
sensitive signals of the success or, unfortunately,
the failure of our climate mitigation efforts.
A real -time report card. Exactly. A real -time
report card on how our actions are impacting
the planet's energy balance. It allows us to
see if policy changes, technological advancements,
emission reductions, are they truly making a
difference in the atmosphere. And are there concerns
that this vital monitoring capability might be
at risk? Unfortunately, yes. There are always
concerns when budget discussions happen around
crucial climate satellites and vital research
programs. We've seen discussions around proposals
affecting major scientific agencies like the
National Oceanic and Atmospheric Administration
or NOAA. Right, NOAA and NASA. And the National
Aeronautics and Space Administration, yes, and
even the Department of Energy. Proposals that
if enacted, could potentially impact this long
-term monitoring capability. In what way? For
instance, we've heard about potential proposals
that could, say, eliminate parts of the National
Oceanic and Atmospheric Administration's research
division, which handles critical CO2 monitoring,
or discussions about maybe cutting some climate
-relevant satellite missions, or even stripping
future National Oceanic and Atmospheric Administration
satellites of specific climate science sensors.
So essentially we're talking about potentially
flying blind to some extent, reducing our ability
to see these changes. That's the worry. When
we lose the capability to measure and monitor
how our world is changing, particularly these
sensitive atmospheric indicators, it undeniably
makes us all less safe. How so? It hinders our
fundamental understanding of what's happening.
It weakens our predictive abilities for the planet's
future. And it leaves us more vulnerable to change
that we can't fully anticipate or prepare for.
It's like dimming the lights in a rapidly changing
room. We just lose our ability to navigate effectively.
And looking ahead. The projections for future
changes in atmospheric temperature, say over
the next 26 years to 2050, they're even larger
than the changes simulated for the period from
1986 to 2024 that we just discussed. That's right.
The rate of change is projected to continue or
even accelerate under many scenarios. So this
research, showing detection was possible over
a century ago, serves as a really stark reminder
that humanity is now more than ever right at
the threshold of what the UN Framework Convention
on Climate Change calls dangerous anthropogenic
interference with the climate system. Indeed.
We are right there. The choices we make collectively
and individually in the very near future, like
this decade, will likely determine whether or
not we cross that critical threshold into truly
dangerous and potentially irreversible territory.
It's not a problem for the distant future anymore.
Not at all. It's a challenge unfolding in real
time, requiring immediate attention and informed
decision making based on the best possible science
and observations. We've walked through a truly
captivating scientific thought experiment today
on meteorology matters, revealing that humanity's
impact on atmospheric temperature might have
been detectable over 130 years ago. It's just
a powerful reminder of how long our actions have
been shaping the very air around us. A long shadow.
It really raises a profound question, doesn't
it? If scientists back in 1885 had truly understood
the full implications of what that stratospheric
cooling signal meant, if they'd had today's clarity,
would it have prompted human societies to follow
a different path, a more sustainable one? It's
impossible to know. But it's a sobering thought.
And what does that tell us about our responsibility
to act on the knowledge, the much clearer knowledge
that we possess today? Something to think about.
Now, if you're curious to learn more about the
complexities of our atmosphere, the forces shaping
our planet's weather, and want to keep up with
current meteorology, you'll definitely want to
follow our very own meteorologist, Rob Jones.
He does great work. He does. You can find Rob
on Instagram. Just search for meteorologist.
Pretty easy to remember. On TikTok, he's TV Meteorologist,
and over on YouTube, follow his channel, Rob
Jones Hurricane. And you can also find the Meteorology
Matters podcast playlist there for more episodes
like this one. Great resources to stay informed.
Definitely. Well, thank you for joining us on
this exploration today. We really hope this Meteorology
Matters deep dive into the historical detection
of human climate influence sparks further curiosity
and critical thinking for you. Until next time,
keep looking up.