Google's earnings will remain a "crapshoot" until it gains more market share in mobile search, Jordan Rohan, an analyst for Stifel Nicolaus, told CNBC on Tuesday.
The analyst told CNBC's Squawk on the Street. that the search giant was riddled with questions about its reach in mobile — a critical area of growth watched closely by analysts as smartphones become more dominant in the technology space.
"If you peel everything back and ask what's the one thing people care about, it's the core Google advertising business," Rohan said. "And what you really want to figure out is, how much is search growing?" he asked.
Investors want to know if Google is "gaining share are they not gaining share," the analyst said. "And that transition from desktop search—where Google keeps all the revenue—to mobile, where they share a lot with Apple and other partners, that's been a...a bumpy transition."
A key problem for Google, however, is that advertisers have not been as willing to pay as much for mobile ads as they are for ads displayed on desktop computers. The smaller display space on mobile devices is a barrier for tech companies to milk more revenues for mobile ads.
Still, Rohan said that mobile traffic makes up about 20 percent of spend, and about 25 percent of paid search clicks on Google. However, he added that it won't be long before mobile makes up about 40 or 50 percent of clicks, which will help drive Google's revenue up.
"At some point, there will be enough mobile devices, enough revenue on that side, that when the mobile...cost per clicks go up, Google's revenue will go up in step. We're not there yet," Rohan said.
"It cant be that many years away, given how incredibly high the appetite is for people on these mobile devices to shift all of their computing." he added. "When that happens it will be easy sailing for Google, but until that happens every quarter is a crap shoot kind of a stock."
Analysts estimate that Internet search giant will report fourth-quarter earnings of $10.49 per share on revenue of $12.3 billion, according to Thomson One Analytics. Rohan's estimates are a little ahead of the street, with an estimate of $10.65 earnings per share.