Changing Spring Insolation Hypothesis

[RodneyS]

Physicist and space scientist Dr. Duncan Steel has written a paper discussing how well-known variations in Earth’s orbit around the Sun result in variations in the solar flux received (at different latitudes and at different times of year), which might be expected to cause changes in the climate in accord with what is actually being observed now, independent of any major contribution from anthropogenic global warming.  Dr. Steel finds that the most substantial variations are occurring at high latitudes across spring: in the northern hemisphere the spring insolation is increasing markedly, while in the southern hemisphere the insolation across austral spring is reducing. In itself this might be anticipated to result in what is actually observed: record melting of ice and snow cover in the Arctic,while there is year-on-year growth of the extent of Antarctic sea ice. See http://www.duncansteel.com/archives/996

 

Dr. Steel welcomes comments and observations on his paper, but only on the substantive subject of how Earth’s shifting orbit is affecting the insolation received at different latitudes and different times of year in the present epoch. 

[Msalgado]

This isn't a paper.  This is a website.  Orbital variation isn't overlooked by climatologists at all.  Its just not a big enough effect to account for any changes.  This "study" is the worst kind of correlation = causation.  I honestly stopped reading when he compared a global forcing to a regional change in insolation.  

[StudentOfClimatology]

This isn't a paper. This is a website. Orbital variation isn't overlooked by climatologists at all. Its just not a big enough effect to account for any changes. This "study" is the worst kind of correlation = causation. I honestly stopped reading when he compared a global forcing to a regional change in insolation.

Redistribution of global insolation across the planetary surface is a global forcing, actually. Ice ages occur when global circulations shift in occordance with the insolation gradient, allowing for colder polar climates while the (initial) tropical warming does a number on the Hadley Cells.

[AvantHiatus]

The Pliocene and earlier geological epochs never had interglacials/ice ages because the CO2 forcing was too elevated. This is simple logic yet you want to again type a wall of text that is inappropriate.

[StudentOfClimatology]

The Pliocene and earlier epochs never had interglacials because the CO2 forcing was too elevated. This is simple logic yet you want to again write a wall of text that is inappropriate.

That's one reason, yes. However, based on the paleo data, ice-ages, as we know them now (or at least the circulation regime that produces them) are largely dependent on the equator-to-pole thermal gradient, not the initial global temperature. So topography/geology is by far the biggest factor. You need a continent at one of the poles to force an ice age.

Back in the Carboniferous age, a monster ice age got going while CO^2 was at 5000ppm. Commonality was a continent sitting at one of the poles. We could (in theory) still enter an ice age circulation with current CO^2 levels, however it'd be warm enough at the high latitudes that ice sheet growth would be negligible.

[AvantHiatus]

That's one reason, yes. However, based on the paleo data, ice-ages, as we know them now (or at least the circulation regime that produces them) are largely dependent on the equator-to-pole thermal gradient, not the initial global temperature. So topography/geology is by far the biggest factor. You need a continent at one of the poles to force an ice age.

Back in the Carboniferous age, a monster ice age got going while CO^2 was at 5000ppm. Commonality was a continent sitting at one of the poles. We could (in theory) still enter an ice age circulation with current CO^2 levels, however it'd be warm enough at the high latitudes that ice sheet growth would be negligible.

I understand your point here and it still holds slightly, however CO2 has never been 5000ppm, except for primordial Earth. Which was a different system entirely with very limited oceans/massively different topography and immense volcanic activity.

 

Carboniferous atmosphere conditions

Mean atmospheric O2content over period duration ca. 32.5 Vol %^[1]

(163 % of modern level)

Mean atmospheric CO2 content over period duration ca. 800 ppm^[2]

(3 times pre-industrial level)

Mean surface temperature over period duration ca. 14 °C^[3]

(0 °C above modern level)

[Msalgado]

Redistribution of global insolation across the planetary surface is a global forcing, actually. Ice ages occur when global circulations shift in occordance with the insolation gradient, allowing for colder polar climates while the (initial) tropical warming does a number on the Hadley Cells.

 

The redistribution of insolation temporally and regionally isn't a forcing in and of itself at all.  Its the subsequent downstream effects.  You drop summer insolation which allows ice to build up which then changes albedo and as you pointed out - circulations.  However, initially a redistribution of insolation has no effect at the TOA which is the definition of what a forcing is.  You are ascribing freedbacks to the initial mechanism as a forcing which is incorrect.

