In what sense is atheism scientific?

I have been reading a bit of Dawkins and the like and they all seem to hold a very strong viewpoint on atheism and its associated ideology. I have not found a direct citation for this but he frequently makes a very close connection, e.g.: An atheist before Darwin could have said, following Hume: "I have no explanation for complex biological design. All I know is that God isn't a good explanation, so we must wait and hope that somebody comes up with a better one." I can't help feeling that such a position, though logically sound, would have left one feeling pretty unsatisfied, and that although atheism might have been logically tenable before Darwin, Darwin made it possible to be an intellectually fulfilled atheist. The Blind Watchmaker (1986) I myself do not see how atheism can be scientific in any way. Atheism is, in a broad sense, the rejection of belief in the existence of deities. Atheism, Wikipedia. The thing is, you cannot prove nor disprove this statement. It's an ethereal concept with no basis in scientific measurement by tests and observation. They seem to be asking a question that has no answer because the whole thing is based on faith. Atheists point out that you cannot prove god exists nor disprove that Thor exists, which is true, so why are they answering this question in the first place and making a very strong connection to its scientific merit? As I see it, atheism seems to have the same passion to try and persuade others of their ideology as any religion, with Dawkins even calling himself a militant atheist. I think agnosticism seems to be the most scientific approach. What might be some reasons atheism could be considered to have a 'scientific' dimension?