For the last several years, when people have instructed me that human activity was causing a dangerous increase in global temperatures, my response has been, "Then tell me, what should the temperature be?" Should it be the temperatures that the planet experienced a thousand years ago, during which Greenland was settled as a farming community and during which wine grapes were grown in Scotland? Should it be the temperatures of three hundred years ago, when the Little Ice Age ended the inhabitation of Greenland and the Thames iced over? Should it be the temperatures of 829 A.D., when the Nile River froze? No response!
Read it all, very handy for those arguments you may have with True Believers.
What's more, every computer model shows that greenhouse warming is associated with a "hot spot" located four to six miles above the equator. We have been monitoring that very spot for fifty years. It doesn't exist. Thus, whatever warming we see is unlikely to be due to the greenhouse effect as the models explain it.