SST’s cooler now than in the Medieval Warming Period

From “The Hockey Schtick“, some inconvenient truth that breaks Mann’s already broken hockey stick into even smaller pieces. A new paper finds significant cooling of Atlantic Ocean over past millennium, making the MWP warmer in terms of sea surface temperature than today. Since land temperatures (including forest lands of Sheep Mountain and Yamal) respond significantly to ocean temperatures (the ocean is the big kahuna of global heat sinks) it is a pretty safe bet that those favored trees (including YAD 061) experienced warmer temperatures during the MWP than today. The eastern tropical North Atlantic reconstruction of SSTs was based on foraminiferal (marine plankton shells) Mg/Ca ratios that resolves multidecadal variability over the past 1700 years. see below:

The paper, published December 29th, 2011 in the journal Paleoceanography finds that Atlantic Ocean surface temperatures have significantly cooled over the past millennium, since the Medieval Warming Period from about 950-1200 AD.

Summer-Fall Sea Surface Temperatures (SSTs) shown in top graph. Iceland Sea Surface temperatures have also declined over the past 1200 years (4th graph). Note also the significant increase of solar irradiance from the Little Ice Age 1550-1850 to the latter 20th century (5th graph).

Key Points:

  • Monsoon season SST is reconstructed for the past 3 millennia
  • Over the past 1700 years, several intervals show multidecadal SST variability
  • Late medieval cooling amounts to approximately 0.5 degree Celsius

PALEOCEANOGRAPHY, VOL. 26, PA4224, 11 PP., 2011

doi:10.1029/2011PA002130

Multidecadal variability and late medieval cooling of near-coastal sea surface temperatures in the eastern tropical North Atlantic 

Henning Kuhnert et al

Multidecadal variations in Atlantic sea surface temperatures (SST) influence the climate of the Northern Hemisphere. However, prior to the instrumental time period, information on multidecadal climate variability becomes limited, and there is a particular scarcity of sufficiently resolved SST reconstructions. Here we present an eastern tropical North Atlantic reconstruction of SSTs based on foraminiferal Mg/Ca ratios that resolves multidecadal variability over the past 1700 years.

Spectral power in the multidecadal band (50 to 70 years period) is significant over several time intervals suggesting that the Atlantic Multidecadal Oscillation (AMO) has been influencing local SST. Since our data exhibit high scatter the absence of multidecadal variability in the remaining record does not exclude the possibility that SST variations on this time scale might have been present without being detected in our data. Cooling by ∼0.5°C takes place between about AD 1250 and AD 1500; while this corresponds to the inception of the Little Ice Age (LIA), the end of the LIA is not reflected in our record and SST remains relatively low.

This transition to cooler SSTs parallels the previously reconstructed shift in the North Atlantic Oscillation toward a low pre-20th century mean state and possibly reflects common solar forcing.

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52 thoughts on “SST’s cooler now than in the Medieval Warming Period

  1. This paper confirms earlier findings using sea shells, which provide high levels of resolution and would be no surprise to anyone who enjoys reading the current literature concerning this area.

  2. At what level of accumulated evidence will Mike Mann and other MWP deniers accept that they are wrong? How much longer can the hockey and the rabid response teams remain in tree ring “hide the decline” fantasy land?

  3. I would think that sea surface Temperatures, would be more representative of the earth’s stored solar energy, than are atmospheric (lower troposphere) Temperatures, given the low thermal mass of the atmosphere compared with the oceans.

    And the oceans are a much better approximation to a black body, as far as radiative cooling of the planet goes, whereas some claim that the atmosphere emits no BB like thermal radiation whatsoever, but only specific molecular resonance spectral lines; that are characteristic of the molecular species and not the Temperature.

  4. So with foraminiferal Mg/Ca ratios as a proxy they find North Atlantic sea temperatures show some evidence of the AMO, a 50-70 year quasi-cyclic variation. However there is a high degree of variation – scatter – in the results, some of the early values would need to be well supported by other data/methods before the extreme variations shown around 350AD could be taken seriously.

    But most damaging to the credibility of their results would seem to be the inability to detect any warming since the onset of the LIA. It seems to be well established from multiple lines of evidence that the AMO has been in a positive phase since ~1920 and this is often invoked to explain (some of ?) the warming since then. Although there is a logical inconsistency in using the AMO which is a description derived from temperature variation as a causal explanation.

