BEIJING—Global stock markets and Wall Street futures tumbled Monday amid concern about the latest coronavirus variant and tighter Federal Reserve policy. London and Frankfurt opened sharply lower. Shanghai, Tokyo, and Hong Kong also fell at the start of a trading week that will be shortened by Christmas. Benchmark U.S. oil fell by more than $3 per barrel. The spread of the omicron variant has fueled fears that renewed curbs on business and travel might worsen supply chain disruptions and boost inflation. “Omicron threatens to be the Grinch to rob Christmas,” Mizuho Bank’s Vishnu Varathan said in a report. The market “prefers safety to nasty surprises.” In early trading, the FTSE 100 in London fell 1.7 percent to 7,143.60 and the DAX in Frankfurt lost 2.4 percent to 15,155.71. The CAC 40 in Paris sank 2 percent to 6,787.68. On Wall Street, futures for the benchmark S&P 500 index and the …