AGU: Link found between cold European winters and solar activity

“Skaters can only do this race every 10 or 11 years because that’s when the rivers freeze up,” Sirocko said. “I thought to myself, ‘There must be a reason for this,’ and it turns out there is.”

Skaters take to frozen-over canals in the Netherlands in Feb. 2012. (Credit: De Vries)

From the American Geophysical Union

WASHINGTON – Scientists have long suspected that the Sun’s 11-year cycle influences climate of certain regions on Earth. Yet records of average, seasonal temperatures do not date back far enough to confirm any patterns. Now, armed with a unique proxy, an international team of researchers show that unusually cold winters in Central Europe are related to low solar activity – when sunspot numbers are minimal. The freezing of Germany’s largest river, the Rhine, is the key.

Although the Earth’s surface overall continues to warm, the new analysis has revealed a correlation between periods of low activity of the Sun and of some cooling – on a limited, regional scale in Central Europe, along the Rhine.

“The advantage with studying the Rhine is because it’s a very simple measurement,” said Frank Sirocko lead author of a paper on the study and professor of Sedimentology and Paleoclimatology at the Institute of Geosciences of Johannes Gutenberg University in Mainz, Germany. “Freezing is special in that it’s like an on-off mode. Either there is ice or there is no ice.”

From the early 19th through mid-20th centuries, riverboat men used the Rhine for cargo transport. And so docks along the river have annual records of when ice clogged the waterway and stymied shipping. The scientists used these easily-accessible documents, as well as additional historical accounts, to determine the number of freezing episodes since 1780.

Sirocko and his colleagues found that between 1780 and 1963, the Rhine froze in multiple places 14 different times. The sheer size of the river means it takes extremely cold temperatures to freeze over making freezing episodes a good proxy for very cold winters in the region, Sirocko said.

Mapping the freezing episodes against the solar activity’s 11-year cycle – a cycle of the Sun’s varying magnetic strength and thus total radiation output – Sirocko and his colleagues determined that ten of the fourteen freezes occurred during years around when the Sun had minimal sunspots. Using statistical methods, the scientists calculated that there is a 99 percent chance that extremely cold Central European winters and low solar activity are inherently linked.

“We provide, for the first time, statistically robust evidence that the succession of cold winters during the last 230 years in Central Europe has a common cause,” Sirocko said.

With the new paper, Sirocko and his colleagues have added to the research linking solar variability with climate, said Thomas Crowley, Director of the Scottish Alliance for Geoscience, Environment, and Society, who was not involved with the study.

“There is some suspension of belief in this link,” Crowley said, “and this study tilts the argument more towards thinking there really is something to this link. If you have more statistical evidence to support this explanation, one is more likely to say it’s true.”

The study, conducted by researchers at Johannes Gutenberg and the Institute for Atmospheric and Climate Science in Zurich, Switzerland, is set to be published August 25 in Geophysical Research Letters, a journal of the American Geophysical Union.

When sunspot numbers are down, the Sun emits less ultraviolet radiation. Less radiation means less heating of Earth’s atmosphere, which sparks a change in the circulation patterns of the two lowest atmospheric levels, the troposphere and stratosphere. Such changes lead to climatic phenomena such as the North Atlantic Oscillation, a pattern of atmospheric pressure variations that influences wind patterns in the North Atlantic and weather behavior in regions in and around Europe.

“Due to this indirect effect, the solar cycle does not impact hemispherically averaged temperatures, but only leads to regional temperature anomalies,” said Stephan Pfahl, a co-author of the study who is now at the Institute for Atmospheric and Climate Science in Zurich.

The authors show that this change in atmospheric circulation leads to cooling in parts of Central Europe but warming in other European countries, such as Iceland. So, sunspots don’t necessarily cool the entire globe – their cooling effect is more localized, Sirocko said.

In fact, studies have suggested that the extremely cold European winters of 2010 and 2011 were the result of the North Atlantic Oscillation, which Sirocko and his team now link to the low solar activity during that time.

The 2010 and 2011 European winters were so cold that they resulted in record lows for the month of November in certain countries. Some who dispute the occurrence of anthropogenic climate change argue that this two-year period shows that Earth’s climate is not getting any warmer. But climate is a complex system, Sirocko said. And a short-term, localized dip in temperatures only temporarily masks the effects of a warming world.

