https://phys.org/news/2018-07-california-climate-goal-earlybut-biggest.html > Further complicating matters is a Trump administration plan to weaken fuel economy standards and revoke California's power to set its own, stricter rules—a move that could cause vehicle emissions to rise even more. > The uneven progress shows the big challenges that loom as California advances toward its more ambitious goal: slashing planet-warming greenhouse gas emissions another 40 percent by 2030.