Those skeptical of the extent of global warming argue that short-term temperature data are an inadequate means of predicting long-term trends and point out that the scientific community remains divided
on whether significant warming will occur and what impact will it have if it does.Option Elimination -
(A) on whether significant warming will occur and what impact will it have if it does - So, the scientific community (SC) remains divided on
1. whether significant warming will occur OR NOT - They are not sure if it will occur or not.
2. if it does, what impact will it have - this is a first conditional, which is used to share the possible condition and its LIKELY result. If it rains, we will stay indoors. So if the rain condition is met, we will stay indoors 100% and not 99.99%. There is a certainty once the sufficient condition is met. But in the first part we are talking about scientific community (SC) not sure. So if SC is not sure then how can we say with certainty that "this will happen."? Wrong. We need a Second conditional to bring that uncertain part.
So the SC is divided into "whether X happens or not" and "Z (impact of global warming) happens or not."
Moreover, "will it" is usually used for asking questions or expressing uncertainty - Given the current economic conditions, will it be feasible for the company to expand its operations into new markets? Of course, the uncertainty part is good, but then the author suddenly shifts from a question to a First conditional and that's where the problem lies. It mixes two uses: "usage of will it" to express questions or uncertainty and "first conditional" to express certainty if the ssufficientcondition is met. So, to clear this mess, we need one type and not both.
So we can have either - "Will it have an impact?" It shares the uncertainty, or if we make a statement (and not a question), we'll invert, "The SC remains divided on whether it will have an impact."
The problem arises when we use a conditional statement (in the then clause) but then mix it with a question (in the then clause). This kind of usage is rare.
(B) on whether warming that occurs will be significant and the impact it would have. There is a shift from whether warming will occur or not to the warming by the way is anyway occuring as you know but will it be significant or not. Not the intended meaning. Wrong.
(C) as to whether significant warming will occur or the impact it would have if it did - "or" here derails the entire meaning.
(D) over whether there will be significant warming or the impact it will have - the same issue of "or." Moreover, the impact by the way is anyway happening but the SC remains divided if there will be more impact or less impact or this impact vs. that impact.
(E) over whether significant warming will occur and what impact it would have - ok. SC remains divided over "whether significant warming will occur or not" (they are uncertain) and "what impact it would have IF IT WERE TO OCCUR" (the uncertainty by Second Conditional). No mix of Question formats with Conditions.