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

[Darvince]

If you're not referring to the current closer to Svalbard, then it looks to me like a failure of data assimilation. A similar pattern, although with a peak speed much lower, appears in the area around the border between the ESS and Chukchi at the same timestamp.

[karl dubhe2]

I found a stupid question to ask.  Well, maybe stupid.   

I noticed in the thread about the 2018 melting season that someone mentioned the effect that the tides would have on the ice in the channels there.

So I looked at the Canadian website that deals with tides currents and all that fun stuff. 

http://www.tides.gc.ca/eng

From a quick look the tides don't seem to be moving up and down very much, the difference in the areas that I checked have a difference of about 0.2 meters or about 0.6 of a foot.  Which is quite different from the values further south.  Wait.   I think I found the answer...

That's not a constant thing, is it?  For some stupid reason I thought the moon orbited around the Earth at the equator, but then I looked again, and that's not right.

So, I suppose the question had something to do with when the tides in the CAA are strongest.   Could there be a relation between the strength of the 'garlic press' season/year to when the moon is higher or lower in the sky in relation to the Arctic?  If there is, has someone looked at the implications? 

This is a terribly rambling question isn't it?

[pearscot]

I'm not ignorant and I have been watching the ice for some time now, but how common is it for the ice to lift from the north coast of Greenland? I was surprised to see that and always considered such ice to be fairly robust/steadfast. Of my own admission, I have been throwing a lot of IQ thoughts to ocean currents and I seek to understand much more about them.

[Rod]

The NSIDC concentration map for today (16 Aug 2018 map) shows ice in the middle of Hudson Bay.  When I first saw it, I thought holly shit!  bbr is right ... and I started to panic. 😏   However, the skies are pretty clear today over the Hudson on worldview, and that ice is not there. 

I am aware of the sensor problem that sometimes sees land as ice and causes ice to appear in the little nooks and crannies when it really is not there.  But this "ice" is in the middle of the Hudson. 

Does anyone know what would cause the sensors to misidentify ice in open water like that?   

I suppose it is theoretically possible that the ice formed yesterday when it was cloudy, and then suddenly all disappeared today when it got sunny.  However, it is not insignificant in size, and it seems unlikely that much ice would appear and disappear so quickly. 

[Wherestheice]

The NSIDC concentration map for today (16 Aug 2018 map) shows ice in the middle of Hudson Bay.  When I first saw it, I thought holly shit!  bbr is right ... and I started to panic. 😏   However, the skies are pretty clear today over the Hudson on worldview, and that ice is not there. 

I am aware of the sensor problem that sometimes sees land as ice and causes ice to appear in the little nooks and crannies when it really is not there.  But this "ice" is in the middle of the Hudson. 

Does anyone know what would cause the sensors to misidentify ice in open water like that?   

I suppose it is theoretically possible that the ice formed yesterday when it was cloudy, and then suddenly all disappeared today when it got sunny.  However, it is not insignificant in size, and it seems unlikely that much ice would appear and disappear so quickly.

I just checked out the temperature at hudson bay, its way to warm for any ice to form, so its a glitch for sure.

[oren]

Hudson Bay only starts refreezing in the second half of October, so don't hold your breath...

[gerontocrat]

I'm not ignorant and I have been watching the ice for some time now, but how common is it for the ice to lift from the north coast of Greenland? I was surprised to see that and always considered such ice to be fairly robust/steadfast. Of my own admission, I have been throwing a lot of IQ thoughts to ocean currents and I seek to understand much more about them.

We had a long discussion many moons ago about landfast ice. Down in the Antarctic there are massive thick ice shelves that are really landfast. Apart from a few remnant scraps there are no real ice shelves in the Arctic. All it takes is some wind and currents and away goes the ice from the shore. And now it has happened twice to the supposedly land fast ice off the North Coast of Greenland (late Feb and now).

Another piece of conventional wisdom bites the dust.

