"Smart" and "Stupid" Questions - Feel Free To Ask

[oren]

 Welcome to the forum Memshin. The first post is the hardest.

[Phil.]

My first post, after lurking for several years! I am not a scientist, but read quite a bit of science in my spare time. This includes reading (and re-reading) large sections of the blog "Science of Doom" to try to familiarize myself with the basics of climate science.
I recently Googled "climate science for dummies" and one of the top results was this: https://sciencetrends.com/climate-change-dummies-basics-climate-change-physics/
The author claims that it is the 'specific heat' of various molecules that determines their green house gas property. This is quite different from what I've read elsewhere, which is that it is the ability of different molecules to absorb and re-emit long wave radiation that is important.
My question is: is there an additional role for specific heat in the dynamics of global heating, or is this author simply mistaken? (He does not seem from the article to be a denier, but might still just be misinformed)

My non expert answer:

I think he is just mistaken.

O2 and N2 being identical molecules on each end of the bond just don't have the modes of vibration to absorb and re-emit long wave radiation. Together with argon makes over 99% of atmosphere have completely negligible GHG effect. Therefore as a result remaining tiny proportions of the atmosphere like 420ppm of CO2 can have significant effects.

If Nitrogen and oxygen were only slightly worse GHGs as per his figures and total GHG effect is around 33C but represented 99% of atmosphere then very large proportion of GHG effect would be down to N2 and O2, and the effect we could get from doubling CO2 from .0028% of atmosphere to .0056% of atmosphere would be far smaller than we need worry about.

>additional role for specific heat
I wouldn't really know. I tend to doubt it but if there is an effect then it is very small.

My expert opinion is that you are right.

[binntho]

I want to add the note that in much geo-scientific literature, 1950 is used as the "now" date.  Per Wikipedia:

Before Present (BP) years is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred in the past. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date of the age scale, reflecting the origin of practical radiocarbon dating in the 1950s.
… 

Stating the baseline is very important and I'm surprised to see how often it's not done. The following is a good example, the graph is found on Wikipedia and shows an estimate for Holocene temperatures. (CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=466269)

Missing from the graph are 1) when does it end, 2) what is the baseline. I've seen this graph and others like it being used by denialists because the "now" in the graph is way below earlier Holocene temperatures.

As to where the graph ends, 0 BP is 1950 and the main axis shows a small extension beyond 0 BP so somewhere around 1970 seems reasonable.

Thanks Tor - I've always thought it was 1970, but 1950 is a much better match. That year also ended at almost -0.2 degrees below the 1961-1990 baseline so things are starting to match up!

But it sill annoys me incredibly every time I see a graph being posted without stating baseline or (when there is any doubt) the year of the endpoint. And that Wikipedia "explanation" needs to be corrected ASAP.

[binntho]

... you should be more careful.

Thanks for the advice, but I am getting too old to take advice and I've never been known to be excessively careful with what I say so I'm not sure that I'm going to change now.

But I love giving out advice, so my advice to you is to be more trusting of the good intentions of people in general, and posters in this forum in particular (with a very few, but richly undeserving, exemptions)  and less willing to jump on people when you don't really know what they are saying.

So I don't really see that we have to have a "before and after" point where "proper" measurements began when we want to talk about AGW.

I have already answered this question ...

Really? It wasn't really a question on my behalf, rather a statement, but if you have posted your take on this particular subject I'd love to read it!

Of course, the bolded statement is absolute bullshit.

Well, perhaps I should clarify: There are of course lots of things one could do, and lots of people are doing them. Greta Thunberg is a great example of an activist that actually does what she preaches, I'd love to see more  of them.

But my point was: Irregardless of what we do, the catastrophe is already here. And nothing that we (meaning the readership of this forum) can do will change that fact.

[Pmt111500]

My first post, after lurking for several years! I am not a scientist, but read quite a bit of science in my spare time. This includes reading (and re-reading) large sections of the blog "Science of Doom" to try to familiarize myself with the basics of climate science.
I recently Googled "climate science for dummies" and one of the top results was this: https://sciencetrends.com/climate-change-dummies-basics-climate-change-physics/
The author claims that it is the 'specific heat' of various molecules that determines their green house gas property. This is quite different from what I've read elsewhere, which is that it is the ability of different molecules to absorb and re-emit long wave radiation that is important.
My question is: is there an additional role for specific heat in the dynamics of global heating, or is this author simply mistaken? (He does not seem from the article to be a denier, but might still just be misinformed)

My non expert answer:

I think he is just mistaken.

