Neat. You responded. At least the goading had the desired effect. Thanks for providing the links, by the way. I hate it when some people ask me to find the papers that support their position, because it is never possible to figure whether those were the studies they were actually talking about.
So, let's take a look at those studies.The first one explicitly acknowledges that if other limits are imposed, CO2 increases do not have sustained effects. Which is the entire point of the discussion we're having.
The second one is more interesting, as it actually tries to quantify the effect across regional variations. However, let's look at some of their conclusions about what would happen out in the field in specific regions: "[...] even though there have been multiple studies in temperate, intensively managed systems, few of the previous experiments have been performed in conditions similar to the growing environments of developing counties, in which the response could be very different (Leakey et al 2012). This is particularly important for dry conditions, for which there are currently no studies, but which prevail in Africa where tuberous crops make up a large proportion of production." This sentiment is prevalent throughout the paper: the CFE is in theory high, but real world impact is difficult to quantify, due to lab conditions rarely mimicking real world farming conditions. Furthermore, it also assumes that fertilization rates are increased along with the CO2 increase to achieve the maximum yields - which is an assumption that needs to be verified before making any conclusions about how much the yield actually is.
The third one is unfortunately pay-walled, so I'll have to skip. These are the days where I wish that I still would have university access to papers.
The fourth one, unfortunately,does not say what you think it does: " Idso remarks that the problem with laboratory experiments is the opposite of what you assert -- it is difficult to grow trees in the lab without constraining their roots and access to resources and work he cites (in less abundance as it was ongoing in 1993) suggested that the response in the wild is even higher." Instead, what it actually says is that: "[...] this response-restricting artifact has often been regarded as producing realistic results. It can be effectively argued, however, that plants in the natural environment can increase their nutrient-gathering capacities at a rate sufficient to meet the real-world rate of rise in growth potential provided by the yearly incremental rise in atmospheric CO2[...]" In short: they're saying that they believe it is reasonable to assume that the growth limits of lab conditions (shallow root systems) are equivalent to the growth limits of natural conditions (poor soils), and one is therefore similar to the other - not that one is higher than the other, and certainly not that there were experiments that supported this. Finally, the paper is actually a bit of a failure: they did a meta-analysis of 342 papers and 1087 experiments, and only a handful was done on plants in natural settings. Furthermore, the entirety of the experiments that were discussed in detail were of pine trees at high altitudes - not crops.
Before I summarize, let me start with a correction on my part. When I said "Plant growth is almost never CO2 limited." I was wrong. It's a pithy sentence, but doesn't hold up under detailed scrutiny. I guess that's why papers contain more than one sentence. A more accurate, single-sentence form of my position is "CO2 is one factor among many that impacts plant growth, and current in-the-field analysis of world-wide crop yields does not exist to support your statement."
But let's take a closer look at what it is that you're arguing, and how it relates to the studies you've produced so far. The key statement you made was this:
By raising atmospheric CO2 from 280 to 400 ppm, we have in fact raised crop yields worldwide by between 10 and 15%
Let's walk through what kind of evidence is required to support this statement:
1) CO2 alone can increase plant growth.
2) Crops, on average, benefit from increasing CO2.
3) Crops, worldwide, increased in yield.
4) Crop yields, world-wide, were increased by 10%-15%.
For 1), that's a check.
For 2), that's sort of a check, but only because you do not have negative responses to increased CO2: corn, for example, does not benefit from CO2 at all. And that's a pretty basic staple in many regions (not to mention a huge industry in the US). On average, crops will benefit. But people who rely on C4 crops will completely miss out, and only experience the downside of Climate Change.
For 3) that's a miss. Your own papers were not able to establish that in-the-field crop yields have increased. The best you have is the nature paper, which is unfortunately pay-walled, and doesn't seem to deal with crops specifically, but only with biomass in general. That's not the same thing.
4) And with that, 4 becomes an impossibly specific claim. In fact, from what I can see so far, it is nothing more than an extrapolation of the Nature paper's numbers to worldwide crops. That's a jump in conclusion that would make Bob Beamon proud.
Now that we have established that you only managed to confirm a basic claim over which there was no argument (the CFE exists), let's talk about your digression into debating styles. You're off to an absolutely terrible start, because you don't even understand the difference between an ad-hominem fallacy and an insult. Here, let me demonstrate.
"You're suffering from smartest-motherfucker-in-the-room syndrome" is an insult. Also an insult: "you're an idiot." An ad-hominem fallacy is "Because you're an idiot, you're wrong." Compare the two with what I wrote in my previous posts. What do you see?
Now we turn to whether you have at any point in time asserted that you're the smartest motherfucker in the room. This is an utterly irrelevant question, considering that I never claimed that you called yourself that. I merely called you that. Do you see the difference there, too? I could go into why I called you that (dogmatic discussion style, word choices, superficial understanding of the fundamental problems you're trying to address, mistaking expertise in one field for expertise in another, and a few more), but none of them are relevant to your particular position. This reflects badly on your reading comprehension. At this point though, it's not your first whiff, so I'm kinda used to it.
Finally, if you make a claim, go support it. Especially if it's something kinda controversial like "people dined on 15% extra crops last year because of the increased CO2". I understand you're not used to having to provide supporting evidence when you teach your classes, but this is not Physics, and you're not the authority. Regardless about how you feel about your knowledge about Climate Change.
In short, while my replies to you here were snarky in style and insulting in words, they were very consciously and purposefully so. Your condescension, snark, and ignorance was clearly not so. You even lag in your ability to approach new information with an open mind, which is especially ironic.
As for my profession: I got out of a career in Astrophysics because I figured that if I had to put up with egos like yours on a daily basis, I might as well get paid for it. Thanks for reminding me that I made the right choice.