    Presumably the inability to detect the known warming from the LIA over the last century is a defect of the foraminiferal Mg/Ca ratios method.
    At least I presume nobody actually thinks that the absence of the post-LIA warming from this record throws doubt on all the other evidence for this last decade being warmer than any in the last two centuries.

  5. I’m perplexed how why you think data showing cooling over the last millennium “breaks Mann’s already broken hockey stick into even smaller pieces?”

    Because of thermal mass I would not expect ocean data to show a recent warming ~ 100 years.

    This long term trend data would seem to support the argument that other climate driving terms are not driving warming, thus supporting CO2 as the cause (as the only rapidly changing driver.)

    Can you explain? This isn’t my field.

  6. I wouldn’t say the graphs are inconsistent. Increasing irradiance corresponds with increasing AMO and a flattening of the sea surface temperature graph. It would make sense that the sea surface temperatures would only flatten out rather than increase, too, because the ocean temperatures are likely based on the temperatures of the last 4000 years or so which have been warmer than today except for the period during the LIA. In other words, the oceans, while warming a bit from their LIA temperatures, are still cooling overall from their Holocene Climate Optimum temperatures. A long period of negative AMO will likely reduce solar irradiation and possibly continue the cooling off of the Atlantic. Notice that sea surface temperatures only leveled off during the period of increased irradiance, they didn’t increase. Any decline in solar irradiance is likely to result in a continuing of the decline.

    This might be the reason why the pattern of the past 2000 years or so has been cool periods with each one being cooler than the previous and warm periods that never quite get as warm as the previous one.

  7. Why did the Medieval Warmed Crusaders head off to do their deeds in the Middle East? Because the land was producing loads of food/wool/wood etc and all the poor serfs were not frozen and miserable!

    Happy New Year to those who know what it means……….

  8. Mann was right!

    People are using information to show he was wrong. All data of all forms must be held and protected in a bunker in an undisclosed location to protect the integrity of the correct view.

    This is bad. Confusing. Complicated. The correct message is very simple.

  9. I have just spoken to Dr Mann. He assures me the problem with the shape of the temperature chart is simply solved by turning it upside down – he also says in climate science this is a typical example of one of several generally acceptable procedures to correct inconvenient data.

  10. @- crosspatch says: December 31, 2011 at 10:41 am
    “In other words, the oceans, while warming a bit from their LIA temperatures, are still cooling overall from their Holocene Climate Optimum temperatures.”

    Thats a credible hypothesis. Every other interglacial period shows a maximum temperature shortly after the rapid melt and shows a gradual decline with pauses and ‘noise’ at the decadal scale for the millenia after that peak.

    @-“A long period of negative AMO will likely reduce solar irradiation and possibly continue the cooling off of the Atlantic. Notice that sea surface temperatures only leveled off during the period of increased irradiance, they didn’t increase.”

    I suspect you meant this the ‘other way round’. Solar irradience is more likely to drive the AMO than the reverse!
    However while SST may show periods of cooling and leveling off in the past, since the 1950s while the AMO was going negative the SST and ocean heat content have increased.
    The rate at which the oceans are losing heat – perhaps gained during the Holocene optimum ~8000 years ago – seems to have slowed and reversed during the last few decades; despite the inability of this study to detect that.

    Something seems to have altered and reduced the rate of cooling of the oceans while solar irradiance has been stable or falling. Land-locked ice around both poles is now melting revealing drift-wood and sea-shore sediments that have been frozen and ice-covered at least since the Holocene optimum. Other evidence such as sea level indicates that the oceans are now at least as warm as they were immediately after the end of the last glaciation during the Holocene maximum.
    There are few candidates for a causal role in this reduced rate of cooling – and warming – of the oceans….

  11. bcwebb says:
    December 31, 2011 at 10:32 am
    “I’m perplexed how why you think data showing cooling over the last millennium “breaks Mann’s already broken hockey stick into even smaller pieces?” ”

    Because it contradicts his multiple attempts at showing constant temps in pre-industrial times.

  12. Solar irradience is more likely to drive the AMO than the reverse!

    Not sure which is the chicken and which the egg but I was assuming more cloud cover during negative AMO meaning lower irradiation of the surface of the ocean. It was all about clouds when I was thinking about that.

