Support the Arctic Sea Ice Forum and Blog

Author Topic: Variability of global temp in transtion to higher average temp  (Read 4735 times)

anthropocene

  • Frazil ice
  • Posts: 113
    • View Profile
  • Liked: 22
  • Likes Given: 2
Variability of global temp in transtion to higher average temp
« on: November 01, 2015, 03:34:14 PM »
Just finished re-reading Richard Alley's "Two Mile Time Machine".  One topic which I haven't seen much discussion about is the idea described in the book of the global temperature being a 'drunk person'. That is, when the temperature is allowed to sit in a stable position it will sit there without varying too much: however when it is pushed out of equilibrium it will vary wildly chaotically around a new average. This is illustrated by the ice core temperature record over the last 100,000 years. More technically I think this would be described by Lorentz attractors; the global temperature will vary only by small amounts from a Lorentz attractor until it is forced away from that attractor when it will vary wildly until it settles down to 'orbit' another Lorentz attractor.
  Now assuming that the ECS for CO2 doubling is  3degC. Have there been any scientific papers discussing this potential variability (over short time-scales) of the global temperature if this 3degC change comes to pass? In other words, the paleoclimate record points to a ECS of 3degC (over long timescales) is there any idea of the variability in the global temperature over shorter timescales after the long term average global temperature has shifter by +3degC? That is, with a global temp change of approx. +3degC could this transition include short term global temperature change of +4degC, +5degC, +6degC....?? 

anthropocene

  • Frazil ice
  • Posts: 113
    • View Profile
  • Liked: 22
  • Likes Given: 2
Re: Variability of global temp in transtion to higher average temp
« Reply #1 on: November 01, 2015, 04:19:46 PM »
Just realised that this discussion is most probably more suited to be in the 'Science' section.

Neven: Feel free to move the thread if you see fit.

Theta

  • Frazil ice
  • Posts: 174
  • Grips
    • View Profile
  • Liked: 0
  • Likes Given: 1
Re: Variability of global temp in transtion to higher average temp
« Reply #2 on: November 01, 2015, 04:44:16 PM »
Some good threads to examine that should answer your question, at least partially.

 https://forum.arctic-sea-ice.net/index.php/topic,1306.0.html

https://forum.arctic-sea-ice.net/index.php/topic,1307.0.html

https://forum.arctic-sea-ice.net/index.php/topic,1308.0.html

https://forum.arctic-sea-ice.net/index.php/topic,852.0.html

A discussion on overall non-linear temperature spikes might be a good idea also because it could give a good insight into what lies in the short term future for humanity, especially from what we have seen of the present El Nino, the Arctic Sea Ice and the Indonesian wildfires.
Can't think of a signature

Neven

  • Administrator
  • First-year ice
  • Posts: 7961
    • View Profile
    • Arctic Sea Ice Blog
  • Liked: 1163
  • Likes Given: 575
Re: Variability of global temp in transtion to higher average temp
« Reply #3 on: November 01, 2015, 05:27:53 PM »
Neven: Feel free to move the thread if you see fit.

Thanks, moved it.

If what Alley says, is correct, does this mean that it isn't possible (or very difficult) to constrain sensitivity using observations?
Il faut comparer, comparer, comparer, et cultiver notre jardin

AbruptSLR

  • Multi-year ice
  • Posts: 19629
    • View Profile
  • Liked: 2236
  • Likes Given: 270
Re: Variability of global temp in transtion to higher average temp
« Reply #4 on: November 01, 2015, 06:31:52 PM »
If what Alley says, is correct, does this mean that it isn't possible (or very difficult) to constrain sensitivity using observations?

I have written about this topic in many different posts scattered across numerous different threads, so it is understandable that with a topic as complex as climate change that confusion remains on this topic; which few scientists and zero policymakers will address honestly/openly.  Effective climate sensitivity is a catch-all term that relates the change in global mean surface temperatures to radiative forcing and adjusted for thermal inertial. 