“Climate is not ruled by one variable,” said Sirocko. “In fact, it has [at least] five or six variables. Carbon dioxide is certainly one, but solar activity is also one.”

Moreover, the researchers also point out that, despite Central Europe’s prospect to suffer colder winters every 11 years or so, the average temperature of those winters is increasing and has been for the past three decades. As one piece of evidence of that warming, the Rhine River has not frozen over since 1963. Sirocko said such warming results, in part, from climate change.

To establish a more complete record of past temperature dips, the researchers are looking to other proxies, such as the spread of disease and migratory habits.

“Disease can be transported by insects and rats, but during a strong freezing year that is not likely,” said Sirocko. “Also, Romans used the Rhine to defend against the Germanics, but as soon as the river froze people could move across it. The freezing of the Rhine is very important on historical timescales.”

It wasn’t, however, the Rhine that first got Sirocko to thinking about the connection between freezing rivers and sunspot activity. In fact, it was a 125-mile ice-skating race he attended over 20 years ago in the Netherlands that sparked the scientist’s idea.

“Skaters can only do this race every 10 or 11 years because that’s when the rivers freeze up,” Sirocko said. “I thought to myself, ‘There must be a reason for this,’ and it turns out there is.”

###

Title:

“Solar influence on winter severity in central Europe”

Abstract:

The last two winters in central Europe were unusually cold in comparison to the years before. Meteorological data, mainly from the last 50 years, and modelling studies have suggested that both solar activity and El Niño strength may influence such central European winter coldness. To investigate the mechanisms behind this in a statistically robust way and to test which of the two factors was more important during the last 230 years back into the Little Ice Age, we use historical reports of freezing of the river Rhine. The historical data show that 10 of the 14 freeze years occurred close to sunspot minima and only one during a year of moderate El Niño. This solar influence is underpinned by corresponding atmospheric circulation anomalies in reanalysis data covering the

period 1871 to 2008. Accordingly, weak solar activity is empirically related to extremely cold winter conditions in Europe also on such long time scales. This relationship still holds today, however the average winter temperatures have been rising during the last decades.

Authors:

Frank Sirocko and Heiko Brunck: Institute of Geosciences, Johannes Gutenberg University Mainz;

Stephan Pfahl: Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland.

==============================================================

I hope to have a copy of the paper soon – Anthony

UPDATE: Dr. Leif Svalgaard provides the paper, as did the AGU press agent Kate Ramsayer per my emailed request, along with a copyright admonishment. Thank you both. Figure 6a and 6b are interesting:

From the paper:

In agreement with the 20th Century Reanalysis central European temperature observations from the CRUTEM3 dataset [Brohan et al., 2006] from winters directly following a sunspot minimum are also significantly lower than the average temperature during the remaining winter seasons (Fig. 6a). The relation between cold winter conditions and sunspot activity is thus not specific to rivers alone (which could also be affected by a number of additional factors, for example warm water from the numerous powerplants constructed along the river). The strong variations of the time series in Fig. 6a, which are largely independent of the sunspot cycle, show the important role of internal, stochastic variability of the atmosphere for European winter temperatures. The relation shown above holds true only for central European temperatures. When the CRUTEM3 winter temperature data are averaged over the whole Northern Hemisphere, no relation to the solar minima is found.

This suggests a regional circulation pattern effect, as the authors state connected to figure 5a and 5b:

To identify the atmospheric circulation anomalies in the North Atlantic and European region associated with cold winters during solar minima, Fig. 5a shows the difference in the geopotential height fields at 500 hPa (Z500) between the winters directly following a year with a sunspot minimum and the remainder of the period 1871 to 2008, obtained from the 20th Century Reanalysis dataset [Compo et al., 1996]. A strong, statistically significant positive anomaly occurs over the eastern North Atlantic in the region of Iceland, while negative anomalies are found over the Iberian peninsula and over north-eastern Europe (the latter being not significant). These Z500 anomalies are associated with an enhanced northerly flow and cold air advection from the Arctic and Scandinavia

towards central Europe, leading to significantly negative temperature anomalies over England, France and western Germany (Fig. 5b). The centre of the cooling is in the region of southern England, the Benelux countries and western Germany down to middle Rhine area. Eastern and southern Germany are not effected as much as the above region. Accordingly, it is only the Rhine and possible some Dutch rivers that provide the possibility to reconstruct this specific temperature anomaly pattern, which corresponds to an anomalously negative NAO and a preference for blockings over the eastern North Atlantic.

