Mustang is correct. You are not.
Fallacy is never correct.
Theories supported by evidence are not "arguments to (sic) ignorance".
Well, you're right. Unfortunately, you're committing a red herring fallacy. The question is whether acceptance or rejection of the theory is done in a logical manner. Just because evidence supports a "working theory" does not mean that it must be accepted as true, simply because a second person does not have an alternative to offer. Doing so is arguing to ignorance.
BTW that should be "argument FROM ignorance" or "APPEAL to ignorance". We have gone over this exact point in discussions past.
For someone who is throwing around ad hominems, you really ought to drop ridiculously petty (and incidentally false) objections. First of all, the Latin phrase is
argumentum ad ignorantiam. This translates into English as
argument to ignorance. Here's a pro tip: Take a Latin course before you try correcting another person's Latin. Also, if you'd but browse an introductory logic book you would know that both English forms (argument to ignorance, argument from ignorance) are used to identify this fallacy, as arguing either to or from ignorance is essentially the same thing. Another course you might want to take.....
It is not being argued here that AGW is correct because the alternative theories lack evidence. It is being argued that the alternative theories are untenable because they lack evidence. AGW is extremely well supported by evidence. Alternative theories are not.
Actually, if you would but read, you will see that Mustang's precise argument was that refuting a working theory requires presenting an alternate theory, and evidence to support it. So it seems that reading comprehension is yet another course you need to take.
In fact, it would be better if you would go back to grammar school entirely.
After all of that, you actually say nothing of substance anywhere, and affirm for everyone the maximum potential of your intellect. Congratulations.