Global warming conjures images of rising seas that threaten coastal areas. But in Juneau, as almost nowhere else in the world, climate change is having the opposite effect: As the glaciers here melt, the land is rising, causing the sea to retreat. The geology is complex, but it boils down to this: Relieved of billions of tons of glacial weight, the land has risen much as a cushion regains its shape after someone gets up from a couch. The land is ascending so fast that the rising seas