Volcanic Legends Keep Erupting

Guest Post by Willis Eschenbach

Once again, Anthony has highlighted a paper claiming that volcanoes have great power over the global temperature. Indeed, they go so far as to say:

 From the reconstruction it can be seen that large eruptions, such as Mount Tambora in 1815, or clusters of eruptions, may result in a hiatus of over 20years, a finding supported by model results.

SOURCE: Determining the likelihood of pauses and surges in global warming, Andrew P. Schurer et al, hereinafter Schurer2015, paywalled here.

Here we go again, sez I, another excuse for the current temperature plateau … and right out of the box, I note that we are dealing with a “reconstruction”, with findings that are “verified by model results”.  Be still, my beating heart …

So I thought I’d give their claim a looksee by comparing their recent (post-1800) eruption dates with the Berkeley Earth land temperature record. You know, first see what the observations have to say.

I’m using a variant of the method that they use in the paper, which is to “stack” the temperature records, aligning them at the year of the eruption. I have used the years since 1800 that they have identified in the ice cores as being the years of the big injections of sulfates into the stratosphere from volcanic eruptions. These include inter alia the eruptions of Pinatubo (1991), El Chichon (1982), Mt. Agung (1963), the big eruption of Krakatoa (1883), and the largest eruption during the period, Tambora (1815). Tambora was the volcano responsible for a few areas having a “Year Without A Summer” in 1816. Here are all of the years of big stratospheric eruptions:

schurer table S3Figure 1. Table S3 from Schurer2015. 

Now, “Crowley and Untermann” is reconstruction of historical stratospheric eruptions based on sulfate levels in ice cores in Greenland and Antarctica. After a bit of searching I found the data here. Figure 2 shows their best estimate from the data of the tropical AOD, based on the ice core sulfates.

AOD crowley & untermannFigure 2. Aerosol Optical Depth (AOD), a measure of the amount of stratospheric aerosols, based on ice core records of the sulfate levels. The dotted horizontal line was the accept/reject line for consideration in Schurer2015. One hemisphere had to be above an AOD of 0.1 to be considered for the paper.

Now, in this graph we can see how much more sulfate aerosols were ejected into the stratosphere by Tambora in 1815 than by any other volcano in the last two centuries.

So I’ve taken those years shown by the dotted lines, and I’ve “stacked’ them in Figure 3, showing the span from five years before to five years after each eruption. In the background of Figure 3 are all of the 11-year spans in the dataset, shown in gray. This indicates the expected variation of the data. Over that, I’ve shown the nine eruptions used for this period in Schurer2015.

stacked eruptions and all yearsFigure 3. Stacked eruptions, aligned on the eruption date at Year 0. In gray in the background are all possible 11-year spans from 1800 to 2014.

There are several things of interest. First, as I’ve discussed before, even the mighty eruption of Tambora doesn’t change the global temperature much if at all. Globally the “Year Without A Summer” is the “Year Without A Difference”. Yes, I understand that in some locations the summer was cooler. But it seems the anecdotes have far outpaced the reality. In Missing The Missing Summer I showed eight datasets which cover the time period. None of them shows an unusual summer in 1816. And in Figure 3 you can see that according to the Berkeley Earth data, globally the “missing summer” of Tambora is scarcely a blip.

More to the point, the average of the stack shows that in general there’s no significant effect from the volcanoes. Nor is there any “dose-related” effect. Tambora, with the largest AOD, doesn’t have a significant temperature drop after the eruption. On the other hand, the largest post-eruption drop is from the eruption with the smallest AOD, that of 1903.

I know that this is difficult to accept after years of hearing how volcanoes strongly affect the climate, but here’s what I say is happening. When the stratospheric aerosols cut down the sun slightly, the tropical surface cools slightly. Because the tropical surface is cooler, the cumulus clouds form later in the day, allowing in more sun. So the weaker sun is compensated for by the longer time that it is striking the surface, and as a result there is very little change in the global average temperature.

In this manner, despite even the size of the 1815 Tambora eruption, and despite the fact that local areas showed cooling after Tambora, the stratospheric aerosols from this huge eruption had little effect on the global average temperature. More stratospheric aerosols are simply balanced out by less tropospheric clouds, and the beat goes on.

Conclusions? Well, my main conclusion is that Schurer2015 way overstates the effect of volcanoes on the global surface air temperature. For them to have a 20-year effect is very doubtful, particularly given the short lifespan of the stratospheric aerosols, as shown in Figure 2. In no case do they remain airborne for more than six years or so. How could their effect last another fourteen years?

In fact, as Figure 3 shows, on average there is no global effect at all visible in the first five years.

So I’ll say, as I’ve said before, that while volcanoes can certainly affect local areas, rumors of the power of volcanoes to affect global average temperatures have been greatly exaggerated.

Best to all,


A Strong Request: If you disagree with something that has been said, please quote the exact words you disagree with. That lets us all be clear about a) the person you are addressing, and b) just what they said that you object to.

Further Reading: As I mentioned above, I’ve written extensively on how little the eruptions affect the temperature. Here is a list of my previous posts on the subject:

Overshoot and Undershoot

Today I thought I’d discuss my research into what is put forward as one of the key pieces of evidence that GCMs (global climate models) are able to accurately reproduce the climate. This is the claim that the GCMs are able to reproduce the effects of volcanoes on the climate.…

Prediction is hard, especially of the future.

[UPDATE]: I have added a discussion of the size of the model error at the end of this post. Over at Judith Curry’s climate blog, the NASA climate scientist Dr. Andrew Lacis has been providing some comments. He was asked: Please provide 5- 10 recent ‘proof points’ which you would…

Volcanic Disruptions

The claim is often made that volcanoes support the theory that forcing rules temperature. The aerosols from the eruptions are injected into the stratosphere. This reflects additional sunlight, and cuts the amount of sunshine that strikes the surface. As a result of this reduction in forcing, the biggest volcanic eruptions…

Dronning Maud Meets the Little Ice Age

I have to learn to keep my blood pressure down … this new paper, “Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks“, hereinafter M2012, has me shaking my head. It has gotten favorable reports in the scientific blogs … I don’t see it at…

Missing the Missing Summer

Since I was a kid I’ve been reading stories about “The Year Without A Summer”. This was the summer of 1816, one year after the great eruption of the Tambora volcano in Indonesia. The Tambora eruption, in April of 1815, was so huge it could be heard from 2,600 km…

New Data, Old Claims About Volcanoes

Richard Muller and the good folks over at the Berkeley Earth Surface Temperature (BEST) project have released their temperature analysis back to 1750, and are making their usual unsupportable claims. I don’t mean his risible statements that the temperature changes are due to CO2 because the curves look alike—that joke has…

BEST, Volcanoes and Climate Sensitivity

I’ve argued in a variety of posts that the usual canonical estimate of climate sensitivity, which is 3°C of warming for a doubling of CO2, is an order of magnitude too large. Today, at the urging of Steven Mosher in a thread on Lucia Liljegren’s excellent blog “The Blackboard”, I’ve…

Volcanic Corroboration

Back in 2010, I wrote a post called “Prediction is hard, especially of the future“. It turned out to be the first of a series of posts that I ended up writing on the inability of climate models to successfully replicate the effects of volcanoes. It was an investigation occasioned…

Volcanoes: Active, Inactive, and Retroactive

Anthony put up a post titled “Why the new Otto et al climate sensitivity paper is important – it’s a sea change for some IPCC authors” The paper in question is “Energy budget constraints on climate response” (free registration required), supplementary online information (SOI) here, by Otto et alia, sixteen…

Stacked Volcanoes Falsify Models

Well, this has been a circuitous journey. I started out to research volcanoes. First I got distracted by the question of model sensitivity, as I described in Model Climate Sensitivity Calculated Directly From Model Results. Then I was diverted by the question of smoothing of the Otto data, as I reported…

The Eruption Over the IPCC AR5

In the leaked version of the upcoming United Nations Intergovernmental Panel on Climate Change (UN IPCC) Fifth Assessment Report (AR5) Chapter 1, we find the following claims regarding volcanoes. The forcing from stratospheric volcanic aerosols can have a large impact on the climate for some years after volcanic eruptions. Several…

Volcanoes Erupt Again

I see that Susan Solomon and her climate police have rounded up the usual suspects, which in this case are volcanic eruptions, in their desperation to explain the so-called “pause” in global warming that’s stretching towards two decades now. Their problem is that for a long while the climate alarmists…

Eruptions and Ocean Heat Content

I was out trolling for science the other day at the AGW Observer site. It’s a great place, they list lots and lots of science including the good, the bad, and the ugly, like for example all the references from the UN IPCC AR5. The beauty part is that the…

Get Laki, Get Unlaki

Well, we haven’t had a game of “Spot The Volcano” in a while, so I thought I’d take a look at what is likely the earliest volcanic eruption for which we have actual temperature records. This was the eruption of the Icelandic volcano Laki in June of 1783. It is claimed to…

Volcanoes Once Again, Again

[also, see update at the end of the post] Anthony recently highlighted a couple of new papers claiming to explain the current plateau in global warming. This time, it’s volcanoes, but the claim this time is that it’s not the big volcanoes. It’s the small volcanoes. The studies both seem to…


UPDATE: I don’t think Willis will mind if I include this excellent graph prepared by Joe D’Aleo of Weatherbell:


As you can see in the bottom panel, the aerosol loading during “the pause” is close to zero. So much for Schurer2015 and their claims  – Anthony

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The Ghost Of Big Jim Cooley
July 22, 2015 2:16 am

Once again I have been given an opportunity to state that, built into the idea that CO2=warming, is that the lower stratosphere will cool, while the lower troposphere will warm. So again then: The lower stratosphere has NOT cooled since 1995. I’ll say it again. The lower stratosphere has NOT cooled since 1995. It did cool, which enforced the CO2 hypothesis, but it stopped cooling in 1995…and even shows a very slight warming. Will someone please put me out of my misery by explaining to me why a big deal is NOT being made of this?

Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 3:04 am

The stratosphere is the clue to understanding the real, long term effects of volcanoes?comment image
Discussed in detail here:

Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 3:06 am

An old plot that needs updating. How the heck you get a sufficient grasp on ozone depletion and recovery to look at this I have no idea. Every dataset I look at since Montreal came along is a nightmare.

Mike Maguire
Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 7:20 am

Great chart. Your trendline from 1995 to the end of the graph has a slope that is too steep. One way to visualize this as being obvious is to see that it starts closer to the lows and ends much closer to the highs. There are numerous ways to draw trendlines though, so I’m not sure what this one is based on.
If it is meant to represent the mid point of some average along the way, look at it this way.
Starting from 1995 to the end…….. during the first ~50% of the trendline, there is close to an equal amount of data points below and above the trendline. This is good. However, after this, during the last ~50% of the trendline, almost all the data points/ “area” are below the trendline. This can mean several things.
1. There was a trend change at around the halfway(50%) time frame from a steeper uptrending slope to less steep slope………in fact, you can make a case for it to be flat or even a slight downtrend after ~50% into the period of the slope you’ve drawn.
2. Since you are using just 1 line to represent the entire period, then clearly, that one line should be placed so that data points are more equally distributed on both sides of the trend line.
3. It looks like you took the trendline from the first half of the period and extended it into the 2nd half of the period, when the trend had changed.
4. This trendline being discussed starts closer to the lows and ends closer to the highs is another way to view it as not fairly representing what the trend of the data is telling us……..unless your definition is different than what I’ve described.

Mike Maguire
Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 7:26 am

The previous comment was directed at the chart/graph of The Ghost Of Big Jim Cooley showing the Lower Stratosphere and Volcanoes, Time vs Temp Anomaly. I realize that it was probably drawn by the source that he used.

The Ghost Of Big Jim Cooley
Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 12:39 pm
Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 2:54 am

Spot on Big Jim!

Reply to  AJB
July 22, 2015 7:39 am

Well, you live and learn. Thanks Jim.

Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 5:48 am

I don’t understand your objection. More CO_2 simply raises the height where the atmosphere becomes transparent to CO_2 based thermal emissions. Since the atmosphere lapses, this reduces the average intensity of outgoing radiation in the CO_2 band. Since the total input energy from the sun MUST be balanced in dynamic equilibrium (on average) by the sum of radiation emitted or reflected directly from the Earth’s surface (all sources) and the radiation emitted or reflected from the atmosphere (all sources) if you drop the intensity of one of the sources, the others must increase to compensate and maintain detailed balance. Nearly all of the ways this can happen involve at least some additional warming.
I don’t see anything in this that requires the stratosphere or troposphere to change temperature — much. One expects surface temperature to increase a bit as one raises the mean emission height. This will raise the temperature of everything coupled to the surface, a bit, as well. But the key is raising the emission height.

Reply to  rgbatduke
July 22, 2015 8:47 am

The emission height does not increase in the saturated bands. Adding molecules merely LOWERS the altitude and raises the lapse temperature of complete absorption. Above this altitude CO2 molecules see no outgoing photons. This was extensively measured in the ’60’s from radiometer equipped aircraft.
This may speak somewhat to the difference between surface and TLT temperatures.

The Ghost Of Big Jim Cooley
Reply to  rgbatduke
July 22, 2015 12:37 pm

The stratosphere cooling is a known effect from anthropogenic global warming, or at least it would be. This has been discussed many times in the past on realclimate, but also right here on WUWT. Indeed, in the paper discussed on the link below, it is said, “[stratospheric cooling] is a more suitable signal of anthropogenic global warming”.
As the lower troposphere warms, the stratosphere should cool. Indeed, I’m surprised that no one like Dr Roy Spencer hasn’t jumped on the fact that stratospheric cooling isn’t happening as PROOF that UAH and RSS data on TLTs are correct.

Reply to  rgbatduke
July 22, 2015 2:26 pm

More CO_2 simply raises the height where the atmosphere becomes transparent to CO_2 based thermal emissions.

More CO2 has a number of associated feedbacks including atmospheric water vapor changes which we are reasonably sure will happen but can’t predetermine. You cant simplify the net effect that like that. It might be true but stating it as fact simply doesn’t follow and is counterproductive to overall understanding.

Reply to  rgbatduke
July 22, 2015 4:45 pm

TimTheToolMan: “More CO2 has a number of associated feedbacks including atmospheric water vapor changes which we are reasonably sure will happen”
There is no evidence whatsoever from the NASA NVAP data to back that statement WRT water vapour.
Here are three analyses:
Vonder Haar
Solomon et al.
Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000–2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% as compared to estimates neglecting this change. These findings show that stratospheric water vapor is an important driver of decadal global surface climate change.

So, rather the opposite, it seems.

Reply to  rgbatduke
July 22, 2015 5:06 pm

@Catweazle. I specifically said “changes” and didn’t give a direction so I’m not sure where your “rather the opposite” comment comes from.
I agree that there is a problem with the AGW theory because a drying of the stratosphere will counteract any additional CO2 above the ERL and so tend to have the effect of decreasing the ERL which is opposite to rgbatduke’s assumption. The net result? Nobody knows.

Joe Born
Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 6:20 am


I don’t see anything in this that requires the stratosphere or troposphere to change temperature — much.

I don’t, either, but I think that’s beside the point. I think The Ghost of Big Jim Cooley is saying that temperatures’ falling in the stratosphere and rising in the troposphere is a consequence of the positive-feedback theories, not of the “greenhouse” effect per se, which is what Dr. Brown was referring to.
I’ve seen that said often, so I’m guessing it’s true, but I haven’t seen causal connection between positive feedback and temperature spread explained. Perhaps The Ghost of Big Jim Cooley or another reader could elucidate.

Joe Born
Reply to  Joe Born
July 23, 2015 4:26 am

I think The Ghost of Big Jim Cooley is saying that temperatures’ falling in the stratosphere and rising in the troposphere is a consequence of the positive-feedback theories, not of the “greenhouse” effect per se.

Oops; I had a brain cramp; sorry for injecting confusion.
Yes, the theory behind the changing temperature spread does indeed seem to be based on the “greenhouse” effect per se, just not on the aspect that Dr. Brown described.
I can’t say I understand it, but it appears to be something about the increased optical density’s causing different gradients. The plausibility argument seems to be that the greater concentration causes more upward as well as downward radiation so that, once you’ve passed the effective radiation altitude (for a given wavelength) the carbon dioxide is more effective at cooling if there’s more of it.
Or something like that.

July 22, 2015 2:24 am

So volcanoes’ are mere eruptions,
On the broad face of the world.

Juan Slayton
July 22, 2015 2:26 am

… much more sulfate aerosols were ejected into the stratosphere by Tambora in 1915 than by any other volcano
Make it 1815 and delete this comment.
: > )

July 22, 2015 2:30 am

“When the stratospheric aerosols cut down the sun slightly, the tropical surface cools slightly.” This reminds me of a PID controller. The big question is just what sets the “set point”. The drifting increase in temps over the past three centuries is like “reset wind-up” on a P controller that lacks an Integral effect.
The next question is that if climate is self regulating controller, what sends it haywire as ice ages hit and what corrects it?

July 22, 2015 2:40 am

2014 was the warmest year in the world. Undipustable fact. And 2015 will be warmer.

The Ghost Of Big Jim Cooley
Reply to  John
July 22, 2015 2:49 am

Can you clarify?

Reply to  The Ghost Of Big Jim Cooley
July 22, 2015 5:59 am

It is obvious. The media of the left said so.

Reply to  John
July 22, 2015 2:57 am

John, you’re a pointless troll. 97% of years in the last 10,000 were warmer than 2014. Get a life. R.

Reply to  RERT
July 23, 2015 11:29 am

There we go with that “97%” thing again….

Werner Kohl
Reply to  John
July 22, 2015 3:10 am

Maybe. Maybe not.
So what? You are completely off-topic.
> Undipustable fact
You don’t understand anything concerning natural science.
There is no undisputable fact.

Eustace Cranch
Reply to  John
July 22, 2015 5:40 am

Thank you for taking the discourse to such an elite level. The spelling is quite creative, too.

STewart Pid
Reply to  Eustace Cranch
July 22, 2015 7:03 am

Indeed …the only undisputable fact is that John is challenged when spelling undisputable 😉
Too funny!!

Reply to  Eustace Cranch
July 22, 2015 10:35 am

Just imagine if there were no spell check. The spelling would be the worst evah!

Warren Latham
Reply to  John
July 22, 2015 6:26 am

You say … “Undipustable” fact !
Please state WHICH world you are on: it would help to know … oh wait … no, I think I saw you last night; just behind that galaxy which is obscured by our moon … yes … perhaps you are the “stratospheric aerosol” everyone’s so eager to meet.
That explains it: no need for you to reply here (unless of course you are a qualified railway engineer).
Do drop in and give us all a thermal emission whenever your next orbit is close.
Thanks awfully.

