I agree with the basic premise but think a pretty important issue is way understated. I.E. A testable means of disproof (which requires specificity) wasn't just an opinion of Popper's, it's a *requirement* (among others) in order to have a 'scientific' theory.
I think it would come as a surprise to most people that, so called, 'global warming' (man induced) doesn't actually qualify as a:"scientific theory" because people tend to mistakenly believe anything, speculation included, that contains a bunch of 'numbers', 'data', and 'research' is automatically 'science'.
Try it. Next time you run across a 'global warming' advocate ask them what testable criteria would disprove it. I'll wager the answer you'll get is 'none' because, they'll argue, "it's a fact" (or claim a "scientific consensus").
Only if you take Popper seriously, which many don't. The concept of "falsifiability" is often useful, but it isn't all that helpful in the observational sciences, like paleontology and astronomy.
The "speculation" behind anthropogenic global warming is rather more scientific than you seem to think.
That rather depends which global warming advocate you ask. James Hansen
would be happy to give you chapter and verse (or he might if he thought that there was any chance that you could follow his argument, or understand the facts that he'd adduce, which does seem unlikely).
Al Gore would probably just refer you to James Hansen (who does seem to be one of the gurus whose ideas Al Gore has publicised over the years).
The short answer to your question is that any sustained and significant decline in global temperature coinciding with a constant or increasing level of greenhouse gases in the atmosphere would disprove the case for anthropogenic global warming.
In my - tolerably inexpert - opinion, the short term variability of the global temperature due to effects like the El Nino and La Nina changes in air and ocean circulation mean that anything less than 0.5 Celcius wouldn't be significant, and the decline would have to be maintained for something like ten years to be counted as sustained.
Nobody got enthusastic about anthropogenic global warming until the blade of the "hockeystick"
had pushed roughly 0.6C above the noise, and it would presumably take a similar decline to excite wide-spread scepticism amongst the scientifically literate.
The scientifically illiterate are susceptible to less fundamental arguments - in Jim's case the unsupported opinion of a scientifically illiterate historian, who seems to think that Freud's and Marx's opinions about the world have the same kind of scientific basis as the case for anthropogenic global warming.
** AGW is a popular hypotheses about world climate - but certainly not a coherent or established "theory " of this planet's future climate.
** Since AGW followers all say the planets' atmosphere is rapidly warming p - an observed failure to do so in the next decade or so would be a major blow for the hypothesis.
I wager the hard core would then claim that the predicted disaster it has been "delayed" through their mighty efforts to alert everyone.
Yes, that was my point, along with that people simply don't know what constitutes a "theory."
Then, to make matter worse, you have demagogues and amateur 'scientists' claiming a "theory" is 'fact' or 'essentially fact'.
Already had that problem.
Doesn't matter because they never definitely state anything. It's all 'could', 'might', 'if, then'...
The observed behavior was they either declare the data invalid or, if that doesn't fly, they scurry off to 'adjust' the, so called, 'theory'... with the caveat that what they 'believe' remain intact. If all else fails they simply explain "there are some unanswered questions but AGW is a 'fact'"
They have a "heads I win, tails you lose" game going.