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pat

Ahhh. The mandatory throwaway line about AGW without any relevance to the core findings at all.

Dave F

I particularly like the way that solar radiation is labled an indirect effect.

Phillip Bratby

I wonder how much the Rhine’s temperature has risen because of all the waste heat that gets dumped into the river from industry and power stations .

John Silver

“Sun’s 11-year cycle influences climate of certain regions on Earth.”
A racist sun, whoda thunkit.

Resourceguy

This is more good niche science released under the watchful censorship of the carbon priests. All the right words are correctly inserted to get published and skirt the enforcers of debate has ended group think. I wonder what the other major factors might be and how they can be juggled precisely so as to preserve the hockey stick and other short-term post-1970 warming explanation. The multidecadal ocean cycles will eventually wipe the bias away but it will just take decades to do it–rather like the long slow uncovering of the tobacco industry lock on public health science.

When one points out that a correlation between solar activity and weather/climate is poor, there is a persistent chorus of people crying “yeah, but you must take into account the lags in the system caused by the thermal inertia of the oceans”. Where is that lag here?

David Ross

“Also, Romans used the Rhine to defend against the Germanics, but as soon as the river froze people could move across it. The freezing of the Rhine is very important on historical timescales.”
However, Roman sources do not mention a frozen Rhine on the day the Germanic hordes crossed it -31 December 406. It was a assumption of the historian Edward Gibbon, a reasonable one given the midwinter date. Winter was not a favoured campaigning season in ancient Europe. The barbarians must have had good reason for their timing. The Rhine freezing may have been an exceptional occurrence in Roman times.
http://en.wikipedia.org/wiki/Crossing_of_the_Rhine

Stephen Wilde

Well, that’s pretty much a summary of my hypothesis is it not ?
But there are two errors:
i) It is a global effect influencing both hemispheres. There is lots of data showing just such changes worldwide between MWP and LIA and LIA to date.
ii) One needs a warming stratosphere above the poles relative to the stratospheric temperatures above the equator if one is to see equatorward / meridional jets. A good example in the short term is sudden stratospheric warming events near the poles which drive cold outbreaks down across the mid latitudes. Hence the importance of the reverse sign ozone response to low solar activity observed from 2004 to 2007 when the quiet sun produced an increase in ozone at the higher levels contrary to expectations.
They additionally concede that the solar effect doesn’t alter system energy content much but does redistribute available energy across the surface which is what I contend.
In the background they assume a continuing CO2 warming effect but in my opinion the system response to any additional warming in the air from CO2 would be exactly the same as the system response to the solar effects i.e. little or no change in system energy content but instead a change in atmospheric circulation adjusting the rate of energy transfer from surface to space.
However, as compared to the solar effects from MWP to LIA and LIA to date the effect of our CO2 emissions would be infinitesimal.
They have to go a couple more logical steps yet.

Alan the Brit

Oh, this obviously comes from the weather not climate department! So, the Sun influences weather, NOT climate. I see, how convenient, despite the fact that climate is weather patterns over a prolonged period of time? Move along nothing to see here, folks!

john robertson

Naturally the Rhine has had no heat added to its waters by the industry and power plants along its course in the last 100 yrs or so. I love how the climate is a complex system when it cools briefly but clearly understood when it warms?JRR Canada

Peter C

“As one piece of evidence of that warming, the Rhine River has not frozen over since 1963. Sirocko said such warming results, in part, from climate change.” Hhmm, perhaps if they quantified the solar effect they might be able to learn a bit more, after all, had not the sun been unusually active during the second half of the 20 th. century? And might that account for the warming as others have suggested is the case?

francois

Totally off topic, but here, I keep reading about harsh winters (the Rhine river, Antarctica) I have not seen in a long time anything about Arctic sea ice, and its melting.

oldchico guy

It seems well known in germany that power plants are warming the Rhine. The attached article is a call for no more power plants on that river. I guess the real test will be in a few years with solary cycle 25minimums predicted to be very low
http://www.dw.de/dw/article/0,,4446561,00.html

gator69

But I guess none of the other solar variations have any effect on climate whatsoever…

RHS

I would suspect in a warming world that eventually this every 10 – 11 year race wouldn’t happen at all. That would be quite measurable. And according to the article, it even happened recently. Better yet, with the demonstrated and expected low sun spot activity from the sun, this race stands a good chance of occurring pretty often over the next several decades.

