There are two aspects of global warming that seem clear to me, the evidence for it is as overwhelming as for the theory of gravity, and we are already, at 400 ppm of CO2, well on our way to dire consequences. I am joined in these conclusions by climate scientists, as well as by people and groups that are following these events very closely.
There are two groups that seem unable to come to grips with this reality, skeptics who believe we'll easily adapt to the changes, and deniers who reject global warming altogether.
The most important deniers are the oil and coal companies and their enablers, members of the U.S. Senate. One of the most important oil company activists are the Koch brothers who have spent hundreds of millions of dollars directly or through groups they support financially. This group are the 21st Century analogues of the 19th Century Southern slave owners whose wealth and ways of life were threatened by the anti-slavery Abolitionists. They are prevailing at this point by their ability to create confusion and doubt about global warming.
The largest part of the skeptics are meteorologists, i.e., the people who report on the weather at your local tv or radio outlet. Along with them I include the large group of ordinary people who feel either that there is no global warming or that human activity has no impact on it. What characterizes this group is quite simple, they have not read enough about global warming. Among meteorologists those that are skeptics have not published. This means, to an academic with many publications like me, they are not acquainted with the literature on global warming as they could be. This is the same with ordinary people, they simply haven't read enough.
This is similar to my experience communicating with people about evolution. Most Americans deny the conclusions of evolution, but whenever they bring up their objections it is clear they simply haven't read enough. What happens both with evolution and global warming, the skeptics will read some popular skeptical work and this forms their entire view. They won't read up on alternate views and come to some conclusions that weighs all the views.
In evolution, the skeptics will read something written by someone naive about the actual processes and come to an inappropriate conclusion, for example, that the 2nd law of thermodynamics obviates evolution. The skeptic will then read no further on the topic and rather seize it as the foundation of an unassailable rejection.
Global warming skeptics are aided by something worse than naivete. Professionals in the Heartland Institute and Cato Institute, financed by the Koch brothers, furnish sophisticated articles supporting denial. They are successful for the same reason, the people who read their material fail to read enough about global warming and instead hold onto it like a dog with bone, and don't read anything that might compromise the denial conclusions.
A very important example of this is one that I have great difficulty understanding. Perhaps the largest fire feeding the skeptics are articles produced by Cato Institute and others claiming that there hasn't been any global warming over the last 15 years or so. I am an applied mathematician with 45 years of experience, going back to slide rule days, and over that time I've learned every way people can lie with statistics. I've read the papers claiming no warming trend and in every case they engage in a type of statistical like called "cherry picking". It is possible to show no increase in warming provided you very carefully choose what years to include.
There are two components to a time series of global temperature, a secular trend, and ancillary deviations in temperature. Important deviation from the secular trend are the El Nino and La Nina fluctuations caused by warming and cooling of the surface of the Pacific Ocean. El Nino raises the temperature above the secular trend, and the La Nina lowers it. El Nino and La Nina raise and lower the global temperature on top of the secular trend masking it. To find the secular trend, which is the real change in the global temperature, the ancillary effects must be removed, but they have to be removed carefully or you will fail to find the truth. If you "cherry pick" a year with an El Nino at the beginning of your series and then "cherry pick" a La Nina at the end of your series, you will have manufactured a flat or negative secular trend, in effect you have found a lie. This is what Cato Institute and the Heartland Institute have done. And the sophistication of their lie has profoundly affected the skeptics. What I don't understand is how the people at Cato Institute can do this. They seem to me to have enough background to know about lying with statistics, so why do they do it?