 

But in any event, that isn't my point.  You can't say that a drop in 2 w/m^2 at 60 north or any other arbitrary location on Earth is the equivalent of a global forcing of 2 w/m^2

[AvantHiatus]

The redistribution of insolation temporally and regionally isn't a forcing in and of itself at all.  Its the subsequent effects which have effects.  But in any event, that isn't my point.  You can't say that a drop in 2 w/m^2 at 60 north or any other arbitrary location on Earth is the equivalent of a global forcing of 2 w/m^2

Addtionally, whatever insolation is lost is picked up somewhere else, and this could lead to changes through it's own right. With the Arctic in it's current shape, I think warming the tropics even more would make things worse off and more prone to abrupt shifts as well as leading to a permanent el nino state.

 

These are long-term factors, our orbital forcing shifts on timescales of 5k years and we would of already overwhelmed whatever signal was there.

[StudentOfClimatology]

I understand your point here and it still holds slightly, however CO2 has never been 5000ppm, except for primordial Earth. Which was a different system entirely with very limited oceans/massively different topography and immense volcanic activity.

Carboniferous atmosphere conditions

Mean atmospheric

O

2content over period duration

ca. 32.5 Vol %^[1]

(163 % of modern level)

Mean atmospheric CO

2 content over period duration

ca. 800 ppm^[2]

(3 times pre-industrial level)

Mean surface temperature over period duration

ca. 14 °C^[3]

(0 °C above modern level)

I meant to type Ordovician, not Carboniferous. My bad there.

You're talking to a paleoclimate major, dude. There's a lot of disagreement about this in the field, actually, because there are a slew of interpolation methods available. The resolution issue is a headache.

But I prefer the Geocarb model, myself: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/phanerozoic_co2.txt

[StudentOfClimatology]

The redistribution of insolation temporally and regionally isn't a forcing in and of itself at all. Its the subsequent downstream effects. You drop summer insolation which allows ice to build up which then changes albedo and as you pointed out - circulations. However, initially a redistribution of insolation has no effect at the TOA which is the definition of what a forcing is. You are ascribing freedbacks to the initial mechanism as a forcing which is incorrect.

Your definition of a forcing is incorrect...you don't need spatial uniformity. As long as the movement is away from thermodynamic equilibrium, it's a forcing.

Also, the polar albedo increase/subsequent cooling is the result of a lack of poleward heat transport, as the equator-to-pole thermal gradient tightens, contracting the Hadley Cells and strengthening the westerlies in accordance with the thermal wind laws.

But in any event, that isn't my point. You can't say that a drop in 2 w/m^2 at 60 north or any other arbitrary location on Earth is the equivalent of a global forcing of 2 w/m^2

It's not "equivalent" in the sense you're thinking, no. The system response is to maintain equilibrium, regardless of the nature or "sign" of the forcing. This can be achieved either thermally or kinematically depending on the spatial dynamics of the forcing. There is essebtially no change in solar insolation from ice age to interglacial. The only difference is the equator-to-pole insolation gradient.

[sokolow]

 

Dr. Steel welcomes comments and observations on his paper, but only on the substantive subject of how Earth’s shifting orbit is affecting the insolation received at different latitudes and different times of year in the present epoch. 

Probably the better move is to welcome Dr. D. Duncan Steel (Space Scientist)'s ~paper~ straight to the garbage can where it belongs.

[StudentOfClimatology]

Probably the better move is to welcome Dr. D. Duncan Steel (Space Scientist)'s ~paper~ straight to the garbage can where it belongs.

That's not how science works. I don't agree with Dr. Steel on the timescale he's looking at (orbital effects don't always do what we think they do), but I'm not going to promote scientific bigotry.

[AvantHiatus]

That's not how science works. I don't agree with Dr. Steel on the timescale he's looking at (orbital effects don't always do what we think they do), but I'm not going to promote scientific bigotry.

Climate science is not like other fields, doesn't matter what we think. It is very well understood and the potential of new discoveries is becoming more limited. Thus any paper opposing modern understanding is likely to be incorrect.

 

The basics are set in stone, yet one can still argue over small figures like ECS and orbital forcing, they are unlikely to change the big picture in the long-haul, which is Earth returning to the greenhouse state without geo-engineering.