Aido

Henrik Svensmark’s excellent book “The Chilling Stars” would have told you that and more.

Edim

“I thought to myself, ‘There must be a reason for this,’ and it turns out there is.”
No sh!t Sherlock.

hpunnett

Ummmm….and the temperature sensors found throught the world are not “regional”. What a laugh!

Peter C says:
August 23, 2012 at 9:56 am
after all, had not the sun been unusually active during the second half of the 20 th. century?
Very likely that is not the case: http://www.leif.org/research/The%20long-term%20variation%20of%20solar%20activity.pdf

Carter

AGW is causing dramatic winters!

mkelly

David Ross says:
August 23, 2012 at 9:49 am
In one the episodes on the various barbarians that ran amuck during the dark ages, it is stated that the Rhine was frozen when it was crossed December of 406.

Aidan Donnelly

The race was run in the winter of 85/6 and again in 86/7 and I was told these had been not been run in around a decade.
I moved to Utrecht in Feb 1986 to work and it was also a cold winter in the UK, which was easy to recall as the British rail trains heaters didn’t work (they usually only worked in summertime) and I recall standing on freezing cold platforms waiting for the train into London with frozen feet and cracked lips. Ironically moving to Utrecht meant I could drive to work in 15 minutes (instead of a 2 hr commute via four BR and Underground trains – I worked right next to London Bridge then) in the warmth and comfort of my Audi. However even then the Thames did not freeze over allowing ice-fairs as in the apparently non-existant LIA 😉

Stephen Wilde

“you must take into account the lags in the system caused by the thermal inertia of the oceans”. Where is that lag here?”
Air circulation changes occur quickly but it takes many years for the effect to percolate through all the oceans.
For continental mid latitudes the change in air circulation has a rapid effect but not so much in areas of a more maritime nature.
The Rhine region, being balanced between the cold north Eurasion interior and the maritime western parts of Europe, may well be a particularly sensitive bellweather for short term variations such that even the effects of a single solar cycle can show up there even though it fails to show up in other regions over such short spells of time.
Over subsequent decades and indeed centuries the system energy content does change a little in response to cumulative changes in the amount of solar energy entering the oceans but it is a long slow erratic process such as that from MWP to LIA to date. However the system response always being negative the solar induced variations are well within the capability of the system to retain stability.
It requires the supplementary forcing of Milankovitch cycles to operate the glacial / interglacial switch.
I have previously explained all the interlinking mechanisms in some detail and this is yet another bit of evidence in support.
In itself this finding is not new. In 2001 even Michael Mann and his colleagues accepted it but then unwisely decided that the effect of CO2 was greater. A major slip up in my view.

Leif Svalgaard says:
August 23, 2012 at 9:49 am
Where is that lag here?
Have you ruled out a ten to eleven year lag? Too coincidental?
But some mathematicians realize in chaos theory that things (variables) have a way of “lining up”, “negating”, or “absorbing the harmonic” so as to make the system appear non-chaotic, no?

There are two large navigable rivers in Central Europe Rhine and Danube. I have some years experience of the Danube’s freezing. When prevailing winter winds are westerly from the Atlantic, the river is navigable, when prevailing winds are sweeping from Siberia, river freezes.
Wind direction is controlled by polar jet-stream, since there is no sun-light in the winter Arctic, but geomagnetic storms are almost as intense, one has to speculate if the polar vortex is responding to variation in the geomagnetic field.
http://www.vukcevic.talktalk.net//MF-PV.htm
NASA implies that it could be.
http://www.vukcevic.talktalk.net/NFC1.htm

Myron Mesecke

Although the Earth’s surface overall continues to warm, the new analysis has revealed a correlation between periods of low activity of the Sun and of some cooling – on a limited, regional scale in Central Europe, along the Rhine.
Although man made structures continue to cause UHI which shows up as artificial warming…

Stephen Wilde

“Peter C says:
August 23, 2012 at 9:56 am
after all, had not the sun been unusually active during the second half of the 20 th. century?
Very likely that is not the case: http://www.leif.org/research/The%20long-term%20variation%20of%20solar%20activity.pdf
Leif’s paper refers to TSI and sunspot numbers and seeks to make an equivalence between 1900 and today notwithstanding that the effect of any given level of solar activity will be modulated by the events preceding it which are quite different for 1900 and today.
There is no discussion in Leif’s paper of changes in UV and other solar effects that might impact on the ozone creation / destruction balance at different levels in the atmosphere or at different latitudes.