David A
Reply to  Warren Latham
July 22, 2015 6:40 am

Dear undisputable John,
Through time, and continues changing of the past, they (the alarmist) will reach their “warmest ever” objective, all the while ignoring that both satellite data sets, calibrated to the most accurate thermometers , immune to UHI, changing stations, homogenization, scarcity of measurements, etc., show that 1998 was the warmest by a factor about 1,000 PERCENT larger then the “warmest year ever” nonsense they manufacture.
They will ignore that the satellite demonstrate that 1998 was considerably, easily and statistically significantly warmer then 2010, 2014 and 2015. They will ignore that the troposphere was supposed to warm FASTER then the surface. They will ignore the increase in global sea ice now enhanced by increasing ice in the NH. They will ignore the flat and very minor sea level trend. They will ignore that even their manufactured warming is far below the IPCC computer model mean on which the predicted harms of CAGW are based. They will ignore the slight increase in NH snow. They will ignore record ice on the great lakes. They will ignore that all the harms of CAGW are failing to manifest, while the benefits, saving massive amounts of fresh water and massive acreage of land are feeding close to one billion people every year.
============================(That is a lot of ignoring)================================
instead they will manufacture a tiny bit of warming, encourage “warmest year ever” nonsense headlines all over the world, while crying doom for humanity, all they while padding their wallets and take home pay while shamelessly preventing real problems from being addressed.
=================================(That is evil=====================================

Reply to  John
July 22, 2015 7:19 am

All you people criticizing John are a bit out of line.

2014 was the warmest year in the world.

John did not specify which world.

Eugene WR Gallun
Reply to  TonyL
July 22, 2015 9:25 am

Aw, com’on. Now that’s piling on!
Eugene WR Gallun

Reply to  TonyL
July 22, 2015 9:38 am

Model World; Model World; Party Time.
Somewhere in the multiverse (which I don’t believe in) there’s a planet doing exactly what the models say.

Crispin in Waterloo
Reply to  TonyL
July 23, 2015 3:25 am

Even in the multiverse there is no planet that can simultaneously lie in so many ways as do the multitude of worthless models that produce their pointless, disagreeing and unphysical predictions of apocalypse.

Reply to  TonyL
July 24, 2015 7:38 am

My son would say “Harsh much?” Sure made me smile
“the multitude of worthless models that produce their pointless, disagreeing and unphysical predictions of apocalypse”
That quote and the models/real data graphs ought to go on billboards 🙂

Reply to  John
July 22, 2015 7:20 am

I stated that at the start of 2015 that no matter what the reality nor data , 2015 would be the ‘warmest year ‘ [because] of the ‘Paris affect ‘ , so it is no surprise to find out that is what is being claimed has it could never have been any other way.
Mile high glaciers could have been seen rolling over the white house and the claim would still have gone up that 2015 was the ‘warmest year ‘

Reply to  John
July 22, 2015 9:17 am

Please insert the following warning when derailing the discussion:

Reply to  John
July 22, 2015 11:53 am

“2014 was the warmest year in the world.”
Since the creation? Which world are you talking about? (Or is this some wonderfully subtle reference to post-Kripke metaphysics?)
“And 2015 will be warmer.”
Same world? (It’s certainly not the one I live in.)

Reply to  John
July 22, 2015 4:47 pm

Stop making stuff up.

Louis Hunt
Reply to  John
July 23, 2015 10:24 pm

John, are you giving us a money-back guarantee that none of the temperature data for 2014 will ever change in the future? Today’s temperatures cannot be considered reliable if they are going to be “corrected” at anytime in the future. The data we have for the years before 2014 have been adjusted, some many times. What makes 2014 so special that its data would be carved in stone and immune from future adjustments?
BTW, what is an “undipustable fact” I don’t see what having pustables in your undies has to do with facts.

July 22, 2015 2:52 am

Willis –
The obvious question which comes to mind given your data and explanation regarding tropical ocean cloud feedback is: what was the effect over land areas? Those areas will see the cooling without the compensating heating your postulate.
Also, I know history is not science, and I’m not even a historian, but it is hard to believe that the stories
crops failing and snow & frost in June (was that New England?) could have no basis in reality at all….

Reply to  RERT
July 22, 2015 3:24 am

Today we have freak rainstorms, hot days in winter, snow storms in summer, floods and drought. In each and every case somebody always points the finger at CO2 and ignores the fact that freak weather has always occurred.
The past was no different. If a crop failed or there was freak weather it is inevitable that people would point the finger at the eruption.
If you had followed Willis’ link to the “Missing the Missing Summer” story you would have found a graph from The Price History of English Agriculture, 1209-1914 which shows that food prices were at their lowest in the years after the eruption which wouldn’t be the case if there was widespread crop failures.
You might argue that England is a small place and doesn’t necessarily represent the whole world, which is fair enough, but if you do want to claim that there was widespread crop failure then find the data (eg rising prices due to scarcity) and point to it.

Sturgis Hooper
Reply to  TerryS
July 22, 2015 6:35 am

Food prices dropped in Britain because of the end of the Napoleonic Wars.

Reply to  TerryS
July 22, 2015 1:02 pm

But the series referred to starts more than 500 years before the well-known Bonaparte was actually born.
And, if I may:
Willis has highlighted the effects – if any – of eruptions in the last 200-250 years.
There have been bigger ones.
What effect would ‘they’ have today – say a Yellowstone event?
Never-mind an Indian Deccan fields . . . . . . .
Do I know? No.

Sturgis Hooper
Reply to  TerryS
July 24, 2015 1:12 pm

I was referring to prices in Britain in the year after Tambora, to explain why they didn’t rise there. On the continent, there was famine, particularly in landlocked areas like Switzerland, as a result of Tambora. Likewise China.
A Tambora today would be bad for agriculture. The world has the ability now to aid regions suffering famine, but a global, or at least NH, crop failure would be calamitous. A Yellowstone? Fugedaboudit!
Happy I’m upwind (usually) from Yellowstone while being too far inland to suffer greatly from the Juan de Fuca Big One. Maybe a sweet spot, geodisaster-wise.

Samuel C. Cogar
Reply to  RERT
July 22, 2015 7:08 am

tropical ocean cloud feedback is: what was the effect over land areas? Those areas will see the cooling without the compensating heating your postulate.

Who cares, other than you?
About 71 percent of the Earth’s surface is water-covered, and the oceans hold about 96.5 percent of all Earth’s water.
And the 29% that is land covered, I’ll make a guess and say that 25% of said land is not located in the equatorial zone where the majority of “heating” occurs.
And the winds push/carry that tropical “heat” toward the poles.

Reply to  RERT
July 22, 2015 7:45 am

It isn’t the event being disputed it is the cause of that poor summer that seems to be in doubt. We often join dots and impute relationships that on deeper investigation aren’t there. Willis’ article seems to do that.

Ben of Houston
Reply to  RERT
July 22, 2015 10:45 am

RERT, to give an explanation, probably there were localized cold areas, especially inland, and I would not be surprised if there were several days of noticable haze across large sections of the globe. However, as a whole, the effect disappears into annual varibility.
Now, if I can give a guess, over time, this black cloud of haze blocking the sun was magnified into legend. Any negative effects were attributed to this cloud (see how in some rural areas they point to pollution causing birth defects despite the pollution being smaller than typical city pollution), while positives were ignored, amplifying the damage of the volcano through the power of selective perception.

July 22, 2015 2:56 am

In scientific literature there is extensive debate about the 1809 “mystery” or “unknown” volcanic eruption, which in strength is believed to be second only to Tambora for eruptions in the last couple of hundred years. Ice cores indicate that there has been a massive eruption in 1809 as well, but no one seems to know where it took place.
I don’t see any discussion of this eruption in your post, but you must be aware of it, as it was posted previously at WUWT and you commented in the threads.
So, is it relevant?
There have been some suggestion that the eruption took place in South America – at the time a sparsely populated region with few people documenting things.
A paper on this eruption can be found here, see references in the paper for more on this.

Mike M.
Reply to  Willis Eschenbach
July 22, 2015 10:24 am

But the Tunguska event was in 1908.

Reply to  Jos
July 22, 2015 10:49 am

If you note, the 1809 eruption is graphed on the big spaghetti-plot, though not referenced directly in the text. It doesn’t seem to be important temperature-wise, as it occurred during a cooling trend and didn’t have a strongly discernable effect.

Werner Kohl
Reply to  lgl
July 22, 2015 3:38 am

Okay the huge drop in temperature occured in 1809.
From where did the nature know that 6 years later – in 1815 – the Tambora will explode?
Crystal ball?

Reply to  Werner Kohl
July 22, 2015 4:08 am

There was a large eruption in 1809 also, and temperature had not recovered in 1815.

Werner Kohl
Reply to  Werner Kohl
July 22, 2015 4:39 am

The WfT graph shows that drop in 1809:
Okay, maybe an effect of the mysterious eruption. But in 1810 the temperature anomaly recovered to values suitable to the trend from 1801 to 1808.
No drop in 1815.

Reply to  Werner Kohl
July 22, 2015 5:17 am
Reply to  Werner Kohl
July 22, 2015 12:23 pm

Igl, the problem was that the temperature was dropping from a peak in 1805 including steep drops in 1807 and 1808, and 1809 corresponds to the end of the drop. Unless you are claiming the entire record was corrupted to show the effect before the cause, the eruption of 1809 cannot be assigned to that temperature drop.

Reply to  Werner Kohl
July 22, 2015 1:16 pm

Willis have used the same silly argument before. Nobody has ever claimed the temperature graph would have been a straight line without the volcanoes. There are lots of natural oscillations like ENSO, AO, PDO.

Reply to  Willis Eschenbach
July 23, 2015 12:08 pm

Willis Eschenbach: “Sheesh … why is this so hard?”
Debating trolls is like wrestling with a pig, Willis.
You get muddy, and the pig enjoys it.
The best thing to do with trolls is to occasionally poke them with a sharp stick, but on no account to feed them.

