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- 01/07/19--09:06: Comment on 2018 –> 2019 by freedomfan
Thank you for your reply. Our reasons for our interest in paleo climate and biosphere productivity versus temperature over geological time are clearly quite different. You appear to be mostly interested in the last glaciation and Holocene. My interest in this discussion is about the period since complex life began, biosphere productivity versus GMST, and the causes of the mass extinction events.
Yes, there is recent evidence that the Permian-Triassic Boundary was a short ice age and a mass extinction event. Baresel et al (2017) https://www.nature.com/articles/srep43630 , give the timing as ~89 ka in the Permian and ~14 ka in the Triassic.
I can’t comment on the impact of drowned forests on atmospheric CO2 and GMST. However, my suspicion is that it is trivial. We’d need to see the estimated quantities and compare these with the masses of C in the biosphere, oceans and calcareous sediments – e.g. as given by Mike Jonas in this comment above https://judithcurry.com/2019/01/04/sea-levels-atmospheric-pressure-and-land-temperature-during-glacial-maxima/#comment-887416 . We’d also need to understand the emissions rates and sequestration rates (oceans, vegetation and weathering) and compare these with the rates from all other sources.
Sorry for being OT, but I tried to locate your posts on Sea Level Parts II and III that were referenced in Part I several years ago. If you have it could you provide the link here? I searched but to no avail.
Tony, the dates are kyr BP (before 1950). 0.4 corresponds to the entire LIA, centered around 1550. The LIA is considered a single ACE, as we lack the resolution to identify warm or cold decades throughout the Holocene. Multiple proxy reconstructions, like Moberg et al., 2005, or Hegerl et al., 2007 support that from c. 1200 to c. 1650 there was a discontinuous period of cooling, and from c. 1650 to the present a discontinuous period of warming.
Here are both records:
While we could subdivide the 0.4 ACE (aka LIA) in smaller warm and cold periods, we lack the resolution to do the same with other ACE.
I did not invent the term ACE. It refers to periods of clear climate change identifiable at the centennial resolution that lasted for a few centuries.
There is a saying in Brazil: why simplify things if we can make them more complicated (and earn a living from it)? I've seen this temperature and CO2 graph before and I think the question of why the scales are set this way (comparing apples and pears?) has been raised.
The chicken and egg question of lag has followers in both camps, however, that there is a feedback between T and CO2 is not in any doubt. How much is from drowned forests (and savannahs etc.) seems to have been overlooked, hence the crude (yep) engineer's, back-of-an-envelope calculation to check on the magnitude. One comment says that "this would be insignificant", the numbers I get shows that this could be a significant part of the feedback. I look forward to seeing this topic being taken up by the professionals and the data refined.
For the present topography such a deep freeze as this has never existed.
And we don't know what would happen in an extra-long GM. The Red Sea data quoted (which does not have currents, tides, geoids and winds) however, does show remarkably consistent max & min. (over the Hanish sill) with near present levels (within 10 m) at today, 120 ka 200 ka 235 ka 335 ka & 410 ka, and low stands at 20 ka, 140 ka and 440 ka.
This does relate to topography and tropical sea surface area and may be of interest.
Thanks for all that. As you may remember I reconstructed CET from it's official start date of 1658 back to 1538 .
As you can see I termed it the ' intermittent little ice age' which is fairly close to your word 'discontinuous'. Figures 1 and 2 might be of particular interest as they provide good resolution as opposed to the coarse sieve of more general reconstructions.
However, As Hubert lamb said about all reconstructions ' we can understand the tendency but not the precision'
The warm spells around 1640 are interesting as is the very cold spell around 1680.
In general we have come to think of the LIA and the MWP as either continuous cold or continuous warm, which does not help our understanding of climate.
There were some very warm spells in the LIA and some very cold spells in the MWP. So intermittently, discontinuously or characteristically warm or cold better reflects both the periods.
ace is interesting. Is there data for the warm ones?
Parts two and three are in my long list of to do articles. I am concentrating on pushing back cet as far as possible as that will give an idea of warm and cool periods which may have an affinity with sea level change
Thanks Tony. Good to know it wasn’t my lack of skills in finding things on the Internet. I’m looking forward to when you do finish it.
There are no extra long GM because they are constrained to a bottom in the obliquity cycle (with adequate climatic lag of ~ 6 kyr), so their length is limited to a slightly over a quarter of 41 kyr or about 10-15 kyr.
I see you have decided that your local Red Sea data can be trusted better than more global reconstructions and δ¹⁸O stacks that are a proxy for global ice. There is a lesson to be learned from the 1470-yr periodicity found in GISP2 during the last glacial and trusted despite not showing in other cores because GISP2 was supposedly a superior core. That avenue leads to the wrong conclusions and publishing articles like Rahmstorf et al. 2003 that looks ridiculous a few years later.