[Tony Mcleod]

Can I ask the brains trust here to tease out the mixed bag of feedbacks that a seaice free NH summer might generate: insulation, albedo, latent heat etc. What is the net flux?

I'm debating some deniers who want to downplay albedo and up-play the insulating effects and conclude it means more heat lost to space - a self-correcting, net negative feedback.

[gerontocrat]

Can I ask the brains trust here to tease out the mixed bag of feedbacks that a seaice free NH summer might generate: insulation, albedo, latent heat etc. What is the net flux?

I'm debating some deniers who want to downplay albedo and up-play the insulating effects and conclude it means more heat lost to space - a self-correcting, net negative feedback.

Tony, it sounds like you are a more patient man than I.

Climate scientists are using super-computers to do the maths for this. Even the computers have forgotten more math than I ever learnt from my Pure Maths degree. So unless you and the deniers have got access to a couple of Cray computers.........

My argument is therefore based on the evidence to date.

The Arctic has been losing ice, especially in the summer. As of today the 21 August, there is well over 2.5 million km2 (about 10 x the area of the UK) of open water where in the 1980's there was ice. Meanwhile Global Surface Air Temperatures rise (and in the Arctic at double the rate of the average?).

An ice-free Arctic summer is just a continuation of that trend, less ice and more open water for longer. There has not been a self-correcting net negative feedback in the last 40 years, so why should more of the same process be different?

And meanwhile the oceans continue to amass heat.

[wili]

There are also the facts that as the water becomes more open, there will be more water vapor in the atmosphere above it, and water vapor is of course an important GHG.

There is also the issue of change of state. A lot of the energy that is newly being held close to the surface by GW is now going into melting ice. Once all/most of that ice is melted, it will mostly go into heat the ocean. The same amount of heat it takes to get ice to go from 0C to 1C can heat the same mass of water up by 10 degrees C, iirc.

Anyway, as g said, there are lots of complicating factors, and pointing out one potential (but mostly false) dampening feedback does not outweigh the plethora of known exacerbating (positive) feedbacks.

[crandles]

I suspect I am in small minority to some extent agreeing with your deniers against the above posts.

I think there certainly is a negative feedback from more open water losing more heat. It certainly isn't the only feedback and I would suggest that in summer the albedo feedback is more important but in winter it is the open water losing more heat that is dominant.

The combination of these two major feedbacks means that heat is accumulated in the summer. Come fall and winter this extra heat is rapidly lost with the freeze up only having been delayed by a week or so, so far and this has little effect on the volume of ice at maximum.

So I think the negative heat loss feedback looks like it will be sufficiently dominant to stop the positive feedbacks creating a run away situation but it cannot reverse the situation already reached.

If you take a different view, how else do you explain the following sort of shapes apparently emerging? Why isn't it continuing to curve ever steeper if you think the positive feedbacks are dominant?

(Note I don't believe the flat trend, I think it will continue downwards while GHGs and ocean temps are rising.)
 

[SteveMDFP]

Can I ask the brains trust here to tease out the mixed bag of feedbacks that a seaice free NH summer might generate: insulation, albedo, latent heat etc. What is the net flux?

I'm debating some deniers who want to downplay albedo and up-play the insulating effects and conclude it means more heat lost to space - a self-correcting, net negative feedback.

Tony, you've gotten very good responses above.  A little bit to add:
Some time back, there was discussion on this forum of a paper that examined the hypothetical of removing all ice from the arctic in spring, and modeling whether it would return.  As I recall, that model yielded a return of the ice--under present status of global warming.

Open water in the arctic ice does, indeed, radiate much, much more heat to space than ice-covered water.  This effect is mitigated somewhat by more humidity, clouds, and fog--which hold back some of the out-going radiation.  Plus, more snowfall in this setting.  Lots of snow on thin ice can insulate the waters below well--but hard to model this, I think.

Annual fluctuations in ice minimums tend to show something of an "autocorrection."  Very low sea ice area in summer is often followed by a higher level for the next year or two.  This impression would suggest that open water in wintertime does, indeed, release very large amounts of heat to space.  A substantial negative feedback effect, in competition with a whole lot of positive feedbacks.  As crandles pointed out.

