The unrest over the U.S. Chamber of Commerce’s policy on climate change has led a fourth company, Apple Inc., to quit the business trade group.Apple Vice President of Worldwide Government Affairs Catherine Novelli sent a letter Monday to chamber President Tom Donohue, saying the company supports limiting greenhouse gases and “it is frustrating to find the Chamber at odds with us in this effort.—Apple resigned its membership “effective immediately,— according to the letter.The tech company’s exit comes after three large utilities — Chicago-based Exelon Corp., California’s Pacific Gas & Electric Co. and PNM Resources, a holding company with New Mexico ties — quit the chamber in the past three weeks.Sportswear company Nike also registered its disapproval of the chamber’s climate change position by quitting the group’s board of directors. Nike said it decided to stay a member in order to try to effect change within the business group.The chamber did not immediately respond to a press inquiry.