When only one proxy shows what you want, the prudent position is to be cautious.
Yes, I read that article, and I agree. But with low resolution it is clear that the long-term trend from c. 1200 to c. 1650 was down, and from c. 1650 to the present it has been up. Judith also had an article on that last point:
It is obvious that there weren't 400 years of warming, but the general trend has been up.
There have not been any known warming ACE during the Holocene. Once the Holocene Climatic Optimum was reached the ACEs are all characterized by cooling followed by recovery. Once the Neoglacial starts the recovery phase, that is usually partial, might be mistaken with warming if out of context, but temperature doesn't usually reach previous levels, so they have to be categorized as recovery. The possible exception is the present global warming that might have exceeded the Medieval Warm Period due to the anthropogenic contribution. In any case no warming Holocene ACEs are found in the bibliography to my knowledge. Holocene climate variability is essentially a study of cooling events. Such a strong bias in climate variability has not been properly addressed to my knowledge.
[…] https://judithcurry.com/2019/01/03/reconstructing-a-dataset-of-observed-global-temperatures-1950-201… […]
Thank you for your honesty, integrity and hard work, Dr. Curry. Happy New Year.
“Everything should be made as simple as possible, but no simpler.” Albert Einstein
Biokinetics imply balance between respiration and photosynthesis that results in increases or decreases in net biome production. Both on land and in oceans. A global process of course as much in high latitudes - especially in oceans - than in tropics.
Carbon dioxide solubility with temperature is a relevant feedback.
These are fast processes and the parsimonious explanation is that the 800 year lag is an artifact of paleoclimatic data sources. Resorting to quibbling about data - and ignoring antiphase polar temperature changes that were at the core of my comment - is disingenuous.
"It is surprising that the cooling bias of Holocene ACEs has not been given any attention."
Events are particular instances of abrupt climate change. Javier is in the grand skeptical tradition of novel Earth system science - but I find these hypothetical enthusiasms less than convincing.
AMOC seems involved in warming and cooling in the Northern Hemisphere. That changes for multiple reasons in a coupled system.
Something relatively recent.
This is still a good place to start.
Thanks for reminding me of that article.
Some seem to want to deny the existence of the long slow thaw. It far predates the current agw scare with it's up to 400 year long epoch, It is a shame that it s not accepted more widely and the overall reasons for it more closely examined.
These include Natural variability including aCe, volcanoes, currents, the sun and the colder period impacting on sea temperatures. Then there is the Man made elements which includes Land use changes, greater pollution first impeding the sun then as it was tackled allowing more sunshine, population increase and uhi, co2 etc.
So many interesting possibilities yet we seem to want to make one element guilty of everything.
I have read your post, Frank Bosse, aka frankclimate, and although I have not studied it in detail or claim to understand exactly what your methods are, I would like to comment here on some analysis I have done using an Empirical Mode Decomposition version called ceemdan with regard to noise and quasi-cyclical structure in the CMIP5 modeled and the observed GMST series. The ceemdan method is wholly empirical and requires no assumed parameters in the decomposition of a time series and that characteristic provides this method with some advantage over other decomposition methods. However, the cyclical estimates found in these series and especially the longer period ones are not at all well understood.
I will here briefly summarize some of my analysis results:
1. Both the observed (Cowtan-Way and HadCRUT4 v5) and modeled GMST series during the historical period yield multidecadal variations that are not part of the secular trend. I see in the range of 3, 10, 20, 30 and 60 to 70 year cycles.
2. The CMIP5 model GMST series in the post historical period have different cyclical character than in the historical period. The series in both periods are not statistically different in character otherwise.
3. The CMIP5 models pre-industrial control (pic) series do not show any statistically significant cyclical structure.
4. While the decomposition of the observed and modeled series during the historical period yields trends that are less (approximately 30% less) than trends determined without decomposition, the estimates of TCR and ECS would not differ significantly from those derived in Lewis and Curry 2018. In other words a judicious selection of time periods can "cancel out" the effects of multiple decadal variations and volcanic events.
5. With ceemdan analysis the CMIP5 model ensemble has an average temperature trend for the historical period slightly greater than that for the observed series - when a combination of the tas(surface air temperature) for land and tos(SST) for the oceans is used for the models. In this comparison, since the observed is essentially a combination of sat and tos, it is more apples to apples. Nic Lewis has made arguments that perhaps the difference that the models see in this case is not the same as that for the observed, although the amount of observed global sea air temperature data is limited. When the sat temperatures for land and sea are used in the modeled global temperature the trends tend to be on average approximately 20 percent higher than when the combination is used.
