Guest post by David Archibald
Baby boomers like me have enjoyed the most benign period in human history. The superpower nuclear standoff gave us fifty years of relative peace, we had cheap energy from inherent over-supply of oil, grain supply increased faster than population growth and the climate warmed due to the highest solar activity for 8,000 years. All those trends are now reversing. But it will get much worse than that. The next glaciation will wipe out many countries and nothing will stop that from happening. For example, the UK will end up looking like Lapland. As an indication of just how vicious it is going to get, consider that there are rocks on the beaches of Scotland that got blown over on ice from Norway across a frozen North Sea. As scientists, our task is to predict the onset of the next glaciation.
Onset of interglacials is driven by insolation at 65°N. That is where the landmass is that is either snow-covered all year round or not. It seems that insolation above 510 watts/sq metre will end a glacial period. For an interglacial period to end, the oceans have to lose heat content so that snows will linger through the summer and increase the Earth’s albedo. Thanks to the disposition of the continents, our current ice age might last tens of millions of years yet. From the Milankovitch data, this graph shows insolation at 65°N from 50,000 BC to 50,000 AD:
The green box has the Holocene ending at 3,000 AD – an arbitary choice. Insolation is already low enough to trigger glacial onset. For the last 8,000 years, the Earth has been cooling at 0.25°C per thousand years, so the oceans are losing heat. We just have to get to that trigger point at which snows linger through the northern summer. Solar Cycle 25 might be enough to set it off. By the end of this decade, we will be paying more attention to the Rutgers Global Snow Lab data.
From the source at: http://most-likely.blogspot.com/2012/03/milankovitch-cycles-and-glaciations.html
Model input is obliquity and precession and model output is the inverted δ¹⁸O record, with zero mean during the Pleistocene, from Lisiecki and Raymo 2004 and Huybers 2007. Lisiecki and Raymo use orbital tuning to constrain the age of the benthic records, while Huybers explicitly avoids this, consequently the two datasets are occasionally completely out of phase, but generally in good agreement, especially in the late Pleistocene.
As fitness function we take the product of the sum of squared errors (SSE) between the model and the two reference records from 2580 thousand years before present, with 1000 year timesteps.
For the longer term perspective, this is a combined crop (to make a continuous timeline) of the two fulls panel from the model prediction of the Milankovitch data.
The time period represented is from approximately 450,000 BC to 330,000 AD. The scale on the vertical axis is change in O18 content. There is a very good hind-cast match between the model and past temperature change as shown by the work of Lisiecki et al 2005 and Huybers 2007. The next glaciation is fully developed between 55,000 and 60,000 AD, with the next interglacial 20,000 years after that.
References
Huybers, P., 2007, Glacial variability over the last 2Ma: an extended depth-derived age model, continuous obliquity pacing, and the Pleistocene progression, Quaternary Science Reviews 26, 37-55.
Lisiecki, L. E., and M. E. Raymo, 2005, A Pliocene-Pleistocene stack of 57 globally distributed benthic d18O records Paleoceanography, 20, PA1003, doi:10.1029/2004PA001071.
Source Data: Download the consolidated data, including orbital parameters, insolation calculations, reference data and model output: Milankovitch.xlsx
beng says:
September 20, 2012 at 6:57 am
We get that the ice-volume itself is not well correlated
Yes, the ice volume includes all the accumulated old ice from previous forcings, so their Figure 3 is what one should look at to see the forcing
Way back somebody said 18O reflects Antarctic T rather than global. If this were the case we would see a continual decline for the last half million years, since the average surface elevation has gradually risen to two miles. What T largely approximates is global albedo = ice sheet extent, which lags insolation considerably. –AGF
Leif Svalgaard says:
September 20, 2012 at 6:00 am
” Figure 3 is what you should look at.”
Fig3 is just a wiggle matching exercise that avoids addressing the points I have made about Fig1.
I’ve just ordered warm woolen socks.
Ulric Lyons says:
September 20, 2012 at 8:21 am
avoids addressing the points I have made about Fig1.
Well, suit yourself.
Leif Svalgaard says:
“The issue was whether we would be hit TOMORROW and an educated guess says not.”
The issue about tomorrow is well defined by the sign in the bar that says “Free Beer Tomorrow”. It says that every day, but since every day is today, not tomorrow, there is no free beer. And I did note that the “when” on a strike was less well defined than the Milankovich “when”, but in that sense, could be a sooner tomorrow than the orbital causes would indicate that their tomorrow will arrive.
Did you get that?
Jim G says:
September 20, 2012 at 4:04 pm
Did you get that?
too deep for little me.
