SALEM, Ore. (AP) — Stymied by a walkout by Republican lawmakers in the Oregon Legislature over a climate change bill, Democrats say they will issue subpoenas to try to compel their return. Oregon has become a front line in the battle over how to address global warming, with Democrats prioritizing a bill that would charge polluters for carbon credits and the minority Republicans objecting, saying it would increase costs for Oregonians. The Republicans walked out of the Senate on Monday before the bill come to to the floor for a vote. House GOP members joined the walkout on Tuesday. The House rules committee late Thursday voted to issue subpoenas ordering absent Republicans to appear before the panel.