[cnt'd]

In type 3 sentence the predicate acts (although the copula “estas” is in the way) as an attribute to the nominal phrase which is the subject [4]. Hence the same agreement rules apply. This also allows in English that the B in 3 can be a noun, but in Spanish (generally) not. So we get “es de buena educación” when we translate “it is basic courtesy”. [3]

In your statement, the A is “to link...” and the B is “basic science”, as can be seen by your usage of the cataphoric “it”. I think that “It is basic science” is of type 3, because I (at least I as a non-native, please comment) see it as attributing the quality “scientific” to the linking of CO2 emission to global warming, and not that you define it as a science. Well, there is no science for that, but many sciences are involved. Another reason why I think it is of type B is the lack of an article. Secondary nouns (the “port” in “port authority”) mustn't have an article, only the whole NP may have one.

If indeed “is basic science” acts as a (predicative) attribute of “to link...”, then in Spanish a nominal phrase is barred in this position. Hence, when a Spanish speaker finds a nominal phrase there, his linguistic gears shortly go haywire and he will try to map this construction to something similar he knows: and as we have seen, the results can be devastating.

As I said, these are only conjectures which arose after a short reflection. I am looking forward to your comments. If these conjectures contain even one grain of salt, the same problem should arise with most expressions of the form "It is (adjective) noun to...", when the noun isn't preceded by an article.

Also please bear in mind, that Spanish is spoken by millions of people in I don't know how many countries. I can only speak for the local variation. Maybe in other locations (Puerto Rico with a strong English adstrate/superstrate/substrate) these problems won't arise.

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[1] As Spanish isn't my mother tongue (although it is my active language) all translation are courtesy of native speakers.
[2] Compare also Russian -ский or Arabic يّ-.
[3] Some fixed expressions ignore this rule: “es un placer”, “es un gusto”, “es la verdad”. Note however that the nominal phrase must have an article.
[4] Actually “estas” is just syntactic sugar, as can be seen in copula free languages.

Nornen, are the phrases below invalid in Esperanto?

Kuŝi kun leono estas stulta ago.

Insulti vin ne estas io, kion mi volus fari.

Promeni dum torente pluvas! Jes, tre bela sugesto.

Aserti ke A post B implicas ke B kaŭzis A ne estas bona logiko.

sudanglo:Nornen, are the phrases below invalid in Esperanto?

Kuŝi kun leono estas stulta ago.

Insulti vin ne estas io, kion mi volus fari.

Promeni dum torente pluvas! Jes, tre bela sugesto.

Aserti ke A post B implicas ke B kaŭzis A ne estas bona logiko.

From his last post, I am thinking that it is the use of a noun with the copula in this way that is confusing to Spanish speakers. One can just as easily say "Aserti ke A post B implicas ke B kauxzis A ne estas logika." The meaning is for all intents and purposes exactly the same (at least I cannot describe the difference between "good logic" and "logical" ).

But, as far as I know it is absolutely valid Esperanto, so I guess that would mean that the problem lies with the translator's knowledge of English grammar.
____

On a side note, I found a cool parsing tool on Stanford's website that makes parse trees for sentences in English and a few other languages: parser.
Here is some documentation for the curious: documentation

I did not read through everything, but S=simple declarative clause, VP=verb phrase, NP=noun phrase, NN=noun, PP=prepositional phrase, etc. The output is a lisp-like list representation of a tree, so the first token in a list (note: (this is a list) ) is a node, and each following list or token is a node or a leaf, respectively. In the simple example you can see that each word (token) is always the leaf of a node that represents what it is, so Esperantist is marked as a noun (NN). They use a lot of very detailed descriptors (not sure what PRP is for 'I' ), so I find it useful to ignore the final descriptor. (treat the ` marks as spaces, I had to add them because lernu does not respect spacing for some reason...)

