It's ugly out there and it could get worse.

Dismal U.S. corporate outlooks and worries about slower worldwide growth have pushed third-quarter earnings estimates into negative territory, which, if it came to pass, would be the first drop in three years.

Third-quarter earnings of Standard & Poor's 500 (^GSPC) companies are now expected to fall 0.1 percent from a year ago, a sharp revision from the July 1 forecast of 3.1 percent growth, Thomson Reuters data showed on Thursday.