My memory is not so good either. You a getting more data which is good. It should be noted that this garden is in an area with a lot of vegetation so temperatures will be lower and relative humidity higher than some environments.
A rooftop garden without growing things may actually increase temperatures due to thermal mass not being able to lose as much heat at night. Eutrophication is a concern so things like nitrates, phosphates, and particulates should be measured. It may turn out that water consumption and added pollution are not problems but it would be good to have numbers before mandating a policy.