Oh, and all this is academic. Lets assume your insanity is true and climate change to this degree is normal and the historical record actually supports that claim. It's bullshit but lets pretend it was real.
See we have other records - archeological, anthropological etc. etc and the thing is - they show that every major climate shift humanity has experienced was a major calamity and we very nearly didn't survive any of them as a species. Every single one came close to an extinction level event for us. Every single one caused massive displacement, starvation and wars.
And we are MORE vulnerable now than we were when those happened. They happened when displacement was a much smaller problem. If you went somewhere else, there was a good chance you could find somewhere that somebody else wasn't already living and prepared to fight to keep you out off... there are no such places anymore. There is nowhere for the displaced to flee but to your country. America can't figure out how to deal with a few hundred thousand refugees from wars they caused - how the fuck are you going to deal when there's a few hundred million or more fleeing starvation and hunger and drought ? Sure it may make some places green which aren't now. Those places won't be producing much food anytime soon though - most of them are areas where the soil is not conducive to farming. No matter how much warmer and wetter you make it - Siberia will not have productive farmland for centuries. The soil is just to dead. And meantime - the places that were good farmland won't be anymore.
Oh and the plagues... you are having a political crisis trying to deal with Zika right now. Malaria kills more people every year than any other cause. Even a small increase in the global average *massive* increases the areas where these diseases can spread. Many economists have calculated that Africa's economic woes can be *entirely* attributed to Malaria. Sure we have wars and corruption but so does everywhere else. We alone have malaria to deal with. With all those productive people dying young. All those kids missing school because mommy is sick, husbands and family missing work to take care of her and all that money wasted on funerals in a classic broken window fallacy.
Imagine America with Africa's economy - all your wealth destroyed, all your resources spent just trying to avoid complete collapse - and for the same reason.
That's the thing you think is not a major problem. Just because nature can be a bitch doesn't mean it's not idiotic to horrible things to ourselves. The lesson to learn from natural climate shifts is not that climate shifts is just something that happens and so what... the lesson is that it has come pretty close to eradicating our species several times, and never failed to cause enormous hardship and uncountable deaths and it will be *worse* next time.
And, much like the zombie appocalypse, in a major climate change scenario - the single greatest threat is not the weather, it's the other humans. Who will happilly kill you for the water you have.