(Updated January 2017 by Dr. Peter Gleick, Pacific Institute)
Scientific understanding of the role of humans in influencing and altering the global climate has been evolving for over a century. That understanding is now extremely advanced, combining hundreds of years of observations of many different climatic variables, millions of years of paleoclimatic evidence of past natural climatic variations, extended application of fundamental physical, chemical, and biological processes, and the most sophisticated computer modeling ever conducted.
There is no longer any reasonable doubt that humans…