While the debate about Global Warming and it's causes has become more heated in recent months that doesnt always mean that there is a great deal more light being shed on the whole subject. One of the most infuriating things is reading comments by people who clearly haven't thought about the logic of what they are saying.
Reading the comments on Global Warming stories can be a particularly depressing experience when you see people taking strong stances on the basis of arguments which are sometimes so patently ludicrous that you wonder how the person failed to understand this.
I came across the following comment in an online newspaper today
"Despite any increase, carbon dioxide remains less than one percent of the greenhouse gas content of the atmosphere. Increases in carbon dioxide are more a symptom of a warming trend than a cause."
I'm sure my readers being the smart bunch that they are will immediately see at least one fallacy in this statement but I'll lay it out anyway because this argument is trotted out so often by Global Warming scpetics that it's become a bit of a mantra.
I dont know if you have ever heard of something called Ricin - if you havent then its basically one of the most poisonous substances known to man. At the present moment I am fairly safe in saying that if you are reading this then you have no Ricin in your body at the moment.
If you will allow me to then I will adminsister to you ( virtually of course) a dose which is so small that it will not amount to even a fraction of 1 percent of the weight of your body. Anyone who thinks the Global Warming scpetics argument is a logical one must of course accept that there can be danger in me giving them such a small dose of Ricin. After all its going to be much much less that 1% of their body mass - so why worry?
CO2 is indeed a small fraction of the atmosphere but it is clearly a fallacy to conclude from this that it cannot have major effects on the way the atmosphere works.
But that is not the only thing implied by the sceptics statement above. There is also the implication that not only is the total amount of CO2 in the atmosphere very small but that the changes to those levels that man is causing are a small amount of that already small fraction - so why worry? This also is illogical reasoning.
It is a trivial thing to find examples where a very small change in something can set off catastrophic changes. In nature there are many examples of state changes where only a very small change in for example the heat content of a material will lead to a sudden state change. As a more dramatic example consider (virtually) placing a small amount of high explosives in your basement. No problem there of course because the high explosive will only be a fraction of the volume of your house. Now we will apply a tiny increase in the energy of the high explosive. Here is the match. Just light it and apply it to the high explosive. I will be standing well back at the other end of the street of course. If you are a Global Warming sceptic who thinks that small increases in small things pose no dangers then I am sure you will be happy to stand there alone and apply the match yourself. No?
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While the article's claim strikes me as obviously fallacious, the example you use doesn't seem quite right either. Carbon has never been zero in the atmosphere, while as you state, the current amount of Ricin in my body is (likely) zero.
Thresholds of instability can occur, however, as there are levels of blood alcohol which would cause death ... and the proverbial straw which broke the camel's back.
We may be equally disturbed at the potential for quacks to take over the public discourse in the wake of the AGW scandals.
Yes Looney I was trying to tease out the two elements of the fallacy here.
the first is the fallacy that a small percentage of something cannot cause a catastrophic reaction within something orders of magnistude larger.
The second element of the fallacy is that a small change in something cannot cause a catastrophic change of state.
For the purpose of illustrating it I chose analogies that illustrate this in a very dramatic way. Like all analogies you can only push them so far though. I think they do illustrate the weakness of such arguments though.
There are some good signs that the AGW debate is grappling with the science now.
There are reports today that the link between hurricanes and AGW has been reviewed by a group of scientists representing both sides of the argument.
Their conclusion appears to be that it is not correct to assume that hurricanes will become more prevalent under Golbal Warming - they may in fact become less frequent. They agree that there is a natural cycle of hurricane activity which needs to be taken account of. That's the good news.
The bad news is that they conclude that those hurricanes which do occur in a warming scenario are likely to be on average between 7% to 10% stronger.
I find it reassuring when the science gets reviewed and conclusions refreshed on the basis of current best information - it means the science is alive and working.
Sorry, but using ricin is a bad analogy.
Ricin, if ingested, is not nearly as dangerous as many people think. In 1985, a study was done of castor bean/ricin ingestion in the 20th century and it turned out that of 851 cases only 15 resulted in deaths.
Eating a small amount of ricin is likely to cause you a stomach upset but not catastrophic harm.
The LD50 for Ricin (lethal dose responsible for killing 50 percent of the test population) is 30 mcg/kg. I think yu will agree that for the purposes of my analogy this is a microscopic fraction of human body weight.
Ricin is indeed sometimes less fatally toxic when ingested orally compared to inhalation or injection (The "umbrella murder").
Would you be prepared to volunteer to ingest 1% of your body weight? I suspect not - and if not then my analogy stands.
For a detailed reference on Ricin toxicity see:
Centre for Defence Information Factsheet: Ricin
The Ricin analogy would have worked if CO2 were a powerful greenhouse gas. But alas, it's actually quite a weak greenhouse gas when compared to others like methane or sulfur hexafluoride.
I use sulfur hexafluoride as an example because it is the most powerful greenhouse gas that has been evaluated, at 22,800 times more potent than CO2. Of course, it's heavier than air so it's not going to be up in the atmosphere to actually cause problems.
Methane is a more reasonable powerful greenhouse gas that does end up in the atmosphere, and it's 25 times that of CO2.
On the topic of CO2's effects on global warming: in the ice records, it's usually the temperature that rises first, then the CO2 content... Suggesting that warmer temperatures are the cause of CO2 and not the other way around.
You might be interested in seeing and hearing this: http://www.youtube.com/watch?v=yLYqzIhhT6o&feature=player_embedded#
Hi Marf -
There certainly are gases which , weight for weight, have a more substantial effect than CO2. but thta was not the point. I was directly addressing the suggestion that something which is a small percentage of cant have a large effect. While weight for weight there are other more active greenhouse gases the effect f CO2 and its greater abundance make it a significant greenhouse gas.
There are actually geological periods when CO2 rose in advance of temperature but I have no difficulty with the fact that the record also shows that the general trend has been CO2 showing a lag.
This is unsurprising as most natural cycles of warming arent likely triggered by CO2 intially - there are other well know forcing factors for climate change.
That isnt really the issue. the issue is what is then the effect of CO2 as its level in the atmsopshpere rises. There have been direct measurements of this and it is clear that rising levels of CO2 are likely to provoke further warming. The only real argument that makes sense is the degree to which this will force warming and whether the contribution of CO2 and other man made gases is greater than or swamped by natural cycles.
The difficulty in solely using the geological record is that we have no evidence that CO2 has ever risen so sharply over such a short time ( over 100 ppm in 100 years I think is the figure)
We are currently conducting a vast experiment with our atmosphere which involves increasing the percentage of a whole range of gases which we know for a fact act as an atmeospheric heat blanket.
If you doubt this check out the atmospheric composition and temperature of Venus and consider the evidence for what conditions would be like on Earth without our blanket of greenhouse gases ( Ice cubes anyone?).
Given these facts it seems likely that with rising temperatures there will also be natural processes which will lead to further rising levels of CO2 and Methane ( for example melting clathrates and melting permafrost) and that there is a severe risk of a positive feedback loop kicking in at some point.
Rum - that was an excellent video that gives an overview of the large range of scientific evidence from various disciplines that points towards AGW. Thank you for posting it. It deserves a proper hyperlink Climate science overview
As the video pointed out it probably won't persuade committed conspiracy theorists as they are generally immune to evidence.
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