Reply to  lgl
July 22, 2015 7:49 am

For the large eruption in 1809, WHY did the temperature start dropping in 1808?

Reply to  usurbrain
July 22, 2015 10:22 am

ENSO perhaps.

July 22, 2015 3:15 am

.One noticeable effect in Willis’ fig 3 is that the range of temps on the after eruption side is about half that on the pre-eruption side. That suggests a net calming effect on temperature change ( warmer winters, cooler summers ) .
There is also a drop in overall level, though much of this drop occurs BEFORE the eruptions, indicating a concurrent change that is being falsely attributed to the volcanic effects.

In this manner, despite even the size of the 1815 Tambora eruption, and despite the fact that local areas showed cooling after Tambora, the stratospheric aerosols from this huge eruption had little effect on the global average temperature.

What is noticeable about Tambora is the strong RISE about 3y after the eruption. This is true for both the 1809 and 1815 eruptions.
This is also seen after El Chichon and Mt Pinatubo, though that is a bit lost behind the large lines used in Willis’ graph.comment image

Reply to  Mike
July 22, 2015 3:33 am

Where this all leads is that the post eruptions cooling of TLS and surface warming has been totally ignore by climate science so far and that the reason for the “hiatus” has more to do with the LACK of volcanoes that caused the late 20th c. warm burst that had everyone getting into hysterics.
To suggest that the piffling amount of activity since 2000 has caused or even contributed to ” the pause ” shows just how desperate they are about reviving this particularly dead horse.
It’s as absurd as to suggest that global warming has caused modern slavery. 😉

Reply to  Mike
July 22, 2015 5:29 am

Little else is needed, but I will add the measured atmospheric clarity chart from WUWT’s solar page – to again display just how little the actual volcanic effect has been measured since the pause began in 1996-1997 time frame.

July 22, 2015 3:26 am

While it’s pretty clear that global temps are not significantly affected by volcanoes, the “year without a summer” seems to be historically fairly well established. Has anyone done a land-only comparison of the 30-60N band only? That’s going to geographically cover most of the sources of the “year without a summer” stories.

John Marshall
July 22, 2015 5:15 am

Wrong Willis. Volcanoes have a big effect on climate, the higher the ejecta the greater the effect. If you mean by “local” you mean on a hemispherical basis then I would agree but not otherwise.
Active volcanoes are mainly fairly above or below the equator. There is little mixing in the atmosphere north/south so effects remain that “local”.
Ejecta includes ,
Ash, can increase albedo so reduce radiation input.
SO2. Will reduce radiation input.
CO2, Will lower temperatures.
So a definite measurable temperature drop.

Werner Kohl
Reply to  John Marshall
July 22, 2015 5:21 am

Yes. But after one year the ejecta will have left the atmosphere for the most part.
Willis described a mechanism which counteracts the reduced input of solar energy. So the temperature drop may be reduced a lot.

Jim G1
Reply to  Werner Kohl
July 22, 2015 6:41 am

Willis qualified his analysis to after 1800. Please note that this is necessary when speaking of volcanic eruptions. https://en.m.wikipedia.org/wiki/Volcanic_explosivity_index. The vei of Yellostone has recently been found to be even greater than indicated in this citation. One of these goes off, game over.

Reply to  John Marshall
July 22, 2015 9:29 am

It would seem to me that almost all of the active volcanoes on earth are either north or south of the equator.

Tom in Florida
July 22, 2015 5:19 am

It seems that the graph added by AW from Joe D’Aleo shows that the large volcanic eruptions counteract any El Nino and/or would contribute to a longer La Nina.

Ian Wilson
July 22, 2015 5:29 am

Only one major problem with Willis’ methodology. What if major volcanic eruptions are a symptom of extended cooling periods. This would mean that each large volcanic eruption in the tropics (or cluster of eruptions) would be preceded by an extended period of global cooling.(say five, ten or even fifteen years).
What Willis should do is normalize his curves in figure 3 to temperatures five (ten or even fifteen) years prior to the eruption rather than the time of eruption.
Just a friendly suggestion.

Curious George
Reply to  Ian Wilson
July 22, 2015 9:27 am

I consulted my tarot card reader: you are right!

Reply to  Ian Wilson
July 22, 2015 10:04 am

Good point Ian, the cause-and-effect relationships have certainly not been empirically established in any of the interactions which govern this whole geo-climatic environment thing.

Reply to  Ian Wilson
July 22, 2015 12:29 pm

No way.
To take this seriously, you would have to propose some mechanism where minute changes in global temperature would have significant effects on geologic changes. Sorry, but that beggars belief. If cold was an instigator of vulcanism, then the tropics would be volcanically silent and most eruptions would occur in winter.
You don’t need just correlation. You need a plausible cause that doesn’t introduce severe disparities with reality.

Ian Wilson
Reply to  benofhouston
July 23, 2015 6:01 am

What if there were external factors that could lead to cold periods on the Earth (e.g. reduced solar activity associated with global cooling) that could also affect the Earth’s rotation rate (by increasing or decreasing the length-of-day). Under these circumstances you might expect to see a reduction in world temperatures that would also be accompanied by increased stresses on the Earth’s crust.
I think that if you look at Willis’ figure 3 very carefully you will see that if he normalizes the curves associated with the volcanic eruptions to a epoch five years prior to the eruption you will see a systematic cooling of the volcanic curves compared to those for randomly selected 10 year periods.

Reply to  benofhouston
July 23, 2015 11:21 am

Change in rotatation? That would affect temperature and volcanos., but we would certainly have noticed such a change if it happened since the invention of the chronometer, and very likely millenia before that, so that is completely irrelevant to that discussion.
Solar activity. Yes it would affect temperature, but I would need some evidence that it affects geological effects. This reduces to my prior post. If this was the case, you would see a large annual swing in volcanos that just doesn’t exist.
All proposals I have heard for the temperature->Volcanoes would have much more significant and quite noticeable effects.
And trying what you say by eyeball, it doesn’t align well at all. You just get an inverted version of figure 3, with a ludicrously wide swath of changes going at year zero. There is a vague downward trend, but it is nowhere near universal, especially if you take the spaghetti splot from the greyed out background into account.
With no plausible mechanism you need some intriguing supporting data.

Ian Wilson
Reply to  benofhouston
July 25, 2015 8:18 am

Benofhouston, Hopefully this will help you understand my point.
The following two statements are independent of each other:
Reduced solar activity —- leads to — reduced the world mean temperature.
Reduced solar activity —- leads to — small changes in the Earth’s rotation — producing stress on crust.
The reduction in the world mean temperatures has little or no connection to the increased stress on the Earth’s crust.
Eventually the stresses in the crust build up and they are dissipated in increased volcanic activity.
Hence, your argument that vulcanism would vary through the seasonal temperature cycle is totally spurious.
And, if you are so sure about figure 3, why not get Willis to re-plot it with the normalization taking place at 5 years prior to the date of eruptions. When I do it by eye, I see a clear negative trends in temperature in the epochs surround large tropical eruptions compared to randomly selected 10 year epochs.

Reply to  benofhouston
July 25, 2015 1:29 pm

Ian, I understand you perfectly. However, I’m rejecting your premise. Any influences on the earth’s crust significant enough to cause vulcanism would be readily measurable and have large influences that we could easily see.
You can’t just say “the sun causes small stresses”. You need a viable mechanism where solar radiation would trigger changes in the geology. As the majority of solar radiation is absorbed in the atmosphere or directly onto the surface, the best guess of a vector is temperature, which reduces back to our first argument. You could also argue changes in the magnetic field, but that has been well monitored for a century for people looking specifically for a connection to earthquakes and volcanoes. If the effect was significant, we would have seen it by now.
As it is, your statement is a magic handwave. Magic handwaves actually have their place in science, but they can only be used when saying “we have no idea about the cause”. Ie: Newton’s statements on the cause of gravity. You cannot use it to say “it was the sun but we don’t know how” unless you can make a clear and unambiguous correlation that has predictive power.
And if you are so sure about figure 3, then YOU plot it. Don’t waste my time, much less Willis’s, demanding that we do the work for you. It’s your theory, provide some evidence that I can take seriously.

July 22, 2015 5:41 am

Not sure about centering on yearly averages. The mysterious 1809 eruption allegedly happened in December 1808, so the ‘following’ year is technically 1809. Tambora happened in April, so you how valid is it to compare the temperature in Jan-Dec 1815 (i.e. including 8 months after the eruption) with the temperature Jan-Dec 1816 (8-20 months after the eruption)?
Second question: how much stratospheric mixing occurs between hemispheres and how fast? Can anyone enlighten?

Craig Austin
July 22, 2015 5:42 am

Terrific paper, it is nice to get a sailor’s perspective on any climate issue. Am I way off by thinking that volcanoes are like temporary large urban heat islands with stratospheric self buffering?

John gorter
July 22, 2015 5:46 am

Extrapolating a bit here, but if there is little lasting effect from successive ‘large’ volcanic eruptions such as those in 1809 and Tambora, potentially using Willis’s regulator, is it possible that end ‘Permian’ volcanism is also overplayed as a cause of this major earth life crisis (and yes I am well aware of the other ’causes’ like impacts etc, and also aware that the extinctions started earlier in the Late Permian).

Reply to  John gorter
July 22, 2015 7:35 am

john gorter. I’m a little suspicious of the “extinction events” notion of evolutionary change. You know, the wayward asteroid! The notion seems to be a plausible explanation for the disappearance of “dominate” species but really never accounts for those that survive and seem to have no special trait that should have saved them (Crocodiles, turtles, sturgeon, sharks, lizards in the case of the asteroid). Not sure if the evolution of life is driven by catastrophe.