Your question definitely didn't belong in the "stupid questions" thread. 

[Ned W]

Your question definitely didn't belong in the "stupid questions" thread.

Yes, I agree with Steve.  This is a great question. 

I think crandles is probably correct, that open water in winter does act as a negative feedback, making the system more stable than it would be otherwise (but obviously not stable enough, since the ice is still going away). 

But mainly I think this is complicated enough that I don't really trust my own "intuition" on it, and I'd say it will take very careful modeling to untangle the processes involved.

This is, like, the exact opposite of a "stupid question". 

[crandles]

  A little bit to add:
Some time back, there was discussion on this forum of a paper that examined the hypothetical of removing all ice from the arctic in spring, and modeling whether it would return.  As I recall, that model yielded a return of the ice--under present status of global warming.

I believe that is likely to be Tietsche et al 2011
Recovery mechanisms of Arctic summer sea ice
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL045698

(There is also a similar paper by Schroeder & Connolley that reached similar conclusions.)

[Dharma Rupa]

Your question definitely didn't belong in the "stupid questions" thread.

Yes, I agree with Steve.  This is a great question. 

I think crandles is probably correct, that open water in winter does act as a negative feedback, making the system more stable than it would be otherwise (but obviously not stable enough, since the ice is still going away). 

But mainly I think this is complicated enough that I don't really trust my own "intuition" on it, and I'd say it will take very careful modeling to untangle the processes involved.

This is, like, the exact opposite of a "stupid question".

I have some doubts about Crandles' analysis in that I don't think open water in winter can be modeled as a single feedback.  To some extent it acts as a negative feedback by allowing more heat to escape the surface, but it also in itself acts as a positive feedback by raising the water vapor partial pressure.

I suspect, but cannot demonstrate, that on the whole it acts as a negative feedback until some threshold is reached with the water vapor, at which point the climate becomes more maritime than desert and the open water on average acts as a positive feedback.

[Pmt111500]

Good discussion and is there's a possible mechanism for a pliocene-like climate to stay stable, instead of running all the way to de-iced conditions of Eocene like some cascading tipping points might suggest?

[Phil.]

There are also the facts that as the water becomes more open, there will be more water vapor in the atmosphere above it, and water vapor is of course an important GHG.

There is also the issue of change of state. A lot of the energy that is newly being held close to the surface by GW is now going into melting ice. Once all/most of that ice is melted, it will mostly go into heat the ocean. The same amount of heat it takes to get ice to go from 0C to 1C can heat the same mass of water up by 10 degrees C, iirc.

Actually the latent heat of fusion of water is ~80cal/gm so that will melt 1gm of ice at 0ºC to 1gm of water at 0ºC, the same amount of heat will heat 1gm of water by 80ºC!

[gerontocrat]

Can I ask the brains trust here to tease out the mixed bag of feedbacks that a seaice free NH summer might generate: insulation, albedo, latent heat etc. What is the net flux?

I'm debating some deniers who want to downplay albedo and up-play the insulating effects and conclude it means more heat lost to space - a self-correcting, net negative feedback.

My last thought is - you can tell your deniers that one thing is pretty sure - in not so many years from now we are going to find out the answer not from a series of mathematical equations, but from actuality.

[Stephan]

My last thought is - you can tell your deniers that one thing is pretty sure - in not so many years from now we are going to find out the answer not from a series of mathematical equations, but from actuality.

Well expressed, gerontocrat. Thank you so much.

[johnm33]

"mixed bag"
One more thing , we'll lose the Beaufort freshwater lens out through the CAA, the ice blocking the channels creates a back pressure preventing Atlantic water entering the Arctic. Lets say it'll be interesting to see how much Atlantic water cycles through the arctic leaving much cooler through Baffin, Hudson and Labrador.

