A potential change in U.S. leadership, combined with China's ambitious new emissions-cutting plan and a European "green recovery," could get the world two-thirds of the way to meeting its climate goals if pledges are met, scientists said Wednesday.

Democrat Joe Biden, who hopes to beat climate-change skeptic U.S. President Donald Trump in November's election, has promised to set a U.S. goal for net-zero emissions by 2050, while China made a surprise vow this week to become "carbon-neutral" before 2060.

The European Union, meanwhile, has agreed to spend at least 30 percent of its hefty coronavirus recovery stimulus on climate action as it advances toward its own net-zero goal, according to new analysis from research coalition Climate Action Tracker.