#21 - A study of 30 years of weather pattern records of

[jm123]

Is this assumption question a defender assumption? I think I looked for an answer that related to why human activity effects the weather. This led me to answer choice C. When I negated C I read it as, even if living organisms have an appreciable large-scale effect on weather patterns, then this is not necessarily due at least partly to the effects of human activity. This does not really do anything with the argument.

E, on the other hand, has an effect on the argument because if we negate that then it is, even if a weather pattern with a natural cause has a seven-day cycle, then that cause may not have a seven-day cycle. Which would ruin our C+E argument in the stimulus that human activity effects the weather.

[stratosm]

I'm still struggling with completely eliminating (C). Can somebody verify whether my explanation is correct?

P1: weekend days tend to be couldier than weekdays.
P2: there cannot be a seven-day cyclical natural cause of large-scale, measurable effects on weather.
C: human activity has at least one appreciable, large scale effect on weather (based on my understanding, it's the effect in premise P1).

(C) is not necessary to be assumed. Living organisms could also have large-scale, appreciable effects on other weather patterns without the effects of human activity involved, but not that particular one discussed in the argument or even a weather pattern appearing in a 7-day-cycle.

It could be the case, for instance, that certain bacteria (through a non-7-day-cyclical mechanism) cause winters to be heavier during leap years than regular years (a 4-year-cyclical weather pattern, not a 7-day-cyclical one)... However, the answer choice is talking about all weather patterns, which is too big of a stretch and therefore not a necessary assumption.

If (C) said "... on seven-day-cyclical weather patterns...", for instance, it would be correct in my opinion.

(E)'s scope, as opposed to (C)'s, is narrow enough to work in this case. We do have a seven-day cyclical weather pattern and if for a natural cause it was not necessary to be seven-day cyclical as well, it would wreck the argument, as it would leave open the possibility of non-seven-day-cyclical natural causes.

A more ideal answer choice would be (E) talking about the particular phenomenon in P1 instead of seven-day cyclical weather patterns...

Can somebody please correct me if I'm wrong of give a more satisfactory explanation? I'm really not sure whether my explanation is okay...

[Paul Marsh]

Hi stratosm! Your explanation is right on the money. (C) is too broad as it necessarily ascribes human involvement to every time living organisms majorly affect the weather. And you are correct about how the negation of (E) would wreck the argument.

Nice going!

[mcn476]

Probably the toughest LR question on the test, and if student feedback is anything to go on possibly of the year thus far. So anyone struggling with it know you're not alone!

Let me see if I can help by briefly outlining my take on it, and how I arrived at the right answer


The author describes a 7-day cycle weather event, namely weekend cloudiness. It gets cloudy at the same time each week, thus that pattern/cycle is 7 days long. Then the author says it’s humans causing that weekly event, because 7-day cycles that occur in nature can’t cause measurable weather patterns. In other words, the author thinks the cause is unnatural (people) solely based on looking at 7-day cycle causes and saying natural ones can't be behind those clouds...but what if some other natural event without 7-day cycles was the cause? What if the cause is, say, twice-daily, or monthly, or annual? Then it could still be natural (non-human) and lead to a 7-day event, such as the one described.

So the author is assuming a 7-day event must have a 7-day cause, and it’s natural 7-day causes the author then rules out as ineffective, essentially. Thus it defaults to humans.

So when we look at (E), it eliminates the possibility that the 7-day event can have a different type of (different cycle) natural cause: any 7-day event (like weekend clouds) with a natural cause must have a 7-day cycle natural cause...i.e. it can’t be monthly, or annually, etc. And since we’ve ruled out a 7-day cycle natural cause already in the stimulus—it's not effective enough—then this 7-day event must be caused by something not natural (like people).

The negation of (E) works pretty well here too: a 7-day event (those clouds) can be caused by natural forces with any type of cycle or time length. Well if that were true, then who cares about a 7-day cycle cause and how ineffective they are...this weekend cloudiness could have been caused by some other natural thing that the author hasn’t considered, and suddenly the argument is in trouble. "It isn't people, it's 28-day lunar cycles." "It isn't people, it's twice-daily tidal flow." And so on.


Put another way, I see it as the author saying "Hey look at that 7-day thing that’s happening. It’s either caused by humans or a 7-day natural cause, but it can’t be the natural cause because 7-day natural causes are insignificant. Guess it's people!" Someone might ask, "Well what about shorter or longer natural causes that could’ve led to it?" And the author’s like (E) "Oh no, any 7-day thing/event with a natural cause has to have a 7-day natural cause, not something shorter or longer like you’re suggesting. And those length natural causes never lead to measurable outcomes like those clouds we're talking about. So my guess is humans."


I don’t know if that helps, but I thought for everyone's collective sanity I’d give it a shot

You definitely helped me keep my sanity intact. Thank you very much.