Defrost Before Using

AITOOW wonders how much arable acerage would be ADDED if we have global warming? They always talk about what will sink. I quick look at the map seems to indicate the opposite. Huge parts of Canada and Russia will become useable. Areas near the equator are already desert. We lose a few islands and coastal areas. Is Brazil the one large land mass in question? And why don't we ever blame rising human consumption on lowering resevoir levels? They make it sound like it is all supply/evaporation driven.