Bob Koss
July 22, 2015 5:56 am

It looks to me like Tambora only had an effect for about 5 months in 1816. It seems their imagination is strong if they feel they can justify a 20 year effect.
I extracted the data for the 42 stations in the ISTI database which have full records 1801-1830. There are another 100 or so which have broken records during the period over half having less than ten years of data. Using just the 42 stations no mystical adjustments are necessary for latitude, elevation or missing data.
Here are a couple graphs of those stations.
1801-1830 annual mean temperature.
1801-1830 May-Sep mean temperatures.

David A
Reply to  Willis Eschenbach
July 22, 2015 11:38 am

Willis, your posts are excellent, but n this one you appear to be century challenged.

Reply to  Bob Koss
July 22, 2015 11:27 am

Bob, that puts a marked drop in temperature just prior to the multiple earthquakes and sand blows along the New Madrid fault in 1811-12. Fascinating that this was during the Dalton minimum.

July 22, 2015 6:10 am

Hi Willis,
Thanks in particular for the link to optical depth data — I wasn’t aware of this source. I’ll use it to redo (independently) my own computation of a “best fit” response function for the temperature using HadCRUT4. Berkeley seems surprisingly different, off the top of my head, especially after El Chichon, where there was strong cooling, lagged by an inexplicable two years. It’s also amusing to see that the temperature “knew” Pinatubo was going to erupt, because it dropped even more before it erupted than it did afterwards. Artifacts like this are common in the volcano vs temprature fit — when I tried this before, there were plenty of eruptions with almost no effect, eruptions where temperature went the wrong way — basically as you show above (but don’t point out sufficiently strongly) — the natural variation on the left is as big or bigger than the supposed response on the right. One cannot really resolve the effect of volcanoes from the natural year to year variation of the temperature record — one barely improves a fit by adding a volcano model to a CO_2 only model as I showed in the last thread, and one can easily get a much bigger improvement with a 0.1 amplitude sinusoid that has no explanation that I know of.
One thing I’m excited by is the opportunity to refit using OAD directly. I inferred it using VEI and ejecta volume and a simple model built using Mauna Loa data, but the latter only covers a few large eruptions and eruption VEI is not a very good proxy for aerosol load. I didn’t realize that ice core data captures the actual optical aerosol load and that this work had been done, so using the data itself (with a presumably better/different proxy if nothing else) will both let me check my own model and will let me better map response to supposed atmospheric transparency.
But I’m pretty certain of what I will find, as it agrees quite well with what you find. Volcanoes have almost no resolvable effect on climate. Big ones, little ones, lots of volcanoes or a few. I’m not even going to model “volcanoes” in my next effort — I’m just going to add NH/SH AOD averaged as a model parameter with some sort of linear/exponential response function (probably a lagged adjustable exponential kernel so that impulses have a year to make themselves felt and then have a model-fit exponential decay effect, but also so that the background gets to contribute and modulate the CO_2 fit). I expect that this will very slightly improve the quality of a CO_2 only fit. I won’t even guess as to whether it will increase or decrease climate sensitivity.
It is remarkable that a paper is being trumpeted publicly even before it is actually published that is so obviously, and seriously, flawed. Aren’t the referees familiar with the data? The hypothesized effect even if real isn’t resolved from the data — the volcano signal is buried in the natural noise — and as you note there may well be feedback mechanisms that partially cancel any cooling response.
This latter seems increasingly likely. One way of interpreting the evidence we’ve both looked at is that aerosols are pretty much irrelevant to climate. Boy, is that one a toughie. Everybody blames aerosols for cooling during the smog era, everybody wants to blame volcanoes for cooling all along the temperature record, and perhaps they do cool, locally, for a year or two, affecting the weather but not the climate. Not resolvably so.
Remove aerosols altogether from the GCMs, and they must radically change to fit the reference data. Since you cannot cancel GHG plus feedback warming against aerosol cooling, GHG plus feedback warming has to substantially decrease. Climate sensitivity plunges. The agreement of the models with the observed climate improves. But the motivation for taking drastic measures to reduce GHG emissions plunges along with the sensitivity. An unwelcome message for those that are suckling at this particular pork barrel teat.

Reply to  rgbatduke
July 22, 2015 6:47 am

You may be right, but I will flog my “Temperate” horse a bit more.
The Faint Sun Paradox: 800 million years ago, the sun was only 70% as bright as today, yet the climate was broadly similar. People tried desperately to invoke CO2 as the reason but it would not work. The answer had to be water vapor and clouds, which means mostly in the tropics. So you are right about that, if you can compensate for the sun like that, a volcano will not have much impact.
But it still does not address temperate zones (particularly NH) which do not have anywhere near the ability to make clouds (or not) from evaporated seawater.

Sturgis Hooper
Reply to  TonyL
July 22, 2015 7:04 am

This 1984 paper found a global T drop of 0.4 to 0.7 degrees C following Tambora:
There were crop failures and famine in Europe, North America and China.
The sun was only about seven percent weaker than now 800 Ma. The faint young sun paradox refers to the early earth, some 3800 Ma.

Reply to  TonyL
July 22, 2015 7:40 am

@ Sturgis:
OK, Thanks. Looks like I got a bit ahead of myself there.
Still, 7% is huge compared to the 1.234 w/m2 “forcing” warmists go on about for CO2.

Reply to  TonyL
July 22, 2015 8:21 pm

Still, 7% is huge compared to the 1.234 w/m2 “forcing” warmists go on about for CO2.

It is about the annual variation in insolation, actually (which is roughly 91 W/m^2). The Earth’s orbit is substantially elliptical. And paradoxically, the Earth is coldest at perihelion (January, SH summer) and warmest at aphelion (July, SH winter). One of many things that I find puzzling in spite of the glib explanations I hear for it. The point is that the climate, while remarkably stable around some fixed point over geological time, hasn’t been stable around the same fixed point. It is currently at least bistable (we’re in an ice age) if not openly multistable as the modes/periods of oscillation have switched repeatedly over the Pleistocene as the periods of glaciation have lengthened and — dangerously — deepened.
Personally I don’t like to think in terms of CO_2 “forcing”, I prefer to think in terms of TOA incoming and outgoing radiation and detailed balance of ins and outs. I think that expressing things as “forcings” is one of many things that has gotten the modelers into trouble. CERES may eventually cure that problem — direct measurements of incoming vs outgoing radiation over several decades may teach us something very important. Inside the Earth-Ocean-Atmosphere system, things are very, very complex. It’s easy to make an assertion like “aerosols are very important to the climate” and have it turn out to be dead wrong, once one has enough data to prove it. And that assumption makes other assumptions wrong, and an entire computational model can fall over like a house of cards. But if one does take the forcings model seriously then yes, the variation due to CO_2 is extremely small compared to both annual variations and annual fluctuations in temperature that one presumes come from modulation of all mechanisms of gain and loss of energy in completely natural climate dynamics, some of which must function as substantial negative feedback systems in order for the system to be as stable as it is.

Sturgis Hooper
Reply to  TonyL
July 24, 2015 11:42 am

July 22, 2015 at 8:21 pm
That is a good way of looking at it.
The sun gets about one percent weaker for every 110 million years you look back in time. This simple linear function might not have applied early in its history, but for as recently as 800 million years ago, it would apply. For 3850 Ma, it yields an estimate of 35% fainter than now.

Reply to  rgbatduke
July 22, 2015 7:09 am

Your comment goes to the essence. And newer papers constrain aerosols to less than half of what CMIP5 generally assumed. Nic Lewis redid his sensitivity estimates based on the new lower aerosol range and IIRC came in about 1.5, down from 1.7 in Lewis and Curry. Cancel the climate alarm.

Curious George
Reply to  ristvan
July 22, 2015 9:33 am

You don’t cut (public) money pipelines leading to pockets of well-meaning billionaires. That would be a dangerous, even subversive, activity.

Reply to  ristvan
July 22, 2015 8:33 pm

Nic Lewis redid his sensitivity estimates based on the new lower aerosol range and IIRC came in about 1.5, down from 1.7 in Lewis and Curry. Cancel the climate alarm.

Yeah, but will any of this hit the mainstream before AR6? Will there even be an AR6? Or will it just be oops, we meant to say Climate, apostrophe,

Never mind.

July 22, 2015 6:25 am

Exaggerated volcanic effects support the warmer’s exaggerated aerosol effects. As a result, we have imaginary zombie volcano effects.
The less effect volcanoes have, the less credibility the warmer’s overinflated direct and indirect aerosol effects have.

July 22, 2015 6:33 am

Very nice explanation for tropical areas (more or less clouds to compensate), which in large measure makes up the global average. But the argument does not address temperate areas at all. In my area (New England), the year without a summer really happened, and people lived through it.You do not even have to go back as far as the Civil War, so it is not ancient history. In the temperate areas, “did not happen because Tropical ….” really does not work.

Reply to  TonyL
July 22, 2015 12:41 pm

I think the best intepretation of the data isn’t that the “Year Without a Summer” didn’t happen, but just that it’s effects on annual temperatures are insignificant. These are the official temperature records at the time and they don’t show a large effect. You could probably see some quite significant effects if you go on short enough time scales, but it’s just lost in the noise from a big picture when discussing global temperature records on an annual basis.

July 22, 2015 6:34 am

I lived in Minneapolis the summer Pinatubo erupted. I remember there was really only a couple of totally sunny days that summer and the strange thing was that a lot of people’s tomatoes didn’t ripen that year. The next summer was back to normal.