Eric Dailey

This article from AGU makes me think that people are paying more than a little attention to Piers Corbyn and his research.

Resourceguy

Oh, I get now this is a positioning article for when the solar minimum rolls around on top of weak predicted cycles of potential Dalton scale. If so, we can expect more simultaneous acknowledgement and discounting of the solar cycle as a climate factor to preserve the high priest carbon mantra and climate model minimizing assumptions in the models. Memo to the high priests, these researchers forgot to insert the EU unity pledge in his science work and also no mention of hemp benefits. Send them a reminder.

davidmhoffer

Figure 6a and 6b are interesting:
>>>>>>>>>>>>>>>>
At first glance it looks like central europe temps are flat while northern hemisphere temps are rising. The I noticed that the central europe scale is from -4 to +2 while the northern hemisphere scale is from -1 to +0.5. This change in scale exagerates a rather minor difference, and there is absolutely no excuse for the paper presenting this information in this manner, it is completely misleading.

vukcevic says:
August 23, 2012 at 10:37 am
one has to speculate if the polar vortex is responding to variation in the geomagnetic field.
NASA implies that it could be.

No, NASA does not support any of your speculations.

Anoneumouse

Perhaps a “”real”” “scientist” would like to look into the history of ‘BONSPIEL’

Stephen Wilde says:
August 23, 2012 at 10:43 am
There is no discussion in Leif’s paper of changes in UV and other solar effects that might impact on the ozone creation / destruction balance at different levels in the atmosphere or at different latitudes.
Slides 25ff show that UV and solar wind wind were the same a hundred years ago as now and that the 2nd half of the 20th century was not a grand maximum.

Pamela Gray

What a load of WAGS. Since the river freezes up at several “locations” on a periodic basis, not only is the Sun fickle (chooses different spots), it isn’t very powerful (is overcome by weather), or else the lack of sun spots would cause the river to freeze at every minimum in the same spot. Furthermore, and the article speaks to this, a river freezes because of weather. So whatever the Sun is doing, it has to have the joules necessary to cause the weather conditions to change sufficiently and then to stick around long enough to cause the river to freeze long enough to skate on it. And it needs to be able to do this at every minimum. The tiny variations in the Sun don’t rise to that ability level.
Just consider the blocking high over Russia. Think of the joules it took to create that high and then leave it in place (keep it a stable high pressure system, set up weak on-coming weather systems that go around it, and put in place down-stream systems strong enough to block the high from moving along). The Sun doesn’t have it, and CO2 doesn’t have it.

Doug Huffman

About complex systems, their models and predictions therefrom, the mathematical economist philosopher Nassim Nicholas Taleb, collaborator with Benoit Mandelbrot – speculates that reality is fractally complex. For instance,
http://www.ft.com/cms/s/2/5372968a-ba82-11da-980d-0000779e2340,dwp_uuid=77a9a0e8-b442-11da-bd61-0000779e2340.html

MarkW

If the earth is indeed warming, then such freezings should have become more rare, if not disappeared altogether in the last 50 to 100 years.
And yet, they haven’t.

MarkW

Leif Svalgaard says:
August 23, 2012 at 9:49 am
——
Apples and oranges.
When talking about global climate, thermal lag matters.
This article is postulating about changes in circulation patterns. Thermal lag does not necessarily apply in that case.

MarkW says:
August 23, 2012 at 11:24 am
Thermal lag does not necessarily apply in that case.
I note the weasel word ‘necessarily’. Either it does or it doesn’t.

MarkW says:
August 23, 2012 at 11:22 am
If the earth is indeed warming, then such freezings should have become more rare, if not disappeared altogether in the last 50 to 100 years.
And yet, they haven’t.

There hasn’t been any since 1963…, so they have become more rare.

DirkH

davidmhoffer says:
August 23, 2012 at 10:47 am
“At first glance it looks like central europe temps are flat while northern hemisphere temps are rising. The I noticed that the central europe scale is from -4 to +2 while the northern hemisphere scale is from -1 to +0.5. This change in scale exagerates a rather minor difference, and there is absolutely no excuse for the paper presenting this information in this manner, it is completely misleading.”
They used autoscaling. You get used to it when using any statistics/math package. You’re a little too harsh in your criticism IMHO. Yes, it would be even better had they used the same scale; maybe they just didn’t think of it.

u.k.(us)

davidmhoffer says:
August 23, 2012 at 10:47 am
Figure 6a and 6b are interesting:
>>>>>>>>>>>>>>>>
At first glance it looks like central europe temps are flat while northern hemisphere temps are rising. The I noticed that the central europe scale is from -4 to +2 while the northern hemisphere scale is from -1 to +0.5. This change in scale exaggerates a rather minor difference, and there is absolutely no excuse for the paper presenting this information in this manner, it is completely misleading.
===============
Nice catch !!

