2010-08-21 07:18:09Basic rebuttal 54: Volcanoes emit more CO2 than humans
Andy S

skucea@telus...
66.183.162.8

Your comments, please:

 =====================

 The rocky outer shells of the Earth--the crust and mantle--contain a huge quantity  of carbon, far more than is found in the atmosphere or oceans. As an important part of the global carbon cycle, some of this carbon is released from the rocks in the form of carbon dioxide, through two main pathways. 

  • Subaerial volcanoes discharge magma, fluids and gasses from vents that are above sea-level. Most volcanoes of this type are found at the convergent boundaries of the Earth's tectonic plates where the plates are coming together. The largest string of such zones forms the Pacific "Ring of Fire".The best estimates of the amount CO2 being released at this kind of volcano range from 65 to 242 million tonnes per year (Morner and Etiope (2002) although Kerrick (2001) reported a rather tighter range of 88 to 110 mT/yr.
  • Submarine volcanoes are mostly located along tectonic plate boundaries where the the plates are moving apart--the Mid Ocean Ridge (MOR) systems--and at which new oceanic crust is constantly being formed. About three-quarters of the magma that is extruded on the planet is comes form these zones. Although the quantities of magma are very large, relatively small amounts of CO2 are released to the atmosphere compared to the subaerial volcanoes, because much of the released carbon is immediately incorporated into carbonate minerals at the sites of the hydothermal vents along the MORs. Estimates of the amounts of CO2 emitted to the atmosphere by Morner and Etiope range from 66 to 77 mT/yr. Kerrick's article notes that the consumption of CO2 at MOR's may even exceed the emissions, making these zones net sinks for CO2. 
Counter claims that volcanoes produce vastly greater amounts of CO2 than these estimates are not supported by any papers published by the scientists who specialize in the study of volcanoes.
 
The burning of fossil fuels worldwide results in the emission into the atmosphere of approximately 30 billion tonnes of carbon dioxide per year, according to the International Energy Agency, the IEA. These estimates are much more accurate than the estimates of volcanic emissions and are about one hundred times smaller. Our understanding of volcanic discharges would have to be shown to be very mistaken before volcanic CO2 discharges could be considered anything but a bit player in contributing to the recent changes observed in the concentration of CO2 in the Earth's atmosphere.
 
None of this is to say that volcanic CO2 emissions do not play an important role in influencing the composition of the atmosphere and the climate over geological time scales. The exchange of carbon between rock and the atmosphere is balanced by consumption of  ocean crust--and the organic carbon and carbonate minerals rafted upon it--at the convergent plate boundaries.  Even small changes in the level of global volcanic activity could, over hundreds of thousands of years or more, upset this balance and materially change the concentration of CO2 inn the atmosphere. But there's no room for reasonable doubt that the changes observed in CO2 concentrations over the past 150 years have been the result of human activities since the industrial revolution, not any sudden coincidental and unrecorded increase in volcanic activity.
 
Volcanoes can--and do--influence the global climate over time periods of a few years but this is achieved through the injection of ash into the high reaches of the atmosphere during the very large volcanic eruptions that sporadically each century. But that's another story...
 
Further reading on CO2 and volcanoes:  Terry Gerlach in Earth Magazine USGS 

  ===========================

This is fairly long rebuttal and, perhaps, not sufficiently Basic from a technical point of view. What I have tried to do is to avoid or explain jargon and to keep on the topic. In many ways, this is less basic than John's Intermediate rebuttal. There is a link in John's rebuttal to Tamino's site that no longer works, I think that Tamino is in the process of moving his blog, which may explain this but I couldn't find the correct link, anyway. 

There's an overlap here with a few other rebuttals that concern volcano-climate interactions and I'll try to do those rebuttals in a similar style, subject to feedback from you all on this one. I'll link between them, also.

 To provide some recent context, I could add something about CO2 emission estimates from the recent Icelandic volcano (the one whose name I can't spell!) but maybe this piece is too long and complicated already.  

PS I have used "gasses" rather than "gases": perhaps, for the sake of consistency, John should lay down the law on how we should spell words: American, British or even Strine. ;-)

 

2010-08-21 07:53:53
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Excellent treatment, fairly comprehensive while still reasonably concise.

I agree with you Andy that this might actually stand as an intermediate rebuttal.