    As for revealing wood dating from the Holocene Optimum, it might mean something or it might not. We don’t know how many times it has been exposed in the past or if it is currently in the same position that it was in the past. That wood might have been transported to that location by the ice or floated there and cast onto the beach by the sea. The problem with shoreline wood residue is that it is (or was) potentially mobile. It may or may not be telling us much by where we find it.

    Just because it is exposed now doesn’t mean it wasn’t also exposed in the 1930’s or at other times.

  13. “And it now appears that Keith Briffa recognized that Southern Hemisphere temperatures were as warm or warmer in the MWP than now.”

    And Phil Jones is co-author of a paper that shows the same thing. Shows both the MWP and the LIA in the SH. Mann must be blowing a gasket.

  14. How on earth did this get past pal review? Surely the whole point of the system is to stop good scientific papers being published? The Team must be furiously emailing each other now – I hope somebody out there is capturing them for our future amusement.

    Let’s hope we have another good year of shooting down warmists in 2012.

  15. izen says:
    December 31, 2011 at 10:11 am

    But most damaging to the credibility of their results would seem to be the inability to detect any warming since the onset of the LIA. It seems to be well established from multiple lines of evidence that the AMO has been in a positive phase since ~1920 and this is often invoked to explain (some of ?) the warming since then.

    If I may
    My understanding is that the AMO wasn’t identified until 1994. Estimates of past AMO are done using North Atlantic SST data.

    Put simply, if this authors paleoreconstruction of SSTs was used to determine the AMO signal, the sign of AMO may have been different.

  16. Izen,

    Sagas mention a Viking swimming out to an island, killing a sheep, and swimming back with the meat to feed an honored guest. No one could make that swim today without hypothermia setting in.

    All the archeology suggests Mann was quite wrong, especially about Greenland. Unfortunately the funding for archeology went down as Mann got pampered.

    You need to study the archeology and geology more, and the “climatology” less.

    It is difficult to guage the ancient shorelines, because the land has also risen due to Isostatic uplift, however there is a clear difference between shorelines created by surf and shorelines created by grinding and slamming ice, and there are definite surf-created shorelines above the current one. In some cases those shorelines hold wood, behind currently-existing ice-shelves, and while most date from the Holocene, I recall reading of some chips that tested as being more recent than the Holocene.

    Also it is interesting to study the Independence I culture, who were the first (we know of) to walk arctic shores. There was enough driftwood for them to heat, cook and even build with it. Eventually they passed the point of “Peak Driftwood,” and had to adjust.

    I get the definate feeling there have been several warm periods since the Holocene where the arctic was more ice-free than it is now.

  17. A warmer and globally synchronous MWP means that climate sensitivity must be higher and positive feedbacks more pronounced to give that degree of climate variation.
    That has obvious implications for the climate response to the increased CO2.

  18. @-Baa Humbug says: December 31, 2011 at 2:12 pm
    “My understanding is that the AMO wasn’t identified until 1994. Estimates of past AMO are done using North Atlantic SST data.
    Put simply, if the authors paleoreconstruction of SSTs was used to determine the AMO signal, the sign of AMO may have been different.”

    Its worse than that.
    The AMO is a postulated cycle. Accurate SST records can only give a couple of apparent peaks. Identifying a ‘cyclic period’ from less than 3 cycles is suspect at best.
    This research is an attempt to identify the AMO from paleoclimate proxy records of SST.
    Although they put the best gloss on it –
    “Since our data exhibit high scatter the absence of multidecadal variability in the remaining record does not exclude the possibility that SST variations on this time scale might have been present without being detected in our data.”
    – it is possible that the AMO is an artifact of the short SST record and spurious curve-fitting. The lack of a detectable AMO in parts of the paleo-record may indicate that it is an a-periodic variation which is sometimes negligible in magnitude.
    As far as I can tell this research does little to decide the issue either way.

  19. @- Caleb says: December 31, 2011 at 2:47 pm
    “All the archeology suggests Mann was quite wrong, especially about Greenland. Unfortunately the funding for archeology went down as Mann got pampered.”

    Do you have evidence for this assertion ?

    A quick search for archaeological investigations of Greenland Norse settlements would seem to indicate a lot of activity in the last decade. Actually MORE than was undertaken in the 70s-80s or at any time before that.
    The Leverhulme Trust, the NSF and the Greenland state all seem to be funding ongoing archaeological research, do you think this has been reduced since whatever year it is you think ‘Mann got pampered’ ?

