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for over 85% of the Earth's
four-and-a-half billion year history the
planet has maintained a worldwide
greenhouse with hot and humid climates
reaching from the equator all the way to
the poles but every so often the earth
experiences a reversal world
temperatures drop and glaciers reach out
to clasp the earth and ice these
conditions have been referred to as an
ice house earth or more commonly ice
ages but catastrophic changes to the
climate don't happen without a recent so
today I wanted to journey back in time
to look at some of the causes behind
these glaciation events and see what ice
ages might be able to teach us about the
future of our planet's climate
the earth has only experienced five
major ice ages the first began 2.4
billion years ago when the only life to
be found on the planet was
ocean-dwelling unicellular and anaerobic
this all changed when evolution
delivered cyanobacteria the first
organism capable of converting carbon
dioxide and water into useful sugars
with the help of the Sun you know
photosynthesis the important difference
here however was in the waste product to
generated gaseous oxygen prior to this
the highly reactive gas had never before
been found in the atmosphere instead
methane a powerful heat absorbing
greenhouse gas was found in abundance
the only problem was in the presence of
oxygen methane reacts to produce carbon
dioxide and water vapor carbon dioxide
while still a greenhouse gas isn't
nearly as good as methane and retaining
heat in the atmosphere while water vapor
mostly would have precipitated out of
the air and into the oceans minimizing
its effects on the climate what this led
to was the atmosphere being gradually
drained of its methane and replaced by
less substantial greenhouse gases until
for the first time ice formed on the
surface of the earth beginning what's
known as the huronian Ice Age the extent
to which glaciers encompassed the planet
during this time is not entirely known
as each subsequent ice age tends to
remove nearly all evidence of those
preceding it but we do know that after
most of the world had been buried
beneath ice for 300 million years the
veil slowly lifted and the earth
transitioned back to a swampy lush
jungle from here it was more than a
billion years before the earth glazed
over with ice once again this time
thought to have been caused by an
increase in volcanic activity now
considering volcanoes have been and
still are one of the largest sources of
greenhouse gases on our planet this
statement at first might seem backwards
but the other major side effect of
volcanism is the creation of new
on the Earth's surface and while it's
easy to assume that after their
formation these rocks remain mostly
fixed and unchanging this isn't true
different aspects of the environment are
always interacting with one another
either physically or more importantly to
us chemically you see carbon dioxide in
the atmosphere can react with water
vapor to form carbonic acid when this
weak acid eventually rains down to the
surface it interacts with newly
generated rock like feldspars leading to
what's known as chemical weathering what
this does is alter the feldspar into
what's known as kaolinite while
producing calcium and carbonate ions
which surprise-surprise react to form
calcium carbonate another rock what this
means is that the formation and
weathering of new rocks can actually
draw carbon dioxide out of the
atmosphere and lock it away into new
rock and shortly after as a result earth
entered into the most severe glaciation
event in history the cryo jinny an ice
age glaciers extended as far as the
equator while the ocean became a mixture
of
ice sheets and sloshed sealing virtually
the entire planet - beneath a layer of
ice but eventually either by chance or
more likely as a result of the extreme
resource limitations of the time this
period saw the evolution of the first
predatory zooplankton which could feast
on the virtually defenseless
phytoplankton providing for the first
time a control mechanism for these
abundant photosynthesizers
so after 100 million years of sustained
volcanism with oceanic carbon retention
and an all-time low the balance of power
shifted back towards greenhouse
conditions and the earth thawed once
more the next ice age wouldn't come for
another 200 million years with what's
known as the Andean Saharan Ice Age and
I have to be honest here not much is
known about this period of glaciation
it's thought to possibly have been the
result of a massive collision somewhere
in the asteroid belt known as the
Ordovician meteor event what this did
was send a large amount of debris into
the path of Earth's orbit which over
hundreds of
thousands of years would fall to the
earth increasing the atmospheric dust
levels to several orders of magnitude
higher than what they are today and when
dust is in the atmosphere the small
particles can sort of act like tiny
mirrors reflecting away sunlight before
it can reach the surface basically the
opposite of a greenhouse gas whether or
not this was the main cause behind the
third Ice Age event we know that only 30
million years were spent under the ice
making this the shortest ice age by far
not long after this however by around
360 million years ago a new evolutionary
path was being explored which led to
another precipitous drop in carbon
dioxide an abrupt rise in atmospheric
oxygen for the first time in Earth's
history plants began to grow on land
before this point life had essentially
been restricted to the oceans but with
the development of things like tree
ferns and like Oh pods Earth's land
masses were rapidly colonized with
carbon dioxide depleting and oxygen
producing life pretty soon plants were
building structures like lignin and
cellulose which due to their complex
structures have incredibly slow
decomposition rates this means there was
enough time for them to get buried
preventing their further breakdown and
storing the carbon in their bodies
beneath the surface into what would
eventually become coal as a result
atmospheric oxygen levels rose to over
35% while carbon dioxide levels fell
below 300 parts per million and the
planet entered the late Paleozoic Ice
