Dressing 'down' when it gets hot

Seems like a sensible idea, doesn't it, especially to save electricity and air conditioning costs.

via the Western Confucian: Should you dress down to beat the heat?

The article has a link to an article about Japan's Prime Minister Yasuo Fukuda dressing in 'laid-back' Okinawan kariyushi shirts.

Note how the articles describe such wear as 'dressing down' and 'laid-back'--how, then, do we distingish 'casual' from 'formal'? Partly by convention, but what does convention say is the difference? The number of layers? Perhaps the stuffy would emphasize wearing business formal even in hot weather, but how many of them would be so enthusiastic about upholding tradition if A/C weren't available?

The poor police officer above still has to wear a tie, while the prime minister's personal security (?) does not.

It is true that with more layers, one can have more ornamentation, designs, variety, and so on, but that doesn't necessarily make such an arrangement or ensemble more 'formal' than one with less layers or simpler. Is this evidence of the influence or power of the elites occupying colder climates over peoples living in warmer climates? [And the accompanying prejudice against other forms of clothing and fashion standards?] Gasp! Cultural imperialism!

I've raised the questions of adapting fashion standards to climate change (or dressing more sensibly when the weather changes) here and here.

More on Karisyushi:
Kariyushi Wear
Mango House
Japan Ministers to Wear "Kariyushi" Okinawan Summer Shirts
Japan Today - News - Abe begins Cool Biz campaign with Okinawan wear
Internet-Okinawa.com Gallery :: Okinawa, October 2005
OkinawaJET.com - Re:Kariyushi Wear - OkiJET Forums
Okinawa busy producing cool Kariyushi wear.
Okinawan-style.com * About Kariyushi
JIN-462 -- Uniforms and Uniformity

So is the Karisyushi original to Okinawa? Or was it adapted from the Hawaiian Aloha shirt? I've seen contradicting claims made in the links above. I'd probably prefer the Okinawan prints over the Hawaiian prints, as there should be more restrained ones available, but I think I still favor the guayabera above all. (A lot of Hawaiian shirts use flowers in the patterns, which can be a bit much--it's not using like using a single flower as a symbol of a clan.)

Aloha shirt - Wikipedia, the free encyclopedia
The Aloha Shirt
Aloha Shirts of Hawaii
Shaka Time
Hawaii Clothing Company
Avanti Shirts
Hawaiian Shirts, Polynesian Aloha Shirts at Hawaiian Shirt Shoppe
The Hana Shirt Company
Hot Shirts
Rainbow Hawaii