Good style, even in formal writing, consists of being as clear and simple as possible. All that is necessary is to avoid colloquial words and usage, not to stretch for formal ones. One option is to leave the sentence out completely. Why apologize for not being an expert? I like "Although I am not an expert in the field, I have tried very hard to understand the main ideas." If it is appropriate to say this at all, that is a good way to say it. If this is a class exercise, and the teacher has told you never to use the first person in formal writing, then, of course, you must not use it. But there's no way to improve it without sounding pompous and stilted. You are telling the reader something personal about yourself, so it is appropriate to write conversationally. You could say "The author makes no claim to expertise beyond a diligent review of the relevant literature." You could also say "This article is based on a review of the literature cited in the references." Those are really awful, though, except as an example of how to write academic prose. Basically these sentences are trying to say "I'm not an expert on the topic but I want to sound as if I were!" "Global warming will have disastrous consequences for the whole world" is fine. For your second option, leave out "the" and write "The consequences of global warming will be disastrous for the entire world." Which is better depends on what you are going to say next; there's a very slight difference in emphasis. The first sentence makes me expect a paragraph about the global scope of the problem, where they will occur. The second one makes me expect a paragraph listing what the consequences will be, what will happen rather than where they will happen.

Hi Jello, number 1 and 2 are correct. 3. In sentence 3 you could use "provided" or "given" instead of made up. A synonym for come across could be "face" or "tackle"

No, in the third sentence, you cannot substitute "provided" or "given" for "made up" without changing the meaning of the sentence (and/or creating an incomplete sentence). "To make up for" has the sense of compensating in a good way for something negative: She tried to make up for lost time by working extra hard. This year's good harvest will make up for last year's bad one. In your sentence, the people faced problems at the trial stage, but the positive feedback they received provided compensation for their negative experience at the trial stage.