Well, let me be the first to say that you are a complete fucking selfish asshole. I imagine the millions of people that are going to die so you can a slightly more pleasant September will go to their graves knowing they died for a good cause. The hot spots on this planet are going to get hotter and the warm places are going to get hot. That means agriculture across the planet is going to be disrupted on the very large scale. Which possibly means millions of people of dying, but that's okay, you can wear a short sleeve shirt in September!
As for those nobodies that live on the coast, which is probably a good chunk of the human population, they'll just have to suck it up. Their cities will disappear and they'll just up and move, like it's nothing. It's just their lives and livelihood, I mean, it's really nothing. The trillions of dollars in infrastructure across the world will need to be replaced or augmented will come out of our pocket change, but that's okay, you're warm in September!
Of course, let's not discus the thousand or millions of species that live on this planet are going to heavily impacted or die. The giant and highly complex ecosystems across world with just have to "suck it up", you know, they don't do anything but make the world livable and the air breathable (I don't mean that figuratively either.) The environment will change in 100 years what would usually take 100,000 years, with a huge mystery of how it will turn out, but who cares, you get to drive a super size truck! I mean, if Mother nature was not such a pussy, she would not have this problem because it is all about YOU.
PS> If you don't like the September's where you live, you can fucking move, you ignorant fuck.