O2 and N2 being identical molecules on each end of the bond just don't have the modes of vibration to absorb and re-emit long wave radiation. Together with argon makes over 99% of atmosphere have completely negligible GHG effect. Therefore as a result remaining tiny proportions of the atmosphere like 420ppm of CO2 can have significant effects.

If Nitrogen and oxygen were only slightly worse GHGs as per his figures and total GHG effect is around 33C but represented 99% of atmosphere then very large proportion of GHG effect would be down to N2 and O2, and the effect we could get from doubling CO2 from .0028% of atmosphere to .0056% of atmosphere would be far smaller than we need worry about.

>additional role for specific heat
I wouldn't really know. I tend to doubt it but if there is an effect then it is very small.

People saying millionths in volume are insignificant do not appreciate how small molecules are.

[Tom_Mazanec]

People who say millionths of volume are insignificant should be challenged to drink a bottle of water with one millionth LSD dissolved in it.

[blumenkraft]

Very good point, Tom.

As a fellow aspie once said, "The dose makes the poison".

Btw, it's the same guy who said, "I'm different. Don't let this upset you."

[Rich]

I like to use the analogy of salt in a food recipe to describe GHG's to a layperson.

With no GHG's, we'd be dead. Earth would be far too cold. We need a pinch to make it just right.

Food with no seasoning can be bland and unappealing. A pinch of salt is often a big improvement. But if we throw in a few tablespoons, we can completely ruin a much larger dish.

[johnm33]

'Specific heat' for heat storage purposes hydrogen bonds are important, so H2O is good and cheap, wood with all its hydrogen bonds is better than concrete, H2O vapour is regarded as a greenhouse gas as is CH4 so maybe there's something in what he says.

[DrTskoul]

Gaaaahh... heat capacity has nothing to do with CO2 radiative absorption properties.  Heat capacity comes into play with water vapor. But what hest capacity does is to actually reduce the temperature increase for the same energy input.

The GHG effect has nothing to do with heat capacity. Let's repeat that again....

[anthropocene]

At last! I can ask a stupid question - this is more than likely been asked before but you can never have too many stupid questions. Greenland melt and SMB are much in the news at the moment. The diagram below (the bottom graph) appears to show the SMB over the "melt" year. At the start mass aggregation is zero - makes sense. Mass is gained from September through winter - makes sense. At the end of May (ish) melting starts and SMB is started to be lost. So far so good. But the "average" graph shows that at the end of the year (End of August) SMB is approx 400Gt higher than 12 months earlier. Even 2011-2012 (the 12 month period of greatest melt?) only gets back to the zero - which means no mass was gained or lost? But Greenland is losing mass in most years. How can this be? What is wrong with the above and how should the graph be read?

[crandles]

Even 2011-2012 (the 12 month period of greatest melt?) only gets back to the zero - which means no mass was gained or lost? But Greenland is losing mass in most years. How can this be? What is wrong with the above and how should the graph be read?

Surface mass balance does not account for glacier calvings.

[binntho]

Even 2011-2012 (the 12 month period of greatest melt?) only gets back to the zero - which means no mass was gained or lost? But Greenland is losing mass in most years. How can this be? What is wrong with the above and how should the graph be read?

Surface mass balance does not account for glacier calvings.

Quite. The Greenland glacier always has a large positive annual snow accumulation. But calvings from sea-terminating glaciers mean  that most years the total ice balance is some hundred of Gt in the red.

[Stephan]

Please also refer to the dmi site and the explanations, that gerontocrat regularly gives in the Greenland melt season thread. Calving is mainly responsible for the overall loss of Greenland mass.

[oren]

It's Surface Mass Balance. In addition to calving, it does not account for marine-terminating glaciers (I think all of Greenland's outlet glaciers) directly melting in the ocean.

[binntho]

It's Surface Mass Balance. In addition to calving, it does not account for marine-terminating glaciers (I think all of Greenland's outlet glaciers) directly melting in the ocean.

Which makes sence since that is probably a much bigger factor than calvings.

[Tor Bejnar]

There are several rivers in Greenland; I'm sure most come from non-marine-terminating glaciers. From here, as an example:

Akuliarusiarsuup Kuua (Danish: Sandflugtdalen) is a river and valley of the same name in the Qeqqata municipality in central-western Greenland. Its source is the meltwater outflow from Russell Glacier, an outflow of the Greenland ice sheet.

