The change in orbital shape was already known as one of the Milankovitch cycles [1]. This study seems to give us the most precise measurement.
In the context of climate change, when Earth's orbit becomes more eccentric (our path over the next 200k years) seasonal changes increase in magnitude.
> In the context of climate change, when Earth's orbit becomes more eccentric (our path over the next 200k years) seasonal changes increase in magnitude.
Isn't that only so on one of the hemispheres? Right now, earth is slightly further away from the sun when its summer on the northern hemisphere which means that our summers are some 5-7 days longer than our winters and our seasons are actually less intense here.
It’s more complex than either case. The eccentricity of earth’s orbit precesses, as well as earth’s axial tilt.
In a circular orbit, the seasonal variation is driven solely by the axial tilt and relative hemispherical insolation bought about by earth’s own shadow, and angle of the sun to terrain.
With a variable distance from the sun, the seasons become erratic, as these two variables precess out of sync - you end up with winters in one hemisphere where the earth is close to the sun, making for mild winter and scorching summer in the other hemisphere. Equally you end up with the earth far from the sun, and bitter winters and cool summers. Finally, you have the precessions 180 degrees out of sync, and you end up with almost no seasonal variation.
So - it makes the overall swings far more extreme, but in some phases can result in milder seasons.
We're headed to the end of the current interglacial, returning to a drastically cooler climate.
The last interglacial (the Eemian [1]) lasted 15k years and was warmer than what we experience today; sea level at peak was probably 6 to 9 m (20 to 30 feet) higher than today; Scandinavia was an island. Then the glaciation returned for 100k years with mile-thick ice sheets covering huge parts of Europe and North America, until the current interglacial got going almost 12,000 years ago. [2]
"The axial tilt varies between 22.1° and 24.5°, over a cycle of about 41,000 years. The current tilt is 23.44°, roughly halfway between its extreme values. The tilt last reached its maximum in 8,700 BCE. It is now in the decreasing phase of its cycle, and will reach its minimum around the year 11,800 CE. ... decreasing tilt may encourage the onset of an ice age ..." [3]
> I'm just some poor slob who visited an ordinary school, not an astronomer, not special in any other way, and I still remember that we learned this stuff back then. Astronomy 101.
Not everyone is required to take Astronomy courses in school. For example, my formal education never included it.
> I am really fascinated to see that Milankovic is finally becoming more relevant today. (Ask about a famous Serbian scientist, and everyone can mention Tesla. Ask for the next one, and observe. But that's a good test
While Tesla was ethnically Serbian, I'd consider him to be an American scientist since that's where he lived for most of his life, and did most of his work. Plus he was born in what is today Croatia. Honestly, though, does it really matter other than for fictional nationalistic bragging rights?
> I bring this up in a comment here, and all I get is downvotes
Because you're acting like a snob?
> It's Milanković actually, and that guy also has his own entry on Wikipedia
Had you taken the care to actually read the article you linked, you'd notice that the name of the cycle is Milankovitch, regardless of the actual name of its eponym:
> The second contribution is the explanation of Earth's long-term climate changes caused by changes in the position of the Earth in comparison to the Sun, now known as Milankovitch cycles
>While Tesla was ethnically Serbian, I'd consider him to be an American scientist since that's where he lived for most of his life, and did most of his work. Plus he was born in what is today Croatia. Honestly, though, does it really matter other than for fictional nationalistic bragging rights?
Yes. It matters if one keeps a tally of what one civilization or another did, like we do for ancient times, and the future will do for us for example.
It also matters if one wants to get an estimation which country, kind of educational system, laws, etc, produces more or less good outcomes (e.g. innovation) in this or that field.
And of course, if the person claimed he is so or that, and cherished that, we should respect them, and not rebrand them. For example there are examples of famous immigrants to US, France, and other places, in literary and other circles, that don't like to adopt their country of citizenship as their nationality. For them their culture is always their other one, and their citizenship is only a matter of residence, convenience etc.
> Not everyone is required to take Astronomy courses in school. For example, my formal education never included it.
No wonder that flat-earthers are still a thing. If that is not basic, fundamental, general education, I don't know what is. The world is officially screwed. I don't give a fuck anymore.
> While Tesla was ethnically Serbian, I'd consider him to be an American scientist since that's where he lived for most of his life, and did most of his work. Plus he was born in what is today Croatia. Honestly, though, does it really matter other than for fictional nationalistic bragging rights?
Exactly, ethnically Serbian, that's the sole reason I used that adjective. Why do you bring up nationalism here? Are we a bit projecting here? I'm not even Serbian or anything close. If you want to consider him an American scientist, that is perfectly fine, you have solid ground for that. Plus, it's pretty irrelevant what the birthplace is known as today. Back then, it was the Austrian Empire, and many Serbs were a part of it at that time..
