In terms of libertarians he's the most lite and electable one, which isn't saying much when your party is full of climate change deniers. And I think libertarians do touch on issues that are important and ignored by politicians but give bad solutions to those problems.
But giving credit where it's due, he does believe in it. But he thinks solely the free market will fix it and wants to remove cap and trade pollution limits. He wants environmental impacts measured by cost benefit analysis which is a horrible way of doing something when environmental degradation is by and large caused by non point sources and attributting personal blame is hard without a strong environmental regulation agency. Also oil suppliers have frequently colluded to prevent emerging technologies from being utilized to replace them. Such as the amazing advances in battery technology bought out and sat upon by car companies. We need to wean ourselves off of foreign oil as soon as possible so the government isn't incentives in continually sticking it's fingers in the middle east. That won't happen without giving incentives and regulating the oil and coal industries. Also he's in support if fracking which causes even more pollution.
Open borders is a bad idea as well, only serving to benefit corporate interests in lowering wages. Flat taxes burden the poor who spend all of their income to get by. And his idea to have a consumption tax based off of usage of money hurts the poor further while benefiting the elite rich who hoard increasingly large sums of wealth. Privitization of schools and prisons are both equally bad ideas for a variety of reasons. Cost cutting free market behavior lowers teaching standards and allows the middle class and wealthy to further outpace the poor in education effectively trapping them in their income bracket. Along that same note public colleges should be federally funded, it will drive costs down due to removing the predatory nature of school loans and allow for rapid economic growth as graduates would quickly be able to spend and participate in the larger market. It would allow for students to move out instead of living with their parents to save money for years. I don't think I need to elaborate on the failings of private prisons as they're self evident.
He's in favor of both citizens united and the tpp. Hes against single payer Healthcare which would drive down costs here and let us join basically every other developed country in the 21st century. He wants to go back to a gold standard currency system which was phased out of this country for a reason.
The only thing I think is a good idea by him (I believe he wasnin support of this but its beem a while) is repealing the bloated welfare system and implementing a universal basic income as a social welfare net. I don't think he goes far enough with it though.