Is an Ice Age Coming? | Space Time | PBS Digital Studios


Earth’s climate shifts
between short periods of warm and long, long
periods of frigid cold. Based on past pans,
there’s reason to think that the current warm
period might be nearly done. Is the Ice Age coming back,
or will human activity swing us wildly in the
opposite direction? We live in an ice age. Our geological period
is the Quaternary, and is characterized by a
massive glaciation– vast ice sheets stretching
from the Arctic all the way down to the Missouri
River through Siberia, much of Europe, and spreading out
from all major mountain ranges. OK, sure. Right now, we’re in a
brief interglacial phase– a relatively summery
stretch in which the glaciers have retreated. These interglacial
periods are short lived. The Quaternary Ice Age has
lasted 2.5 million years so far. It’s 10,000 to 15,000-year
warm patches are separated by glacial periods that last
several times as long as. The current respite is
called the Holocene era, and it began around
11,000 years ago. Temperatures rose, glaciers, and
woolly mammoths migrated north, and humans thrived. This new era of
warmth and plenty saw the rise of agriculture,
writing, cities, and technology. All of our recorded, even
our remembered history, is of the Holocene. You might forgive
us for imagining that these relatively
summery millennia are normal for this planet. That is not the case. The current interglacial
is already long. Does this mean that the
glaciers are overdue? Is winter coming? To answer these
questions, we need to understand what triggers
the march of the glaciers and why they eventually retreat. In fact, we know the
broad answer to this, even if the details
are under debate. Earth’s motion around the
sun changes, and with it, the intensity and
distribution of sunlight. It was Serbian scientist
Milutin Milankovitch who realized that the
gravitational tug of Jupiter and Saturn would lead to
three periodic shifts that might explain the
enormous climatic swings of the Quaternary period. These are the
Milankovitch cycles. Let me summarize. One– the elongation
or the eccentricity of Earth’s elliptical orbit
shifts from almost completely circular to somewhat more
elliptical in 100,000-years cycle. At the absolute
maximum eccentricity, Earth’s most distant
point from the sun– the Aphelion– is
about 30% further than the closest
point, the Perihelion. One hemisphere will experience
summer at Aphelion and winter at Perihelion and milder
seasons all around. That’s the north at the moment. The Southern Hemisphere is
closer to the sun in summer and further in the winter,
so more extreme seasons. However, the difference
in sunlight intensity due to this difference
in distance from the sun is much less than
the simple difference due to the seasons themselves. So this shouldn’t
be a huge effect. Two, the pointing of
Earth’s axis precesses. It rotates 360 degrees over
approximately 26,000 years. In addition, the long axis
of Earth’s elliptical orbit also precesses. Together, these two effects
define where in the orbit the seasons occur. They combine to produce a
21,000-year cycle called the precession of the equinoxes. So eventually, the north’s
mild Perihelion winter will turn into a
cold Aphelion winter. And 3- Earth’s tilt changes. Our spin axis is now tilted
at 23 1/2 degrees relative to the axis of our orbit. This obliquity oscillates
between 22.1 and 24.5 degrees over 41,000 years. High obliquity means
more extreme seasons. But it’s low obliquity that
ultimately leads to a colder global climate climate. Because then the highest
latitudes, where glaciation begins, never get much sun. Now, Milankovitch
predicted that obliquity would drive climate
variations, because it governs the strength of the seasons. But how can we test this? Paleoclimatology. We can reconstruct our
planet’s climate history by digging holes. First, glacial ice cores. The most famous is the nearly
four-kilometer-deep hole drilled in the Vostok
Glacier in Antarctica. This glacier was built up
by millennia of snowfall. Each year’s layer carries
bubbles of the Earth’s atmosphere from that time. Isotope ratios and greenhouse
gas content in those bubbles traces global climate
over the past 420,000 years. Second– oceanic sediment
cores reveal the changes in ocean floor sea life,
whose composition also depends sensitively on
ocean temperatures and salinity, and so also on
global climate and ice volume. Ocean cores get us a climate
record back tens of millions of years. If you look back to the early
Quaternary– earlier than, say, a million years ago– it
seems Milankovitch was right. Temperature goes up and down
on the roughly 40,000-year time scale of changing obliquity. But then, around 800,000
to 900,000 years ago, something changed. As Earth reached the depth
of the current ice age, the cycle shifted. Now the warm periods come
only once every 100,000 years. They seem to follow the change
in eccentricity, not obliquity. Every time Earth’s orbit becomes
more circular, the planet warms and the glaciers go away. As eccentricity increases
again, the glaciers return. This is totally weird,
because eccentricity should produce a much smaller
effect than obliquity. So what changed? It’s not entirely clear. But it may be that we’re
now so deep in the ice age that it takes all of
the Milankovitch cycles together to cause the
glaciers to retreat. Eccentricity and
obliquity and precession must line up perfectly. The eccentricity
cycle is the longest, and so the shifts
correspond to its period. OK. So we’re now in a warm interlude
in the depth of an ice age. You might be wondering, when are
the glaciers going to rush down from the north, bringing polar
bears, white walkers, Tontons? One thing is for
sure– the glaciers will come from the north. The vast oceans of the
Southern Hemisphere provide a powerful buffer
against changes in temperature. Ice struggles to
build up on water. But even now, northern winters
see ice and snow cover the land all the way down to the
continental US, Europe, and China. In summer, it
retreats completely. But if the climate were
a little bit cooler, then summer may
not be warm enough to melt all of the winter snow. Then it would build
up year after year, slowly creeping south. Now, by themselves,