[Tony Mcleod]

Thank you all the contributors - exactly the sort of back and forth I hoped for. There are so many competing feedbacks.
There is a line of denier argument that I often hear, it goes something like: the extra warmth means more ice is lost allowing that heat to be radiated to space thus cooling things down. To which I can't help but respond with: so warming leads to cooling? But its still warmer. Then the heads explode.

The fact that it is rapidly warming and ice steadily disappering, its hard not to assume there is a net positive feedback right now.

Just had a skim read of this:
Arctic plant diversity in the Early Eocene greenhouse, here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3282332/

It cites "mean annual temperature ranging from 8 to 15°C [7–9]. Warm month mean temperatures probably reached 19–20°C or higher, and winter temperatures were above freezing"
with alligators and tapir.

There wasn't much negative feedback happening back then.

[crandles]

Certainly the equable climate of the early Eocene is a problem climate models have difficulty explaining. So yes it is a valid point to bring this up. At some point I would expect things to differ from what the models suggest. Water vapour partial pressure hmm water has low residency time in atmosphere so adjust fairly quickly and what reason for expecting the models to have it wrong. Possibly doubtful, but what do I know, the models are likely to be wrong somewhere.

Perhaps more useful to ponder whether the effect is likely to be sudden or emerge slowly at first then accelerate and also whether it is likely to be soon.

It is certainly possible the models are badly wrong, but I don't see any reason to see why it should emerge soon. Is guessing now/soon like winning the lottery, a raffle or just rolling dice? A reasonably large raffle seems the most appropriate suggestion to me. YMMV

Also if it emerges slowly at first then accelerates then maybe we would see it in deviation from the trend. At present the trend seems to be getting less steep.

[oren]

TM, it's natural that the more heat in the system, the more heat is radiated to space. Your deniers could point out that thanks to black body radiation behavior, warmer surface temperatures increase radiated heat. Does that mean we are saved? Sadly no. It's a negative feedback, but one that only serves to slow down the trend. Not "warming causes cooling" but "warming requires progressively more energy to warm further". The fact that temperature trends are rising steadily should worry us even more, considering this.
Note most deniers and trolls (on this forum as well) are not really looking for facts or explanations. Typically they want to affect you, and are not affected themselves at all, a one-way transmission which you imagine is a bi-directional discussion. So your energy might be wasted.

[Ned W]

There is a line of denier argument that I often hear, it goes something like: the extra warmth means more ice is lost allowing that heat to be radiated to space thus cooling things down. To which I can't help but respond with: so warming leads to cooling? But its still warmer.

That kind of situation sounds self-contradictory, but it's actually quite common in environmental systems. 

Say you have one unit of warming that is externally forced. 

A negative feedback will partially counter that forcing.  Maybe the negative feedback is a multiplier of -0.2.  That reduces the warming to 0.8.  But this lower warming makes the negative feedback weaker, so it adds back 0.04 (-0.2 * -0.2) of warming.  Another iteration of the negative feedback reduces it by -0.008 (-0.2 * -0.2 * -0.2).  After an infinite number of iterations, the initial warming settles in at 0.833333 units:



So the negative feedback has reduced the amount of warming, but it hasn't caused actual cooling, just a reduction in the warming.

A positive feedback will have the opposite effect.  It will amplify the initial warming, and will also amplify itself.  For example, a positive feedback that is a multiplier of +0.2 will increase the initial warming to 1.2 units, then will amplify itself to add another +0.04 units, and another +0.008 units, etc.  Eventually, the warming will approach a limit of +1.25 units:



So the negative feedback reduced the warming, and the positive feedback amplified it. 

People often make the mistake of thinking that the negative feedback must turn warming into cooling (reverse the sign of the original effect), or that positive feedback must cause the warming to spiral out of control.  Neither of those happens as long as the absolute value of the multiplier is less than one (i.e., it's within the range [-0.9999, +0.9999]).

If the multiplier is greater than +1, or less than -1, the system will run away on either the positive or negative side, respectively.  That is rare in most environmental systems (fortunately).

