Christian Science Monitor: Efforts to combat global warming, triggered and reinforced by rising levels of carbon dioxide as humans burn fossil fuels and convert forests to farmland, largely focus on preventing CO2 from entering the atmosphere in the first place. But small groups of researchers are pursuing a complementary approach. They are looking for ways to remove CO2 already in the air. On small scales, the approach has been used since the 1930s at dry-ice facilities, as well as to scrub CO2 from the air on submarines...