Science is always working on global warming these days, so there are lots of articles out there on it. Here's another one on worms and global warming - it says (for those who don't want to read this long and technical piece) that a study made in England found higher temperatures actually decreased the worms' effect on the increase of CO2, meaning they would not aid in global warming, but help minimize it.
http://www.co2science.org/scripts/CO2ScienceB2C/articles/V5/N18/COM.jsp