Jim G1
July 22, 2015 6:51 am

We have beds of bentonite in WY that are 14 feet thick. This is burried and compressed volcanic ash from major Yellowstone eruptions. Once one visits one of these mines it becomes more apparent what the capacity of a true super volcano is to change the climate. Of course, none of these has occured post 1800. I’m just saying, keep it in mind when discussing climate and volcanism.

July 22, 2015 7:21 am

Hi Willis,
Thanks for bringing this up, but I do have a couple questions.
1) In your figure where you stack the various eruptions, you set the temperature for the year in which the eruption happened as “0”. This would assume that the volcano has no effect on temperature in the year of the eruption. Is this really a fair assumption? I’m especially thinking about eruptions which occur early in the year. Would it maybe be better to set the year before the eruption to zero?
2) You state “…particularly given the short lifespan of the stratospheric aerosols, as shown in Figure 2”. Given the short lifespan, is using the average temperature over the course of an entire year too long? Maybe that averaging is masking some of the (hypothetical) decrease in temperature. On the other hand, maybe a shorter averaging period (such as monthly) would just introduce too much noise.

Reply to  Jimmy
July 22, 2015 12:48 pm

1) If that was the case, year 0 would be the bottom, lower than both the year before and after, such as the 1832 line. However, since we don’t have a clear indication of that. However, without a consistent pattern, I would not think that a different baseline would change the conclusion
2) Yes, using the average over a year is too long for volcanos, and that is the entire point. This article is a rebuttal to claims that volcanos have a significant effect on long term global temperatures. Obviously they do not. You could almost certainly see the “year without a summer” on a monthly or weekly average, but it fades into the noise on long term scales.

Reply to  benofhouston
July 22, 2015 3:43 pm

Actually it appears there is only one case from the graph where the year before was not higher so it could change the conclusion!
And using the average over a year is a big problem because in some cases the eruption occurred at the end of the year, in others at the start. And there may be cases where there were multiple eruptions months apart.
Repeating the exercise using the yearly average starting from the MONTH the eruption occurred would be best (but multiple eruptions months apart is still an issue).

Reply to  benofhouston
July 24, 2015 10:23 am

Hi Benofhouston,
In reply to my question about whether using the year of the eruption as baseline, you stated “If that was the case, year 0 would be the bottom, lower than both the year before and after…” I don’t think that would necessarily be the case for a couple of possible reasons: 1) Any cooldown in the year of the eruption could be masked by averaging it with the pre-eruption “warmer” temperatures (As a thought experiment, imagine a hypothetical situation where an eruption on July 1 immediately lowered temperatures by 0.5 deg for exactly 18 months. The yearly average for the year of the eruption would only be down by 0.25 deg, while the year after the eruption would be down by 0.5 deg; year 0 would not be the lowest). 2) We don’t know what kind of lag there might be between the eruption and the (presumed) global climate signal. 3) There’s still the background of natural, non-volcanic variability, which I think Willis has presented a compelling argument as being able to pretty severely mask any volcanic signal that might exist.
I should explain that part of what made me ask the question in the first place was that I noticed that for almost every eruption (1963, I think, being the exception), year -1 was warmer than year 0 in Willis’ figure, which indicates at least the possibility of a climate effect in the year of the eruption.
From Willis “So many rings in the circus … so little time …”
I must thank you again for taking the time that you do to jump into circus rings such as this.

July 22, 2015 7:24 am

In case any one is wondering why volcanoes can be so effective , but only in the direction that suits ‘the cause ‘ the answer is that it is all part of the ‘magic of CO2’ that means cold is proof ,warmth is proof , rain is proof , draught is proof etc of CAGW , although to date ‘rains of frogs ‘ have not be claimed to be ‘proof’ it is only a question of time.

July 22, 2015 8:18 am

Willis when it comes to volcanic effects versus the climate your views are in the distinct minority.
This article is good but it needs to emphasize the prolonged minimum solar /volcanic climate connection( which it does not mention ), and other prolonged minimum solar climate connections such as an increase in galactic cosmic rays more clouds, a more meridional atmospheric circulation due to ozone distribution/concentration changes (which it does not do ) which all lead to cooler temperatures and more extremes .
In addition they do not factor the relative strength of the earth’s magnetic field.
When this is added to the context of this article I think one has a comprehensive explanation as to how the start of the Little Ice Age following the Medieval Warm Period may have taken place and how like then (around 1275 AD) is similar to today with perhaps a similar result taken place going forward from this point in time.

I want to add the Wolf Solar Minimum went from 1280-1350 AD ,followed by the Sporer Minimum from 1450-1550 AD.
This Wolf Minimum corresponding to the onset of the Little Ice Age.
John Casey the head of the Space and Science Center, has shown through the data a prolonged minimum solar event/major volcanic eruption correlation.
Today, I say again is very similar to 1275 AD. If prolonged minimum solar conditions become entrenched (similar to the Wolf Minimum) accompanied by Major Volcanic Activity I say a Little Ice Age will once again be in the making.
Milankovitch Cycles still favoring cold N.H. summers if not more so then during the last Little Ice Age , while the Geo Magnetic Field is weaker in contrast to the last Little Ice Age.
I would not be surprised if the next Little Ice Age comes about if the prolonged solar minimum expectations are realized in full.

Once my low average solar parameters are attained we will see if this line of reasoning on the climate going forward is correct. I think it will be and that is the danger because mainstream keeps pushing global warming.

July 22, 2015 8:22 am

Here is the data and the real story showing volcanic /climate connections. It is quite clear and has the data to back it up with.
To further argue this point is a waste of time.

July 22, 2015 8:27 am

Willis say below which I say you are 100% wrong and all data sources other then yours show that what you present is false.
I know that this is difficult to accept after years of hearing how volcanoes strongly affect the climate, but here’s what I say is happening. When the stratospheric aerosols cut down the sun slightly, the tropical surface cools slightly. Because the tropical surface is cooler, the cumulus clouds form later in the day, allowing in more sun. So the weaker sun is compensated for by the longer time that it is striking the surface, and as a result there is very little change in the global average temperature.
In this manner, despite even the size of the 1815 Tambora eruption, and despite the fact that local areas showed cooling after Tambora, the stratospheric aerosols from this huge eruption had little effect on the global average temperature. More stratospheric aerosols are simply balanced out by less tropospheric clouds, and the beat goes on

July 22, 2015 8:35 am

>>Ian Wilson July 22, 2015 at 5:29 am
Only one major problem with Willis’ methodology. What if major volcanic eruptions are a symptom of extended cooling periods. This would mean that each large volcanic eruption in the tropics (or cluster of eruptions) would be preceded by an extended period of global cooling.(say five, ten or even fifteen years).
What Willis should do is normalize his curves in figure 3 to temperatures five (ten or even fifteen) years prior to the eruption rather than the time of eruption.<<
No. Willis is showing there is no correlation between eruptions and lower temp. Barring the observation about reduced temp. ranges post eruption that would seem to be the case. Your observation suggests that dropping temps and volcanic activity are related to something else. Others have suggested that volcanic activity increases during periods of low solar activity. Can willis' data be plotted against the correspomding solar cycles?

July 22, 2015 8:35 am

The human mind is pre-set to look for patterns as a way to simplify the flood of data it encounters. Even if a perceived pattern leads to logical fallacies (‘post hoc ergo propter hoc’, the fallacy of accident, false cause, etc.), if it *seems* to show a correlation once, we tend to accept a coincidence as a connection and use it for future generalizations without subsequent re-examination.
When a coincidental relationship fails to repeat, we find it more convenient to add caveats, codicils, and conditions than to entertain the idea that we may have been wrong on the first guess.
This is how superstition, mythology, and the belief in miracles and magic are born.

July 22, 2015 10:38 am

I agree with you Willis! Good post!

July 22, 2015 11:16 am

Deep oceans and volcanoes have something new in common. They both have great potential for excuses and with limited data reliability for global application.

July 22, 2015 11:23 am

Page keeps returning to the ad forcing me to scroll back to where I was before. Unaccepable.

Reply to  jst1
July 22, 2015 12:24 pm

I use Chrome with Ad Block Plus extension. No ads, just the ‘about these ads’ link at the top.

July 22, 2015 12:18 pm

The volcanic /climate connection may be short lived but it is real .

July 22, 2015 12:40 pm

TABLE 3. Effects of Large Explosive Volcanic Eruptions on Weather and Climate
Effect Mechanism Begins Duration
Reduction of diurnal cycle blockage of shortwave and emission of longwave
radiation immediately 1–4 days
Reduced tropical precipitation blockage of shortwave radiation, reduced evaporation 1–3 months 3–6 months
Summer cooling of NH tropics and subtropics blockage of shortwave radiation 1–3 months 1–2 years
Stratospheric warming stratospheric absorption of shortwave and longwave
radiation 1–3 months 1–2 years
Winter warming of NH continents stratospheric absorption of shortwave and longwave
radiation, dynamics 1 year one or two winters
Global cooling blockage of shortwave radiation immediately 1–3 years
Global cooling from multiple eruptions blockage of shortwave radiation immediately 10–100 years
Ozone depletion, enhanced UV dilution, heterogeneous chemistry on aerosols 1 day 1–2 years

July 22, 2015 1:29 pm

Willis – you are obviously aware of some fairy tales about volcanoes. The biggest fairy tale of all is that volcanic eruptions are followed by an imaginary “volcanic cooling.” It simply does not exist as I proved in my book “What Warming?” in 2010 (see pp. 17-21). Any and all alleged volcanic “coolings” identified on global temperature graphs are simply misidentified La Nina valleys. Comes from their neglect and ignorance of the fact that all global temperature curves are a concatenation of the two ENSO phases. Best known is the “cooling” that follows Pinatubo. Roy Spencer insist on marking this 1993/94 La Nina valley as “volcanic cooling” on his monthly El Nino chart despite my having explained to him that he is wrong.

