By Tobias Carroll Rarely a week goes by without there being some awful thing happening in nature that reflects the effects of climate change. Sometimes it’s salmon migration running afoul of the weather; at others, it’s allergies getting more intense. This week’s indicator is a big one — and that’s meant in the literal sense of word. Big as in “the size of New York City” big. Not just “the size of Manhattan,” which would be alarming enough on its own. The whole city. All five boroughs. What, you might ask, was this big? An ice shelf in Antarctica, located in the eastern portion of the continen…