shifts in Earth’s orbit aren’t enough to
radically change climate. But they are enough to trigger
positive feedback cycles. As ice cover
increases, Earth starts to reflect more
incoming sunlight. Its albedo increases. More ice means less
absorbed sunlight, lowering global temperature and
allowing even more ice to grow. The glaciation initiated
by the Milankovitch cycles accelerates. A second feedback cycle
is equally important. Cooler oceans are better
at absorbing carbon dioxide from the atmosphere, and so
the Earth’s natural greenhouse effect is diminished. There is an
unfortunate combination of orbital properties that
kickstarts this process. First, low obliquity means less
overall sun at high latitudes where the glaciers start. Second, high eccentricity means
one hemisphere experiences a bad winter at Aphelion,
further from the sun. Earth also moves slower at
Aphelion, and so those long, cold winters are
not counteracted by the short, warmer summers. And third, the procession
of the equinoxes sends the glacier-prone
Northern Hemisphere into a bitter Aphelion winter
while the eccentricity is high. So when does this happen next? Well, right now,
obliquity is decreasing, and it will bottom out
in around 12,000 years. It’s currently winter at
Perihelion in the Northern Hemisphere, but it’ll
persist completely to the bad situation
in 10,000 years. So over 10,000 to 12,000 years,
all of that points to cooling. What about the 100,00-year
eccentricity cycle that seems to define the overall cycle? Well, actually,
we’re just coming out of a peak in eccentricity. That should’ve been bad. And perhaps it would have
meant that the upcoming cooling trend would bring
the glaciers with it. However, we may have
dodged a bullet. See, the recent eccentricity
maximum was a sad little pig, and our orbit remains
pretty circular. See, as well as the
100,000-year cycle, there’s a longer 400,000-year
cycle on top of that. Roughly, every fourth
eccentricity peak is very low. That just happened. And the next peak
will be weak, also. We got lucky. We’re in a long, stable,
low-eccentricity phase. Because of this,
climate models predict that we have another
25,000 to 50,000 years of interglacial
period left And that’s only if you ignore
anthropogenic climate change. Human influence on the climate
messes with the whole equation. With CO2 now at 400
parts per million, it’s higher than at any point
in the Quaternary period. It’s been predicted
that this may extent the current
interglacial for 100,000 years. So we’ve probably at least
offset the next glaciation, although it wasn’t coming
any time soon, anyway. The real question is have we
ended the entire Quaternary ice age? Also possible. However, the recent
increase in greenhouse gases is so large and so sudden that
there’s no precedent anywhere in the climate record. This makes modeling our
influence a huge challenge. But don’t mistake that
for a lack of certainty. Our influence is
certainly enormous. There is another
climate extreme that’s much less fun than a
long, mild interglacial. That’s a sweltering
greenhouse climate, like the one that
dominated the Mesozoic when the dinosaurs roamed, or Venus. See you next week for more
cold, hard facts on Space Time. Last week, we wrapped up our
conversation on dark energy, talking about anti-gravity,
negative pressure, and conservation of energy. You guys had some
pretty deep comments. 4798Alexander4798
asks, is the universe behaving its way because math,
or is math behaving its way because universe? Whoa. Mind blown. This is a pretty
fundamental question. My guess– the universe
doesn’t know any math. It failed pre-calc. It wouldn’t know a hypotenuse
if you slapped it with one. Mathematics is a model
that we use to describe the behavior of the universe. The astonishing
thing is that it has such incredible
predictive power. Ryan Lidster and
a few others have wondered whether the energy lost
in the cosmological redshift of photons could account for the
energy gained by dark energy. OK. So to summarize, as
the universe expands, the energy in matter in
any one co-moving volume or expanding volume
is conserved. It gets more spread out, but
the method doesn’t disappear. But photons also get spread
out and they get red shifted, so they do lose energy
inversely proportional to the increasing scale factor. Now, Physics Girl has
an excellent video describing this effect. Link in the description. So could this lost energy
become dark energy? No. The scales are way off. Photons make up only a
tiny energetic contribution to the modern universe–
far less, even, than baryonic
matter, which itself is far less than dark energy. The radiation-dominated era
ended around 50,000 years after the Big Bang. These days, photons just
don’t have enough energy left to contribute. Yet dark energy
continues to be created. Eugene Khutoransky points
out that the idea that energy is not conserved in
an expanding universe is still pretty speculative. And yeah, there is
some speculation here, but I don’t think it’s
a speculative statement to say that the law of
conservation of energy, as we learned when we
studied Newtonian mechanics, is a feature of flat spacetime. Curved spacetime changes things. Even gravity from a
Newtonian perspective requires the invention
of a new quantity– gravitational potential
energy– in order to preserve energy conservation. Described in general
relativity, you can still come up with
conserved quantities– energy analogies
that are invariant in, say, an expanding universe. But, for example, a stress
energy momentum pseudo tensor isn’t mathematically the same
thing as classical energy. This gets us back to the idea
of whether the universe knows math. The universe is mechanistic
and its behavior results in emergent
mathematical laws that allow us to model and
predict its behavior. Conservation of
energy is one such law that work in flat space time. But energy itself
is not a thing. We draw energy life bars
in our animation sometimes, but the universe doesn’t have
any hidden energy counter. It just acts according to
a deep, and presumably very simple, set of fundamental
rules that give rise to mathematical relationships. And we shouldn’t mistake
those relationships as themselves being fundamental.