This part bothers me a bit:

"The burning of fossil fuels worldwide results in the emission into the atmosphere of approximately 30 billion tonnes of carbon dioxide per year, according to the International Energy Agency, the IEA. These estimates are much more accurate than the estimates of volcanic emissions and are about one hundred times smaller. Our understanding of volcanic discharges would have to be shown to be very mistaken..."

Bold mine to highlight a mental clash.

Just quickly, "...about one hundred times smaller" I think is intended to read "...which are about one hundred times smaller?"  I can see this is meant to convey the orders of magnitude difference in emissions, but you could well emphasize that important factoring matter w/a simple graphic.

Also, what I read from this paragraph (imagining I'm fresh to the subject) this is that while we know with a fair degree of accuracy our C02 emissions via fossil fuel use, we don't actually have a very good handle on volcanic emissions. As opposed our conclusions suffering purely from a mistake, this leads me (again thinking as though I'm new to this) to wonder  whether improved measurement of volcanic emissions might change our perspective. That possible confusion can be nicely cleared up by emphasizing (sorry, redundant) the magnitude difference in emission. Again, a graphic would really help here.

All that said, what a great writeup!

 

2010-08-21 09:23:18Thanks
Andy S

skucea@telus...
66.183.162.8

Thanks Doug.

If I confused you, I'll certainly confuse my target audience; so yes, I'll certainly rewrite that sentence. 

A graphic would be helpful, I agree. I think this will call for an area chart since the comparative ranges of volcanoes and the IEA numbers are so large and a ( linear) bar chart wouldn't work. 

2010-08-21 09:37:42Pick a Language and Stick with it!
MattJ
Matthew Johnson
mej1960@yahoo...
64.105.35.191

You are using the British spelling of 'tonne', but the American sense of the word 'billion'!

 

NB: I don't believe Wiktionary when it says the usage (of 'billion to mean 10^12) is obsolete even in British English.

 

Finally, I agree that this is intermediate level, not basic. To make it basic, at the very least, we would have to replace fancy words like 'emission' and 'discharge' with more common words like 'release'.

2010-08-21 11:07:53
Andy S

skucea@telus...
66.183.162.8

Matt: I added 10^9 after billion, just to be sure but it has been a long time since I have seen billion used as 10^12 (and I'm a long-in-the-tooth Brit).

"Tonnes"  are metric tons, even in American spelling, but in checking this I realized I had abbreviated million tonnes incorrectly as mT, whereas it should have been Mt, so thanks for for the nudge. I agree that this is not basic enough but the pedant in me doesn't want to oversimplify it.

 

Doug: I reworded that sentence and added a graphic.

Perhaps the basic version should just be the graphic and a couple of lines saying where the numbers came from.

The latest iteration follows... 

 =====================

The rocky outer shells of the Earth--the crust and mantle--contain a huge quantity of carbon, far more than is found in the atmosphere or oceans. As an important part of the global carbon cycle, some of this carbon is released from the rocks in the form of carbon dioxide, through two main pathways. 

  • Subaerial volcanoes discharge magma, fluids and gasses from vents that are above sea-level. Most volcanoes of this type are found at the convergent boundaries of the Earth's tectonic plates where the plates are coming together. The largest string of such zones forms the Pacific "Ring of Fire".The best estimates of the amount CO2 being released at this kind of volcano range from 65 to 242 million tonnes per year (Morner and Etiope (2002) although Kerrick (2001) reported a rather tighter range of 88 to 110 Mt/yr.
  • Submarine volcanoes are mostly located along tectonic plate boundaries where the the plates are moving apart--the Mid Ocean Ridge (MOR) systems--and at which new oceanic crust is constantly being formed. About three-quarters of the magma that is extruded on the planet is comes form these zones. Although the quantities of magma are very large, relatively small amounts of CO2 are released to the atmosphere compared to the subaerial volcanoes, because much of the released carbon is immediately incorporated into carbonate minerals at the sites of the hydothermal vents along the MORs. Estimates of the amounts of CO2 emitted to the atmosphere by Morner and Etiope range from 66 to 77 Mt/yr. Kerrick's article notes that the consumption of CO2 at MOR's may even exceed the emissions, making these zones net sinks for CO2. 
Simply adding these minimum and maximum figures together gives a range of 65 to 319 Mt/yr. Counter claims that volcanoes produce vastly greater amounts of CO2 than these estimates are not supported by any papers published by the scientists who specialize in the study of volcanoes.
 
