The world is warming up. This we know. Over its long, long life, the Earth has gone through multiple cycles of cooling and heating up again, or glacial advance and retreat. These are largely attributed to small shifts in the Earth’s orbit, which change the amount of solar energy received by the planet. To find reasons for the current heating up of the globe, however, we must look to no one but ourselves. As we pump greenhouses gases into the atmosphere, wrapping ourselves in a giant, insulating, carbon dioxide blanket, the sea level rises and the ice sheets shrink; the…