    @- “I get the definate feeling there have been several warm periods since the Holocene where the arctic was more ice-free than it is now.”

    I hesitate to rely on your ‘definate feeling’ in the absence of supporting evidence. In fact given the evidence refuting them I think they may be indefinite….

    http://www.climatescience.gov/Library/sap/sap1-2/public-review-draft/sap1-2-prd-ch8.pdf

    “Ice cover in the Arctic began to diminish in the late 19th century and has accelerated during the last several decades. The current reduction in Arctic ice is the largest in at least the last few thousand years and is progressing at a very fast rate that appears to have no analogs in past records.”

  20. What do we know about the relationship between sea surface temperatures and the temperature of the ‘body’ of the ocean? I understand the link between SSTs and the weather, but what is there in our body of knowledge about the behaviour of the oceans? We know that churning goes on, we know that if the SST is warmer than the air above then heat will logically be transferred to the air. But what about heat being transferred downwards, from the sea surface – and then where? Does excessive heat get bundled away into the deep ocean for the longer term or in contrast released elsewhere back into the air at a later date, like a month later?

    What do we know about how the oceans really behave?

    Lastly, if this AGW is true, it should be showing up on local measurements quite clearly by now. SSTs in shallow seas in industrialised areas – such as the Baltic Sea, Mediterranean and the Sea of Japan should be spiking sharply. Shouldn’t they?

  21. Simplistically, I know that if I sprinkle a kettle of boiling water over a cold bath tub, not long after the whole body of water has the same temperature.

    How does this apply to the oceans?

  22. @- John Billings says: December 31, 2011 at 6:19 pm
    “What do we know about the relationship between sea surface temperatures and the temperature of the ‘body’ of the ocean?”

    A very great deal. Try using ‘thermocline’ ‘ocean mixed layer’ and ‘meridional overturning circulation’ in a science search engine.

  23. If we were to have another and equal little ice age starting now then 200 years from now what would be the SST, ocean heat loss and how much more ice would there be on land?

  24. I hesitate to rely on your ‘definate feeling’ in the absence of supporting evidence. In fact given the evidence refuting them I think they may be indefinite….

    http://www.climatescience.gov/Library/sap/sap1-2/public-review-draft/sap1-2-prd-ch8.pdf

    bigger quote:
    “Ice cover in the Arctic began to diminish in the late 19th century and has accelerated during the last several decades. The current reduction in Arctic ice is the largest in at least the last few thousand years and is progressing at a very fast rate that appears to have no analogs in past records. Because ice cover is diminishing so rapidly, a comprehensive investigation of past warming events in the Arctic is essential.”

    What is being talked about is speed of reduction. Later on it predicts could ice free by 2040.

    So with MWP it’s long warm period- compared to ours, ours started in 1850- a century and a half compared to many centuries. I didn’t see any evidence that present arctic sea ice is lowest in thousands of years. And if by 2040 there was seasonal free ice, it would more striking evident of a rapid reduction. I don’t many are now comfortable with there being good chance of the arctic being seasonal ice free by 2040- or within 28 years.

  25. crosspatch says:
    December 31, 2011 at 10:41 am

    http://wattsupwiththat.com/2011/12/31/ssts-cooler-now-than-in-the-medieval-warming-period/#comment-848837

    In reply:
    I have been reading John Kehr’s book.The Inconvenient Skeptic.Where he talks about decreasing summer insolence for the last 6,000 years or so.At the 65 degrees North level.Where such decrease is especially important.That it has been in negative insolation trend for the last 3,000 years.The last 1,000 years is the coldest of the present interglacial period.It will be colder in the next 1,000 years too.Because summer insolation will continue to decrease.

    Already young glaciers have started growing within the last 1,500-2,000 years ago.That were bare of ice before then.Some as young as the Fremont Glacier in Wyoming USA.Where it is found to have been started during the little ice age.That means only around 350 years or so.

    It is the cooling summer months that is the critical factor for the next glacial age to show up.Right now we are in what John calls a Climate Autumn.That means we are facing continued cooling in the future.All due to decreasing summer insolation in the high northern latitude.

