Boxer calls Obama's emissions target "credible"

The 17 percent figure is contained in the House-approved climate bill, but the Senate plan would require a 20 percent reduction. Boxer's committee approved that plan 11-1 earlier this month with no GOP members participating.

Senators including Max Baucus (D-Mont.), who cast the lone committee vote against the bill, want the 2020 emissions target scaled back. Both bills would require 83 percent cuts by 2050.