I don't think most of them actually have. But a few loudmouths like James Hansen at NASA can make it seem that way though.
As engineers, you and I are trained to look for cause and effect and try to understand the relationship between these.
I never fails to be amazed by the number of people that I would otherwise assume to be intelligent people than are simply unable to apply deductive reasoning to the simplest of problems.
A very simple fact should cause most people to question whether CO2 is a factor in global warming:
In all the ice core data that shows temperature change vs atmospheric CO2, CO2 increases lag temperature increases by hundreds of years.
Many people simply don't seem to be able to understand that this places rises of CO2 into the category of effect, rather than cause.
When people cannot use logic to correctly interpret even simple relationships like this, they are subject to being convinced by propaganda.
For over half a century of my life, I had always thought that everyone else had the same intelligence, logic and reasoning capability that I did. Naturally, I knew there were some gross retards, but I went through life believing that everyone else was the same as me-- or at least that I was no different/better than anyone else.
Then one night I was watching a comedy show on teevee. It was Gallagher, the comedian, who I have found to be a pretty astute observer of mankind and its foibles. At one point in the show, he pointed out something that has enlightened my life immensely. He said:
"Remember, intelligence is distributed on the bell curve. At any point in time, 50% of the people walking past you are morons."
I had minored in Psych in college, so I was very familiar with bell curve distributions, means, medians, standard deviations, etc. But what he pointed out was an epiphany to me.
And he is correct. 50% of the population is sub-100 IQ, below average, sub-par, i.e., morons. And they are propagating their sub-par progeny at a greater rate than those above average.
And we are letting them vote and determine the fate of our country...
Maroons!