[sokolow]

That's not how science works. I don't agree with Dr. Steel on the timescale he's looking at (orbital effects don't always do what we think they do), but I'm not going to promote scientific bigotry.

I'm on mobile, and it sounds like this needs some heavy context. Could you do me a fav and summarize for me who Duncan Steel is, his prev pubs & qualifications as a climate scientist, and if you have a minute I would also appreciate if you'd give us a rundown on this paper's publication and reception history among reputable researchers in the field, what journal it was in, the status accorded that journal, and the like

Also can you give a summary of the paper's methodological and theoretical basis, the data it uses, how this paper is situated relative to similar undertakings / how novel it is, whether it has precursors, and a sketch of its findings as well as how plausible they are? If its outside the mainsteam can you walk us through what powerful observations or insights justify considering his claims?

I know it takes a lot of time to write that stuff up! but we should probably do that groundwork so we can get to discussing science and don't waste each others' time talking about the brain dribbles of some weird crank, fraud, or fabulist.

[sokolow]

I'd hate to promote scientific bigotry!

[StudentOfClimatology]

Climate science is not like other fields, doesn't matter what we think. It is very well understood and the potential of new discoveries is becoming more limited. Thus any paper opposing modern understanding is likely to be incorrect.

The basics are set in stone, yet one can still argue over small figures like ECS and orbital forcing, they are unlikely to change the big picture in the long-haul, which is Earth returning to the greenhouse state without geo-engineering.

We understand radiative forcing very well, but we're really lacking in the kinematics department (circulation, etc). Unfortunately, all it'd take is a slight (yet persistent) circulatory shift to amplify AGW significantly (paleoclimate data suggests this occurs apruptly at specific thresholds, with a net 3.5-5K per a doubling of CO^2 concentration).

So that's where I think we should be investing our time and effort.

[StudentOfClimatology]

I'm on mobile, and it sounds like this needs some heavy context. Could you do me a fav and summarize for me who Duncan Steel is, his prev pubs & qualifications as a climate scientist, and if you have a minute I would also appreciate if you'd give us a rundown on this paper's publication and reception history among reputable researchers in the field, what journal it was in, the status accorded that journal, and the like

Also can you give a summary of the paper's methodological and theoretical basis, the data it uses, how this paper is situated relative to similar undertakings / how novel it is, whether it has precursors, and a sketch of its findings as well as how plausible they are? If its outside the mainsteam can you walk us through what powerful observations or insights justify considering his claims?

I know it takes a lot of time to write that stuff up! but we should probably do that groundwork so we can get to discussing science and don't waste each others' time talking about the brain dribbles of some weird crank, fraud, or fabulist.

Sure. I'm on mobile too, though. I haven't finished reading the PDF yet, so I'll get back to you once I can get to a PC. Hard to do adequate research at a stoplight..haha.

[sokolow]

Not substantive beyond a possible diagnosis of physicistitis but round the BBQ we're skimming this guys CV and homepage, and whatnot, and

"that's a lol"

But is it worth changing the pika av...

[RodneyS]

This isn't a paper.  This is a website.  Orbital variation isn't overlooked by climatologists at all.  Its just not a big enough effect to account for any changes.  This "study" is the worst kind of correlation = causation.  I honestly stopped reading when he compared a global forcing to a regional change in insolation.  

It's a 49-page paper on Dr. Steel's website.  Regarding your assertion that "orbital variation isn't overlooked by climatologists at all," Steel states in the Preamble:  "The material I discuss in this document has been reviewed by a handful (6 or 8) of my astronomer colleagues (and I have also presented it as a research colloquium a couple of times). They have been uniformly stunned by the error apparently made by climatologists in assessing how the solar flux at Earth at different times of year varies over extended periods (decades to centuries to a millennium), this error involving a misunderstanding of the implications of Kepler’s second law of orbital motion. Nevertheless, any responsibility for mistakes made in this document and the calculations that are represented herein remain the fault of myself."  

 

Additionally, Steel states earlier in the Preamble: "But correlation does not prove causality: sometimes an apparent correlation can also be a case of coincidence."  

