Palm trees are spreading northward. How far will they go?

What does it take for palm trees, the unofficial trademark of tropical landscapes, to expand into northern parts of the world that have long been too cold for palm trees to survive? A new study, led by Lamont-Doherty Earth Observatory researcher Tammo Reichgelt, attempts to answer this question. He and his colleagues analyzed a broad dataset to determine global palm tree distribution in relation to temperature. "In our paper, we draw a fully quantitative line in the sand and ask, 'How cold is t