Two downtown theaters host free readings of new plays tonight, one dealing with global warming, the other dissecting modern relationships, both featuring strong female leads. At the Ohio Theater (66 Wooster St) the 2009 ENVISION Lab series continues with a reading of Lenora Champagne’s new play Staying Afloat, about the effects of global warming — whereby two women end up stranded on an iceberg with a polar bear (free, 7:30pm, RSVP at 212-268-3717, reservations@vandv.org or by going here). InViolet Repertory Theater Company presents a free reading of two new plays (repeating tomorrow night) at the Kraine Theatre (85 E 4th St). The plays Consumption, by Melanie Angelina Maras, and See Jane Talk, by Megan Hart follow female characters through relationships and life lessons (free, 7pm, RSVP to invioletrep@yahoo.com).