The Daily Climate: The most pressing example of climate change’s impact is not monster hurricanes, retreating glaciers or water wars. It’s the humble swimming sea snail. The tiny pteropod has difficulty growing a shell in a warmer planet’s acidified ocean waters. Given the snails’ role at the base of the cold-water food chain, its struggle threatens the entire polar ecosystem, through salmon to seals and whales. The problem is one of many associated with ocean acidification already underway as a …