Age
ironically it got so cold that many
plants had trouble growing and oxygen
content was so high that fires could
burn hotter and larger than they can
even now helping to periodically remove
vegetation and return carbon to the
atmosphere on top of this around 25
million years into this Ice House event
the Earth's mini landmass is assembled
into a single monolithic continent
Pangaea with an interior too vast for
most moisture to seep in from the oceans
the water that kick-starts chemical
weathering wasn't coming in contact with
the rocks at the core of the lane
as a result of having two major carbon
sinks weakened co2 could once again
begin to build back up in the atmosphere
just a nudge is all it takes and from
here as some ice melt began to occur
this revealed the darker surfaces
beneath otherwise known as decreasing
the albedo of the planet's surface
leading to greater heat absorption
creating a feedback loop until the earth
was again free from ice from this point
the earth had to wait another two
hundred million years before South
America broke apart from Antarctica
opening up the Drake Passage and
allowing for the formation of the
circumpolar and Arctic current what this
did was isolate the southern continent
from the warmer equatorial currents that
otherwise would have been forced to
circulate around the pole cut off from
Equatorial heat Antarctica formed
massive ice sheets 41 million years
before there would be ice found at the
North Pole but slowly as the continents
continued to break apart the shoulders
of North America and Eurasia closed in
around the Arctic Ocean again blocking
those warm equatorial currents from
entering the waters here meanwhile the
Indian subcontinent was colliding with
Asia and as a result was building the
Himalayas or in other words exposing
more rock for the same chemical
weathering we talked about earlier
leading to more co2 leaving the
atmosphere and therefore decreasing the
world temperatures enough for ice to
form at the North Pole officially
marking the start of the quaternary ice
age some 2.5 million years ago due to
the recent timing of this glaciation
this is also the ice age we know by far
the most about and some of the ice
created during this glaciation is still
on earth today by drilling into the
ancient ice preserved beneath Antarctica
and analyzing the composition of the
trapped air bubbles we've been able to
determine historic carbon dioxide levels
dust concentrations and even reconstruct
temperature now looking at this it's
pretty easy to see the correlation
between carbon dioxide and temperature
but their correlation with dust might
not be as obvious you see when the earth
gets
colder the air overall cannot hold as
much moisture and the planet as a whole
becomes drier exposing the surface and
allowing for greater amounts of dust to
be kicked into the air so knowing this
in going back to this graph what we can
see is that there's a spike in dust
particulates every time the earth's
temperature reaches its periodic minimum
but what I really wanted to use this
graph to explain was the cycle of colder
temperatures followed by relatively
warmer ones all during an overall ice
age these cycles are what's known as
glacial interglacial and it's likely
that all previous ice ages experienced
similar patterns to these the cause of
this glacial interglacial cycle has to
do with the way or ways the earth orbits
around the Sun the Earth's orbit
periodically changes in three main ways
precession obliquity and eccentricity
now correlating any one of these cycles
to D place your interglacial patterns is
difficult because they all happen
simultaneously and the effects of one
may either cancel out or exaggerate the
effects of another but simply put we can
see that the Earth's relation to the Sun
is the source of cyclical changes to the
Earth's climate what this also reveals
is that changes in relation to the Sun
are not responsible for beginning or
ending any of the ice ages if they were
we'd see ice ages not just behaving but
actually occurring cyclically as well
each one is truly unique what we can
learn from this is that while smaller
variations in the Earth's climate can be
caused by changes in the Earth's
position relative to the Sun the larger
climactic changes ie the ice ages or
global warming events have and always
will be determined by the composition of
our atmosphere using this graph then we
can see that without humans the earth
would be on track to re-enter a far
colder glacial period sometime in the
upcoming fifty thousand years but now
showing modern carbon dioxide levels we
can see that what we've been putting
back into our atmosphere pales in
comparison to anything we've seen
previously over the past few hundred
thousand years and if we've learned
anything at this
it's that because of the Earth's
inherent composition which was
determined billions of years ago during
its formation the planet naturally
favors greenhouse conditions every time
the climate has diverged from this it
was in large part due to the removal of
greenhouse gases from the atmosphere and
the only way the earth could return to
such conditions was for these gases to
be replenished today we're putting this
carbon back into the atmosphere and
simultaneously reducing the planets
ability to absorb and sequester it given
enough time the earth will react in a
huge way to this change for the warmer
which is a problem not because I don't
like warm weather but because humans
evolved during and as a result of the
Icehouse conditions experienced by the
earth historically these are the ideal
conditions for human life
and while the cycles of global warming
and cooling have never fully eradicated
life on Earth they have been responsible
for mass extinction events nearly every
time
hey so I hope you enjoyed and if you did
well you're in luck actually because
this was part one of a two-part Ice Age
series and next time we'll be going a
bit more in depth about that ice age
were in right now so subscribe and stay
tuned of course if you'd like to help me
in this process you can always check out
my patreon like all of these people
going by on screen it's a big help
getting these videos done thanks