John Robson: For the past 2.5 million years the Earth has been unusually cold, with repeated glaciations whose periodic advances and retreats science cannot model or predict. In fact we are still in an “ice age” today, with significant polar ice, though in a relatively warmer “interglacial”. Fortunately. Civilization would be impossible without the warming that started suddenly 12,000 years ago, and would become very difficult if the glaciers began another sudden advance. If the Earth actually is now warming, relative to 15,000 years ago or indeed the “Little Ice Age” from the end of the Middle Ages into the mid-19th century, it would be neither surprising nor man-made.