Thus whether a given perturbation in radiative forcing (say modern society rushing up to the IPCC's "Carbon Budget" as fast as it can, and then slamming on the socio-economic breaks as hard as it can); might still increase the effective climate sensitivity through the rest of this century depends on a large number of factors including:
(a) resonance around strange attractors [like a strong El Nino acting to: (1) increase deep atmospheric convection in the Equatorial Pacific conveying water vapor high into the troposphere thus creating high clouds that act as a positive feedback by trapping long-wave radiation trying to escape into space; while at the same time pushing dry air from the troposphere towards the surface where it desiccates low cloud cover, thereby reducing an otherwise negative feedback as low clouds tend to reflect incoming solar radiation back into space; or (2) increasing the advection of water vapor from lower latitudes to both of the polar regions thus increasing the rate of Polar Amplification; or (3) accelerate ice mass loss from the WAIS thus contributing to Hansen et al. (2015) positive feedback where the freshening of the surface waters in the Southern Ocean both increase sea ice extent thus reducing the radiation of long-wave radiation to space and also by decreasing the rate of the MOC thus creating greater temperature gradients between the tropics and the polar regions thus contributing to extreme weather events and a possible flip to an equable climate say by the end of this century.]
(b) The rate of activation of non-linear feedbacks (both positive and negative) [like increasing wind velocities from increasing storm activity accelerating the rate of trans-evaporation resulting in higher than expected amounts of water vapor in the atmosphere; and/or a temporary surge in vegetation growth triggered by increasing atmospheric CO2 concentrations, followed in several decades by a surge in the release of CO2 & CH4 temporarily sequestered back into the atmosphere by heat and drought/flood stress.]
(c) The rate at which Earth Systems state-dependent tipping points on individual feedback mechanisms are reached [like the accumulation of sufficient heat content in the ocean so that changes in the paths of warm ocean currents trigger Clathrate Gun scenarios along continental slopes in various portions of the ocean such as the Arctic Ocean, the Southern Ocean, etc.]
(d) The rate at which the negative forcing of aerosols is eliminated [like a rapid switch to renewables drastically reduces anthropogenic aerosol emissions to this negative forcing is reduced faster than previously expected].

Edit: I add that the US DOE is so concerned that the current generations of ESMs do not adequately bound climate sensitivity in future projections that they are currently spending hundreds of millions of dollars to create the state-of-the-art ACME ESM in order to try to get a better handle on this difficult issue.
« Last Edit: November 01, 2015, 06:45:59 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19629
    • View Profile
  • Liked: 2236
  • Likes Given: 270
Re: Variability of global temp in transtion to higher average temp
« Reply #5 on: November 01, 2015, 06:47:06 PM »
I remind readers that the thread entitled "IPCC possible scenario: 9C over next century or so" addresses some of these issues/concerns, & can be found at the following link:

http://forum.arctic-sea-ice.net/index.php/topic,1020.0.html

In particular, I draw attention to my Reply #26 in that thread that includes the following:

Mark Pagani, Zhonghui Liu, Jonathan LaRiviere, Ana Christina Ravelo (2009), "High Earth-System Climate Sensitivity determined from Pliocene CO2 Concentrations", Nature geoscience, doi:10.1038/NGEO724

http://people.earth.yale.edu/sites/default/files/files/Pagani/1_2009%20Pagani_NatureGeosci.pdf

Extract from Pagani et al 2009: "Data and modelling for the middle Pliocene (~3–3.3 Myr) indicate that the global mean temperature was 2.4–2.9 "C warmer than preindustrial conditions, and ~4 "C warmer during the early Pliocene (~4–4.2 Myr; ref. 5). If changes in carbon dioxide and associated feedbacks were the primary agents forcing climate over these timescales, and estimates of global temperatures are correct, then our results imply a very high Earth-system climate sensitivity for the middle (3.3 Myr) to early (4.2 Myr) Pliocene ranging between 7.1 ± 1.0 "C and 8.7 ± 1.3 "C per CO2 doubling, and 9.6±1.4 "C per CO2 doubling, respectively."

Caption for the attached image: "Estimated CO2 trends considering probable oceanographic changes at each site. Each line represents a modified CO2slope for each site and the dashed green line (1012(alt)) represents an alternative nutrient scenario for Site 1012 (Supplementary Information). Vertical grey lines intersect CO2 concentrations at 3.0–3.3 and 4.0–4.2 Myr, the time intervals representing the Earth-system climate sensitivity estimates presented in the text."

Finally, I point-out that while most scientists assume that it would take centuries, or millennia, to reach ESS values of 7.1 to 9.6 C reached during the Pliocene; this many not be true given the rate and nature of our current anthropogenic forcing.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Theta

  • Frazil ice
  • Posts: 174
  • Grips
    • View Profile
  • Liked: 0
  • Likes Given: 1
Re: Variability of global temp in transtion to higher average temp
« Reply #6 on: November 01, 2015, 08:30:14 PM »
I remind readers that the thread entitled "IPCC possible scenario: 9C over next century or so" addresses some of these issues/concerns, & can be found at the following link:

http://forum.arctic-sea-ice.net/index.php/topic,1020.0.html

In particular, I draw attention to my Reply #26 in that thread that includes the following:

Mark Pagani, Zhonghui Liu, Jonathan LaRiviere, Ana Christina Ravelo (2009), "High Earth-System Climate Sensitivity determined from Pliocene CO2 Concentrations", Nature geoscience, doi:10.1038/NGEO724

http://people.earth.yale.edu/sites/default/files/files/Pagani/1_2009%20Pagani_NatureGeosci.pdf

Extract from Pagani et al 2009: "Data and modelling for the middle Pliocene (~3–3.3 Myr) indicate that the global mean temperature was 2.4–2.9 "C warmer than preindustrial conditions, and ~4 "C warmer during the early Pliocene (~4–4.2 Myr; ref. 5). If changes in carbon dioxide and associated feedbacks were the primary agents forcing climate over these timescales, and estimates of global temperatures are correct, then our results imply a very high Earth-system climate sensitivity for the middle (3.3 Myr) to early (4.2 Myr) Pliocene ranging between 7.1 ± 1.0 "C and 8.7 ± 1.3 "C per CO2 doubling, and 9.6±1.4 "C per CO2 doubling, respectively."

