I think many alarmists are not hucksters, but do suffer from delusions of grandeur or megalomania

All female youth team at United Nation climate change talks

Three young women are on their way to Bonn to take part in climate change negotiations that will shape the future of the planet. They will be joining other young people from across the world to demand tough action from world leaders.
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We will be there to make sure that the survival of thousands of vulnerable people is being considered by world leaders who decide on the future of our climate".

Megalomania: Information from Answers.com

Whereas it is possible, in the case of megalomania, for an actually important man/woman to be preoccupied with his/her own actual importance, a person suffering from delusions of grandeur would stubbornly entertain patently false, generally fantastic and often highly complex ideas of his/her own importance, often with a supernatural or science-fictional bent.