[SteveMDFP]

A negative feedback will partially counter that forcing. . .

A positive feedback will have the opposite effect.  It will amplify the initial warming, and will also amplify itself.  For example, a positive feedback that is a multiplier of +0.2 will increase the initial warming to 1.2 units, then will amplify itself to add another +0.04 units, and another +0.008 units, etc.  Eventually, the warming will approach a limit of 
 . . .
If the multiplier is greater than +1, or less than -1, the system will run away on either the positive or negative side, respectively.  That is rare in most environmental systems (fortunately).

Nice summary.  I'd add one point.  Complex systems dominated by negative feedbacks tend toward a stable equilibrium.   Complex systems dominated by positive feedbacks tend to oscillate.  Not just climate.

Though over thousands of years we *do* see oscillations in climate.  To me, this suggests climate is dominated by slow positive feedbacks in general.  (Slow when not accelerated by humans, anyway).   This shouldn't be a controversial interpretation here, I think, as we often discuss a wide array of positive feedbacks to climate effects.

That is, the feedbacks tend to work in both directions, going up and coming down.  Under positive feedback domination, after reaching maximum, decreases in climate temperature would tend to decrease temperatures further.  Limiting factors come into play at maximum and minimum points.

[Phil.]

A negative feedback will partially counter that forcing. . .

A positive feedback will have the opposite effect.  It will amplify the initial warming, and will also amplify itself.  For example, a positive feedback that is a multiplier of +0.2 will increase the initial warming to 1.2 units, then will amplify itself to add another +0.04 units, and another +0.008 units, etc.  Eventually, the warming will approach a limit of 
 . . .
If the multiplier is greater than +1, or less than -1, the system will run away on either the positive or negative side, respectively.  That is rare in most environmental systems (fortunately).

Nice summary.  I'd add one point.  Complex systems dominated by negative feedbacks tend toward a stable equilibrium.   Complex systems dominated by positive feedbacks tend to oscillate.  Not just climate.

Though over thousands of years we *do* see oscillations in climate.  To me, this suggests climate is dominated by slow positive feedbacks in general.  (Slow when not accelerated by humans, anyway).   This shouldn't be a controversial interpretation here, I think, as we often discuss a wide array of positive feedbacks to climate effects.

That is, the feedbacks tend to work in both directions, going up and coming down.  Under positive feedback domination, after reaching maximum, decreases in climate temperature would tend to decrease temperatures further.  Limiting factors come into play at maximum and minimum points.

Usually oscillation results from a combination of positive and negative feedback with a different timescale for each.  Think of it as a delay between the two processes, it's what causes the well-known 'feedback' encountered in PA systems, the nett feedback must be large enough to be unstable (greater than 1) otherwise you don't get oscillation.

[Ned W]

To me, this suggests climate is dominated by slow positive feedbacks in general.  (Slow when not accelerated by humans, anyway).

I think the obvious indicator that the climate system's feedbacks are (net) positive is that climate sensitivity (ECS or whatever other version you prefer) is almost certainly larger than the no-feedbacks sensitivity of approx. 1.1 C (this does include the Planck feedback but nothing else).  If it were net-negative, then ECS would be lower than 1.1, rather than higher.

Of course that argument is dependent on having estimates of ECS that don't come from models of known feedbacks... but there are other ways of estimating ECS.

[crandles]

Nice summary.  I'd add one point.  Complex systems dominated by negative feedbacks tend toward a stable equilibrium.   Complex systems dominated by positive feedbacks tend to oscillate.  Not just climate.

Though over thousands of years we *do* see oscillations in climate.  To me, this suggests climate is dominated by slow positive feedbacks in general.  (Slow when not accelerated by humans, anyway).   This shouldn't be a controversial interpretation here, I think, as we often discuss a wide array of positive feedbacks to climate effects.

