Google earned more than half of the $8.8 billion spent worldwide by advertisers on mobile internet ads in 2012, giving the search giant a 52.36 percent share of global ad revenue.

This year, both the global mobile ad market and Google’s share therein is expected to almost double, with eMarketer forecasting mobile internet ad revenues of $8.85 billion for Google in 2013 from $15.82 billion overall, far ahead of second-placed Facebook, which is tipped to earn $2.04 billion (12.9 percent share).

Twitter, meanwhile, is on track for a relatively slight $310 million, and a 1.95 percent share, although the former is more than twice what the micro-blogging social network earned in 2012. Twitter’s share of U.S. mobile advertising is also expected to be slightly higher at 3.6 percent.

(Source: eMarketer. Twitter image via Shutterstock.)