Study: Ammonium as ice core proxy shows strong Medieval Warm Period in the tropics

The MWP has been vigorously argued to be a regional northern hemisphere phenomenon only, but this new study finds it in South America. In this new paper they write:

“The most striking features in the reconstruction are the warm temperatures from ∼1050 to ∼1300 AD compared to the preceding and following centuries, the persistent cooler temperatures from ∼1400 to ∼1800 AD, and the subsequent rise to warmer temperatures which eventually seem to exceed in the last decades of the 20th century the range of past variation.

While the onset of the warm period around 1050 AD is almost consistent within the dating error (±60 years at 1000 AD) with the perception of a Northern Hemisphere (NH) MWP from 950 to 1100 AD, it is remarkable to note that it seems to have lasted about 200 years longer in the tropics.”

Figure 7. Reconstructed tropical South American temperature anomalies (normalized to the 1961–1990AD average) for the last ∼1600 years (red curve, smoothed with a 39‐year Gaussian filter). The shaded region envelops the ±2s uncertainty as derived from the validation period. Poor core quality precluded any chemical analysis for the time interval between 1580 and 1640 AD

When I first saw this paper (PDF here h/t to Dr. Leif Svalgaard) I was intrigued by the idea, especially since it demonstrated the MWP very well. The authors also say that “The last decades of the past millennium are characterized again by warm temperatures that seem to be unprecedented in the context of the last ∼1600 years.”

But then a question arose in my mind; how well have they separated all of the Ammonium from worldwide Ammonium fertilizer use (which started in the late 1800’s)  from the proxy samples? They do touch on the subject, but I’m not convinced that they have separated the impact. They cite Mann and Jones in the references, and use principal component analysis methods (PCA) so that makes me wonder even more. Perhaps Steve McIntyre or Jeff Id can have a look to see how the PCA was carried out, since I’m no expert in it.

The authors do mention dust accumulation related to tracking South American weather patterns, saying they appear unchanged, but I’m not sure dust is a good indicator of lack of mixing and transport via the global water cycle of Ammonium (NH3 and NH4) which is highly soluble in water.

Chemical fertilizers were introduced in the mid 1800’s; Ammonium Sulfate and Ammonium Nitrate were commonly used. Ammonium Sulfate was originally a by-product from coal gas manufacturing. The quality wasn’t great as a fertilizer but it was used some in the 1800’s.

Ammonium Nitrate was used mostly after World War I as it was the principal ingredient used in explosives. WWI demand increased Ammonium Nitrate production and following the war, was used in agriculture in significant volume. World War II caused even more of an increase in production, and again after WWII production increased globally.

UPDATE: reader “Jaymam” points out this graph, production of Ammonia

http://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Production_of_ammonia.svg/500px-Production_of_ammonia.svg.png

Production trend of ammonia between 1947 and 2007 Approximately 83% (as of 2004) of ammonia is used as fertilizers either as its salts or as solutions.

When rainwater and Ammonium Nitrate NH4NO3 mix, you get ammonium ions (NH4+) and nitrate ions (NO3) in solution. Some nitrogen gets used by plants, the remainder is either retained in the soil or transported in runoff. As we all know, rainwater runoff of fertilizer is a big problem, and it is clear that ammonium ions get into the water cycle. This is confirmed by Tiwari et al who did a study of ions in rainwater and found “High concentrations of ammonium in rainwater due to agricultural activity…”

So with increasing use of Ammonium fertilizers in the 20th century, how can we be sure it hasn’t contaminated the Ammonium ice proxy record during the same century?

Still, I find the study interesting for it’s uniqueness.

Abstract:

Ammonium concentration in ice cores: A new proxy for regional temperature reconstruction?

T. Kellerhals,1,2,3,4 S. Brütsch,2 M. Sigl,1,2 S. Knüsel,1,2 H. W. Gäggeler,1,2

and M. Schwikowski2,3 Received 15 June 2009; revised 22 December 2009; accepted 8 March 2010; published 31 August 2010.

