This post was written by Adam Hadhazy, an intern at SciAm.com. You hear a lot about carbon these days, what with concerns about oil use contributing to global warming and skyrocketing fuel prices. But for all the scientific studies of atmospheric carbon, and for all the angst (and some would argue, wars) caused by the carbon in oil wells, it turns out that we know very little about the "deep carbon" hidden farther underground as well as underwater. To address this gap in our collective understanding, the Carnegie Institution of Washington, with funding from the Alfred P. Sloan Foundation, is holding a conference, the first of its kind, in Washington, D.C., from May 15 to 17. "We want to look at carbon from the Earth's surface down to its core," says Ronald Cohen, a research geophysicist at the Carnegie Institution's Geophysical Laboratory who will be a keynote speaker at the event. "We don't think it's that common once you get much past the surfaceâ¬but then again, we just don't really know." Figuring out what's happening beneath our feet is important in predicting climate change, say conference organizers. Global warming models are all based on known "surface" carbon, such as the carbon dioxide gas belched out by cars and coal-fired power plants as well as the natural amounts that animals and humans add with every breath. (A blogger did some calculations and determined that if we each breathed half as much, we'd cut down global production of carbon dioxide by 4 percent annuallyâ¬check it out.) If carbon beneath us that we haven't factored in should somehow get unleashed, those already disconcerting projections about drastic global warming may look rather tame. For example, if ocean temperatures rise sufficiently high, that change could unlock the huge amounts of methane gas now safely trapped on the seafloor. Cue scary musicâ¬methane is 23 times more powerful than carbon dioxide per unit as a greenhouse gas. "We think some of this methane has gotten out in the past and it's helped trigger some mass extinctions," Cohen says. Beyond such looming questions about geologic carbon are how the ill-understood workings of bacteria and other life forms deep within Earth could influence climate change. The discoveries of whole communities of bacteria living miles below ground or so deep in the ocean that sunlight doesn't reach them have revealed that life does indeed find a way. "Deep life is synonymous with dark life," says Katrina Edwards, an associate professor of biological and earth sciences at the University of Southern California, and also a keynote speaker. "Our knowledge drops off the table once we leave the light." All these unseen tiny creatures may have a big impact on Earth's "carbon budget" and how this carbonic currency cycles through the environment. The conference devotes a whole day to pooling knowledge about how much life may be percolating below Earth's surface and in the murky depths miles underwater. "We know more about other planets than we do about deep-sea life. It's less like field work than it is like space exploration" in trying to reach and understand these ocean floor life-forms, Edwards says.