After historic floods devastated Midwestern agricultural states this spring, some fund managers are evaluating how climate change will affect the long-term value of companies that make or sell products ranging from tractors to fertilizer. The issue is not simply the unpredictability of the weather. Instead, fund managers say, they are struggling to model how extreme weather events from droughts to more powerful storms will affect commodity prices and, in turn, spending by farmers on equipment or seeds. In November, the U.S. government published a report that found climate change will boost costs in industries including farming and energy production by increasing the frequency and severity of storms. The U.S.-China trade war has also clouded the outlook for U.S. […]