Standard & Poor’s 500 Index E-mini futures expiring in September climbed 1.8 percent to 1,906.25 at 7:40 a.m. in New York and gained as much as 2.3 percent. Futures on the Dow Jones Industrial Average added 261 points, or 1.7 percent, while those on the Nasdaq 100 Index also rose 1.9 percent.