[1] We present a reconstruction of tropical South American temperature anomalies over

the last ∼1600 years. The reconstruction is based on a highly resolved and carefully dated

ammonium record from an ice core that was drilled in 1999 on Nevado Illimani in the

eastern Bolivian Andes. Concerning the relevant processes governing the observed

correlation between ammonium concentrations and temperature anomalies, we discuss

anthropogenic emissions, biomass burning, and precipitation changes but clearly favor a

temperature‐dependent source strength of the vegetation in the Amazon Basin. That given, the reconstruction reveals that Medieval Warm Period– and Little Ice Age–type episodes are distinguishable in tropical South America, a region for which until now only very limited temperature proxy data have been available. For the time period from about 1050 to 1300 AD, our reconstruction shows relatively warm conditions that are followed by cooler conditions from the 15th to the 18th century, when temperatures dropped by up to 0.6°C below the 1961–1990 average. The last decades of the past millennium are

characterized again by warm temperatures that seem to be unprecedented in the context of the last ∼1600 years.

Citation: Kellerhals, T., S. Brütsch, M. Sigl, S. Knüsel, H. W. Gäggeler, and M. Schwikowski (2010), Ammonium concentration in ice cores: A new proxy for regional temperature reconstruction?, J. Geophys. Res., 115, D16123,

doi:10.1029/2009JD012603.

PDF here

Advertisements

49 thoughts on “Study: Ammonium as ice core proxy shows strong Medieval Warm Period in the tropics

  1. The part from 400AD to 1600AD matches Cook’s tree ring data quite nicely.
    The part past 1600AD seems to rise rather sharply.
    But, as usual, the graph cuts off at 2000.

  2. Loehle’s multiproxy T-reconstruction (without tree rings) is the only legitimate standard of comparison.
    This ammonium proxy looks pretty good up to about the 1800s — afterwards, looks like the fertilizer version of UHI effect.
    co2science.org has great collections of prior studies showing evidence of Medieval Warm all over the globe.
    “Unprecedented”? not very

  3. For ice proxies, cutting off at 2000 makes sense. Ice usually takes a few years to settle into some kind of stable state. Trying to extract meaning from more recent ice is difficult because of this.

  4. Isotopes might be useful in determining the provenance of the ammonia. If modern sources are affected by the use of mineral fertilizers, the nitrogen isotopes ratios in modern precipitation could be significantly different than ratios derived from medieval organic (presumably) sources.
    A similar test is often used (using N and O isotope ratios) to determine provenance of nitrates in soil and water. With ammonia you couldn’t use oxygen, but perhaps hydrogen could substitute for the second isotope if it were needed.

  5. I would be very careful here. Often proxies are picked because they tend to prove the point sought, and discarded when they do not (because they are then deemed unreliable). It is always about money, fame, and control.
    On the other hand, so far this seems to show the highs lower and the colds milder. That surely is the pattern of the Southern/Western Hemisphere, with deep seas and smaller land masses. And a continent covered in 2 miles of ice at its fore.
    But I also find it disturbing that the medieval warm period cannot even equal normalcy. Does this even make sense? How can half the planet only reach average temperature in 1998. The answer is that it can’t.
    There is something seriously wrong here.

  6. I have a question, too. Why is the uncertainty constant? I think it should be larger as you go backward in time.

  7. Since the CO2 warming has allegedly kicked in since 1975, the “unprecedented climate change” in tropics has caused 0.2 deg C. But something has been warming the tropics since 1700.

  8. @rbateman:
    I guess the proxy actually ends in 1995, and that is because of the 30yr smoothing. Therefore there’s nothing questionable about that.

  9. “The MWP has been vigorously argued to be a regional northern hemisphere phenomenon only”
    Yes, and Leif’s taken that position with his research paper 1160. Does this new ammonium paper force you to throw 1160 in the bin now Leif? ammonium proxys => MWP was global?

