Thermo Fisher Scientific Inc.’s third-quarter earnings climbed 9 percent, helped by revenue growth in key segments, and the Waltham scientific instrument and laboratory supply maker raised its forecast for 2012. The company said it earned $290.4 million, or 79 cents per share, compared to $265.4 million, or 69 cents, in last year’s quarter. Revenue grew 5 percent to $3.09 billion. The performance beat Wall Street expectations. Thermo Fisher expects adjusted 2012 earnings of $4.81 to $4.88 per share, up from its forecast $4.74 to $4.84.