DirkH

BTW, look at that decidedly non-warming Europe in Fig 6a…
Yes, that’s where the template for the Kyoto treaty was cooked up in the 90ies, in Bonn, near the river Rhine…
and where, to this day, the biggest and most plentyful green nutcases abound…

John Finn

Myron Mesecke says:
August 23, 2012 at 10:37 am
Although the Earth’s surface overall continues to warm, the new analysis has revealed a correlation between periods of low activity of the Sun and of some cooling – on a limited, regional scale in Central Europe, along the Rhine.
Although man made structures continue to cause UHI which shows up as artificial warming…

UHI doesn’t affect the satellite record.

davidmhoffer

DirkH;
They used autoscaling. You get used to it when using any statistics/math package. You’re a little too harsh in your criticism IMHO.
>>>>>>>>>>>>>>>>>>>>>>>
That’s an acceptable excuse for an amateur who uses the tools infrequently and may not notice or even understand the effect. Professionals publishing data upon which the FOW (Fate Of World) rests have no such excuse. We’d crawl all over Mann for pulling such a stunt, and we mock Jones for needing to find someone to help him produce a graph in Excel, do we not? We need higher standards on simple things like this across the climate debate which is why I called it out.

davidmhoffer

While I’m on my rant about scaling and how it skews perception, I may as well throw in a rant on one of my pet peeves which is the use of anomalies. Itz like looking at an ant through a big magnifying glass. Looks awful scary until you take the magnifying glass away…. and itz just a tiny insignificant ant. That’s what anomalies do.
I don’t know what the “base temperature” is that these anomalies are derived from. Let’s say for sake of argument that it is 10 degrees C. Plot the anomalies from a base temperature of 10 C on a scale relevant to the human experience, say from 0 degrees C to 20 degrees C. The average human being would look at the resulting graph and probably respond along the lines of “that’s what’s going on? That’s nothing!”

davidmhoffer,
Here is a Pat Frank chart showing how anomalies skew perception.
And this very mild global temperature non-event is what all the alarmist arm-waving is about. As we see, the current stasis in global temperature is very unusual. CO2 is doing nothing, except following temperature. Therefore, the entire AGW foundation is built on shifting sands.

As a vivid skater when I was much younger and living in Holland, I am very much in interested in this paper, but I don’t see the connection yet, i.e between the solar cycles and freezing up of all the waters between the 11 cities in Friesland/ Holland (11 steden tocht = the 11 cities tour). Perhaps I am missing something.
However, if 1963 was the last time the Rhine froze up I can do some simple calculations with what I figured out already. 1963 is ca. 18 years of warming from the end of a cooling period. We are currently 17 years into cooling period from a warming period. Assuming complete symmetry I calculate that the rate of warming in 1963 will be the same as the rate of cooling in 2013. From that I would expect climatic conditions in Friesland in 2013 to be similar to those of 1963, at least in winter.
Brace yourselves. That would mean that in 2013 we can expect an elf steden tocht!
(It is not actual temps that is important for “weather”. Is the acceleration/deceleration of temps. that causes certain predictable weather patterns)

Jim G

Leif Svalgaard says:
August 23, 2012 at 11:34 am
MarkW says:
August 23, 2012 at 11:24 am
Thermal lag does not necessarily apply in that case.
“I note the weasel word ‘necessarily’. Either it does or it doesn’t.”
Not necessarily. Not everyone thinks totally in black and white terms when complex systems are involved where other variables may have an effect. Open your mind.

Stephen Wilde

Leif said:
“Slides 25ff show that UV and solar wind wind were the same a hundred years ago as now and that the 2nd half of the 20th century was not a grand maximum.”
The 5 cycles leading up to 1900 and those leading up to now are somewhat different and 1900 was not so far along the trend of increasing ocean heat content since the LIA as is 2000.
Despite the similarities between 1900 and now we cannot expect the same climate setup.