Global Warming activists consider the evidence in favor of human-induced warming incontrovertible. However, climate change science is anything but certain. Heated controversy surrounding the history, magnitude, cause, future impact, and even the existence of global warming continue unabated. Models of future climate change are based on questionable assumptions that arrive at a wide range of estimates depending on the assumption. The historical record is based on ice core samples, tree rings, and coral, which can only be found in a few, unique areas around the world. The current record of surface temperatures and air temperatures often give conflicting information. "Uncertain" is the only irrefutable claim to be made about climate change science.