  10. The temperature fluctuations 400 – 1900 vary only about 0.4 C in contrast to the Loehle non-treering proxy global reconstruction, for instance, which varies over 1 C …
    http://www.drroyspencer.com/wp-content/uploads/2000-years-of-global-temperature.jpg
    …or the Moberg NH reconstruction (red line & ignoring the meaningless heavy black line) which varies 0.8 C…
    http://commons.wikimedia.org/wiki/File:2000_Year_Temperature_Comparison.png
    This may be a product of the 39 year smoothing in which case surely the graph should not extend to 2000.

  11. Although the search for new proxies should be encouraged, I think that more evidence is needed of calibrations from other sites. The paper argues that this site locality has special properties that isolate it from plausible interferences, so that makes it hard to find a location for other comparison sites.
    One has to ask the obvious question of what happened to the temperature (or to early ice movement) at bedrock level, because it should have been warm enough in 400 AD to have exposed bedrock and no ice. But the ice thickness seems to start abruptly at roughly 0.5 m. per year, in the absence of statements to the contrary. The paper would benefit from a statement about why the glacier, just here, seems to have emerged at 400 AD, full-born.

  12. The worldwide nature of the MWP and LIA points to the involvement of variations in jet stream positioning in both hemispheres.
    Now it seems that in the MWP Greenland was more habitable than at present which suggests that the jets shifted more poleward back then than they have during the Current Warm Period.
    So the evidence of the jets suggests a warmer MWP than today which is an indication that the Ammonium proxy is not as accurate as would be a proxy created from jet stream positioning.

  13. “it is remarkable to note that it seems to have lasted about 200 years longer in the tropics.”
    Not so remarkable in the context of latitudinal jet stream movements.
    The further poleward one goes the shorter the period that a poleward region would be situated equatorward of the polar jet.
    Furthermore I have proposed a warm ocean cycle on a 500/1000 year cycle driving the poleward jet shift to create the MWP (and the Current Warm Period) so obviously the effects would start first and end last in the tropics.

  14. “A further prominent characteristic is the sustained
    warming trend that started ∼1720 AD and continues until the
    end of the record. The beginning of the temperature increase
    is coeval with the end of the Maunder minimum of observed
    sunspot numbers around 1715 AD.”
    So all the temperature rise from 1720 to date is 95% likely to be a natural recovery from the LIA ?
    And the jets have been moving slowly and irregularly poleward since then until the end of the 20th Century and solar activity levels have moved slowly and irregularly upward until the end of the 20th Century.
    Now since 2000 we have a cessation of warming, a more equatorward set of jets and a less active sun. Meanwhile CO2 continues upward.
    Despite their final concession to the AGW theory this is a heavily anti AGW piece of work.

  15. Lord Christopher Monckton sat before Congress last spring between 4 IPCC members.
    It is kind of interesting that during this hearing the woman scientist who sat to the right of Lord Monckton brought up the fact that there was a global warming period before the one we were in now that was much stronger than the present one.
    This was based on her personal research in the western USA where she noted the timber line had been higher than the present day timber line.
    No one on the Congressional panel picked up on what she was saying. Even her colleagues missed it.
    Here we are, saying it again.
    Paul
    Paul

  16. meemoe_uk says:
    September 2, 2010 at 12:39 am
    Yes, and Leif’s taken that position with his research paper 1160.
    This was not the intended meaning of that slide [‘shine at any rate on me’]. I wanted to stress the importance of confirmatory data from other regions. Data like discussed in the Kellerhals et al. paper.

  17. It seems even farming/ranching would have upped the ammonia level even without fertilizer due to the degradation of urine.