[binntho]

There are several rivers in Greenland; I'm sure most come from non-marine-terminating glaciers. From here, as an example:

Akuliarusiarsuup Kuua (Danish: Sandflugtdalen) is a river and valley of the same name in the Qeqqata municipality in central-western Greenland. Its source is the meltwater outflow from Russell Glacier, an outflow of the Greenland ice sheet.

Well,  they won't be coming from the sea terminus, at least. But Greenland is overly blessed with large sea terminating glaciers, filling the deepest valleys (soon-to-be fjords) and having the largest drainage basins.
EDIT: I assume that the deepest valleys have the largest drainage basins, perhaps that's an assumption too far?

[oren]

This paper discusses the components of mass balance (SMB and Discharge/Dynamics) for each Greenland drainage basin.
https://www.williamcolgan.net/pubs/S0012821X14006360.pdf

[Tor Bejnar]

Yup; what did what's-his-name say to Watson?     (My point was that Greenland had some non-marine-terminating ice-sheet-outlet glaciers; you can find them by following rivers to their source, and people like to name rivers.)

Re Greenlandic drainage basins, I found A River Network Preserved Beneath the Greenland Ice Sheet - EOS

An ancient drainage basin covering one fifth of Greenland predates the ice sheet and strongly influences the modern Jakobshavn Glacier, according to a new analysis of ice-penetrating radar data.
...

Interesting question you posed, Binntho! 
Wikipedia:

Jakobshavn Glacier drains 6.5% of the Greenland ice sheet

Is this the deepest cut and largest basin?

Hydrologic drainage of the Greenland Ice Sheet has some data one can mine.

From Sciencing

The longest [fjord], named Scoresby Sund, lies in Greenland, extends 217 miles inland and is 4,900 feet deep. Scoresby Sund is one of the deepest fjords in the world.

[oren]

Yup; what did what's-his-name say to Watson?     (My point was that Greenland had some non-marine-terminating ice-sheet-outlet glaciers; you can find them by following rivers to their source, and people like to name rivers.)

And a good point it was. I was about to write "almost all" Greenland glaciers, but the couldn't think of an example and wrote "all" instead, to my shame.

Here's a huge map of surface velocities (click and zoom to appreciate), taken from https://www.cambridge.org/core/product/D22454AF22391DF03754BE6DF4C70366/core-reader

[oren]

And another amazing resource I only recently discovered.
http://polarportal.dk/en/greenland/glacier-front-positions/
If you click on Glacier Fronts, you can see a map and a satellite animation for each glacier.

[binntho]

So according to that paper, some 60% is due to SMB and the rest to other factors such as ice dynamics ... probably means ice flowing down and melting/breaking away in the low-lying glacial tongues.

Surprisingly, a very large part of Greenland bedrock is below sea level, and the drainage basins of Ice are not the same as the (eventual) drainage basins of water (a well known phenomenon).

Attached picture from https://www.geological-digressions.com/beneath-the-ice-greenlands-bedrock/

[binntho]

Of course, as the ice continues to melt, isostatic rebound will lift the underlying bedrock, leading to some surprising effects elsewhere. When a continental crusts rises due to isostatic movement, other parts of the ocean floor sink (i.e. general sea level does not rise!) and gravitational effects of dwindling ice are partly (and much more slowly) compensated for by rising bedrock.

[CalamityCountdown]

This is probably off topic even for this thread, but I wonder if it would be feasible to try to attack Fox News broadcast licences for censorship of "climate change" news. The campaign might well be successful even if it only served to heighten awareness of how Fox News censors reporting of  climate change.

The fact that in the US only 27% of Republicans rate climate change as important to their vote for Congress. (versus 75% of Democrats) signifies a huge divide
https://news.gallup.com/poll/244367/top-issues-voters-healthcare-economy-immigration.aspx

and based on conversations with viewers on Fox News, it seems like the network has a significant influence on this result. Oh  yeah, and there is another key fan of Fox News who is influenced by their censorship of climate change news

https://www.vox.com/2019/3/22/18275835/fox-news-trump-propaganda-tom-rosenstiel

[Klondike Kat]

Even that Gallup poll did not have climate change very high.  The only issue of lower importance was the investigation into the Russian involvement in the 2016 election.

[denkar]

Gaaaahh... heat capacity has nothing to do with CO2 radiative absorption properties.  Heat capacity comes into play with water vapor. But what hest capacity does is to actually reduce the temperature increase for the same energy input.

The GHG effect has nothing to do with heat capacity. Let's repeat that again....

