Kind: captions
Language: en
this is our climate what do I mean most
of us have heard of the ice ages from
movies 20,000 years ago places like New
York City were covered in ice but that
wasn't the only time there were a bunch
of ice ages going back millions of years
and here's the crazy part by looking at
cores of mud from the bottom of the
ocean we can tell that these ice ages
actually came and went on a schedule
like clockwork in fact the entire world
got hotter and colder with the ice ages
so what caused these huge swings in
Earth's climate
actually it was clockwork corresponding
to slight shifts in Earth's orbit
now called Milankovitch cycles after the
Serbian scientists who started to figure
this out
we know that the gravitational pull of
the Sun Moon and other planets makes the
Earth's axis wobble like a top on a
cycle of about 20,000 years the tilt of
the earth also shifts about every 40,000
years and the shape of Earth's orbit
around the Sun goes from more circular
to more like an oval on a schedule of
about a hundred thousand years all of
these changes affect how heat from the
Sun warms the northern hemisphere where
ice sheets can grow so the same types of
planetary movements that create our days
weeks and years actually seem to also
create something like super seasons our
climate but that's only part of the
story because with the orbital cycles
when the Northern Hemisphere warms the
whole planet warms and when the northern
hemisphere cools the whole planet cools
changes in Earth's position set the
tempo of the climate clock but they
don't explain why the shifts in
temperature are so extreme and why their
global going from times when New York
City could be covered in a thick layer
of ice the times like today when it hits
a hundred plus in summer so what else is
going on here a major clue came when
scientists extracted cores of ice from
Antarctica dating back hundreds of
thousands of years and inside of them
were trapped little air bubbles of
ancient atmosphere they revealed the
amounts of carbon dioxide in the
atmosphere going back 800,000 years
remarkably the rhythm of this record
matches that of the ice ages recorded in
the ocean months almost perfectly
we know that co2 is a greenhouse gas a
gas that traps heat on the planet so
this could explain those huge global
shifts but where did the co2 come from
why would gas in our atmosphere match
the tilt and wobble of Earth this is
where that can of soda comes in
[Music]
these are carbon dioxide bubbles now
visible because I just depressurize the
can of soda one theory is that as the
ice sheets melt they release pressure on
the world's volcanoes setting them off
like a freshly open can of soda but that
can only account a little bit for what
was going on another theory is that the
oceans act like a sea of soda how do I
get a ton of bubbles to come out by
stirring it up the same thing happens
with the world's oceans they also
contain carbon dioxide and our planet
the Blue Marble is 70% ocean now even
though a can of seawater doesn't have
quite as much carbon dioxide as a can of
soda that's still a lot of carbon
dioxide in all of the world's oceans and
when I should start to grow that changes
everything
the wind patterns change which shifts
ocean currents and that changes how the
ocean mixes scientists believe that the
biggest reason co2 tracks the orbital
cycles is because when the planet warms
just a touch that enhanced ocean mixing
and then just like our stirred soda the
oceans lost some of their fizz to the
atmosphere and more co2 in the
atmosphere meant more heat trapped on
the planet but today there's another
source of carbon dioxide every year
humans dump over 30 billion tons of
carbon dioxide into the atmosphere
that's well over 50 times the amount
that comes from volcanoes as a result
we're warming the planet 10 times faster
than anything we've ever seen before the
tight link between the orbital cycles
and the atmosphere is gone
we've actually broken the climate clock
[Music]