A simple example:
(ROOT
``(S
````(NP (PRP I))
````(VP (VBP am)
``````(NP (DT an) (NN Esperantist)))))

And my first sentence:

(ROOT
``(S
````(NP (PRP It))
````(VP (VBZ is)
``````(NP
````````(ADJP (RB very) (JJ basic))
````````(NN science)
````````(S
``````````(VP (TO to)
````````````(VP (VB link)
``````````````(NP
````````````````(NP (DT the) (NN percentage))
````````````````(PP (IN of)
``````````````````(NP (NNP CO2))))
``````````````(PP (IN in)
````````````````(NP (DT the) (NN atmosphere)))
``````````````(PP (TO to)
````````````````(NP
``````````````````(NP (DT the) (NN heating))
``````````````````(PP (IN of)
````````````````````(NP (DT the) (JJ whole) (NN earth))))))))))
````(. .)))

sudanglo:Nornen, are the phrases below invalid in Esperanto?

Kuŝi kun leono estas stulta ago.

Insulti vin ne estas io, kion mi volus fari.

Promeni dum torente pluvas! Jes, tre bela sugesto.

Aserti ke A post B implicas ke B kaŭzis A ne estas bona logiko.

As far as I know, these examples are valid in Esperanto. Also kaŝperanto's "Estas tre baza scienco ligi..." is valid in Esperanto in my opinion.

I am going to quickly inteject, I do not know it this will be relevent..

When I started learning Japanese, I tried to translate English phrases into Japanese, although they looked good to me, as they had everything an English sentence would, when I used them on actual Japanese people, some were bewildered and bemused, or thought I was attempting to say something else. Well, I thought well, maybe I translated it wrong, and tried again with another wrong translation.. At this point, I 'gave' up..
A bit later, I read a blog on the internet which asserted that when learning another language, you cannot use features in your native language like you would the second one, this blog was in regards to Japanese..
Hmmmm, here is an example of a English phrase which is slightly different in Japanese, "How are you?", -> "Genki (desu ka)?", which actually means "Are you healthy?", which a japanese will respond with, yes or no, or some other degree..

I guess my point is, you cannot expect a speaker of another language to think like a speaker of your language. Each language has its own quirks, which makes people think slightly different.

I can also see how one may be confused by "it is simple science", as it indeed looks very idiomatic or metaphorical..

Sudanglo, if someone claims that they do not understand a statement, you do not have to be such a jerk about it, this is suppose to be a language learning site, be more supportive, not so rude.

Surely SciBerC the discussion is not about the explication of some point that is causing difficulty to an unsophisticated beginner (Nornen is far from that), but rather about what is acceptable in Esperanto (can be considered valid and consistent with established usage).

Nornen, I grant you that given that Esperanto is a second language for all, there will be a tendency to import structures and meaning from the mother tongue of the speaker (hence the desirability of authors submitting their efforts, before publication, to scrutiny by speakers of other languages).

Yet, in practice, because Esperanto is a second language for all, I think it may follow that there is a greater general willingness on the part of the Esperantists to seek out plausible meaning - to be more flexible with regard to the unfamiliar.

Happily, because Esperanto has evolved in an international environment, it follows that over the years there has been a sort of Darwinian process in operation resulting in rejection of those structures which give too much difficulty in interpretation, and the incorporation into the language of those deemed comprehensible, despite not appearing in certain languages.

In other words, I think that transpositions from the speaker's mother tongue, may not be such a serious issue for Esperanto as it may seem from a theoretical viewpoint.

Back in my komencanto days when I began my first message conversation with Toni, a Hungarian guy who frequently sends postcards to users on this site, I had a lot of similar troubles interpreting the meaning of phrases he was using. A large part of that was just inexperience and unfamiliarity with things like adverbial participles and the finer aspects of the accusative. I understood the meaning of each word, but with some phrases I was left guessing the intended meaning. It takes some time to learn to think in Esperanto when reading/writing it, and I obviously still have some native English influence on my thought patterns.

I do agree with sudanglo in that this is a non-issue if both parties have learned Esperanto and are not new beginners. I really doubt that progresantoj can't formulate a good guess as to the meaning of "it is basic science", and if they can't then they are not as progresinta as they thought. nornen formed a few correct guesses, but his test subjects did not. I don't know how well they understand English or how practiced they are, but I would especially expect someone who speaks English to understand this phrase. Possibly they understood it well enough, and figured that a direct translation would be understood by native Spanish speakers.

SciBerC's Japanese example is one where if I saw "Cxu vi sanas?" as the initial message in a tujmesagxilo conversation I would understand it to be a simple greeting. Surely there are phrases that I would not understand, but a well-learned Esperantist is going to know to avoid the true fixed expressions. Every Japanese and Chinese Esperantist I've conversed with I have always understood (they have mostly all been more experienced than I). I recall a thread from a year or two ago where a Chinese Esperantist was complaining about the corruption at the chauffeuring school he was studying at. He was "sokita" that they would demand bribes to give decent training. Being the newly enlightened Esperantist I was, I totally missed that he obviously meant "sxokita", and figured that there was some Chinese expression that was equivalent to "phoughshared" (it conveys an image of being disturbed or turned over, like a ploughshare would do to a field).

kaŝperanto:[...] and I obviously still have some native English influence on my thought patterns.

