EMarketer just posted new data on its blog showing comparative shares of time spent per day per medium. What stands out for me is that mobile is up 28 percent this year to 50 minutes per day.

Also interesting — and perhaps alarming depending on where you sit — is that this beats time spent with newspapers (30 minutes). In fact, it’s only surpassed by radio (96 minutes), Internet (155 minutes) and TV (264 minutes).

Mobile is the fastest growing of all these decidedly more mature media, and could soon surpass radio and Internet (TV could take a lot longer). As for Internet, Morgan Stanley projects mobile users to surpass desktop users by 2014.

Of course that deserves a few caveats, being a user count (not minutes spent) and a global figure. In other words it includes emerging markets where mobile Internet is leapfrogging the more complex infrastructure requirements of fixed Internet telephony.

Time spent on desktop also tends to be higher per user too. Searchers for example tend to be in more of a lean-back mode involving a broader range of topics, research areas or entertainment. Microsoft in fact has reported that completed search sessions happen faster on mobile.

But then there are things like gaming and social networking that are not only top mobile activities, but also involve long session lengths. Lots of moving parts here and different things to measure (user counts, session lengths, data transferred, page views, etc.).

But, regardless, it’s clear mobile is growing faster than other media in most if not all of these metrics.