    I am surprised that he has not done a guest post here to bring up evidence on why we should not worry about the AGW hypothesis.He has made some observations.That I have yet to see mentioned in this fine blog.One that utterly destroys the idea that CO2 is a climate driver.

    It is the Milankovitch Cycle.The one that is well supported by research.And explains quite well the erratic temperature changes during the current interglacial period.Also shows a strong relationship with sea level changes as well.

    This is an area of topic that is not explored much by anyone.But John made an effort with his book.Here is the link about his book.There is a free chapter one for reading in the below link:

    http://theinconvenientskeptic.com/the-book/

  26. The current reduction in Arctic ice is the largest in at least the last few thousand years

    That is pure speculation. There is no possible way anyone can know that and I believe we have fairly solid evidence that it isn’t true.

  27. In fact, I would be willing to say the Arctic had less ice 2000 years ago during the Roman Warm Period in addition to the Medieval Warm Period. If we can infer from Alaska glacial activity, we know that the glaciers in Alaska are currently much advanced from where they were less than 500 years ago. We can tell when they cut through various stands of forest in the past 1000 years. I will grant you that there is less ice now than there was in 1940 but I am not prepared to say that there is less ice now than at any time even in the 20th century. There is evidence that the arctic was fairly warm from, say, 1925 to 1935.

  28. The Milankovitch cycle is a primary enabling factor but you will notice that we come out of glacials very quickly. Much quicker than the slowly changing Milankovitch cycle. We also go into the slowly. The last of the glacial ice from the last ice age probably lasted until about 8000 years ago. The last of it probably failed causing the 8.2ky event when a huge glacial lake in Canada dumped out to the Arctic ocean. This huge pulse of fresh water likely changed North Atlantic circulation for a while.

    What likely happens, in my opinion, is that insolation increases and the glaciers begin to melt back at the front edge but those glaciers are very thick. At this point there is little change in climate in Northern Europe, for example, because the North Atlantic circulation hasn’t changed yet. Lake Bonneville and Lake Missoula are filling up. But finally, a certain event happens that makes all the difference: the arctic ocean ice melts. Once that happens, once the Arctic ocean is ice free or even partially ice free in summer, the albedo of the polar region suddenly changes a great deal.

    We actually do see the Greenland temperature begin to gradually rise until there is a point where it begins to skyrocket. I believe that point is where the Arctic becomes mostly ice free in summer. The ice on land might still be thousands of feet thick and last for another 4 thousand years but the ocean circulation changes to the modern pattern once the Arctic is ice free.

    From about 9000ya to around 5000ya we start to see insolation begin to decline. The monsoon begins to shorten, Syria and Iraq are deforested during that period, mostly by human activity. At about 5000 years ago we see severe drought conditions setting in over that part of the world. The Dead Sea level begins to drop and by 4000 years ago has fallen over 50 meters. The Levant is now becoming desert. This worsens over the next 2000 years. Now we are in a position where insolation will actually pick up a little bit. If you look at this:

    Notice the trace labeled 65N just above the ice core traces. We are actually in a period where insolation is going to increase for a few thousand years. We might not get into a situation for a full on ice age for another 50,000 years. It looks like we get about 2000 years of increasing insolation from about here on out. The key, though, seems to be the insolation required to clear the Arctic of ice. If we ever get a summer where the Arctic ocean stays 75% or greater covered with ice, we are probably toast.

  29. @- crosspatch says: Re: The current reduction in Arctic ice is the largest in at least the last few thousand years –
    “That is pure speculation. There is no possible way anyone can know that and I believe we have fairly solid evidence that it isn’t true.”

    Amazing, you claim that it is impossible to know that present ice reduction is the largest for several thousand years…. AND that we have solid evidence… which contradicts the initial claim that it is impossible to know.
    I do so like paradoxical sentences!

    “In fact, I would be willing to say the Arctic had less ice 2000 years ago during the Roman Warm Period in addition to the Medieval Warm Period. If we can infer from Alaska glacial activity, we know that the glaciers in Alaska are currently much advanced from where they were less than 500 years ago.”