  1. The Cloud Mystery, a documentary featuring the theory of astrophysicist Henrik Svensmark offers a different explanation from the majority opinion that APG CO2 has caused the climate to warm. Svensmark thinks that what has caused the climate to warm is an increase in the heliosphere, particularly during the 20th century. The heliosphere expands during periods of high solar magnetic activity and wanes during low solar magnetic activity. When the heliosphere is larger and stronger it better protects the earth from cosmic radiation. When the heliosphere is smaller and weaker it protects the earth much less. Cosmic radiation causes cloudiness and a cooler climate. The isotopes cosmic radiation produce, C14, Be10, and Ti 41 appear in geologic strata that indicates cooler temperatures.

  2. I was eating all the info up until you started claiming, like the mainstream nuts, that we humans play a huge role in climate change. Check ur facts.

  3. Cycles in climate change that last thousands to hundreds of thousands of years.Yet only in the last 30 years have we collected truly accurate satellite information measuring temp and gases on a global scale.Pretty much nothing for the previous hundred years before that,except from a few scattered weather stations.Before that a few ice and seabed samples that take data from only a couple of specific points on the globe.How can you possibly say man is destroying the climate with such massive margins of error due to timescales involved astronomically, and the way we collect data.

  4. Greenhouse gas driven climate change is a mirage. It's a false narrative created to exploit cap and trade among other financial considerations. It doesn't exist.