July 22, 2015 1:46 pm

“They cannot be identified, either visually or by any other method, in the global temperature records”
Right, with your eyes closed it probably is,

Reply to  lgl
July 23, 2015 3:20 am

All your data seems to show is that, at best, without historical knowledge of which years were ‘eruption heavy’ it would be impossible to identify them.
Also it seems that the climate already knew about 1809/15 and 32 sometime in advance and so did some pre-emptive cooling. Warming in the case of 1832!

Reply to  3x2
July 23, 2015 6:08 am

Missing word there, sorry, “…it probably is difficult”
Like I said earlier, there are also ENSO, AO/NAO, PDO/NPI …
Here is adding an ENSO recon from KNMI. (Note the BEST coverage in 1800 is only eastern north america, europe and india as far as I can see, so the global impact was perhaps around the half of this)

Reply to  Willis Eschenbach
July 23, 2015 12:38 pm

No, the scaled ENSO minus the BEST record shows that huge drops in forcing occurred.

Reply to  Willis Eschenbach
July 23, 2015 12:55 pm

… and the obvious explanation is the volcanoes.

July 22, 2015 3:10 pm

Every major volcanic eruption has been documented with a degree of global cooling..
The nonsense about the lack of a major volcanic eruption not producing a global cooling effect to some degree is just that, nonsense. Table 3 from the above detailed volcanic study shows the clear effects a major volcanic eruption will have on the atmosphere and has overwhelming support other then the few that have posted their counter assertions here which are 100% false.

Reply to  Salvatore Del Prete
July 22, 2015 8:00 pm

Willis did not deny that volcano-injected particles decreased solar radiation to the surface, which is the subject of your reference.
He suggests that decreased solar radiation is compensated by fewer tropical clouds and thus lower cloud albedo.

Reply to  donb
July 23, 2015 7:16 am

And his conclusions are wrong in the short run as table 3 clearly shows from the study I sent in my above post at 3:10pm

A Crooks
July 22, 2015 4:18 pm

As I geologist what I find interesting is that it is almost impossible to spot the KT boundary (with dinosaur extinction) without resorting to Iridium geochemistry. There appears to have been such a small perpetuation of the sedimentary record that you cant spot it – which implies that global climate was not as greatly affected as we are expected to believe. I don’t expect volcanoes would have a bigger effect.

Reply to  A Crooks
July 23, 2015 9:32 am

@A Crooks
July 22, 2015 at 4:18 pm
“As I geologist what I find interesting is that it is almost impossible to spot the KT boundary (with dinosaur extinction) without resorting to Iridium geochemistry”.
I assume you’ve read Richard Muller’s Book “Nemesis – the death star”, in which the Alvarez project to prove the collision cause of the Dinosaur extinctions is described.
I’m frustrated by my inability to find any follow up on the Alvarezes’ tentative explanation of a dwarf twin star to the sun with a periodicity of 26 million years as the motor behind such collisions (after a projectile travel period of 4 million years to reach the inner planets).
Have other Iridium layers coinciding with major extinctions been found, and do any of them support this cycle?

July 22, 2015 7:53 pm

Large nuclear bomb tests made in the late-50s and 60s injected radioactive particles into the lower stratosphere that were wonderful tracers of how such injected particles evolved. This could be analogous to volcano-injected particles and aerosols. The NRC supported collection of air samples via high flying jets to study how such particles moved and dispersed. Injections in the Pacific at low to mid latitudes were found to circle eastward around the Earth a few times while gradually widening. It required some time for the particles to cross the equator.
This might indicate that after a large volcano, any cooling would be largest in a latitude band, and that a few years might be required for the effect to disperse worldwide. Of course, these bomb particles may have been removed from the troposphere by rain rather quickly compared to aerosols.
It might be interesting to examine temperature records in the same latitude band as these large volcano eruptions.

July 22, 2015 10:13 pm

Consider when there is a full solar eclipse, the temperatures dramatically drop for a few minutes. Ash/Dust in the upper atmosphere from volcanoes does the same, but not for years and years. And there is really nothing we can do about it. If Mt.Vesuvius creates a Plinian eruption like in AD 79, this would cause a lot of dust but it was preceded by a bad earthquake. Same as the Thera eruption. (Santorini in 1300 BC) It was massive and records of it are recorded in Northern Europe and China, and in Eqypt. Bit difficult to put its affect in a time line. But at this time there was a swarm of earthquakes, long droughts and more volcanic eruptions. And of course the displaced sea peoples and the Jewish exodus from Egypt. Records in Egypt about a long drought, causing people to eat children, is terrible really. Thank goodness we have the Red Crescent and Red Cross nowadays.

July 23, 2015 7:49 am

lgl- your diagram makes our points. Look at table 3 if you get a chance it is telling and an excellent summary of volcanic effects and where they might be and duration of time.

July 23, 2015 10:07 am

Willis: Temperature data is often noisy enough to obscure the signal from volcanos. This problem gets worse the further back in time (fewer stations) you go. If you go to WoodForTrees.org, you can plot monthly data and averages of N months of data to smooth out noise. If you gradually increase the N, El Chichon and Pinatubo become very clear with N is 30. 30 Months appears to be enough to remove most of the noise from El Nino events. With a 30 month average, the 1997/8 El Nino event has disappeared, but the cooling from El Chicon and Pinatubo remain with an amplitude of almost 0.5 degC despite the averaging.
Can I detect Tambora using this approach? Not for sure. 1808 and 1815 (Tambora) are one cold period of about a decade. 1832 and 1835, possible. 1883, probably. 1903 probably, but stayed cold for rest of decade. 1915, biggest cooling signal in 20th century with no candidate volcano. (Novarupta, 1912 was followed by 3 warm years, not cooling.) Spotting the volcano is much easier this way.

Reply to  Willis Eschenbach
July 23, 2015 2:27 pm

Willis , did you look at table 3? If not you should.

Reply to  Willis Eschenbach
July 23, 2015 3:58 pm

Willis: Thanks for the reply. Sorry I wasn’t particularly coherent earlier. Perhaps this link to WFT will help:
I’m working with BEST data; Box 1) From (time) = 1900; Box 2) To (time to) = 2010; Box 3) Mean (sample) = N = 31. If I understand correctly, Box 3) means that the monthly temperature for January 2000 is average with the 15 months before and the 15 months afterwards and reported above January 2000. The same procedure creates about 12*111 = 1332 individual datapoint that are plotted for this time period. If you want to view the raw monthly data, change to Mean (sample) = 1 or put nothing in Box 3. (Putting compress = 12 in Box 3 may produce the annual averages you used in your post. Add series can overlay raw and smoothed data.)
If one successively tries values of N=7, 13 (somewhat like annual data, but more data points), 19, 25, 31, and 37 in Box 3, a signal for Pinatubo first stands out from the noise with N = 19 and a cooling of 0.5 degC. Increasing N above 19 smooths out some of the cooling and removes some of the noise.
Now let’s look for El Chichon in 1982. It is difficult to see because the second strongest El Nino since 1950 occurred in early 1983. (See link to MEI index.) The peaks for the 1983 and 1998 El Ninos are still visible with N=19 and N=25, but not with N=31. At this point, I become convinced I can “spot the 1982 volcano” and I can’t see a clear signal for the 1983 and 1998 El Ninos.
If you look at Paul_K’s Blackboard analysis of Pinatubo, he thinks that maximum cooling occurred about 18 months after the eruption. With N=31, the datapoint for 18 months after the eruption is the average of months 3-34 after the eruption. If Paul_K is correct, I have averaged all of the months of strongest cooling with some months of modest cooling, but no months when Pinatubo wasn’t having some effect.
So empirically and theoretically, N=31 months appears to do a good job of preserving the signal from strong volcanos and removing some of the high-frequency noise. And we should expect to see maximum cooling with this much smoothing 1-2 years after the actual eruption date, not in the same year as the eruption. (There are certainly better ways to smooth over 31 months, but they require more effort on my part.)
I’ll leave it up to you to see if you can “Spot the Volcano” elsewhere in the BEST record with Box 3 = 31 (or whatever value that you think is most appropriate). I will note for the record that the strongest cooling (0.5 degC) with Box 3 = 31 was around 1915 and I can’t associate that cooling with a major volcano. It appears to be a false positive. The strong warming about 1913 is where one would expect to see cooling from Novarupta/Katmai in southern Alaska. (Although this was the biggest eruption since 1900, volcanos at high latitudes are supposed to be less efficient at cooling the planet and this one was very far from the Antarctic ice core you used to select volcanos.) You may conclude that most major volcanos have produced about 0.5 degC or more cooling (smeared out by averaging), but my method still gives some false positives and false negatives. IMO, you couldn’t “spot the volcano” without this type of smoothing simply because the noise is too strong.