The burning of fossil fuels worldwide results in the emission into the atmosphere of approximately 30 billion (10^9) tonnes of carbon dioxide per year, according to the International Energy Agency, the IEA. These estimates are much more accurate than the estimates of volcanic emissions and the fossil fuels emissions numbers are about 100 times bigger than the volcanic CO2 fluxes. Our understanding of volcanic discharges would have to be shown to be very mistaken before volcanic CO2 discharges could be considered anything but a bit player in contributing to the recent changes observed in the concentration of CO2 in the Earth's atmosphere.
 
 
 
 
None of this is to say that volcanic CO2 emissions do not play an important role in influencing the composition of the atmosphere and the climate over geological time scales. The exchange of carbon between rock and the atmosphere is balanced by consumption of  ocean crust--and the organic carbon and carbonate minerals rafted upon it--at the convergent plate boundaries.  Even small changes in the level of global volcanic activity could, over hundreds of thousands of years or more, upset this balance and materially change the concentration of CO2 inn the atmosphere. But there's no room for reasonable doubt that the changes observed in CO2 concentrations over the past 150 years have been the result of human activities since the industrial revolution, not any sudden coincidental and unrecorded increase in volcanic activity.
 
Volcanoes can--and do--influence the global climate over time periods of a few years but this is achieved through the injection of ash into the high reaches of the atmosphere during the very large volcanic eruptions that sporadically each century. But that's another story...
 
Further reading on CO2 and volcanoes:  Terry Gerlach in Earth Magazine USGS 

  

 

2010-08-21 13:12:11Love the graphic!
rockytom

rockytom@comcast...
71.228.108.140

Andy S., Great job.

Tom

 

2010-08-21 14:42:34Punchy graphic
doug_bostrom

dbostrom@clearwire...
184.77.83.151

The clouds tell a thousand words!

I'm in a possible minority of one in thinking John's original arguments to mostly be in reach of high school graduates, those who did not sleep through class. I'm also loathe to assume average people don't grasp the meaning of such words as "emissions." All the same ultimate simplicity is the mission here so perhaps this could be used as an intermediate argument, with a simplified version for basic.

How about dumping the carbon cycle, lumping together terrestrial and marine igneous emissions, keeping the emphasis on relative sizes per the graphic?

2010-08-21 16:16:15Lovely - but...
gpwayne
Graham Wayne
graham@gpwayne...
217.44.86.17
Hi Andy - your rebuttal is excellent, but I have to agree with others that it's intermediate...
2010-08-21 16:24:40Use quotes from USGS and cloud graphic alone.
villabolo

villabolo@yahoo...
76.93.65.8
In my opinion, Andy's rebuttal should be nothing more than a direct quotation from the USGS source he cited coupled with the cloud graphic. The simpler the answer is, the easier it will be for people to remember. This answer can be that simple without ommiting any information. 

I don't even believe we need an intermediate level for this rebuttal, or even an advanced level. 

I would also stress the point with a simple taunt of a question directed at Deniers like, "How do they know that volcanoes emit more CO2 than Humans? What proof of any kind have they ever presented?"

 

2010-08-22 06:13:03Making it more basic
Andy S

skucea@telus...
66.183.162.8

I'm listening! Thanks, everyone.

I'll save the previous version as a basis for updating the intermediate argument, once we get around to doing those. I have shorttened and simplified the text and added another graph.

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

 

The rocky outer shells of the Earth--the crust and mantle--contain a huge quantity of carbon, far more than scientists estimate is present in the atmosphere or oceans. As an important part of the global carbon cycle, some of this carbon is slowly released from the rocks in the form of carbon dioxide, through vents at volcanoes and hot springs.  Published reviews of the scientific literature by (Moerner and Etiope (2002) and Kerrick (2001) report a minimum-maximum range of emission of 65 to 319 million tonnes of CO2 per year. Counter claims that volcanoes, especially submarine volcanoes, produce vastly greater amounts of CO2 than these estimates are not supported by any papers published by the scientists who study volcanoes. 

