You take it on faith, faith in your own reasoning and observational abilities, that God does not exist, or at least that he is something you do not have to be concerned about in your disbelief.
You take it on faith, you have faith in the testimony of other researchers, that the data and results that you read in scientific papers are legitimate, based on their reputation or the prestige of the journal it is reported in. (You don’t have time to replicate everything and certify to yourself that all is as reported.) That faith can be justified or shown to be false, but it is still faith for the time being.
 …And even after you certify it to yourself, if you do, you still have to have faith in and believe in the adequacy of your own senses, reasoning and abilities. (Which again, for illustration, brings up the topic of synesthesia. Oh yeah, and dementia. )