  18. Also, ammonia isn’t only very soluble in water, it is volatile. It can be transported through the atmosphere.

  19. How they can say the current warming is unprecedented is beyond me, yes according to the graph the temp level is high but the rate of increase has been seen at 850 and at 1050. If the current warming was CO2 related the rate of increase upto 2000 should be the steepest part of the graph. We are recovering from an Ice age still.

  20. I read the article and found the calibration data rather impressive. It will be interesting to read what scientists with expertise in climate proxies think. I think that the reason for largely excluding athropogenic effects on is that the atmospheric live of the amonium compounds in the atmosphere is only a few days. Thus, they are measuring relatively local effects (unlike measurements of CO2). Also, I guess that they are assuming the effects of human agriculture in the region are small or negligible relative to the natural releases in the nearby Amazone region. Again, it would be interesting to read more criticism of the paper and the amonium proxy.

  21. Stephen Wilde says:
    September 2, 2010 at 2:27 am
    ..so obviously the effects would start first and end last in the tropics..
    ~
    Interesting comments, thanks.
    Anyone aware of any magnetosphere satellites positioned to study dayside reconnection? I was just wondering about the effects on the equator ward reconnection on the dayside magnetosphere. We always think about the “rubber band like spring back of the night side,” and have satellites watching the nightside reconnection, but what about the dayside, the side that is first impacted by the daily solar winds and sometimes just rips huge holes in the magnetosphere depending of IMF.

  22. Stephen Wilde says:
    September 2, 2010 at 2:42 am
    …..Despite their final concession to the AGW theory this is a heavily anti AGW piece of work.
    __________________________________________________
    I would not be surprised if the statement “The last decades of the past millennium are
    characterized again by warm temperatures that seem to be unprecedented in the context of the last ∼1600 years.”
    And the data neglecting to delete the Ammonium from fertilizer use and therefore showing higher present temperatures, was the price that was paid to get this paper published.

  23. Carla says:
    September 2, 2010 at 6:52 am
    what about the dayside, the side that is first impacted by the daily solar winds and sometimes just rips huge holes in the magnetosphere depending of IMF.
    The ‘huge holes’ were just NASA hype. Reconnection on the dayside is a rather sedate affair. It is only when the field line gets really stretched out in the tail that they ‘snap back’.

  24. What do you guys think of the joke I wrote yesterday?
    A progressive activist and a stubborn old engineer walk into a bar. The engineer orders a beer. The activist orders a beer but asks the bartender to hold the CO2 and make the engineer pay the bill for the more expensive beverage.
    The bartender says: “Take your dumbsh*t nonsense down the street, chump.”
    The engineer laughs.

  25. And in sub-tropics, check-out the SANTA ANNA entrenchment dates (~20 AMS) in the UT Austin Laguna project (Butzer paper) published in the journal Geomorphology 2008 (proceeding sof the Binghampton Conf. in Austin, cf. also the papers based on data from desert region of N. Chile, with changes in the El Nino over the last 7KY). This stuff is all over the place (nothing new under the sun!) if you look! The noted event is the 7 m arroyo entrenchment in Arroyo del Pueblo near Saltillo, S. Coahuila (MX), in circum 1400’s, when things are hot and dry in N. Mexico.

  26. Ken Coffman says:
    September 2, 2010 at 7:51 am

    Alternate solution: Bartender drains the overflow bucket into a cup & dutifully serves the flat draught to the activist “That’ll be four bucks”.
    Aternate 2: Bartender serves fresh beer to the engineer “That’ll be two bucks”. Engineer pours fresh beer on the activist’s head, sops up the drippings with a bar rag, wrings out the rag into a glass, & serves the CO2 free beer to the activist, “That’ll be eight bucks for CO2 removal”.

  27. That’s not a strong medieval warm period, it’s a weak one.
    It’s peak is equal to the level in 1900, maybe just hitting the low in 1960.