6. If ceemdan trends for the published forcing, ocean heat content (OHC) change (or the net TOA radiation) and global temperature series is used, the approximate same ECS (or better the feedback parameter) values are found for those for the observed and CMIP5 modeled that are reported in Lewis and Curry 2018. If the combination global ceemdan temperature trends are used for the modeled estimates those estimates will be 20% lower than the all sat case. Most of the difference between the model ensemble combination average and the observed in this case then has to be due to the differences in the changes in forcing and OHC used in the estimates.
7. It is important to remember that when the model ensemble average is referenced there are significant differences between individual models where models have multiple runs that can make the statistical comparison possible.
8. Recent ceemdan analysis of mine with RCP 8.5 CMIP5 model runs from the historical period through to the year 2300 show that the estimated feedback parameter decreases (higher sensitivity) on average something less than 10% over the long term (2100 to 2300). This change is in good agreement with what was found in Lewis and Curry. I am in the process of looking at just how well my results are in agreement with the 4XCO2 CMIP5 experiments.
I am only interested in my analysis for learning for own benefit and perhaps encouraging someone in the field at looking in depth at applying my methods or at least evaluating them.
I liked some of the questions and replies on this thread concerning issues where there are not good answers yet supplied by the science and the assumptions that are currently required to make some of these comparisons.
It is too bad that personality infighting has to detract from those important discussions.
Unfortunately I am not too familiar with antiphase polar T changes & the link gave a 404, so I am not able to add anything on how this relates to the points raised in my post. In a nutshell: max and min sea levels are largely determined by the topography of the continental shelves; cooler T over PRESENT lands is affected by altitude (patm) - hence the exposed shelves at -100 to -120 m were slightly warmer & this allowed more tropical and sub tropical forest growth - such as the Atlantic Rain Forest - and these forests (covering an area about the size of Brazil) were drowned and the corbon stored presumably lost into the atmosphere in a very short period.
If I may, I'll restrict future replies to these questions.
I have done a new data search and will post a reply tomorrow.
Eh uma bagunça!
<blockquote>I find these hypothetical enthusiasms less than convincing.</blockquote>
And that is your problem. You guide yourself by your opinion instead of by the evidence.
There are multiple articles studying Holocene cold events and many of them have been identified and even named. For example:
Wanner, H., Solomina, O., Grosjean, M., Ritz, S. P., & Jetel, M. (2011). Structure and origin of Holocene cold events. Quaternary Science Reviews, 30(21-22), 3109-3123.
Perhaps you could point me in the direction of a study on one or several warming events during the early or middle Holocene. There are lots of studies on cooling events, you would think that if you are right there should be some on warming events.
<i>"Based on a statistical analysis of proxy time series we demonstrate that, at the multidecadal to multicentury timescale, several cold relapses interrupted periods of relatively stable and warmer climate."</i>
From the conclusions in Wanner et al., study above.
You not only display a strong bias yourself, but you try to disguise it in vain behind ad hominem attacks against anybody with a different opinion.
<blockquote>we seem to want to make one element guilty of everything.</blockquote>
Climate has a high level of short term noise arising from complexity generated chaos. But to move in the same direction for hundred of years in the midst of so much internal variability, requires a long-term external forcing.
Several such long term forcings exist, from igneous provinces, tectonics, orbital changes, greenhouse gases. They are not difficult to conceptualize. Therefore, yes. Sometimes one element is guilty of driving climate in one direction for a long time.
There is one such element that is not accepted. Long periods of very low solar activity can cool the planet for hundreds of years. The evidence is surprisingly strong, but even more surprising is how strongly it is denied by all except paleoclimatologists.
The LIA was such a period. Its cooling was driven primarily by low solar activity and took place during the winter months (both hemispheres) of certain years. The recovery from the LIA has taken place once low solar activity ended, and has been mostly unforced, as there is an optimal temperature solution that corresponds to the current Milankovitch orbital situation. To that natural unforced warming, anthropogenic forcing has been added.
That's why the cause is not being found. We have no modern experience with the effects of very low solar activity (just getting a primer), and since the warming was unforced, no other forcing but anthropogenic is found.
The Younger Dryas and the 8.2 KY event?
There is quite obviously warming and cooling - abrupt climate change internally generated - seen everywhere and at all scales. And I showed evidence of that and discussion of complex causality. Do you need more - or is that enough for you to ignore utterly in favor of personal disparagement?
Greenland Temperature Reconstruction
You have a list and an idiosyncratic interpretation - your hypothetical enthusiasms that brook no doubt or disagreement ever. I of course have profound doubt about all your habitually oversimplified notions you are so adamant about. Where have we heard that it is all in irrefutable data? Oh right - just about everywhere. There was a tweet feed on top that you should look at.