WASHINGTON (AP) — President Joe Biden takes center stage in a two-day climate summit highlighting America’s return to the fight to curb global warming. The all-virtual summit that begins Thursday will feature 40 world leaders and lots of other advocates and experts but is clearly Biden’s show. Biden is expected to promise that America will cut its carbon pollution at least in half compared with 2005. Then he’s going to challenge other nations to be just as ambitious. Also key will be financial help to poorer nations. The summit will be livestreamed so anyone can watch the cajoling, conflict and pathos.