I think that humans are capable of influencing local climate including humidity from forest removal and building cities etc. I believe that it is very difficult if not impossible to distinguish that ''footprint'' from the noise of natural variability. Same goes for co2. For example, the correlation of increased co2 and rising temps does not prove causation simply because of the above point. But there are also other considerations like co2 saturation and heat transfer. In other words, no one knows and if they say they do, they are just whistling Dixie.