Reply to  Willis Eschenbach
July 24, 2015 2:37 am

Willis: Thanks for a second reply and the plot. You wrote: “I’m sure that you can see the problem … the temperatures started dropping in all three cases well before the eruption … which, unless we are into reverse causality, means that those temperature drops were not caused by the eruptions.
When you average in 15 months from before the month of the eruption – which should be random noise – and 15 months after the month of the eruption – which should be cooling plus noise – I expect to see cooling on the date of the eruption. Above I said: “And we should expect to see maximum cooling with this much smoothing 1-2 years after the actual eruption date, not in the same year as the eruption.” So I would mark Pinatubo and El Chichon with a band 1-2 years after the eruption date and expect to see a minimum temperature caused by the volcano around that period. So I don’t think this plot demonstrates “reverse causality”. It looks about right to me.
The boxcar filter was the only tool available at WFT, so I didn’t have a choice. I don’t have any personal experience with smoothing. What filter would you recommend for this situation? Every filter introduces some distortion, but it is common for signals to be obscured by noise. A citizen scientist’s job to extract those signals when possible without introducing artifacts. (Some climate scientists seem to have other agendas.) Ideally, one would take Paul_K’s best-fit curve for temperature vs time and put that signal through the filter to establish how much distortion it causes and whether it introduces any artifacts. The filter I used will certainly widen the period of volcanic cooling and reduce its depth. If one doesn’t want this kind of distortion, can you remove high frequency noise after a Fourier transform and transform back into the time domain?
If you plot the raw monthly data and smoothed data on the same plot (or look at Paul_K’s modeled fit to monthly data), it is obvious that the noise is comparable to the signal we expect to observe. In that case, we have no possibility of “Spotting the Volcano” without processing the signal. So our inability to “Spot the Volcano” in noisy monthly data or yearly averages (which recompressing an event into 4-5 still noisy data points) doesn’t tell us that a cooling of about 0.5 degC doesn’t follow most eruptions.
Should the existence of a modest number of false positives and false negatives in a smoothed record be a concern? Not necessarily. All major volcanos are not created equal (especially in latitude) and we have other forced and unforced variability to contend with. If half of the cooling events with an amplitude of at lest 0.4 degK were false positives and a signal was detected within +/-1 year of the expected minimum for 80% of large volcanos, this would be a situation unlikely to occur by chance. It makes me uncomfortable to not see an unambiguous signal from the biggest volcano, Tambora, but it took place during a period with the poorest temperature data and seven years after another eruption. I suppose someone has modeled what was expected to happen during this period, but most modelers (unlike Paul_K) tend to use high climate sensitivity and high sensitivity to aerosols. So the inability to see their predictions of a 1-2 degK cooling following Tambora doesn’t prove anything to me without first seeing what reasonable alternative models (like Paul_K’s) hindcast.
FWIW, I suspect my crude smoothing is resolving a roughly 0.5 degK cooling event following Pinatubo, El Chichon, and other major volcanos. It is far short of publishable proof.

Reply to  Willis Eschenbach
July 26, 2015 1:55 pm

Willis: Thanks for the reminder of Brigg’s comments on smoothing. His main objection is to using smoothed data as input into another analysis – for example, looking for correlation. I haven’t committed that sin. And I am somewhat aware of the distortion smoothing can introduce.
When I made my plots at WFT, I overlaid the raw and smoothed data. I certainly knew what before and after looked like.
I used EXCEL to create a model signal, add noise and then smooth it with my crude boxcar filter. The signal was a sine curve: sin(PI()*t/60). t runs from 1 to 1000 months. The lower half of the sine curve was a model for 8 volcanic cooling events lasting 60 months with a maximum cooling of 1 vertical unit (which I will call degC).
I used 2*Rand()-1 to create a series of random numbers from -1 to +1, which I multiplied by an adjustable constant (currently 1) to create noise. Then I created autocorrelated noise from the simple noise by adding noise for month t to an adjustable percentage (currently 90%) of the correlated noise for month t-1. Then I created a signal plus noise and a signal plus autocorrelated noise to display with and without smoothing.
With 60 monthly data points to characterize a trough, signal with almost any amount of uncorrelated noise wasn’t very challenging. (Annual data could be more challenging.) Smoothing mades things a little clearer and reduced the apparent amplitude of the sine curve by 25%.
Auto-correlated noise is far more challenging – the sine signal was essentially invisible. The smoothing pulled 8 minima from data with no apparent pattern. However, one maximum was missing and a second was ambiguous and could have been missed. The amplitude of the troughs varied from -0.5 to -1.5. One maximum was at 2.5! The smoothed signal was a very distorted version of the original sine curve function.
If you wanted to invest the time, you could probably convince yourself that smoothing (hopefully with a more sophisticated filter) can help you recover a known signal from autocorrelated noise – albeit imperfectly. The same technique might help pull a real – albeit imperfect – volcanic signal from the temperature record and possibly explain why noise might still render some signals weak or undetectable. Enough smoothing to suppress the 1998 and 1983 El Ninos is important. For some eruptions, the smoothed curve is still likely to be ambiguous.

July 24, 2015 6:51 am

Willis is consistent in one area he always approaches the climate as a single cause and effect when the reality is there are multiple forcings going on at the same time which obscures the climate /item exerting a given force on the climate at a given point of time.
What could one say accept that is not how it works.

Reply to  Willis Eschenbach
July 24, 2015 11:38 am

” You may wonder why I so rarely reply to you. It is because you are consistently either too stupid or too deliberately underhanded to quote my words, despite my repeated requests that you do so.”

False dichotomy.
There might be a third option, namely that he’s getting under your skin for cause.
A wise man would ignore him, so I guess that option is off the table.

Reply to  Salvatore Del Prete
July 24, 2015 1:04 pm

Salvatore writes: “Willis is consistent in one area he always approaches the climate as a single cause and effect when the reality is there are multiple forcings going on at the same time which obscures the climate /item exerting a given force on the climate at a given point of time. What could one say [except] that is not how it works?”
So what? The IPCC has the same difficulty with respect to GHGs and climate change. Volcanos, at least, are the biggest known forcing, though difficult to understand due to their transient nature. To further their political objectives, the IPCC works only with climate models with high climate sensitivity to forcing and high sensitivity to aerosols. Those models out to produce cooling signals which ought to stand out more clearly from the noise in the temperature record.* Willis has good reasons to be skeptical, especially with all of the hype about the “Year without a Summer”. For Pinatubo and El Chichon, however, we aren’t dealing with an assumed forcing estimated from the amount of aerosol estimated to have been ejected into the stratosphere, we have measurements of the actual forcing (change in SWR). There is less reason for skepticism here.
And during Pinatubo, we have satellite measurements of incoming and outgoing radiation. After climate scientists failed to create a model (mixed layer size, flux into the deeper ocean, climate sensitivity) that was consistent with all of this data, Paul_K did so at the Blackboard. That model said that Pinatubo produced a maximum cooling of 0.6 degK 18 months after the eruption. However, changing the parameters of that model produces other outcomes that are still consistent with the noisy data. It would be very interesting to see if other major volcanos did produce cooling of about 0.5 degC. Willis keeps telling us that volcanos don’t produce any detectable cooling, but he hasn’t processed the data in a way that is capable of “spotting volcanic cooling” of this size. As with the Hockey Team and the MWP, the question is whether Willis will process the data in a way that optimally and fairly reflects the magnitude of temperature change given the noisy data. (My crude methodology isn’t completely convincing.)
*I made a quick search to see just how much cooling models actually predict after Tambora. Gavin’s name is on a modeling paper, but it didn’t disclose a maximum hindcast global cooling (:)). They used a Tambora that was only 2X and 3X the size of Pinatubo, elsewhere you can find 6X. Zorita has a very crude study whose output shows -0.75 degK after both 1808 and 1815. The CMIP5 project made hindcasts for the last millennium, but a review made no mention of Tambora – the biggest transient forcing during the millennium. Following the usual slimy methodology, that project allowed the modelers to choose their preferred forcing input, the biggest of which was only 2X Pinatubo. (The rest are overlaid and can’t be seen.) As usual, Willis has pick a weak spot of the consensus doesn’t appear to want to confront.

July 24, 2015 11:46 am

Willis , the simple truth is your view on the climate and my view are the opposite.
I simply disagree with many of your conclusions on the climate 100% ,nothing more ,nothing less.
Time will show which one of us is more correct. take care

Reply to  Willis Eschenbach
July 25, 2015 11:07 am

Thanks. Not personal at all you are a brilliant writer and good communicator and I wish we did agree more.

Sturgis Hooper
July 24, 2015 12:01 pm

FWIW, maybe not much, my opinion is that large, tropical volcanic eruptions cool the globe or a hemisphere for a few years at most, ie they affect the weather. Big eruptions at higher latitude might actually have a slight net warming effect. The mix of ash, SO2 and other ejecta matters. There are of course also more pronounced local to regional effects.
The rare supervolcano eruptions may have a more lasting effect, influencing climate, but within a fairly brief period, conditions return to whatever state normal functioning of the system dictates.
However, even flurries of regular but large volcanic eruptions (up to VEI-7) do not affect climate, as imagined by Mann, et al, to try to explain away the LIA, the better to get rid of the MWP. Nor can the two decade-long plateau in recent warming be hand waved away by volcanism not in evidence.

Reply to  Sturgis Hooper
July 24, 2015 12:06 pm

Sturgis ,look at table 3 of this report. I think they have it about right.

Sturgis Hooper
Reply to  Salvatore Del Prete
July 24, 2015 1:06 pm

I neglected to mention the differing effect with season.
I’m dubious of an interdecadal, climatic effect of volcanic eruptions, even in the LIA. I’d put it the other way around. The LIA was already frosty, with many regions at the margin of agriculture. Thus the effect of Tambora, which occurred during the Dalton Minimum, the last severe blast of the LIA, was magnified relative to say, Krakatoa (adjusted for magnitude, of course).

July 29, 2015 8:12 pm

Reblogged this on Climate Collections and commented:
Excellent discussion on volcanic aerosols with outstanding Weatherbell graphic added.

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