I ask, because the portrayals of ancient egyptians (in the tomb paintings) portray people who seemed to wear very little clothing, compared to today. Modern egyptians appear to wear long robes, or full western style clothing-whereas, 4000 years ago, most more (if the old paintings are accurate), just simple loincloths.
Is this evidence that the climate was warmer back then?
I think the amount of clothing modern Egyptians were is more influenced by the dictates of religion than climate.
Although some elements of attire are attributed to the religion, the more traditional dress in Egypt such as the *galabaya * for men and head scarves for women goes back even before Islam. (I don’t know if the same is true of the severe attire in a much more religiously conservative country like Saudi Arabia.)
Egypt today is pretty damn hot, especially in the southern parts of the country where these depictions are most famously found, such as the temples at Luxor, Aswan, and the Valley of the Kings. Loincloths would probably be comfortable even today in temps ranging from 90-110[sup]o[/sup]F (although it can get cool at night and chilly in the winter). So there is not much need to suppose that it was warmer back then.
The amount of clothing worn in any tropical or subtropical lowland area is almost entirely due to cultural demands rather than comfort. Minimal clothing is most comfortable in such areas.
The fact that people in the US are more likely to walk around in shorts and tanktops in the summer now than they were during the Victorian era has nothing to due with climate change. 
why do you think long robes are more uncomfortable in the desert than being uncovered??
Without air conditioning, the desert sun is, well… HOT!
Exposing your skin to the sun leads to dehydration and nasty sunburns. The first rule of survival in the desert is cover up. It is actually more comfortable than shorts and no shirt. (sorry, my experience is limited to shorts–no loincloths 
)
(And as for why the ancient Egyptians didn’t cover themselves: I dunno. Maybe they had air conditioning
Traditional Arab garb, as also worn in Egypt…the ankle-length, long-sleeved shirtlike garment plus the Arafat-style turban is remarkably comfortable in hot, dry weather, and it does protect against sunburn.
I would think that Western-style clothing is very uncomfortable over there.
Given the obvious benefit to covering up outdoors alongside the ancient art, is it possible that loincloths-only was indoor wear? I’m pretty sure that even thick-walled buildings get pretty hot in a 110º summer.
Of course, there are lots of cultural and artistic reasons to depict people in less than realistic garb: cf. the abundance of nudity and flowing cloth in Renaissance European art.
Another thought: there seems to be a variety of dress depicted, from skirts to full-body garments (for instance, here ). In my head I had only remembered the loincloths; I don’t like to think about what that says about me. Just how prevalent as a percentage are loincloth-wearers in Egyptian art?
Is that guy on the left about to brush the pharoah’s cat?
Good point, but I imagine condidtions along the Nile and in the delta would be quite humid and have much more vegetation.
A bit humid along the seas, but very dry most everwhere else, in my experience.
I think the OP is probably mistaken. I am not sure but I suspect in the main only the servants were depicted solely in loinclothes. Most people had longer dresses e.g. see here
The move from loincloths to lots and lots of cloth could easily be explained by the advances in clothmaking through the millenia.
If I was to find a tribe of native Americans in Brzail that were still “untouched” by the outside world, it would be likely that they would wear very little. And if I was to travel back in time to ancient Britain, all the Celts would be fairly near naked as well. Yet I doubt that the temperature of ancient Britain was ever all that similar to modern Brazil.
Where on earth did you get that idea about the Celts? Conventionally, they went naked into battle, but there is an abundance of evidence, archaeological and literary, that they habitually wore clothes. For example, many fibulae have been found, and it’s hard to see how naked people would wear them.