> Because you're acting like a snob?
A snob? For stating what is a simple and harmless truth? I'd rather say that I caught some subset of the HN target demographic on the wrong foot. But it's okay, no one likes to get called out for their bullshit. Intellectual honesty is dead anyway, in a world where "fake it till you make it" is seriously considered good career advice.
> Had you taken the care to actually read the article you linked, you'd notice that the name of the cycle is Milankovitch, regardless of the actual name of its eponym:
I'm perfectly aware. But I choose to not follow here. You know, English is not the only language on this planet. I am not a native English speaker as well, so why should I care..
> A snob? For stating what is a simple and harmless truth?
No, for being annoying about it.
> I'm perfectly aware. But I choose to not follow here. You know, English is not the only language on this planet. I am not a native English speaker as well, so why should I care.
Because you went and decided to call out an English speaker, who was writing English, on the "incorrect" spelling of an English word? Sure, in Serbian it might be "Milanković's cycles", but in English it's Milankovitch.
> Ask about a famous Serbian scientist, and everyone can mention Tesla. Ask for the next one, and observe. But that's a good test, to see who really gives a damn about science
It is a horrible test. There’s a large difference between being interested in the history of science, and who did what and where they hailed from, and actually being interested in science.
Just because I don’t care to read tabloids about the personal lifes of actors and where they are from doesn’t mean I don’t like movies.
Wrong. It's a perfect test, to see whether a so called climate scientist is actually worth his salt.
> There’s a large difference between being interested in the history of science, and who did what and where they hailed from, and actually being interested in science.
I fundamentally disagree. If you are really interested in science, but not in the history of science, you are doing something very, very wrong, and you are bound to repeat a lot of mistakes if you are not willing to learn lessons from history. But my suspicion is, while many people claim to be interested in science, because it's 2018 and it is definitely fancy to do so, they deep down do not care. Participating in bullshit events like "marches for science" is a really poor disguise, in my opinion.
I was not, I have never been to Serbia in my whole life.
I learned this in school nonetheless, I don't know what so say anymore.
Many more had this covered in school as well, I believe, but hey, maybe you simply forgot? I find that lack in general education in that regard a bit disturbing.
But let me compliment you that you actually went ahead and learned a bit more about the details on your own volition. That means there are at least two of us on here..
> Ask about a famous Serbian scientist, and everyone can mention Tesla. Ask for the next one, and observe.
I was going to mention Mohorovičić [1], but it turns out he was Croatian (which to me means that Milanković and Mohorovičić were both Yugoslavians, but the Serbs and the Croats don't seem to view things that way).
Then I remembered the Serbian-American inventor/engineer Michael (or Mihajlo) Pupin [2], who really deserves to be better known. Besides being an inventor, he won a Pulitzer prize in 1924 for his autobiography, "From Immigrant to Inventor". Anyway, that's the main reason I'm posting this comment, to attempt to rescue Pupin from semi-obscurity.
But while I'm here, I'll mention that I didn't learn about Milankovitch cycles in astronomy courses, but in geology courses, because of the cycles' influence on the timing of the Ice Ages.
But at least you learned about it.. thank god, I was starting to lose my faith in humanity.
And thanks for the shout-out to Mr Pupin and Mr Mohorovičić, and for providing some links as well, I wholeheartedly approve of any attempts to rescue important characters from their undeserved obscurity. Really appreciate it.
> I bring this up in a comment here, and all I get is downvotes. Which tells a lot about HN, I think.
You've managed to be dismissive of everyone that knows slightly less than you, everyone that didn't cover this in school, and at the same time dismissive of everyone that knows much more, climate scientists.
Apparently you think this is universal knowledge but somehow has escaped the attention of climate scientists.
I expect this is the danger quote "“The climate cycles are directly related to how Earth orbits the sun and slight variations in sunlight reaching Earth lead to climate and ecological changes,” said Kent, who studies Earth’s magnetic field. “The Earth’s orbit changes from close to perfectly circular to about 5 percent elongated especially every 405,000 years.” which comes from here (https://news.rutgers.edu/earth%E2%80%99s-orbital-changes-hav...)
It is extravagant and ludicrous to claim that the signal of human influence (CO2 ppm?) on the climate is magnitudes higher than that of the Milankovitch cycles -- which have been driving the regular glaciations and interglacials over the last 3 million years.
That said, we do use ice cores from periods that would cross multiple of these cycles. If these cycles change how we estimate those values, then the statistical models we’ve built based on them will need to adjust accordingly. So, it’s not that it doesn’t have an impact, just that the impact probably doesn’t change the trend line.
