U.S. climate envoy John Kerry defended his negotiations with China — and angrily rebuffed what he called a “stupid” lie that he routinely travels by private jet — during a grilling by House Republicans on Thursday before he sets out on his next climate mission to Beijing. The questioning in Thursday's hearing by the Republican-led House Foreign Affairs Committee's oversight subcommittee underscored the risks for Kerry that rising tensions between the two rival countries will stymie progress in what scientists stress are essential cuts in fossil fuel emissions over this decade. Republicans' questioning of Kerry on his climate diplomacy at times broke down into challenging the existence of the scientifically established fact of climate change and openly insulting the former secretary of state, who is a longtime target of political hardliners.