The recession’s squeeze has pushed ZenithOptimedia’s bullish outlook for online ad spending downward a bit, as the Publicis Groupe media shop is predicting global online ad revenues to rise 21.2 percent this year and about 18 percent in 2009. The company will present its forecast on a panel at the UBS Global Media and Communications (PDF) conference in New York this morning, on a panel with Interpublic Group’s Magna and WPP’s GroupM.

SEE ALSO: Online Ads’ Global Share To Break 10 Percent Mark In ‘08; Internet Ads To Rise 26.7 Percent: Zenith

This year’s forecast is down a quite bit from Zenith’s expectation in June for global internet ad spend to grow 26.7 percent this year. Still, considering that Zenith sees the globe’s total ad market sinking into negative territory with a 0.2 percent decline, online is still relatively strong. In North America, Zenith is calling for internet advertising to rise 18 percent as well, with Western Europe lagging with only 12 percent gains this year. With next year looking very uncertain, Zenith is projecting 17.9 percent growth. With hope for an economic comeback not likely to happen before 2010, Zenith is calling for 21.3 percent gain. Beyond that, Zenith’s online forecast has the internet taking a 15.6 percent share of global ad dollars in 2011, 5.2 percentage points ahead of magazines and 5.6 points behind newspapers, after having narrowed the gap from 15.1 points in 2008.

We’ll have GroupM’s latest forecast here at at 5 AM PT, as well as coverage of Magna’s ad spend predictions later this morning at the UBS MediaWeek conference