The burning of fossil fuels results in the emission into the atmosphere of approximately 30 billion tonnes of carbon dioxide per year worldwide, according to the International Energy Agency, the IEA. These fossil fuels emissions numbers are about 100 times bigger than even the maximum estimated volcanic CO2 fluxes. Our understanding of volcanic discharges would have to be shown to be very mistaken before volcanic CO2 discharges could be considered anything but a bit player in contributing to the recent changes observed in the concentration of CO2 in the Earth's atmosphere.
 
 
 
 
Not only would the estimated yearly amounts of CO2 released by volcanoes have to be very wrong, but to explain the twentieth century run-up in CO2 concentrations, it  would also require a dramatic increase in the rate of volcanic activity, for which there is no historical evidence. We can conclude that there is no room for reasonable doubt that the changes observed in CO2 concentrations over the past 150 years have been the result of human activities since the industrial revolution, not any sudden coincidental and unrecorded increase in volcanic activity.
 
 
 
 
 
Volcanoes can--and do--influence the global climate over time periods of a few years but this is achieved through the injection of ash into the high reaches of the atmosphere during the very large volcanic eruptions that occur sporadically each century. But that's another story...
 
Recommended further reading on CO2 and volcanoes can be found here:  Terry Gerlach in Earth Magazine USGS 

  

  

2010-08-22 06:29:03
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Great revision.

"(10^9)" -->"3x10^9)" ?

"...no historical evidence." --> "...no historical or observational evidence." ?

Still getting hung up on:

"These estimates are much more accurate than the estimates of volcanic emissions."

I'm wondering, is that sentence really necessary? Perhaps I've missed some skeptic emphasis on yet another kind of uncertainty.  Anyhow, this  sentence still suggests to me (thinking as a lay reader) that our estimates of volcanic emissions are not good, possibly not good enough to draw conclusions. If this is not some kind of skeptical argument, maybe just drop it, rely on "Fossil fuels emissions numbers are about 100 times bigger than even the maximum estimated volcanic CO2 fluxes." ?

Revisionitis, clause creep:

"Not only would the estimated yearly amounts of CO2 released by volcanoes have to very wrong, but to explain the twentieth century run-up in CO2 concentrations, but it  would require a dramatic increase in the rate of volcanic activity, for which there is no historical evidence." 

2010-08-22 06:32:24Type - a "but" too much
BaerbelW

baerbel-for-350@email...
93.231.136.135

Hi Andy,

in this senctence - below the first graphic, the highlighted "be" is missing and a "but" seems to be too much:

"Not only would the estimated yearly amounts of CO2 released by volcanoes have to be very wrong, but to explain the twentieth century run-up in CO2 concentrations, but it  would require a dramatic increase in the rate of volcanic activity, for which there is no historical evidence."

I'm not even sure if the first "but" is needed. Instead the second half could perhaps be worded like this with an additional "also":

"Not only would the estimated yearly amounts of CO2 released by volcanoes have to be very wrong, but to explain the twentieth century run-up in CO2 concentrations, it would also require a dramatic increase in the rate of volcanic activity, for which there is no historical evidence."

Cheers
Baerbel

2010-08-22 06:50:37
Andy S

skucea@telus...
66.183.162.8

Thanks Doug and Baerbel, I've made the changes above according to your suggestions.  

Doug: the "10^9" was to specify that the billion was a US not an old British billion [10^12] (I added it after a comment by Matt, above). On second thoughts, I think I'll remove it since  it is more confusing than anything. If people think that we need to specify what we mean by billion very time we use it (a lot of people don't know what 10^9 means anyway) then we should do that consistently throughout SkSc. My view is that the US usage is now firmly entrenched.

2010-08-22 06:56:55
doug_bostrom

dbostrom@clearwire...
184.77.83.151
I agree on deleting the exponent, it's likely to trip up the target reader for this.
2010-08-22 07:01:54Oops, forgot the little green detail
doug_bostrom

dbostrom@clearwire...
184.77.83.151
Gets my vote!
2010-08-24 05:38:50Quote the USGS
nealjking

nealjking@gmail...
91.33.120.144

Andy B,

I'm going to agree with villabolo: All you need to do, and all you should do, is quote the USGS. 

All that geology that you trot out in this write-up is overkill, like killing a fly with a steam hammer. 