  5. Trouble: The Milanchovich cycles don’t correlate with the ice ages. What about solar variability? Could this have been the real cause of the cycles of warmth and cold? After all, the sun is the source of all energy, and adding more “blankets” won’t keep a bed warm if nothing living is in it.

  6. Lots of good info but delivering everything as sound bites, "but then!…", "what changed?!…", "but what about!…", "well actually!…" it's so disjointed.

  7. Great work…..thanks! I'm surprised that you didn't mention the recent failure of the "Gulf Stream" that was caused by the Gulf oil spill, as its well documented….and its failure is having, and wll have even more, as the years go by. AND there is the effects of Nemesis and its orbiting planets (such as Nibiru) which are also well documented. Altogether…..we're in deep doo doo! D

  8. Ice Ages are caused by comet impacts throwing dust into the upper atmosphere blocking sunlight. Ice Ages can come on in a single year. The comet swarms causing these impacts is coming right up:
    ‘’Several diverse sources have suggested that a catastrophic celestial impact events may occur in Earth's near future. Analysis suggesting that minor cosmic events have already occurred during calendar year 2017. This web page shows cosmic events relating to a possible swarm of incoming comet fragments, some of which have already impacted Earth. Future impact events may well occur that could cause blast, tsunamis', and a major weather change resulting in a new Younger Dryas like Ice Age. Impacts in the Atlantic ocean, Caribbean and Mediterranean sea are anticipated. Peak threat times are September/October 2022 or maybe 2023. ”

  9. So we should be doing all the things we shouldnt be doing to combat the cooling by heating things up. I think we should all by a cow a first class round the world ticket to maximise the greenhouse gas emissions.

  10. The next ice age will arrive the day after tomorrow, as predicted by the most accurate weather forecast. It is caused by anthropogenic CO2 that blocks the sun's direct infrared radiation, 50% of the solar radiation energy is in the infrared spectrum range. This is a full blown anthropogenic global cooling reversed greenhouse effect.

  11. PBSIs part of the left wing Global Warming scam. This is bogus info on CO2 and climate change. Human activity is a miniscule component of climate change.

  12. might not happen in our lifetime but its a cycle the earth and sun follows its coming, Global Warming is the greatest scam ever invented by a politician.

  13. Absolutely no ice age coming for tens of thousands of years – detailed explanation here:

  14. Maybe some body should focus some super computers on the climate instead of some of the tasks that are presently employed?

  15. i'm watching hurricane Dorian coverage…….kinda bored watching news babes on the beaches looking at waves & vids of cars driving through water…….

    so after a week of "scientific" modelling & 100s of "projections,
    guess what?
    right, they haven't a clue what the hurricane is gonna do!!
    but they can tell us exactly what the weather will be in 200 years? seriously?
    so much for climate science — what a joke.

  16. Why do they make the earth& sun look like they are the same size? Very misleading. They should show the earth the size of a marble & the sun a basketball……so people better understand the difference in size. See " the size of our world" website

  17. Goes into millenial long solar orbits, goes into millenial long axis rotation, etc. Fails to mention solar cycles and the fact that we may be going into an extended solar minimum, wherein the human variable into climate change is ultimately trumped out by the Sun chilling out. Noice.

  18. "…or, you know, Venus…" well, how about Mars ? both atmospheric CO2 concentrations abvove 90% – what could make them so different ? maybe distance from the sun ? atmoshperic pressure ? oh dear, it's all so complicated, maybe CO2 isn't the one-size-fits-all explanation the Goracle spouted to all gen x-y-z, etc. … and where the hell is that Ice Free Arctic Ocean he predicted for 2013, or was it 2015, 2017 ? Finally, children, would you really rather have a mile of ice on your heads ?

  19. Man made Climate change is a lie expect snow and ice in the North by 2027 Piers Corbyn has been studying since he was 14 and he is old now.

