BUT, CO2 IS PLANT FOOD… how can that be bad for anything?
Ah, the wonders of unintended consequences.
It appears that vines such as poison ivy, oak, sumac, and kudzu are especially good at utilizing the increased atmospheric CO2. I confirm the below reports with my own experiences this past April clearing a hill side of invasive Tamarisk interwoven with poison oak vines leaving me with the worst (80% coverage) case of poison oak I’ve experienced. Now that hillside is covered with recovered poison oak consisting of monster leaves the size of fig leaves -
just don’t try to cover up your privates with it 
Unlikely Fan of Global Warming: Poison Ivy
May 30, 2006
Global warming may spell bad times for polar bears but it seems to be a boon to poison ivy. A six-year experiment to find out how increased levels of carbon dioxide affect forests uncovered a surprising result: In the area used for the experiment, poison ivy grew like crazy. Melissa Block talks with ecologist Jacqueline Mohan is a scientist at the Ecosystems Center in Woods Hole, part of the Harvard Forest in central Massachusetts.
Poison Ivy Growing Faster, More Virulent
July 20, 2010
Lewis Ziska, plant physiologist for the U.S. Department of Agriculture’s agricultural research service, says rising carbon dioxide levels and forest disruption are making poison ivy spread faster, grow larger, show up in new places and become more toxic. He tells host Michele Norris what makes the plant uniquely affected and how to treat skin that’s been exposed.
Dandelions, Poison Ivy Grow With Global Warming
by John Nielsen
July 12, 2007
A pair of new studies shows dandelions and poison ivy are expected to thrive as carbon dioxide, the main gas responsible for climate change, builds up in the atmosphere.