And you always will, and we all always will. I will always have German thought patterns influencing my Spanish, and both German and Spanish thought patterns influencing my Esperanto. We can strive to minimize this effect; we positively should strive to do so and no mistake. But it would be delusional to believe that at some point in the future we could negate completely this influence.

And this is not a bad thing. Our brain, our thoughts, our person, the monster behind the mask of our faces is partially defined by our language patterns. Our mother tongue is part of the bricks and glue that build our person and personality.

kaŝperanto:I do agree with sudanglo in that this is a non-issue if both parties have learned Esperanto and are not new beginners.

I am not sure about this. Maybe it is a not-much-of-an-issue instead of a non-issue. The exact example of "it is basic science" may not be very troublesome, but you might find another experienced Esperanto speaker who finds it difficult to interpret. Once again, I repeat: I do not deem it incorrect or "bad" or "improper" Esperanto. Nevertheless, I still think that it is an English modism (for instance: had you written "Estas tra baza sciencajxo" I wouldn't even have looked twice at the sentence), as does also SciBerC from Australia (I suppose his mother tongue is English).
We should always bear in mind that the person we are talking to, has his own dictionary, his own parser, his own experiences which will have a high impact on the way he will analyse and understand our utterances.

Returning to the original question of OP: The important thing in this context is -in my very personal opinion- to be aware that misunderstandings are more likely to happen if the interlocutors are from different linguistic backgrounds. The farther away the backgrounds are, the higher the probability. Even more: not only to be aware that this might happen, but to anticipate it. And most important of all, not to judge the other party or deem their Esperanto improper, because their way of talking is different to ours.

I suppose I meant that two very experienced Esperantists would either never use such phrases, or would be sufficiently able to comprehend those few minor ones that the other might use. I can definitely see "It is basic science" being problematic due to its use of "It is", but "to do blah is basic science" should be very simple to understand (X is Y). Any ambiguity might stem from the accepted meanings of "science" in Esperanto and English. In English "I'm doing science" or "I'm doing math" are common uses, but the definitions of the words in Esperanto don't really support this usage. And "I'm doing.." is particularly idiomatic and ambiguous, and "I am practicing" or "I am utilizing" would be the most correct meanings to translate.

scienco - tuto de scioj (kaj kontroleblaj esploroj) pri la naturleĝoj aŭ pri certa temaro <--how would one "do" this?
matematiko - scienco pri nombroj kaj figuroj, kaj ties propraĵoj

In any case, I would bet that these misunderstandings would be all but eliminated if both parties use very high precision of language. It is obvious that "baza scienco" is a questionable phrase, since "it is a basic whole-of-knowledge-and-verifiable-research-concerning-the-natural-laws-or-of-a-certain-subject" does not make much sense. In my English understanding "science" is used to describe using the scientific method or to describe something that is using said method. "It is science" or "It is chemistry" are perfectly understandable to me, but their real meanings would require more precision to translate into Esperanto, apparently. The meaning is more vague and general in English, at least in common parlance.

sudanglo:Yet, in practice, because Esperanto is a second language for all, I think it may follow that there is a greater general willingness on the part of the Esperantists to seek out plausible meaning - to be more flexible with regard to the unfamiliar.

I think lack of willingness isn't the problem. If we weren't willing to try to understand other people's Esperanto, I guess we wouldn't be here at lernu. Also when two people talk deliberately with one another, I think there will never be a lack of willingness. (Unlike e.g. at the work, where people have to talk with you although they don't want to. There it may happen that they play silly buggers.)

The problem isn't the lack of willingness, but the lack of capacity (ability? kapablo). It can and will happen that I will use expressions I know from German or Spanish, more or less verbatim in Esperanto. Because I simply can't imagine that the intended meaning isn't that obvious after all (what I called in the other post a "hidden" modism). In this case, no matter how much willingness the listener employs, the meaning might elude him because he lacks the capacity to imitate (basically reverse-engineer) my thought patterns.

sudanglo:Nornen, are the phrases below invalid in Esperanto?

sudanglo:[...]what is acceptable in Esperanto (can be considered valid and consistent with established usage).

The fact whether a sentence is valid, i.e. well formed, in Esperanto might have only a marginal impact on whether it is understandable. For instance "*Mi mangxis terpomfritoj." is clearly ungrammatical due to the missing accusative, but I doubt that anybody, no matter their mother tongue, would have problems understanding it. We have the speaker (mi), the act of eating (mangx), the reference to the past (is) and chips (terpomfritoj, something fried closely related to apples that grow in the earth). As nowhere on earth chips eat you (not even in Soviet Russia), the only interpretable meaning is "Mi mangxis terpomfritojn."

It is different with errors like this:

Milan:Skribu tiun tekston, kiun vi volas aliuloj legi antaux ol ili renkontos vin.

For anglophones (or anybody who has studied English) this error can be corrected quite easily, because although this construction is invalid in Esperanto, it is well defined in English.

Made up:Mi volas vin mangxi

This is even more troublesome, because it is indeed a grammatical sentence in Esperanto, but it doesn't mean "I want you to eat." Here it should be expected that it is quite difficult for non-English speakers to correct the error.

Actually nobody:La Hyundai havas multajn malsamajn modelojn, pli potencajn kaj malpli potencajn. Tamen la plej potenca Hyundai, kiun mi mem neniam veturigis, estas la Santa Fe V8.

I haven't read this error in Esperanto, but I have heard it a lot of times in English[1]. Same problem here: [tbc]