I wrote,
“Since we are BELOW that level NOW and the chart he posted shows that it stay below that level for next 50,000 years and that he labeled it as “The next glacial period” surely that is no red herring sir?”
Dr. Svalgaard writes:
“Perhaps I should have said “just plain wrong”, as clearly we at the present are not in a ‘glacial period’”
Sigh,
I never said we are in a glacial period.The whole argument I have been advancing is that the chart in figure 1 shows the indication that it will ALWAYS be below the 510 level for the next 50,000 years.That means that it favors cooling and ice advancement.
I have given YOU links to John Kehr’s charts showing some evidence that we are indeed sliding towards the next glacial period.Glaciers that did not exist 3,000 years ago are now here and growing.The each successive warm periods peak is below the previous one all an indication of a cooling trend.
David A. states which you have not once disputed:
“Insolation is already low enough to trigger glacial onset. For the last 8,000 years, the Earth has been cooling at 0.25°C per thousand years, so the oceans are losing heat.”
There have been science papers showing evidence of a cooling ocean for a long time as this CHART shows for the Atlantic:
http://theinconvenientskeptic.com/wp-content/uploads/2012/01/Chap_10_Illustration_93-550×382.png
Comparisons of past few interglacials in the climate autumn phase of the cycle:
http://theinconvenientskeptic.com/wp-content/uploads/2012/01/Chap_9_Illustration_81-550×464.png
The decline’s are quite similar.
http://theinconvenientskeptic.com/chapters-8-10/
Beng
Not sure what more to explain. Things like “and as soon as the insolation goes up again, the temperature will follow” is demonstrates the lack of understanding “the critical physical importance of focusing on the rate of change of ice volume, as opposed to the ice volume itself Temperature will follow thousands of years after the insolation goes up again, because something correlating with ice volume, guessing albedo, is driving temperature. It’s not temperature driving ice volume. So forget about 65N insolation, temperature is not supposed to correlate with that. Focus on the integral and you will see the next ice age is thousands of years over due. The integral has been dropping for millennia and the planet has “never survived” a drop like that before. The onset is NOW (if we have not managed to offset it a few hundred years by GHG).
Leif Svalgaard says:
September 20, 2012 at 5:42 pm
Jim G says:
September 20, 2012 at 4:04 pm
Did you get that?
“too deep for little me.”
But was there a little smile from little you?
sunsettommy says:
September 21, 2012 at 6:44 am
David A. states which you have not once disputed:
“Insolation is already low enough to trigger glacial onset.
I could spend all my time disputing Archibald’s dubious claims, but, frankly, I don’t have the time for that. The fact is that the insolation the next 35,000 years is going up, so I do not believe any ‘glacial onset’ will be ‘triggered’. And ‘lgl’ we are not ‘overdue’ for a new glaciation.
lgl says:
September 21, 2012 at 9:47 am
the planet has “never survived” a drop like that before. The onset is NOW
http://www.sciencemag.org/content/297/5585/1287
“the current warm climate may last another 50,000 years. The reason is a minimum in the eccentricity of Earth’s orbit around the Sun”
****
lgl says:
September 21, 2012 at 9:47 am
Beng
Not sure what more to explain. Things like “and as soon as the insolation goes up again, the temperature will follow” is demonstrates the lack of understanding “the critical physical importance of focusing on the rate of change of ice volume, as opposed to the ice volume itself Temperature will follow thousands of years after the insolation goes up again, because something correlating with ice volume, guessing albedo, is driving temperature. It’s not temperature driving ice volume. So forget about 65N insolation, temperature is not supposed to correlate with that. Focus on the integral and you will see the next ice age is thousands of years over due. The integral has been dropping for millennia and the planet has “never survived” a drop like that before. The onset is NOW (if we have not managed to offset it a few hundred years by GHG).
****
Thanks for responding.
Temperature will follow thousands of yrs after? Almost all of 65N land now isn’t glaciated — it’s low-albedo land, after the seasonal snow melts. So insolation changes (gradual as they are) will have an immediate energy impact (thru temp & evaporation to some extent). Hardly any time-lag for bare land.
And the onset is now?!? Ummm, okaaaaay….but I thought nature followed physics pretty closely. 🙂
IOW, if the physics decreed that the climate should’ve fallen into a new glacial period, it would have. If you’re saying the climate is close to a glacial stage, I agree from the ice-core patterns that this is likely (the LIA made the first subtropical & tropical mountain glaciers since the early Holocene). But w/the present climate’s lack of glaciers in sensitive lower-latitude areas & the resulting low positive-feedback from albedo changes, natural cyclic excursions may be limited enough to get thru the present insolation minimum. JMHO.