  28. Well Michael Mann’s “hockey stick” is also just a regional phenomenon; and not global.
    Just go and look at his graph in that original IPCC report. Prominent at the top of the chart are the words “Northern Hemisphere”
    I rest my case.
    Dr Willie Wei-Hock Soon and Dr Sally Baliunas did an investigation of dozens of scientific paper reports from all over the globe; published in all sorts of peer reviewed scientific journals; and their paper about all those studies concluded that the MWP and the LIA were indeed totally global events.

  29. The Greens were having a picnic and they played their favorite game, “Red Rover, Green Rover, We Dare the Oil Men Over.”
    How long and how many Greens does it take to plug in a light bulb?
    First the have to fly in on their private jet, sail over to their private island on their private boat to have a group discussion with the poorer members camped out on the island. Then…
    It just goes on from there.
    Paul

  30. I was struck by the fact that the temp rise from the top of the MWP to our last decade was 0nly 0.4C (and the error bars around 1250 are this high) – and this a period where feverish revisions were made and are still being made to push the temp up as high as possible – less than 1/2 a degree since 1100AD! Is this the Armageddon we have been talking about?

  31. I have always found the argument that the MWP is not a global event largely based upon the scarcity of available data covering the Southern Hemisphere to be absurd. It is difficult to see how the lack of data can prove something negatively. At best, the lack of data merely raises a position that it is not possible to confirm that an event happened in the area since there is insufficient data to confirm the event one way or the other.
    Of course, whilst this is not quantative, the best evidence for events actually having happened is the recorded historical record both written and archaeological (eg., we know that it was warmer in Greenland during the MWP because of the Viking settlements which are now revealing themselves as the ice melts.). In this regard, Machu Picchu is of utmost relevance with respect to the Southern Hemisphere. This was built high (about 2,450 metres) in the Andes circa 1400-30s. It is clear from the design that it was built with farming in mind (see the step/terrace layout of the fields). Accordingly, at the time it was built farming at this altitude and latitude was possible. It is not today. This clearly establishes that in about the mid 1400s it was warmer in this part of the Southern Hemisphere than it is today and this fact (and it is a fact) supports the view that the MWP was not limited to the Northern Hemisphere. One explanation (and I am not saying that this is the explanation since there are many competing theories) for the abandonment/collapse of the settlement at Machu Picchu is that the climate cooled/changed (in around 1500 – 1550s) making farming no longer viable.
    Further, I have never heard a person who denies the global effect of the MWP put forward a convincing explanation as to how it is possible to have significant warming over a substantial area (possibly the whole area) of the Northern Hemisphere but have no warming in the Southern Hemisphere. What were the driving factors involved in warming the Northern Hemisphere and why were these driving factors not also present in the Southern Hemisphere or if so present why did they not similarly drive the climate in the Southern Hemisphere.

  32. Dave F
    September 1, 2010 at 11:51 pm
    “I have a question, too. Why is the uncertainty constant? I think it should be larger as you go backward in time.”
    Measurement uncertainty indicates how closely a measurement of a sample matches the actual value of that sample. It is a characteristic of the system used to make the measurement. As the measurement system is constant in time, the uncertainty is constant in time. BTW, ±2 sigma is probably pretty conservative.
    bob the tester

  33. The article does not provide a data archive. Nor is the data at NCDC. Nothing seems to change. Maybe somebody can ask the authors for the data.

