...."wonderful opportunities for unqualified people to write a book that will be purchased by those who hold similar opinions."
I presume You're talking about unqualified People like these:
Al Gore - An inconvenient truth.
The economics of climate change - Nicolas Stern.
Bring on the Apocalypse - George Monbiot.
Actually this list runs into the hundreds and I don't have time to list them all. That said there are many books written on the subject where the author has no formal qualifications but have fallen for the story for different reasons.
Al Gore because it has made him over 100 million dollars, Monbiot because He's a lost cause and will remain a greenie no matter what the evidence says and Stern because, well, again He's fallen under the spell too.
By the way file this under more madcap climate scare stories. From todays Guardian:
http://www.guardian.co.uk/environment/2013/apr/08/climate-change-air-turbulence