The way this issue usually comes up in blogs is that someone claims, "I bet one volcano produces more CO2 in one day that all of humanity has done in 200 years!" To which the simple and unanswerable response is, "The USGS states that the average annual CO2 output of volcanoes worldwide is about 1/250 of the human annual output."

 End of story.

2010-08-24 08:14:04Second revision
Andy S

skucea@telus...
66.183.162.8

Neal and Villabolo, thanks, but I disagree. John's one-liner tweets already do what you are advocating. I think that the Basic Rebuttals should go further than simply stating "Skeptical argument X is wrong because authority Y says so". We have to at least go one step further and explain why (in simple, non-technical terms) the skeptical argument is wrong and to try to educate everyone a little on the underlying science. 

When I'm writing a rebuttal, I'm not just responding to the simplified headline, for example "Volcanoes emit more CO2 than humans" but to try to address the underlying argument of the skeptical claim in a bit more depth. Some people coming here, for example, may have just read Ian Plimer's book or read a post on WUWT and would be looking for more than a "not-so" statement. Oversimplifying the skeptical argument to just a few words and then taking just a few words to contradict it could easily look to be a bit of a straw-man approach. We have to persuade people that the science is sound and that the skeptical arguments are flimsy, not just baldly assert it.

Most of the basic rebuttals published so far have been very good, in my opinion. They have been written with an original voice and have often made old arguments new by using fresh metaphors. I have learned a lot by reading them, even though I was, in most cases, already familiar with the more "advanced" rebuttals.

I do agree, however, that this particular rebuttal was too long and complicated. I have trimmed it down to fit onto one page and be less than 300 words by cutting out the second graph and one paragraph.

Further comments would be very welcome. 

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

 

The solid Earth contains a huge quantity of carbon, far more than scientists estimate is present in the atmosphere or oceans. As an important part of the global carbon cycle, some of this carbon is slowly released from the rocks in the form of carbon dioxide, through vents at volcanoes and hot springs.  Published reviews of the scientific literature by Moerner and Etiope (2002) and Kerrick (2001) report a minimum-maximum range of emission of 65 to 319 million tonnes of CO2 per year. Counter claims that volcanoes, especially submarine volcanoes, produce vastly greater amounts of CO2 than these estimates are not supported by any papers published by the scientists who study the subject. 

The burning of fossil fuels results in the emission into the atmosphere of approximately 30 billion tonnes of carbon dioxide per year worldwide, according to the EIA.  The fossil fuels emissions numbers are about 100 times bigger than even the maximum estimated volcanic CO2 fluxes. Our understanding of volcanic discharges would have to be shown to be very mistaken before volcanic CO2 discharges could be considered anything but a bit player in contributing to the recent changes observed in the concentration of CO2 in the Earth's atmosphere.
 
 
 

 
Volcanoes can--and do--influence the global climate over time periods of a few years but this is achieved through the injection of ash into the high reaches of the atmosphere during the very large volcanic eruptions that occur sporadically each century. But that's another story...
 
Recommended further reading on CO2 and volcanoes can be found here:  Terry Gerlach in Earth Magazine USGS 

  

 

2010-08-24 09:12:50Convinced
Michael Searcy

scentofpine@yahoo...
72.91.223.97

You've convinced me.  I was leaning toward the "less is more" approach, but I agree with your reasoning, Andy.  Thumbs up from me.  Love the graphic.  A few minor items.


"The sold Earth"

Um....

 


"published by the scientists who study volcanoes"

 

May want to change "volcanoes" to "these environments" or "these mechanisms".  Just a thought.  A lot of "volcanoes" in that sentence.

 


"according to the International Energy Agency, the IEA"

 

The reference should actually be to the U.S. Energy Information Administration (EIA).  The acronym in the graphic is correct.

2010-08-24 10:10:01
Andy S

skucea@telus...
66.183.162.8

Thanks for the suggestions, Michael. The "sold Earth" was a Freudian slip I made due to last-minute revisionitis (copyright D Bostrom).

The EIA/IEA muddle occurred because I checked the  EIA reference against numbers in the IEA report as well as numbers from the CDIAC and thoroughly confused myself as to what reference I ended up quoting. Thanks for spotting the error.