Re 'dominated by'

You could also take the view that heat out varies with 4th power of temperature and this is a strong negative feedback that dominates the system and tends to prevent run away situations. Taking bathtub analogy for climate: Increase the rate of flow into the bathtub or close part of the drain hole(s) and the level goes up but stabilises rather than continuously rising because the rate of outflow depends on the height of water.

Generally we tend to consider this part of the setting for climate and don't call it a negative feedback. If taking this view, yes positive feedbacks dominate and slow positive feedbacks can and do cause slow changes to different states.

So take your pick on whether positive or negative feedbacks dominate. 

[gerontocrat]

TM, it's natural that the more heat in the system, the more heat is radiated to space.

This extremely not "stupid question" seems to open up Pandora's box. Ice-free seas in winter will do more than radiate energy into space. Some (I wonder what proportion) of that energy will be trapped by the atmosphere at least for some time, i.e. at least initially we end up with a warmer more energetic atmosphere. What will that do to weather systems ? For how long will the ice not freeze ?

Last winter the ice in the Bering Sea was always far less than half its historical average. So the ice did not really return, and if my memory serves me right, there were many winter storms. Did the storms stop the ice returning or did the ice free ocean and a warmer atmosphere  provoke the storms or both ? And now we have more test beds. E.g. the Laptev is totally surrounded by land and in winter normally totally iced up ocean. This year the Laptev is as near as makes no difference ice free, and the above average and very early melt has led to very high SST anomalies. Will this significantly delay refreezing? Will we see significant weather impacts ?

And the Atlantic front? What is going to happen this autumn and winter?

[Dharma Rupa]

You could also take the view that heat out varies with 4th power of temperature and this is a strong negative feedback that dominates the system and tends to prevent run away situations.

Please explain.  I'd say justify too, but I think an explanation would cover that.

(This could explain why we are not Pluto or Venus, but I don't understand it.)

[Ned W]

It's called the Planck feedback.  Emitted thermal radiation is proportional to the 4th power of the temperature, in kelvins.  So as an object's temperature increases, the loss of energy via radiation also increases.  It's the most important negative feedback.

More here:

https://en.m.wikipedia.org/wiki/Stefan–Boltzmann_law

[aperson]

You could also take the view that heat out varies with 4th power of temperature and this is a strong negative feedback that dominates the system and tends to prevent run away situations.

Please explain.  I'd say justify too, but I think an explanation would cover that.

(This could explain why we are not Pluto or Venus, but I don't understand it.)

The Stefan-Boltzmann law for black body radiation says that the amount of energy radiated from a black body varies with the 4th power of the surface temperature of the body. If you want to go full Venus, you'll need to add energy at a rate strong enough to dominate this effect, see: https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law

Edit: Thank you Ned for correcting my error.

[Ned W]

Nice one, aperson!  Except it's surface temperature, not surface area...
 

[Dharma Rupa]

You could also take the view that heat out varies with 4th power of temperature and this is a strong negative feedback that dominates the system and tends to prevent run away situations.

Please explain.  I'd say justify too, but I think an explanation would cover that.

(This could explain why we are not Pluto or Venus, but I don't understand it.)

The Stefan-Boltzmann law for black body radiation says that the amount of energy radiated from a black body varies with the 4th power of the surface temperature of the body. If you want to go full Venus, you'll need to add energy at a rate strong enough to dominate this effect, see: https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law

Edit: Thank you Ned for correcting my error.

Ok....so the hotter the body is the more-more it radiates...How "Grey" is the Earth?

NVM -- I gather that the planet is going to attempt to get rid of heat faster as it gets warmer, all other things being equal (which they aren't).

[Tony Mcleod]

Note most deniers and trolls (on this forum as well) are not really looking for facts or explanations. Typically they want to affect you, and are not affected themselves at all, a one-way transmission which you imagine is a bi-directional discussion. So your energy might be wasted.

Not "warming causes cooling" but "warming requires progressively more energy to warm further".

Yes. The number of data able to be absorbed by a denier varies with the 4th power of the veracity of that data.