    Your willingness to say stuff might carry more weight if there was evidence.
    Contrary to the first claim in your wonderful paradox sentence it IS possible to determine from multiple lines of evidence the ice extent conditions in the Arctic over the last few thousand years. There IS solid evidence, but it shows the opposite of what you claim.
    Alaskan glacial activity is NOT a good indicator of Arctic ice conditions, it is subject to influences from rainfall variation from pacific climate factors.
    What the Alaskan glaciers DO show is an overall LOSS of ice in the last 50 years unprecendented in the past record.

    The evidence indicating ice conditions in the Arctic ocean come from surf-cut beaches on areas now (or until recently) ice locked in Greenland and Canada. There are no beaches more recent that ~5.5kyrs.
    Driftwood dating also shows nothing more recent indicating the lack of open ocean and drifting ice.
    But the key indicators of ice extent in the Arctic are sea floor sediments that indicate the extent of algae blooms associated with ice cover and the type of ice-rafted sediments dropped from melting floating ice. try – Macias-Fauria et al.

    http://www.springerlink.com/content/922v30um17650817/

    “The twentieth century sustained the lowest sea ice extent values since A.D. 1200: low sea ice extent also occurred before (mid-seventeenth and mid-eighteenth centuries, early fifteenth and late thirteenth centuries), but these periods were in no case as persistent as in the twentieth century. …The present low sea ice extent is unique over the last 800 years, and results from a decline started in late-nineteenth century after the LIA. ”

    As another poster has pointed out the Milankovitch cycle is actually near a minimum for solar isolation during the summer at 65N, given the very slow timescale of the cycle it will change little from this minimum for about 1kyr. The graph you link is too coarse a resolution to show this, try an alternate more detailed source.

    You clearly have a complex personal narrative of the history and future of the Arctic climate, perhaps it would benefit from the addition of some facts?

    http://bprc.osu.edu/geo/publications/polyak_etal_seaice_QSR_10.pdf

  30. I am lucky enough to go salmon fishing in southern Iceland once a year.

    One very noticeable thing in the banks of most of these rivers is the thick tree trunks and root systems which can be found about a foot below the present day land surface.

    I suggest these trees probably flourished in the MWP in warmer conditions than found today.

  31. izen says:
    December 31, 2011 at 2:54 pm
    A warmer and globally synchronous MWP means that climate sensitivity must be higher and positive feedbacks more pronounced to give that degree of climate variation.
    That has obvious implications for the climate response to the increased CO2′
    —————————————————————————————————————-.

    I think not Izen. Climate sensitivity is a CAGW term referring to CO2 doubling. The CO2 trend was flat prior to the mankinds industrial output. (at least according to the questionable ice core records)
    Their is no MWP correlation to CO2, therefore todays temp swings are well within earth’s normal temp swings.

  32. @- David says: January 1, 2012 at 4:43 am
    “Climate sensitivity is a CAGW term referring to CO2 doubling. ”

    Wrong.
    Climate sensitivity is a scientific concept that exists entirely independently of the AGW theory. It would exist even if there was no role for CO2 in the climate and no human influence. It refers to the climate response to changes in the energy balance. So how much it warms, or cools when the Sun alters its output is a measure of climate sensitivity.
    It is most often related to a CO2 doubling because that is the most obvious and biggest change in the energy balance that is happening to the climate at present. But it can be expressed as degrees(Temp) per Watts/m2.

    “Their is no MWP correlation to CO2, therefore todays temp swings are well within earth’s normal temp swings.”

    The ‘NORMAL’ temp swings of the Earth are a measure of the climate sensitivity. A global change in energy balance is required for a ‘normal’ temp swing as seen in the LIA, MWP or after a major volcanic eruption or de-glaciation event.
    The greater the ‘normal’ temp swing for a small energy change then the greater the climate sensitivity.

    I find this mistake is often made. People seem to think that if they can show that the climate underwent big changes in the past then the big changes happening now can be ignored as just more of the same.
    But the bigger the changes in the past to what are small changes in energy balance then the greater climate sensitivity, the stronger positive feedbacks because only that can explain that size of past variation.
    So the greater the past temperature swings the more sensitive the climate and the more serious the effect of the around +3W/m2 extra energy from the doubled CO2.

    If you could accurately estimate the energy change that caused the MWP due to reduced volcanic and increased solar activity, and could accurately estimate the amount of global climate warming it caused then you would have a good handle on the climate sensitivity.
    Unfortunately our knowledge of the precise amount of energy change that drove the MWP and how much warming there was globally in not accurate enough to provide a good estimate. But the warmer and more global the MWP then the climate sensitivity must be higher and the greater the energy effect of the rising CO2.

