Looking at multiple places, it appears like the Linux desktop has been on something of a roll lately with the market share starting to trend upwards. As always with any kind of statistics gathering, you need a pinch of salt.
On the NetMarketShare website, the Linux share as we reported last month suddenly had an upwards surge from 1.36% to 2.87%. You could easily write it off once but here we are again and the Linux share has risen up to 3.17%. Even on their stats, it rising twice in a row is quite rare and never usually this much either. Looking into their stats further, it appears Ubuntu is the clear winner and what's pushing it going from 0.27% in March up to 2.11% in May.
It's somewhat backed up by Steam's statistics too, when you look at their monthly hardware survey. The Linux user share on there has risen now three months in a row which we keep an eye on with our Steam Tracker, and the trend there is pretty darn clear. Currently Linux is sat on 0.91% according to Valve's Steam survey.
We can speculate as much as we like as to why but we may never really know what's going on. More people at home, more people using Linux in the home than the old Windows machines at the office? Could be any mixture of things but it's still interesting to see.