Minimum in eccentricity means ice age, Leif
http://virakkraft.com/Milankovitch2.png
Eccentricity was low 400 kyr and 750 kyr ago too. It didn’t help ‘us’ then and it will not this time. The planet does not even survive a minimum in obliquity. Not one single time last 800 kyr without ice buildup.
There is only one logical conclusion, down, soon.
Dr. Svalgaard writes,
“I could spend all my time disputing Archibald’s dubious claims, but, frankly, I don’t have the time for that. The fact is that the insolation the next 35,000 years is going up, so I do not believe any ‘glacial onset’ will be ‘triggered’. And ‘lgl’ we are not ‘overdue’ for a new glaciation.”
Ok,then that mean you do not agree with David’s first chart information which you should have stated earlier since it does make clear that it stays BELOW the 510 mark for the next 50,000 years.
Even YOU say this in the very first comment:
“Luckily, the slide into a glaciation is long and slow, tens of thousands of years, and, of course, the sun has nothing to do with it [Jupiter has].”
Yes even YOU admit that the future is a cooling one that will become Glacial winter.
I also showed you links several times about the declining insolation rate that you have not once acknowledged here it is one last time:
http://theinconvenientskeptic.com/chapters-8-10/
I am a little confused by your seemingly contradictory statements.
Thank you for your patient replies.
Following is a recent short summary of the progress of climate science, written by Albert Jacobs.
http://www.friendsofscience.org/assets/documents/fosQ3Extr-Terr.pdf
sunsettommy says:
September 22, 2012 at 10:21 am
Ok,then that mean you do not agree with David’s first chart information
I almost never agree with what Archibald claims.
Yes even YOU admit that the future is a cooling one that will become Glacial winter.
Absolutely, but it will take a ling time [60,000 years] and there is first a warming until 35,000 years.
lgl says:
September 22, 2012 at 9:14 am
Minimum in eccentricity means ice age
No, it means that things are ‘normal’. You get an ice age glaciation when the eccentricity is high and we are farthest away from the sun in January. In the next 100,000 years the Earth’s orbit will be nearly circular, so the ‘eccentricity mechanism’ will not work, so no glaciation on account of that, but then the tilt of the axis will determine the insolation and that will cause a small glaciation maxing in 63,000 years.
Allan MacRae says:
September 23, 2012 at 5:40 am
Following is a recent short summary of the progress of climate science
http://www.leif.org/research/Temp-Track-Sun-Not.png
Leif Svalgaard says: September 23, 2012 at 5:08 pm
Too cryptic Leif – I left my Enigma machine in the submarine.
Care to provide a legend and source for the red lines, etc.?
Allan MacRae says:
September 23, 2012 at 7:41 pm
Care to provide a legend and source for the red lines, etc.?
The heavy black curve is Soon’s version of Total Solar Irradiance form an earlier WUWT post. The red lines [there are three of them on top of one another] are modern reconstructions of TSI by myself, Dora Preminger, and Karel Schrijver using different methods. It is clear that they do not match the black curve. The detailed references and calculations I have provided many times elsewhere and I could do that again, but it often turns out that people don’t really want to look at them because they are inconvenient truths. If you have interest we could start on that educational journey.
Leif
You get an ice age glaciation when the eccentricity is high
No you don’t. There are glaciations at every eccentricity minimum last 800 kyr.
lgl says:
September 24, 2012 at 8:05 am
“You get an ice age glaciation when the eccentricity is high”
No you don’t.
So, you claim that there are no glaciations when eccentricity is high…
Leif Svalgaard says:
September 23, 2012 at 1:14 pm
“You get an ice age glaciation when the eccentricity is high and we are farthest away from the sun in January.”
You get glaciation even when eccentricity is low, and we were farthest away from the sun in January 11kyr ago when de-glaciation was happening. Currently obliquity is decreasing:
http://stratus.astr.ucl.ac.be/textbook/chapter5_node12.xml#climatic_precession
Leif
No, I claim there are glaciations at every eccentricity minimum last 800 kyr. There are also glaciations when eccentricity is high if obliquity is at minimum.
lgl says:
September 24, 2012 at 1:17 pm
No, I claim there are glaciations at every eccentricity minimum last 800 kyr. There are also glaciations when eccentricity is high if obliquity is at minimum.
Just the other way around. The big glaciations are with high eccentricity, the tilt is a smaller effect, but still enough to cause glaciations when none result from a circular orbit.