Climate Desk: Piermont Marsh seems an unlikely place to learn about drought. This warren of narrow streams and muddy, reed-choked embankments clinging to the edge of the Hudson River twenty miles north of Times Square is the domain of crabs, worms, herons, and other water-loving creatures. But as Columbia University climatologist Dorothy Peteet paddles a narrow aluminum canoe deep into the marsh, she insists that buried deep in this black, sulphur-stinking muck are clues that could reveal when, and how badly,...