The weird thing is that they are actually arguing that the warmer Arctic is a sign that its cooling down. There is a psychological inability to concede the facts. Its truly down the rabbit hole stuff.

[gerontocrat]

Note most deniers and trolls (on this forum as well) are not really looking for facts or explanations. Typically they want to affect you, and are not affected themselves at all, a one-way transmission which you imagine is a bi-directional discussion. So your energy might be wasted.

Not "warming causes cooling" but "warming requires progressively more energy to warm further".

Yes. The number of data able to be absorbed by a denier varies with the 4th power of the veracity of that data.

The weird thing is that they are actually arguing that  the warmer Arctic is a sign that its cooling down. There is a psychological inability to concede the facts. Its truly down the rabbit hole stuff.

You are a very patient man, Tony. I am not (any more).

In the end one has to stop being polite and change the focus of the argument.. e.g. " Does it worry you that you are playing Russian Roulette with the lives of your family?". It might at least bring an end to what is basically a fruitless exercise with these people.

[SteveMDFP]

Yes. The number of data able to be absorbed by a denier varies with the 4th power of the veracity of that data.

Funniest line I've read on ASIF all month.  Well done.

[SteveMDFP]

In the end one has to stop being polite and change the focus of the argument.. e.g. " Does it worry you that you are playing Russian Roulette with the lives of your family?". It might at least bring an end to what is basically a fruitless exercise with these people.

When discussing one-on-one, I agree.  When discussing in a public forum, I strongly disagree.  Especially online, the reading audience can be very large.  When we cede this ground to the deniers, many good people believe the lies and stupidity.

[Pmt111500]

"NVM -- I gather that the planet is going to attempt to get rid of heat faster as it gets warmer, all other things being equal (which they aren't)."

Theory says so, and a solid dry planet would probably cool down pretty fast. On Earth, in practise this leads to more water vapor getting higher up in the atmosphere thus keeping the temperatures higher on the surface. Taking atmosphere in account, earth radiates more when hotter, we just don't notice it easily here on the ground. Please check this also from elsewhere, it's been a while when I last had to write this down, and may have mixed up some words.

[Dharma Rupa]

"NVM -- I gather that the planet is going to attempt to get rid of heat faster as it gets warmer, all other things being equal (which they aren't)."

Theory says so, and a solid dry planet would probably cool down pretty fast. On Earth, in practise this leads to more water vapor getting higher up in the atmosphere thus keeping the temperatures higher on the surface. Taking atmosphere in account, earth radiates more when hotter, we just don't notice it easily here on the ground. Please check this also from elsewhere, it's been a while when I last had to write this down, and may have mixed up some words.

That's pretty much what I was thinking, that the net result would be somewhat less than the 4th power.

[jdallen]

"NVM -- I gather that the planet is going to attempt to get rid of heat faster as it gets warmer, all other things being equal (which they aren't)."

Theory says so, and a solid dry planet would probably cool down pretty fast. On Earth, in practise this leads to more water vapor getting higher up in the atmosphere thus keeping the temperatures higher on the surface. Taking atmosphere in account, earth radiates more when hotter, we just don't notice it easily here on the ground. Please check this also from elsewhere, it's been a while when I last had to write this down, and may have mixed up some words.

The challenge is, the earth is not radiating from a uniform surface of static density and composition. Aside from the surface, you have varying amounts of radiation being emitted at varying wavelengths from every level of the atmosphere, and those emissions are not in uniform directions.

[Ned W]

That's pretty much what I was thinking, that the net result would be somewhat less than the 4th power.

That's not quite how I would put it.  Integrated OLR is pretty much proportional to the 4th power of temperature; it's just  that it's the temperature of the mean altitude of emission that matters -- roughly 5km in mid-latitudes, I believe.  The relationship between temperatures at the surface and this altitude is reflected in the lapse rate.

And one aspect of AGW is that the mean altitude of emission increases as CO2 concentration increases.  In fact, this is kind of key to the whole thing.

