I've heard a number of folks wish they could track how many observations individual users have performed in a GLOBE team. We're working on building that out on the website, along with tracking individual student contributions for schools. In the mean time, I made this spreadsheet which will figure it out for you if you know the user's UserID. Enter the date range, protocol and a list of UserIDs, and the spreadsheet will present how many measurements that user has performed for that protocol and date range. As a reminder, UserIDs are located in GLOBE Observer under the gear/settings icon, and under Account Settings if logged in on the website. UserIDs are not publicly available - only the User can see their UserID.
You can find the spreadsheet here.
Note - on downloading the spreadsheet, you will probably need to "enable content" to allow it to call the GLOBE API to populate the information.