 

Finally, his point about global forcing (in the Introductory Summary) is that "perihelion has been progressing further into winter (i.e. the one day per 57/58 years produced by precession) and closer to the vernal equinox. The effect of this is that on every day during the first half of each year the Earth has been getting progressively closer to the Sun compared to the same day-of-year on the preceding orbit, and so the solar power to the planet has been consistently increasing across those six months in terms of year-to-year comparisons. In the second half of the year the converse is true, with the Earth becoming progressively further away on each day-of-year. The result of this would be expected to be, in the northern hemisphere, milder winters, warmer springs, and cooler latter halves of the year; whereas in the southern hemisphere spring would be cooler and summer warmer."

[PhillipS]

Dr Steel's basic premise is just wrong.  Climatologists do understand how varying insolation affects Earth's weather and climate.  The technical terms for the effect of annually varying insolation is "seasons".  Perhaps you've heard the term and just didn't understand it.  Certainly Dr. Steel didn't.

[StudentOfClimatology]

Dr Steel's basic premise is just wrong. Climatologists do understand how varying insolation affects Earth's weather and climate.

Being one myself, I can tell you we certainly do not understand how long term orbital forcings alter climate. We still have no workable theory for the ice age/interglacial cycle, as far as modeling is concerned.

It was once thought that albedo changes in the northern high latitudes were responsible, however, that theory has been destroyed.

[sokolow]

Any word on the reception of Steel's paper / blogpost in the broader climate science community and how its been discussed and critiqued?

[Msalgado]

Your definition of a forcing is incorrect...you don't need spatial uniformity. As long as the movement is away from thermodynamic equilibrium, it's a forcing.

Also, the polar albedo increase/subsequent cooling is the result of a lack of poleward heat transport, as the equator-to-pole thermal gradient tightens, contracting the Hadley Cells and strengthening the westerlies in accordance with the thermal wind laws.

It's not "equivalent" in the sense you're thinking, no. The system response is to maintain equilibrium, regardless of the nature or "sign" of the forcing. This can be achieved either thermally or kinematically depending on the spatial dynamics of the forcing. There is essebtially no change in solar insolation from ice age to interglacial. The only difference is the equator-to-pole insolation gradient.

 

Of course you don't need spatial uniformity.  That wasn't the point.  My definition of radiative forcing is spot on.  

 

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-2.html

 

And its not equivlant in any sense. A 2 w/m^2 localized forcing has no where near the same effect as a 2 w/m^2 global forcing.  The whole point is that the system response is completely different.  I'm not sure why you're repeating back to me things I already said, though.  I pointed out that there was no net change in global forcing, but thanks for telling me that?  

 

When CO2 is doubled, there's a global forcing.  When insolation is distributed differently, there is no change in the energy budget globally.  The changes come later after ice sheets build up and other feedbacks kick in.  There's a fundamental difference there.  If tomorrow, we double the amount of CO2 in the atmosphere, there is an IMMEDIATE responses in outgoing IR globally.  However, insolation changes don't have that effect globally.  

[StudentOfClimatology]

And its not equivlant in any sense. A 2 w/m^2 localized forcing has no where near the same effect as a 2 w/m^2 global forcing.When CO2 is doubled, there's a global forcing. When insolation is distributed differently, there is no change in the energy budget globally.

No, you're describing the *sign* of a given radiative forcing...orbital forcings are also "global", just not uniform in signature. Redistributing insolation throws the system out of internal equilibrium. A forcing doesn't have to change the macroscale budget at all...I'm not sure what you're trying to argue?

The changes come later after ice sheets build up and other feedbacks kick in. There's a fundamental difference there.

Actually, the highest resolution proxy strongly suggests that it has more to do with abrupt (threshold based) changes to global circulation that result from the redistribution of insolation, which then allows the ice sheets to build up. The typical ice age circulation looks nothing like the interglacial circulation, especially in the tropics and mid-latitudes. Otherwise those multi-mile thick ice sheets, with their high albedo, would be nearly impervious to slight shifts to insolation distribution.

To think, it can all go down like that without any change to the "sign" of the forcing...

[Msalgado]

You're the only one bringing up sign into this.  I don't believe I ever mentioned it.  In any event, I'm not sure if you believe that a change of 2 w/m^2 in insolation at 60 north is the same as a forcing change of 2 w/m^2 globally due to CO2 but I have no idea why you're going to such lengths to defend the claim they are.  I'll defer to you on ice age mechanics as I am not a paleoclimatologist and have a cursory familiarity with the mechanics of glaciation and deglaciation but the rest of your posts leave me scratching my head quite a bit.