Between the Rio Earth Summit of 1992 and the United Nations climate conference (COP21) which began on Monday in Paris, the need to combat climate change has gained palpable urgency. Countries once in denial or dithering have now fallen in line as they face the overwhelming science that demands action, the threat of food shortages and hotter years. The minimum expectation from the two-week Paris summit is an international agreement, with hopefully workable means to enforce it. Businesses, led by Microsoft founder Bill Gates, have pledged investments in technology to cope with climate change, hoping to persuade others to join in. Yet, all of this is still a beginning of sorts, according to experts at Wharton and the University of Michigan. The presence of U.S.…