Playing football in the day with proper shade is better than playing at night during the summer because of humidity. God damn the humidity you get at night in the summer in Abu Dhabi. Here is the thing though, 20 kms away from the shore line and you get cool air (at night) and a lot less humidity in the dessert so any stadium could be fine to play in. It is just that anything near the coast is miserable. Winter in UAE is very nice, very moderate to play football but the competition won't be happening then, just no way, all parties will not agree. In UAE, the city of Al Ain, part of the Emirate of Abu Dhabi, it isn't as bad as the city Abu Dhabi, an island, because it has no coast. The heat comes from direct sunlight, cheap methods of shading should drop the tempratures significantly. You don't need air conditioners, you need air circulation/ventillation to drop it even further but I am no building scientist. Ask Sergio, he may know.
All I know is that, a big deal is made of the stadiums when the WC is in 10 years times, by that time Qatar would have built a Nuclear power plant, purchased a couple of hundred wind turbines and better solar panels than what they have today + what they learned from Abu Dhabi's experimental city 'Masdar'. It really isn't a big deal when you look at it from an experimental point of view. The amount of research that can be done on this is monumental, you'd just hope for it to actually be useful to the world.
Examples:
1. Research in thermal bridging.
2. Renewable energy.
3. Concrete mixtures.
4. Expediated construction techniques.
5. Architectural advantages and disadvantages.
6. Transportation research.
The 100 billion pounds is not that much if you think about it, that is 10 billion every year for a rich country looking to build its cities and attract population. It really is nothing actually when you looked beyond the WC. Qatar for all its noise is still pretty empty, some proposed stadia are in cities that do not even exist yet. Al Wakra city is one of the biggest cities in Qatar and it has population of only 30 000, less people than the amount of the stadium in it will hold for the WC. Lusail is the newest city to be under development and the capacity of the stadium is 86 000, more than twice the population of Al Wakra. So the 100 billion will be spent on building entire cities and towns, to become the permenant residency for people who want life by the beach, a step away from both sides of the world and pay no taxes. And if you know what buildings, roads, sewage, cost you will see that 100 billion can be easily and quickly consumed. Especially when it is a Middle Eastern country 'friends' with the USA.