Dr. T. is absolutely correct on this.

[SteveMDFP]

This is probably off topic even for this thread, but I wonder if it would be feasible to try to attack Fox News broadcast licences for censorship of "climate change" news. The campaign might well be successful even if it only served to heighten awareness of how Fox News censors reporting of  climate change.

Fox News Channel doesn't have a broadcast license.  It's a cable channel.  The FCC doesn't regulate cable content, unfortunately.

[philopek]

This is probably off topic even for this thread, but I wonder if it would be feasible to try to attack Fox News broadcast licences for censorship of "climate change" news. The campaign might well be successful even if it only served to heighten awareness of how Fox News censors reporting of  climate change.

Fox News Channel doesn't have a broadcast license.  It's a cable channel.  The FCC doesn't regulate cable content, unfortunately.

Yeah, probably the first round of CB-Channel owners were powerful enough to dodge that bullet.

Just imagine what would have happened (in fact happened in other places) when an average citizen would have been the first cable broadcaster of significance.

Another reason why concentrated wealth is a key-issue for many grievances on planet earth.

[Rich]

This is probably off topic even for this thread, but I wonder if it would be feasible to try to attack Fox News broadcast licences for censorship of "climate change" news. The campaign might well be successful even if it only served to heighten awareness of how Fox News censors reporting of  climate change.

Fox News Channel doesn't have a broadcast license.  It's a cable channel.  The FCC doesn't regulate cable content, unfortunately.

Why single out Fox?

ABC News spent 6 minutes on climate change in 2018, 1 minute less than they spent on the royal baby.

[nanning]

<snippage>
Dr. T. is absolutely correct on this.

Welcome to the forum denkar! Nice to see new members with a good understanding of physics.

[slow wing]

Q. Can it? My response to this statement on the 2019 Melting Thread.

There is more than enough heat in the deep water to melt the ice and keep the arctic ice free year round. 

However, the heat can not move upwards through the halocline. 

The halocline is 50 meters thick (at least) and is very difficult to breach.  If it ever happens, look out!   The arctic will be a completely different place.

I've often wondered if/why the thermal conductivity of seawater is insufficient for significant melting of the ice just by thermal conduction, when the halocline is stable.

So let's see...


Consider the year-round loss of ice thickness due to thermal conduction from a 1-degree-C-warmer layer at a 50 meter depth.


ASSUMPTIONS & PROPERTIES:

• Approximate as a thermal gradient of 1 degree (K) / 50 meters = 2e-2 K/m
• Thermal conductivity of seawater is 0.6 W/mK (It may be a little less as temperature isn't stated and thermal conductivity, of fresh water at least, falls with temperature)
• heat of melting for ice is 334 J/g
• density of ice = 0.9 g/cm^3
• 3.1e7 seconds/year
• 1 W = 1 J/s, by definition

CALCULATIONS:

Upwards heat flux = (temperature gradient) x (thermal conductivity) = 2e-2 K/m x 0.6W/mK = 1.2e-2 W/m^2

Thermal energy added to ice in 1 year = (Upwards heat flux) x (time in 1 year) = 1.2e-2 W/m^2  x 3.1e7 s = 3.7e5 J/m^2; multiply by 1e-4 m^2/cm^2 = 37 J/cm^2

Depth of ice melted = thermal energy added / (heat of melting x density)
= 37 J/cm^2 / (334 J/g x 0.9 g/cm^3) = 0.12 cm depth



CONCLUSIONS

So the thickness of ice melted over a year in the above scenario is only of order a millimeter.

Indeed, the thermal conductivity of seawater is insufficient to provide significant melting from deep layers of warmer, saltier water below the ice.

[Michael Hauber]

A surprising result.  I think there can also be some transfer of heat through eddies - the Arctic is not perfectly still but has significant currents.  See page 7 of this presentation  If momentum is transferred vertically due to mixing, I'm sure heat is as well. 

[DrTskoul]

Mike,

That is true for liquids that are not stratified with density. Try it at home with water and oil. It is generally more difficult to induce eddies across a cline. The description in the presentation is accurate for the top ocean layer generally across the boundary layer and deeper within the top 10-100 m.

[crandles]

Eddies, would think so at least to some extent. Not much with oil and water due to big difference in density and hydrophobic nature of oil, but with slight differences in salinity would expect some. OTOH if 50m+ depth perhaps not that much?

Possibly also 'double diffusion'?

i.e salt moves downwards slightly more than upwards while heat move upwards slightly more than downwards. Any heat moving up into layers of less salty water above can then move up by convection.