There are multiple cycles in that theory, not just one, so the influence on our climate depends on the periods of all these cycles, and involves potential amplification due to their harmonies. The largest observed signal in the geological record of the last 3 million years is a ~100k cycle of interglacials within an Ice Age.
Accordingly we should expect the current interglacial to end "soon" and enormously thick ice sheets shall grow again -- we're 12k years into the Holocene; the last interglacial lasted 15k years.
TLDR; Scientists believe the Earth's orbit oscillates between circular and more elliptical due to the gravitational pull from Jupiter (big) and Venus (close). It takes 405k years to complete a cycle.
> it will give scientists a much more accurate method of dating prehistorical events — the dates of fossils, for example.
> “The dream is have a framework independent of the fossils that you can plug the fossils into and see more interesting things — the coexistence of disparate forms, or of similar forms widely separated in location. Now we can place things more accurately in time rather than depending on the fossils to tell us what the time is.”
It's also fascinating to see how it was done:
>By comparing the amount of decay of uranium to that of lead trapped in zircon, the layers in the Arizona core can be dated quite accurately.
What do you mean by fundamental here? For studying astronomy at an university? Then yes, agreed, but I am wondering about the very basic understanding of the principles at all, are you implying that kids today don't learn this anymore? You know, what our solar system is, what the earth is, and it's, well, shape..
This particular cycle was not taught in the Astronomy PhD courses where I attended. Your comment near the top of this thread appears to claim that it's a part of 'basic astronomy'. That is not correct. The precession of the equinoxes is basic astronomy.
(Ha. Firefox's spellcheck doesn't have "precession" in it.)
Guess I should consider myself lucky that I had a physics teacher who taught us about the thing that we stand on and live on, what it is, where it is, what's around and how our solar system works.
Ha, I am really shocked now. Honestly, I can't believe this. I should probably not dare to ask someone on HN if they ever heard about the Milk Way or something.
You think this is equivalent to knowing about the Milky Way? You seem to have put some major significance on something that really has very little baring on our day to day lives. Im sure most countries teach a good deal about the solar system and the planets, It's taught at a very young age in the UK and its refined through the years of school to the point where you should have a good understanding of it all. But we never put any emphasis on this. You know why? Its irrelevant at that level. Unless you are studying for a degree or even higher this won't have any baring on what you are learning.
At times of higher eccentricity you get more pronounced differences between summer and winter. If this coincides with a glacial period (and it has) that probably means that the glacial period sets in faster / is colder than when the orbital eccentricity is low -- but it also means that interglacials set in faster and are warmer.
Because eventually perigee coincides with summer or winter in either the Northern or Southern hemisphere (and then the apogee will coincide with the other hemisphere's opposite season, naturally), so one of them will get more sunlight (heat). BUT! The Northern hemisphere has much more landmass than the Southern one, which accentuates the differences between seasons because land heats up faster in the summer and cools down faster than the oceans in the winter, and also land provides a platform for ice accumulation. This is the reason that glacial periods involve much more ice in the Northern hemisphere than in the Southern hemisphere.
It is generally believed that glacial periods set in when the Northern summer coincides with the furthest point from the Sun on Earth's orbit, while interglacials set in when the Northern summer coincides with the point of closest approach to the Sun. Summer is the key because once ice lasts past the summer then summer cannot heat up the Northern hemisphere as much as usual: ice reflects a lot of the Sun's energy. Conversely, if the summer is warm enough to melt more snow and ice than was accumulated during winter, then you can't have a glacial period.
It is important to note that there are other orbital cycles that matter here, especially the precession of the equinoxes, which is the cycle that relates which hemisphere gets its summer closest to the Sun. Earth's axis of rotation itself rotates, very very slowly. The precession of the equinoxes is a 25ky cycle.
Another cycle is the angle of the Earth's axis of rotation to the ecliptic. This varies a fair bit over the years, and this one is (IIRC) the most chaotic of the orbital cycles.
All of these cycles, known as the Mylankovitch cycles[0], have winter/summer difference accentuation/attenuation effects. The Mylankovitch cycle theory is that when these coincide in certain ways you get glacial or interglacial periods.
yeah makes little sense since the earth is closer to the sun in january. if anything higher eccentricity should reduce seasonal differences. (seasonal differences being driven mostly by earth tilt, not distance from sun)
In the context of climate change, when Earth's orbit becomes more eccentric (our path over the next 200k years) seasonal changes increase in magnitude.
[1] https://en.wikipedia.org/wiki/Milankovitch_cycles#Orbital_sh...