The world’s climate is changing; this is well documented. Many climate parameters reflect the changes we see all over the world today: the atmosphere and the oceans are getting warmer, CO2 levels in the atmosphere are increasing, sea level is rising, and snow and ice are melting away. The earth’s climate has always varied, and there have always been physical explanations for these variations. Over the last 30 to 40 years, however, the climate has changed more rapidly than can be explained by natural causes.