[sailor]

A surprising result.  I think there can also be some transfer of heat through eddies - the Arctic is not perfectly still but has significant currents.  See page 7 of this presentation  If momentum is transferred vertically due to mixing, I'm sure heat is as well.

I am convinced people overlook the effect of eddies as Chukchi currents push against the edge of the pack, create fingers of ice that are surrounded by the currents and slowly mixed with the different temperature and salinity fluid. It is very fast if one rewinds the season and looks at it. With the SSTs maps this can be seen, I highlight four instances during this season, but there’s much more, especially in the most degraded part of the edge that gets mixed in hotter water easily.

[DrTskoul]

Are those horizontal or vertical eddies ?

[Michael Hauber]

Mike,

That is true for liquids that are not stratified with density. Try it at home with water and oil. It is generally more difficult to induce eddies across a cline. The description in the presentation is accurate for the top ocean layer generally across the boundary layer and deeper within the top 10-100 m.

Maybe, but the article I quoted seems to think that there is something going on for the ocean in general, and the article doesn't seem to be limited to the mixed layer, with comments that vertical mixing is much weaker than horizontal mixing due to temperature gradient induced stability, which would not apply to the mixed layer.  And much of the general ocean has much stronger vertical temperature gradients, and I'd guess stronger density gradients and therefore stability than the Arctic?

[sailor]

Are those horizontal or vertical eddies ?

Cannot answer shortly...
Vertical eddies, produced at the vertical boundaries of the current as a result of shear flow. The shear would induce smaller vertical eddies and then 3D turbulence.  Eddies can break the horizontal stratification at the boundaries; let’s assume for a moment that the current won’t sink right away so let’s assume everything happens in the mixing layer. I bet powerful eddies can produce Kelvin-Helmholtz instability energetic enough to fold the stratification layer of the current boundary, grabbing the ice on top, and slowly mixing the water beneath ultimately in all directions within the eddy. At least I have observed these currents for years in the melting seasons and that’s how I understand what I see. They can be seen at the ice/water interface of the West Spitsbergen current too.

Probably this happens within the shelf, but at the Beaufort sea there are powerful jet-like secondary currents that project well into the Gyre. Was fun to watch them in 2016 around Big Block.

[RoxTheGeologist]

Q. Can it? My response to this statement on the 2019 Melting Thread.

There is more than enough heat in the deep water to melt the ice and keep the arctic ice free year round. 

However, the heat can not move upwards through the halocline. 

The halocline is 50 meters thick (at least) and is very difficult to breach.  If it ever happens, look out!   The arctic will be a completely different place.

I've often wondered if/why the thermal conductivity of seawater is insufficient for significant melting of the ice just by thermal conduction, when the halocline is stable.

So let's see...


Consider the year-round loss of ice thickness due to thermal conduction from a 1-degree-C-warmer layer at a 50 meter depth.


ASSUMPTIONS & PROPERTIES:

• Approximate as a thermal gradient of 1 degree (K) / 50 meters = 2e-2 K/m
• Thermal conductivity of seawater is 0.6 W/mK (It may be a little less as temperature isn't stated and thermal conductivity, of fresh water at least, falls with temperature)
• heat of melting for ice is 334 J/g
• density of ice = 0.9 g/cm^3
• 3.1e7 seconds/year
• 1 W = 1 J/s, by definition

CALCULATIONS:

Upwards heat flux = (temperature gradient) x (thermal conductivity) = 2e-2 K/m x 0.6W/mK = 1.2e-2 W/m^2

Thermal energy added to ice in 1 year = (Upwards heat flux) x (time in 1 year) = 1.2e-2 W/m^2  x 3.1e7 s = 3.7e5 J/m^2; multiply by 1e-4 m^2/cm^2 = 37 J/cm^2

Depth of ice melted = thermal energy added / (heat of melting x density)
= 37 J/cm^2 / (334 J/g x 0.9 g/cm^3) = 0.12 cm depth



CONCLUSIONS

So the thickness of ice melted over a year in the above scenario is only of order a millimeter.

Indeed, the thermal conductivity of seawater is insufficient to provide significant melting from deep layers of warmer, saltier water below the ice.

The layer down to the halocline is typically mixed as the ice freezes. Cold briny water is formed from expulsion, sinks and the upper layer becomes mixed.

The strong stratification in the melt season is unlikely to allow much heat to propagate by conduction. I'd expected much more heat to be transferred as ice freezes, and to stop it thickening as quickly throughout the freeze.

