>making it almost impossible to reliably grow crops
Not even remotely true, agriculture will produce smaller yields but you can grow things in a pretty wide range of temperatures. The greater difficulty is drought and the difficulty of irrigation without some massive desalination plants.
>sea walls to protect cities from rising sea levels
Oh noes, sea levels rise a few meters. You act like it's the fucking biblical flood.
> expensive green house farms to produce crops that can no longer be field farmed
Not true and do you know how fucking hot a greenhouse gets?
>decrease in fresh water
Is largely dependent on aquifiers draining, We're not in medieval Europe where agriculture is entirely rainfall-dependent, and again, you are talking about a decrease in precipitation (which is why crop yields drop).
> increasingly authoritarian in response to the threat of mass migration, social instability
What comes first, the Malthusian crisis or the social instability? We live in an unstable world because of an unstable economic and political system, because there are actors in the world who sow chaos and death. See: Iraq War and the Middle East turning into a war zone because Dick Cheney wanted to be as evil as humanly possible. Climate change has not in recent history produced any drastic outcomes; the causes of growing instability are all about the political and the economic system.
>The increased carbon in the atmosphere will make the air less breathable
Carbon emissions, as much as they exist, constitute a vanishingly small part of the content of the air we breathe. There is no expected decrease in the oxygen content of the air, certainly not a drastic one. Smog emissions from the local factory are a far greater effect on local air quality than overall carbon content in the air.
There's so much disinfo and scare tactics in these scenarios. I can give you some credit, maybe you're new to this, but the concern over climate change (so far as it is a real concern) has to do with agricultural profitability, rather than existential threats. It's just sad to see leftypol using right-wing argumentation tactics to say climate change is real, rather than the factual temperature data and models (which do indicate a rise in temperatures, but the total rise from 1950 to now is less than a degree C).
It's not like we were ever allowed to actually vote on any of this. So far as people have a right to vote, they overwhelmingly vote against climate doomerism, because it's such an obviously elite-centered agenda. The few times Green parties are given any significant electoral power, they show their true colors and ruthlessly attack the lower classes, as they did in Germany.
For what it's worth, the actual consensus does not acknowledge the "doomer" models, but there is so much screeching from the ecologists that it's hard to know that if you're an impressionable youth or just rely on publications to give you accurate information. This story of imminent collapse is an old one, going all the way back to Malthus, and it will always find its partisans. If a university wants to protect its reputation, it doesn't sell the doomer model, even in this political climate. That's why it has to be promoted by the Club of Rome (literally some of the Porkiest aristocrats you can find) and is popular among the Davos crowd more than it is among academics even. One way it seems academic, though, is that one of the criteria for promoting in the academy is an incredulous belief in whatever dogma is fashionable, if you yourself are not an expert in the field. This doesn't always hold, but it does sink its teeth into a lot of young people who do not have reasonable ability to compare to any other source or their evidence. I know we were told in middle school science class one day to write an imagined news article about global warming, where the result was that you were expected to declare that it was true or you get a non-passing grade. It's basically a "when did you stop beating your wife" exercise.