  34. Carla says:
    September 2, 2010 at 6:52 am
    Stephen Wilde says:
    September 2, 2010 at 2:27 am
    ..so obviously the effects would start first and end last in the tropics..
    ~
    Interesting comments, thanks.
    Anyone aware of any magnetosphere satellites positioned to study dayside reconnection? I was just wondering about the effects on the equator ward reconnection on the dayside ..
    ~
    Just so you didn’t think I was out to lunch with the dayside connection muzing..
    [blockquote][b]Multiple rifts in Earth’s magnetic shield[/b]
    20 Jan 2010
    The Earth’s magnetic field protects our planet from most of the permanent flow of particles from the solar wind. Fissures in this magnetic shield are known to occur, enabling the solar wind to penetrate our near-space environment. A study based on data collected by the four ESA Cluster satellites and the CNSA/ESA Double Star TC-1 spacecraft, provides new insight into the location and duration of these ruptures in the Earth’s magnetic shield.
    ..Reconnection between the IMF and the Earth’s magnetic field critically depends on the angle between these fields. Space physicists have made a distinction between reconnection when both fields are in opposite directions, or anti-parallel, and component reconnection, when the IMF is neither parallel nor anti-parallel to the terrestrial magnetic field. The distinction is important since component and anti-parallel reconnection have different onset characteristics and lead to different duration of the fissures in the magnetic shield. The distinction between these two types of magnetic reconnection has been the subject of hot debate among space scientists for many years.
    ..For the first time, four spacecraft flying in constellation (the ESA Cluster mission), have provided unambiguous evidence of[color=Yellow] anti-parallel reconnection at high latitude on the dayside magnetopause, occurring quasi-simultaneously with a period of low-latitude component reconnection[/color] detected by the Sino-European Double Star TC-1 satellite. TC-1 and the Cluster array (with the Cluster spacecraft separated by ~2000 km) are more than 30,000 km apart (Figure 1). The 3D reconnection picture, determined by repeated sampling of the ion diffusion region and associated magnetic null fields (i.e. the heart of the reconnection process), is shown in Animation 2.
    “These observations support the idea that both anti-parallel and component reconnection occur at the dayside magnetopause under the same IMF conditions and that both phenomena might be the local signatures of a global reconnection picture”, says Professor Malcolm Dunlop from the Rutherford Appleton Laboratory, Didcot, UK.
    “This remarkable set of observations shows that magnetic reconnection at the magnetopause is not as simple as it is described in textbooks! It also demonstrates the need for the capability to study magnetic reconnection at multiple scales simultaneously”, says Matt Taylor, acting Cluster project scientist at the European Space Agency.
    Reference publication
    Dunlop, M.W., Zhang, Q.-H., Xiao, C.-J., He, J.-S., Pu, Z., Fear, R.C., Shen, C., and Escoubet, C.P., Reconnection at high latitudes: Antiparallel merging, Phys. Rev. Lett., 102, 075005, 2009. DOI: 10.1103/PhysRevLett.102.075005[/blockquote]
    http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=46333

  35. But then a question arose in my mind; how well have they separated all of the Ammonium from worldwide Ammonium fertilizer use (which started in the late 1800′s) from the proxy samples?
    Surely by watching closely birds while depositing its Sh## (“guano”, Quechua word for Sh##, pronounced: Gooahnoh) on the pacific islands…
    The mentioned authors have a ROBUST knowledge of GUANO.

  36. Usually flies (this is not a joke) have a very developed sense of smell for detecting ammonia, which is the result of the decomposition of aminoacids (NH3). These insects are attracted by ammonia being emmited from residues to deposit their eggs on them.
    You can try the following experiment, to attract flies (and if lucky some proxy seeking new age scientists):
    Dissolve some ammonium sulphate in water, add some milk of lime, ammonia will be produced and flies and researchers will come….