[DrTskoul]

Thank you for the answer. Very interesting. Just to make sure I did not misunderstand the answer what I asked, by horizontal eddies I meant eddies that they are rotating along an axis that is “horizontal” while the vertical eddies are due to flow around obstructions and the axis of rotation is perpendicular to the ocean surface. 

Anyway, here is an interesting graphic

[DrTskoul]

Replace thermocline with halocline for arctic ofean

[jai mitchell]

ASKING FOR A FRIEND


Why did CO2 go up during the interglacials over the last 800,000 years?

[sailor]

Thank you for the answer. Very interesting. Just to make sure I did not misunderstand the answer what I asked, by horizontal eddies I meant eddies that they are rotating along an axis that is “horizontal” while the vertical eddies are due to flow around obstructions and the axis of rotation is perpendicular to the ocean surface. 

No only vertical eddies that form in the shear layers (and stratified layers at the same time) between the currents and the surrounding ocean.
I was avoiding word halocline because I suspect this happens really in the shallow shelves as in Chukchi, where flow is vertically narrow.

[vox_mundi]

Some further info on internal waves along a halocline.



https://www.hydro-international.com/content/article/mysterious-underwater-waves

Interfacial Waves
Interfacial waves, propagating along a thermocline, are similar to surface waves. But, since the density contrast between underwater layers is much less than that between water and air, the acceleration of gravity that a displaced fluid parcel senses is reduced by approximately a factor thousand, the ratio of the cross-thermocline density difference to mean density. Therefore, interfacial waves attain larger amplitudes (up to hundreds of metres), have longer periods (longer than 10 minutes, say) and have wavelengths (up to kilometres) that are short compared to those of surface waves of identical period. Interfacial waves of tidal period (internal tides), for instance, are much shorter than the thousands of kilometres long surface tides.

Underwater interfacial tides steepen and form trains of solitary waves (see Figure 1, showing temperature as a function of time-depth). Strong accelerations in these solitons have likely caused reported submarine crashes. Because of the proximity of the interface to the surface, converging and diverging currents associated with solitary waves strain short surface wind waves, leaving an imprint at the surface that can be spotted from satellite or, as in Figure 2, airplane. Here, a front marks the transition between salty North Sea water on the left and fresh river Rhine water on the right that flows out on top of it. At the interface between the two, internal solitary waves are present. These are imaged at the surface while propagating towards the reader and quite distinct from the short familiar wind waves. Compare also to the tanker in the upper right of this photo.

[DrTskoul]

ASKING FOR A FRIEND


Why did CO2 go up during the interglacials over the last 800,000 years?

Temperature driven by orbital parameters.

The most viable hypotheses for the cause of glacial/interglacial CO2 change involve the extraction of carbon from the surface ocean by biological production, either at low or high latitudes, necessarily allied with changes in the marine calcium carbonate budget.

Glacial/interglacial variations in atmospheric carbon dioxide

[vox_mundi]

ASKING FOR A FRIEND


Why did CO2 go up during the interglacials over the last 800,000 years?

In previous warm periods, it was not a CO₂ spike that kickstarted the warming, but small and predictable wobbles in Earth’s rotation and orbit around the Sun. CO₂ played a big role as a natural amplifier of the small climate shifts initiated by these wobbles. As the planet began to cool, more CO₂ dissolved into the oceans, reducing the greenhouse effect and causing more cooling. Similarly, CO₂ was released from the oceans to the atmosphere when the planet warmed, driving further warming.

The speed at which CO₂ is rising now has no comparison in the recorded past. The fastest natural shifts out of ice ages saw CO₂ levels increase by around 35 parts per million (ppm) in 1,000 years.Humans have emitted the equivalent amount in just the last 17 years.

https://earthobservatory.nasa.gov/features/Milankovitch

http://www.sci-news.com/othersciences/paleoclimatology/rule-ice-age-04646.html

https://www.google.com/amp/s/theconversation.com/amp/the-three-minute-story-of-800-000-years-of-climate-change-with-a-sting-in-the-tail-73368

[petm]

Be sure that your friend understands that a thing can be both a cause and an effect (hence feedbacks). Don't want them to fall for the false denier meme that temperature can drive CO2, so CO2 cannot drive temperature.

[DrTskoul]

Diving through the halocline

[DrTskoul]

Last one.

A nice thesis:

The impact of near-inertial waves on the Arctic halocline

And very educational course slides:

Ocean Dynamics