(1) Increased CO2 raises the mean height at which OLR can escape.
(2) In the troposphere, temperature decreases with height, so the air at the (new) height of emission is cooler
(3) Because of Stefan-Bolzmann, the flux of OLR is a function of temperature, so air at a cooler temperature emits less
(4) This means that the Earth is now receiving the same radiation but emitting less, causing it to warm up.
(5) Eventually, the warming proceeds to the point where the new, higher altitude of emission is warm enough to be emitting the same flux of OLR as before, at which point incoming and outgoing radiation are in equilibrium, but with the Earth at a higher temperature.

[Dharma Rupa]

(5) Eventually...

OK, but the whole point about global warming is that we haven't reached that point and at the moment the radiation is somewhat less (on average) than the 4th power.

For now, we have the effective radiative surface area increasing as the CO2 and H2O partial pressure rises, and the quantity of heat leaving not quite matching the quantity coming in (plus the almost negligible quantity due to fission),

[Pmt111500]

(5) Eventually...

OK, but the whole point about global warming is that we haven't reached that point and at the moment the radiation is somewhat less (on average) than the 4th power.

For now, we have the effective radiative surface area increasing as the CO2 and H2O partial pressure rises, and the quantity of heat leaving not quite matching the quantity coming in (plus the almost negligible quantity due to fission),

Black-body radiation law can be made more realistic for objects with ghg effect, by adding negative/positive terms for objects that are warming/cooling, so kind of yes. I've forgotten the actual functions for grey-body (like earth's surface) radiation. I think all the gases having ghg-effect should have their own variable added to the basic fourth power law and that the forcings Ned is calculating are one way to do this. No doubt there are interdependencies at least between co2 and water vapor inserted on more realistic tries to depict this.

[Chuck Yokota]

Is there available a graph of the decadal averages for the north of 80 temperature? I'm interested in seeing how much the winter temperatures have increased.

[crandles]

https://tamino.wordpress.com/2018/08/29/arctic-heating/

might be worth a look though it looks like it includes significantly lower latitudes:

Let’s take a look at the data from NASA, and from Cowtan & Way, for the region from latitude 64°N to the pole, which we’ll call the Arctic.

Think someone found the data for the dmi 80N charts and maybe someone did it from that.

GISS 64N to pole temps included here
https://data.giss.nasa.gov/gistemp/tabledata_v3/ZonAnn.Ts+dSST.txt

[Dharma Rupa]

Is there available a graph of the decadal averages for the north of 80 temperature? I'm interested in seeing how much the winter temperatures have increased.

This won't exactly answer your question, but it will provide some hints:

http://sites.uci.edu/zlabe/arctic-temperatures/

[Phil.]

Is there available a graph of the decadal averages for the north of 80 temperature? I'm interested in seeing how much the winter temperatures have increased.

This help?
http://ocean.dmi.dk/arctic/plus80n/anoplus80N_summer_winter_engelsk.png

[josh-j]

This help?
http://ocean.dmi.dk/arctic/plus80n/anoplus80N_summer_winter_engelsk.png

It wasn't me asking but that is a very useful graph, thanks!

[Phil42]

Hi, I have two rather simple question I unfortunately don't know the answer to. Please also correct me if something I wrote is wrong, I love to learn new stuff.

1) During the melt season, as I understand it, there is top melt (from exposure to the sun and warm air temperature) and there is bottom melt from the water underneath the ice (this gets more significant with strong winds because the warm water which is usually further down gets mixed with the colder water above).

So to my question: Which of those factors is more prevalent / contributes more to melt?


2) During the freezing season, does it even matter if the air is -5°C or -20°C. It might sounds stupid, but in my understanding water freezes at ~0°C, so does the amount below 0 make a difference?
I ask this because of the very high winter temperature anomalies in the arctic where temperatures sometimes spike up a lot but still stay under 0°C by a significant amount.


3) During the freezing season, how does cloud cover affect the ice. In summer it protects the ice from exposure to the sun, does it also have an effect in winter when there is no sun (apart from precipitation)?