SAN FRANCISCO (AP) – A federal judge hearing lawsuits that accuse big oil companies of lying about climate change is turning his courtroom into a classroom. U.S. District Judge William Alsup has asked lawyers for two California cities and five of the world’s largest oil and gas companies to present the best science now available on global warming. Legal observers say they’ve never previously heard of a court holding a tutorial on climate change, and they are eager to see how the oil companies explain global warming on Wednesday. Alsup is considering two lawsuits filed by San Francisco and neighboring Oakland against Chevron, Exxon Mobil, ConocoPhillips, BP and Royal Dutch Shell. They allege the companies mounted campaigns to downplay the risks of global warming and discredit research that human activity was to blame The companies argue Congress has encouraged oil and gas development.