Caption for the attached image: "Estimated CO2 trends considering probable oceanographic changes at each site. Each line represents a modified CO2slope for each site and the dashed green line (1012(alt)) represents an alternative nutrient scenario for Site 1012 (Supplementary Information). Vertical grey lines intersect CO2 concentrations at 3.0–3.3 and 4.0–4.2 Myr, the time intervals representing the Earth-system climate sensitivity estimates presented in the text."

Finally, I point-out that while most scientists assume that it would take centuries, or millennia, to reach ESS values of 7.1 to 9.6 C reached during the Pliocene; this many not be true given the rate and nature of our current anthropogenic forcing.

Wasn't there a 6C rise.in temperature over 13.years during one of the past extinctions?

Perhaps this note is important for future trends also?
Can't think of a signature

AbruptSLR

  • Multi-year ice
  • Posts: 19629
    • View Profile
  • Liked: 2236
  • Likes Given: 270
Re: Variability of global temp in transtion to higher average temp
« Reply #7 on: November 02, 2015, 02:47:44 AM »
Instances of abrupt change in the past may, or may not, be relevant to calibrations of modern ESM projections.

Edit: Further, the only 6C change in 13-yrs that I recall was localized to Greenland and was not associated with a global mean temperature change.
« Last Edit: November 02, 2015, 07:53:50 AM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Pmt111500

  • Guest
Re: Variability of global temp in transtion to higher average temp
« Reply #8 on: November 02, 2015, 06:09:30 AM »
I've forgotten where I got this image, (ok, found it, the image is from Bernard Etkin editorial on Climatic Change, 2010 (http://link.springer.com/article/10.1007%2Fs10584-010-9821-x?LI=true#page-1) , could be I grabbed this from SkS sometime in 2010), but I think the producer of it intended it to be shared. Here we see 3 or maybe 4 more or less stable regions (these I added afterwards) of relationship between T and CO2 during the last 420000 years as seen in the ice cores and later record. Then there's the intrusion of fossil carbon to the atmosphere. I'm rather surprised by the amount of weather stability we still seem to have. I'm expecting this to change once the Arctic Ice goes seasonally ice free, letting the Pacific weather systems move through the Arctic to the Atlantic, or rarely, the other way around. This we've seen happening a couple of times in the 'split polar vortex'-situations. That might well be a 'temporary new normal', at least for the higher latitudes.

(added:) As the image doesn't include the few more or less reliable estimates of this relationship in the further past, it should be noted that the x-scale isn't actually following the radiative cooling law (the plot should be lin-log or some such for easier reading) , so linear extrapolations from this are not the real thing. Also, the estimates of the glacial Global temperatures have varied somewhat as there are pretty few long records from subropics and tropics, so the y-scale might as well be somewhat wrong. But the relationships are there.

Changed the image to set text labels and decrease the readability of the graph:
HCO (Holocene Climate Optimum) - Interglacial Highs
Holocene - normal Interglacial
D-O events - and the similar episodes in earlier glacials


« Last Edit: November 02, 2015, 11:12:52 AM by Pmt111500 »

anthropocene

  • Frazil ice
  • Posts: 113
    • View Profile
  • Liked: 22
  • Likes Given: 2
Re: Variability of global temp in transtion to higher average temp
« Reply #9 on: November 03, 2015, 12:08:27 AM »
Thanks all for the information and links - looks like I have a lot of reading to do.....

Not sure my question will be answered in there but thinking about it, that is more likely because the intended question is not clear or doesn't make much sense. I will go and read and then see if I can phrase it better.

Neven "If what Alley says, is correct, does this mean that it isn't possible (or very difficult) to constrain sensitivity using observations?"

In other places (e.g. AGU Youtube videos) Alley repeatedly states that there is a long tail to the distribution of possible sensitivities to increasing CO2. So the ECS is likely to be within the IPCC range but there is always the chance of significantly more warming.
What seems to be suggested in "Two Mile Time Machine" is that the longer term warming value of the ECS may be what the temperature settles down to eventually.  Before then the temperature may 'bungee' (his word) higher and lower than the longer term stable temperature. However it is hard to say because the section is hard to be 100% certain about (unusually for Alley) because it jumps between referencing global temperatures and Greenland temperatures. So it is not clear if what was meant was that
1)Greenland temperatures vary significantly as global temp increases  before both stabilise at a new level or
2)  global temperatures jump around a lot before levelling towards the new stable value (with Greenland temp being taken as a proxy for the global temperature).
  It would seem almost physically impossible for global temperatures to go up and down in the time periods being mentioned so 1) is the most likely conclusion and I've misread what is written.