NEW YORK/LONDON—Global stock markets faltered on Friday, while benchmark bond yields gave up earlier gains after data showed U.S. job growth slowed considerably in November and markets stayed volatile as investors assess implications from the new Omicron coronavirus variant. After opening higher, Wall Street’s main indexes quickly turned negative in morning trading. European markets also lost gains. MSCI’s gauge of stocks across the globe shed 0.52 percent. Omicron has gained a foothold in Asia, Africa, the Americas, the Middle East, and Europe and has reached seven of the nine provinces of South Africa, where it was first identified. Many governments have tightened travel rules to keep the variant out. “The top issue is still this whole Omicron variant. There are enormous amounts of uncertainty there,” said Randy Frederick, vice president of trading and derivatives for Charles Schwab in Austin. “Volatility means big moves in both directions and we have had …