2010-08-24 18:58:26Billions and Billions... (BHA)
MattJ
Matthew Johnson
mej1960@yahoo...
64.105.35.191
Well, I can't ask you to take my word over that of the Oxford Dictionary;) http://www.oxforddictionaries.com/page/114
2010-08-24 19:03:02Sleeping through High School
MattJ
Matthew Johnson
mej1960@yahoo...
64.105.35.191

Doug-

Well, of course you are right. But the problem is that the target audience we are trying to convince IS the people who slept through high school!

Worse yet, in my home state, high school education was poor enough when I went through it: I distinctly remember one clown who had a temper tantrum and started throwing desks when I told him he was wrong to claim that the moon was a million miles away. But since then, it has only become worse: we are now 48th state in a nation of 50 in education, which places us about as close to bottom as you can get. And they still give us 55 votes in the Electoral College!

For the same reason, I would really, really prefer simpler, more common alternatives to 'subaerial', 'extrude' and 'discharge'. Even those who know these words may feel somewhat put off by them. I would even suggest referring to the word lists on http://en.wiktionary.org/wiki/Wiktionary:Frequency_lists#Top_English_words_lists while writing these articles.

Of course, I would not insist that EVERY word in the article be on one of those lists. But it is still a good guide to let you know when the word is not so common. Notice that none of  'subaerial', 'extrude' and 'discharge' are on the list of 1000 most common words.

2010-08-24 19:58:38on 2nd revision
nealjking

nealjking@gmail...
84.151.29.177

Andy S,

- I like the 2nd revision better: You lost the graph, and it is shorter.

- In general, I'm in favor of explanation over authority. However, keep in mind that we do have the intermediate version which is intended to provide contact with the scientific background (not to mention the advanced version).

- However, when we're talking about the amount of CO2 emitted by volcanoes and humans, this is a measurement. Unless you go into the technique and methodology of the measurements (and why would you?), there isn't a whole lot to explain: the deniers are just making it up, and they can't point to any numbers. They're making you jump through hoops to provide explanation without their even having gone through the effort to make a plausible argument.

- So I still favor shorter, on this one. Migrate the geology to the intermediate version, if it's lacking there.

That said, I do like the graphic: It makes a visual statement that is in-line with the facts: Volcanoes are relatively insignificant.

2010-08-24 20:59:32Good to go in my view
gpwayne
Graham Wayne
graham@gpwayne...
217.44.86.17

Thumbs up from me, Andy. I also agree entirely with this statement: "We have to at least go one step further and explain why (in simple, non-technical terms) the skeptical argument is wrong and to try to educate everyone a little on the underlying science".

My approach has been consistent with this view. I assume I only get one shot at the undecideds (no denier will be reading this except to try to find flaws) and I'm going to give them value for money, as it were.  

2010-08-25 00:49:08
Ari Jokimäki

arijmaki@yahoo...
91.154.102.68

"by (Moerner and Etiope (2002)"

Remove the first parenthesis before the word "Moerner".

Otherwise it's thumbs up.

2010-08-25 06:09:03Comment
Robert Way

robert_way19@hotmail...
142.162.177.145
Love the graphic
2010-08-27 07:01:36Ready to go.
Niamhaill

niamhwynne@yahoo.co...
109.255.157.58
Love the cloud graphic!
2010-08-27 09:24:57Published
John Cook

john@skepticalscience...
124.187.125.135

This has been a great discussion thread. A few comments:

  • Although the convention is to update the initial post when revising the rebuttal, I actually found it quite fascinating watching it evolve throughout this thread, getting simpler and simpler. Yep, that's entertainment for me. I need to get out more often.
  • The initial version is indeed a better intermediate version than my current intermediate rebuttal. Andy S, I'd like to replace my version with yours - but do you want to make any changes to it in light of the fact that it will be an intermediate version and therefore doesn't need to be "dumbed down" in any way? If so, perhaps start a new thread "INTERMEDIATE VERSION: Volcano etc" with the updated version and we'll go through the procedure again although it should be pretty close to ready to go as you've already been through the wringer already.
  • Agree with the sentiment that our rebuttals should educate and not just rebut - that's always been a philosophy of mine. Ideally, you want to turn the skeptic argument into a teachable moment and do 3 things: rebut the skeptic argument, teach the reader some science and expose the skeptic's rhetorical techniques.
  • The graphic is fantastic - note to all authors, simple, clear graphics like this are pure gold - the more of them we can use in our basic rebuttals, the better!