We shouldn't accept climate change as inevitable or stop trying to effect change. That said, what sort of clothing is out there which might help as we feel more negative effects?
The main thing I'm thinking about is dealing with heat, but I guess part of the question involves a little forecasting about the types of challenges people will face in the future.
The best clothing for a hotter environment is a tad counterintuitive, because it's less comfortable in the short term... you want full sleeves, full pants or a long skirt/kilt/toga/whatever (I'm reasonably certain that if heat waves continue cranking it up, these are going to become a unisex thing, whatever we're gonna call them...). You want everything loose so there's room for evaporation to happen (it's your body's natural swamp cooler), you want large openings everywhere so the air can ventilate, and you want lighter colors that reflect. You'll also want to cover your head, preferably withsomething wide (and/or includes the little neck covering flap deal) that creates a lot of shade, but it's currently more common in deserts to see less shade producing scarves/wraps.
You'll feel hotter in the immediate, and overdressed, but you'll overall be absorbing less energy from direct sunlight, and that means a more stable amount of body heat overall, and less risk of things like cancer.
I wear loose t-shirts, jeans, and a wide boonie/fishing hat. Less overall clothing is better, but more coverage is also better. Gotta find that balance is all.
TL:DR, the clothes most people associate with the Middle East... clothes that are worn by people who've dealt with a hotter climate for millennia. The white robe looking getup is what's gonna work best in a hotter climate.
That's one "study" with one guy wearing different clothes one time. And the black outfit was noted to absorb more heat than the white outfit. It was seemingly postulated the extra heat was lost before being transferred to the one guy due to the clothes being loose and billowing in the wind or allowing hot air to rise through the clothing creating convection. They didn't outright say, but it seemed like the white clothes weren't as loose and flowing. Either way they very much attribute the "cooling" to the fit and not the color.
It's not just the material, it's the specific weave too I think?
I'm not originally heat tolerant, personally, so when I visited Cuba I brought a lot of linen clothes and they did wonders. Just pants and tunics, and a brimmed hat. I looked like a drug lord but never overheated.
According to @guyrocket@kbin.social, one type is called a kaftan. A quick search yielded at least a dozen different sites, like Temu or kafko.
Full disclosure, I have never worn any of these, nor have a shopped for these or even visited those sites before. I just wanted to help and did a quick search.
I come from hot, humid climates. What we usually wore were materials like linen. Since they were wetter environments, shorts and shirts reigned supreme. Longer clothing loses the thermodynamic benefits when wet.
Well, or even more effective, just put your clothing into water. I even have a vest that is specifically designed for that:
You'll put it into water and evaporation is keeping you cool with a relatively stable temperature. For example: I sat around a few people who were clearly not "enjoying" the heat, while I was quite comfortable (and I'm really sensitive to heat and would normally escape hot places instantly).