  37. Leif Svalgaard says:
    September 2, 2010 at 7:17 am
    Carla says:
    September 2, 2010 at 6:52 am
    what about the dayside, the side that is first impacted by the daily solar winds and sometimes just rips huge holes in the magnetosphere depending of IMF.
    The ‘huge holes’ were just NASA hype. Reconnection on the dayside is a rather sedate affair. It is only when the field line gets really stretched out in the tail that they ‘snap back’.
    ~
    Not so worried about the NASA hype. Just wondering again about dayside reconnection, or if it’s “sedate” then just wondering about our daily sedation. lol
    keywords dayside and equatorial latitudes.
    Sun Often “Tears Out A Wall” In Earth’s Solar Storm Shield
    ..The simulation also showed how the leaks develop. As solar particles flow out from the sun, they carry solar magnetic fields past our planet. Li’s team realized that the solar magnetic field drapes against Earth’s field as it passes by. Even though the two fields point in the same direction at equatorial latitudes, they point in opposite directions at high latitudes, When compression forces the opposite fields together, they link up with each other in a process called magnetic reconnection. This process tears the two holes in Earth’s magnetic field and appends the section of the solar field between the two holes to Earth’s field, carrying the solar particles on this section into the magnetosphere, according to Li’s team. “We’ve found if the door is closed, the sun tears down a wall. The crack is huge – about four times wider than Earth and more then seven Earth diameters long,” said Li, whose paper will be published in an upcoming article of the Journal of Geophysical Research.
    Bill Steigerwald
    NASA Goddard Space Flight Center
    http://www.nasa.gov/mission_pages/themis/news/themis_leaky_shield.html

  38. Carla says:
    September 2, 2010 at 12:11 pm
    Just so you didn’t think I was out to lunch with the dayside connection muzing..
    Of course reconnection takes place on the day side. Already Dungey in 1961 knew that. Every field line that ‘snaps’ on the night side was a field line that connected on the day side and then was dragged onto the night side. It is just that there are no spectacular phenomena associated with the day side reconnection. They only come after the connected field line has been stretched [and stressed] on the night side.
    Here is how all that works: http://www.leif.org/research/suipr699.pdf

  39. Carla says:
    September 2, 2010 at 12:37 pm
    This process tears the two holes in Earth’s magnetic field and appends the section of the solar field between the two holes to Earth’s field, carrying the solar particles on this section into the magnetosphere, according to Li’s team.
    Look at figures 11 and 12 from my old [1973 !] paper on that:
    http://www.leif.org/research/Geomagnetic-Response-to-Solar-Wind.pdf
    There you can see the two ‘cracks’ or ‘huge holes’ [one in the North and one in the South] – called the cusp and the cleft that open up. Although some solar particles can sneak in that way, the real action comes when the field lines snap back again on the night side and propel the particles [mostly originating from the Earth’s ionosphere and not the solar wind at all] towards the Earth causing aurorae and magnetic storms.

  40. The alarmist word “unprecedented” always bothers me. A impatial scientist might be more likely to say “the highest temperaturers were …”.

  41. So, we have incontrovertible evidence for the MWP in Greenland, North America, Europe, Russia, China, and now the tropics, South America, New Zealand, South Africa…
    Can we expect the ‘experts’ to stop saying it was a regional event now?
    This opens the path to an understanding of the ~900 year cyclicity in warm-cold periods.

  42. I have the impression, looking at some temperature proxy data for the Holocene, that as well as a steady decline in temperature over the last 6-8k years, recently the warm periods have been getting shorter (Minoan, Roman, Medieval, Current) while cold periods (Dark ages, LIA) get longer. Its rather vague of course. But if real, the next cold period could be a not-so-little ice age.

  43. Leif Svalgaard says:
    September 2, 2010 at 12:51 pm
    Carla says:
    September 2, 2010 at 12:37 pm
    This process tears the two holes in Earth’s magnetic field and appends the section of the solar field between the two holes to Earth’s field, carrying the solar particles on this section into the magnetosphere, according to Li’s team.
    Look at figures 11 and 12 from my old [1973 !] paper on that:
    http://www.leif.org/research/Geomagnetic-Response-to-Solar-Wind.pdf
    There you can see the two ‘cracks’ or ‘huge holes’ [one in the North and one in the South] – called the cusp and the cleft that open up. Although some solar particles can sneak in that way..
    ~
    Thank you Dr. S., for the link an “oldie but goodie.”
    Sometimes while observing the NICT pressure simulations of Earth’s magnetosphere interaction, we are seeing a hole open between the clefts? Clefts are obvious in the simulations, as well as the flow.
    Happy Friday

Comments are closed.