  20. Your a good spokesman, you held my attention through out the commentary, thanks for the info ,it seems none biases, after what Al Gore got away with ,I don't trust most commentaries, on this matter of our climate, good job

  21. We are entering a Grand Solar Minimum which causes cooler temperatures worldwide. Look up Dalton Minimum & Maunder Minimum, Wolf Minimum, Sporer Minimum. They occur in cycles based upon sun cycles. Man has no effect on the climate. It's the sun. Read "Upheaval" by John L. Casey.

  22. Here's wanting to be able to explain as this fellow does. Yet would it make any difference in personal interactions specifically involving conversations with those that acknowledge climate change, but denied human influence regarding it?
    Some so-called Christion folks eminently deny the need or ability to do anything about climate change.
    Asking a perceived intelligent acquaintance although less adamant still denying the same.
    Backing away from these situations. I can't help wondering is it just as well for them? Given the world political atmosphere and the almost unimaginable sea change needed to implement policy.
    I am now teetering at the ledge of cynicism while pondering. Has the time come to hunker down into survival mode and watch civilization crumble?

  23. The last ice age was actually caused by an asteroid impact in Greenland around 12 to 13 thousand years ago, which kind of messes this all up a little. Also ocean levels are rising! Meaning less ice on the ice caps, meaning there could be global warming.

  24. It's the destroyer/God's wrath. The "chemtrails" are part of it and were also seen by ancient man. Check out the content in the description of my video titled "sun wake". Then should read the Kolbrin bible, Book of Manuscripts, Chapter 3 – The Destroyer.

  25. Just look at your Vostok data.
    You can find for example. a time of about 5000 years, were the Temperature dropped about 2 degree Celsius and the CO2 dropped about 10 ppm.
    It is said that since 1850 (industrial age) the temperature increased by about 1 degree Celsius and the CO2 increased by about 120 ppm.
    Just look at the relation:
    2 degree Celsius = 10 ppm
    1 degree Celsius = 120 ppm
    It is not relevant that it was sudden. A slow process is for the climate system more relevant than a fast process.

    If I put water in a freezer, the water will turn to ice very fast
    If the water is slowly cooled to the same temperature, the water will also turn to ice.
    However, the effect is the same.

  26. You had joy, you had fun , you had seasons in the sun,.. t.jackson. yes, it's my choice of what type atmosphere and place I choose, hhhmmm. Spookie

  27. It's awfully difficult for me to believe in climate change meteorological models that claim to predict 5, 10 , 20 or 100 years out when meteorology fails to get the 5 day forecast right . I watched them not be able to forecast 5 hours out during hurricane Dorian .

  28. Here's the thing though how does that explain the eternal ice age that happened a long time ago? I think the sun's solar cycles might have something to do with it.

  29. No, for an Ice age to be coming, it would need to have gone first. We live in (a (somewhat hot period) of) an Ice Age, that Earth has been experiencing for millions of years…


  31. Lying, Democrat garbage. He baits us until 10:47 when the global warming garbage finally comes out. Dude, 400 ppm is LOW! It was as high as 7,000 during the CLIMATE OPTIMUM. Funny how it's named that, huh?

  32. Wait, what? "Cold hard facts?" That's what you call this? It's a shame. It was actually interesting until you looked down your nose at us with your global warming nonsense.

  33. 20,000 years ago the ocean level was purported to be 400 feet lower. That would be the end of the iceage. I'm 64. I live on Galveston Island and as a child I played upon the beach and the sea level has not risen. This is the end of the natural global warming. The iceage cycle has begun. If the (LOL) scientists are lying, with record cold and snow throughout the world, I being an old man, I can only surmise that the new iceage cycle has begun. I will not see glaciation but, I have food saved for years. Food is cheap and my gardening is for growing seeds. Think about SOYLENT GREEN and the timeline was 2022. Look at the real news and weather as kangaroos are hopping over snow drifts and Hawaii having record cold and snow at the lower elevations of 6,000 feet. With crop failure because of shrinking growing season, think about the movie SOYLENT GREEN and the timeline was 2022.