    Unless you also have some evidence that the MWP was driven by a greater energy change in W/m2 than we are seeing from CO2 at the present ?

  33. Peter Miller writes,
    “I suggest these trees probably flourished in the MWP in warmer conditions than found today.”

    The trees flourished just before settlement because no one was cutting them down. Iceland’s historical deforestation was largely a result of tree-clearing for land and wood during the Norse settlement period. Subsequent grazing and erosion made conditions worse for people as the climate cooled. A lot of interesting environmental archaeology has been done on the Norse settlement period. Here’s a recent example:

    http://hol.sagepub.com/content/21/6/979.abstract

    If you’ve been traveling to Iceland for years, you’ve no doubt noticed the resurgence of trees under government planting and protection programs.

  34. @izen says:
    January 1, 2012 at 8:16 am

    “…Climate sensitivity is a scientific concept that exists entirely independently of the AGW theory. It would exist even if there was no role for CO2 in the climate and no human influence. It refers to the climate response to changes in the energy balance. So how much it warms, or cools when the Sun alters its output is a measure of climate sensitivity….”

    It appears you are the appointed “Officer of the Day” required to fend off anything that might be detrimental to belief in CAGW. So, since you made the definitive statement above, tell us, or give us the mathematical equation that describes climate sensitivity.

    Just a note in advance: If it resembles this: Q = ε σ Ts^4 + C dTs/dt
    then I refer all to this:

    The Cold Equations
    Posted on January 28, 2011 by Willis Eschenbach

    http://wattsupwiththat.com/2011/01/28/the-cold-equations/

    and suggest that Izen be left to talk to himself.

  35. JimF,

    I agree. And I notice that Izen still refers to the AGW conjecture as “AGW theory”.

    If AGW were a theory, it would be able to make accurate predictions. If it were a hypothesis, it would be testable. Neither of those is the case. AGW is simply a conjecture, and attempting to elevate it to the status of a “theory” has a whiff of desperation about it.

  36. Izen: But the warmer and more global the MWP then the climate sensitivity must be higher and the greater the energy effect of the rising CO2.
    =========================================
    ….or none at all
    You just said the climate is sensitive to something besides CO2.

  37. Per @izen says on January 1, 2012 at 8:16 am
    “…Climate sensitivity is a scientific concept that exists entirely independently of the AGW theory. It would exist even if there was no role for CO2 in the climate and no human influence. It refers to the climate response to changes in the energy balance. So how much it warms, or cools when the Sun alters its output is a measure of climate sensitivity….”

    Actually, that seems to describe exactly the hypothesis posted here yesterday:
    Unified Theory of Climate

    http://wattsupwiththat.com/2011/12/29/unified-theory-of-climate/#comment-849390

    or independently developed here:
    THE “GREENHOUSE EFFECT” AS A FUNCTION OF ATMOSPHERIC MASS

    http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/FunctionOfMass.pdf

    I think we’re getting somewhere. Maybe 2012 will drive the stake through the heart of the “global warming” vampires who desire to suck the lifeblood out of the world’s economically developed peoples. Let’s hope so.

  38. @- JimF says: January 1, 2012 at 5:48 pm
    “So, since you made the definitive statement above, tell us, or give us the mathematical equation that describes climate sensitivity. ”

    Climate sensitivity = surface temperature / radiative forcing

    No complex symbols or advanced math required.
    The problem is determining climate sensitivity, however if you can derive it from past changes in radiative forcing and temperature change such as the glacial cycles or volcanic eruptions then the equation can be re-arranged to –

    Surface temperature = climate sensitivity x radiative forcing

    which would enable you to determine the surface temperature from the measured radiative forcing from raised CO2.

    It aint rocket science…..

    @- Smokey says:
    “If AGW were a theory, it would be able to make accurate predictions.”

    Such as; The troposphere will warm but the stratosphere will cool with increased CO2, and the measured spectrum of the down-welling LWIR and outgoing LWIR will alter to reflect the energy imbalance – radiative forcing.
    (both experimentally confirmed)

    @- Latitude says:
    “You just said the climate is sensitive to something besides CO2.”

    I didn’t, but the climate reacts to the energy balance, a radiative forcing, positive for an addition of CO2 or an increase in solar irradience, negative for SOx injected into the stratosphere by volcanic eruptions, or a reduction in solar insolation.
    How much the surface temperature (in degrees C) changes in response to a radiative forcing (in W/m2) depends on the value of the climate sensitivity.

    This is all rather basic stuff, and is a long thread subject digression from whether the research discussed in the thread article does help determine whether the AMO actually exists….

  39. @- JimF
    “Actually, that seems to describe exactly the hypothesis posted here yesterday:
    Unified Theory of Climate -[link]-
    or independently developed here:
    THE “GREENHOUSE EFFECT” AS A FUNCTION OF ATMOSPHERIC MASS
    -[link]-
    I think we’re getting somewhere. Maybe 2012 will drive the stake through the heart of the “global warming” vampires who desire to suck the lifeblood out of the world’s economically developed peoples. Let’s hope so.”

    Thats just silly. The air pressure can be the same during the day and night with very different temperatures because the rate energy is added and lost varies (clear skys v cloudy nights).
    The air pressure can be very different but the temperature may be the same under other circumstances. All these air pressure/mass follies are just re-inventing the lapse rate.

    AS for the ‘Twilight’ inspired metaphorical rhetoric… the scientific research to determine the impact of raised CO2 on the climate is not evidence that anybody working on the issue are trying to “suck the lifeblood out of the world’s economically developed peoples”.
    There are political forces around who might have that ambition, or something like it. But they are invariably driven by religious or idealogical extremism, not an interest in the physics of radiative transfer in the atmosphere.

  40. izen says:
    January 1, 2012 at 7:03 pm

    “…Climate sensitivity = surface temperature / radiative forcing….”

    Interesting formula. Why doesn’t it work? CO2 has risen for the last dozen years (that is your “radiative forcing”, right?) but temperature is flat. How can that be? Sho’ ’nuff, it ain’t rocket science – rockets tend to work. I suppose however, the heating is in “the pipeline”?

    In a later post (January 1, 2012 at 7:35 pm) you state: “…There are political forces around who might have that ambition, or something like it. But they are invariably driven by religious or idealogical (sic) extremism, not an interest in the physics of radiative transfer in the atmosphere….”

    Yeah, but it is a few scientists who are “interested in the physics, blah, blah…” who keep priming the pump of fear these ideologues feed on, while fighting tooth and nail to exclude any other viewpoint concerning the science of climate or the rigors thereof, from being considered. They are indeed a ghoulish cabal.

  41. When will the editor of Paleoceanography receive the ‘call’ that requires them to renounce their heretical beliefs and fall on their own sword ?

  42. Izen posts…

    @- Latitude says:
    “You just said the climate is sensitive to something besides CO2.”

    I didn’t, but the climate reacts to the energy balance, a radiative forcing, positive for an addition of CO2 or an increase in solar irradience, negative for SOx injected into the stratosphere by volcanic eruptions, or a reduction in solar insolation.
    How much the surface temperature (in degrees C) changes in response to a radiative forcing (in W/m2) depends on the value of the climate sensitivity.
    This is all very basic…”
    ————————————————————-
    Really Izen so you claim climate senstivity is the same for all W/m2 forcing. There is no difference if the forcing is CO2 induced, or TSI induced. This is basic all right, but basically wrong. Now for some really basic radiative balance theory. At its most basic only two things can effect the energy content of any system in a radiative balance. Either a change in the input, or a change in the “residence time” of some aspect of those energies within the system.”

    It therefore possibly follows that any effect which increases the residence time of LW energy in the atmosphere, (green house gases) but reduces the input of SW energy entering the oceans, (atmospheric heating causing more cloud cover oand or water vapor) causes a net reduction in the earth’s energy balance, proportioned to the energy change involved, relative to the residence time of the radiations involved. The critical fact is that the energy is CUMLITIVE for everyday of “residence” and some of this energy may increase DAILY for as many days, months, years or decades that a change in TSI or cloud cover continues. Hence my paraphrase of an old maxim, ” A SW photon in the ocean is worth two LWIR photons in the atmosphere,” Of course it could be 30 to one for all anyone knows.

    Izen, every year the TSI changes by about 100 W/m2. And when the earth is recieving that increase of 100 W/m2, the atmosphere is about 4 degrees cooler.

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