  34. Think. If we are burning fossil fuels and release (Not manmade co2 as this co2 is already captured) we do not effect anything but greed for the global warming fraudulent claims. The United Nations wants to invade our country with 650 million minorities. I'm mixed blood NATIVE AMERICAN. If our country's carbon footprint is so important, why does the United Nations wants to invade our country with 650 million minorities? The Muslims controlled United Nations is committing genocide as Islam teaches to kill Jews and Christians. These genocidal invaders are using the genocidal GLOBAL WARMING FRAUDSTERS to enhance their agenda. Anyone who presents themselves with alarmist global warming needs to be charged with genocide and crimes against humanity. If you talk to me, I'm 64 and I know the truth. My IQ is not that of a school child that is being indoctrinated by socialist. Nobody has been educated that our founding fathers had given thanks to the IRAQUOIAN NATIVE AMERICAN PEOPLE for the founding of the constitution of the United States. Search, SPANISH AND MEXICAN INDIAN POLICIES and learn that Spanish and Mexicans were invaders upon Native American lands. Mexicans say that they are taking back their lands and they are going to kill the white people and black people. Muslims say they are going to take over this country and Islam teaches to kill Jews and Christians. Global warming is a hoax and criminal fraudulent claim. 1986 blood quantum law eliminates 10s millions of mixed blood native Americans having right to minority status. Global warming is used by our government, as today over 100 million NATIVE AMERICAN PEOPLE are BY MARRIAGE and BY BLOOD (terms used by our government upon tribal rolls) to disenfranchised NATIVE AMERICANS. Understand, in a few generations BY MARRIAGE and BY BLOOD will make our country majority native Americans. The United Nations wants to invade our country with 650 million minorities. They know that the iceage is coming. Agenda 2030 the United Nations will try to exterminate all stupid people. The iceage cycle has begun and you cannot stop it. You can only prepare.

  35. Ehhh. What a dissapointment. Sucha an interesting and awesomely made video explaining the macro reasons guiding the climate. But nooooo. He had to ruin this at minute 11 by talking some moronic propaganda. IPCC is sponsoring this video or what? Why YTube people are so damn afraid.

    "no presedent anyway in the cliate record". = You mentioned ice cores YOURSELF.
    As mentioned above – during jurassic period for ex CO2 concentration was few times higher then now.
    "our influance is certainly enormous"
    . CERTAINLY? REALLY? CERTAINLY? You were jsut talking about factors that just from the logic point of view are enormous in terms of influance. But yea – sure. OUR input is enourmous. No real, UNTEMPERED date support this – but sure. ENORMOUS.

    Minwhile goverments are taxing the shit out of us using this moronic argument.
    0,04%(in atmosfere) * 0,03% (max human contribution to co2 amouunt in atmos) = 0,012% of max possible contribiution. You usually round this kind of thing to ZERO.
    Add to that than green house effect is mostly due to water waport and co2 is becoming even more irrevelent.

    But hay – dude says ITS ENORMOUS.

    I myslef dont mind Earth becoming much much greener thanks to more CO2.

    FFS what a waste of good video.

  36. THIS AGAIN???? JFC you morons don't get that the Earth heats and cools yet? Or youre simply indoctrinated Marxists using this naturally occurring cycle to steal the Constitutional Rights of American Citizens. The latter is my bet. "Never let a good crisis go to waste" so the left makes one up out of thin air instead. YOU WILL BAKE THEM A CAKE!

    finally EVERYTHING i EVER heard about climatechangehype makes sense!
    i suddenly hate all those asses that took out single info parts to push their agenda -.-

  38. But how did ice age start anyway?
    Answer: 20 million years ago South America separated from Antarctica witch formed the forever lasting cold current around Antarctica. Before that it was deflected up and warmed by the land bridge.
    But then the biggy. 2 million years ago a land bridge formed between Central America and South America. Where the Panama Canal is now. This formed the Gulf Stream and sent a lot of moisture up to Green Land and the North Pole. Witch was the fuel for forming billions of tons of snow to make the ice caps. Then the video explains the rest with the solar cycles and such.
    The ice age will continue to rule for millions of years until Antarctica moves. But it’s kinda stuck. It’s all about continental drift. That determines everything on this planet. Unless an asteroid hits or something crazy.

  39. Imagine a 100,000 seat football stadium, with 400 seats reserved for the CO2 team. Do you really think THEY'RE going to be doing all the cheering?


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