Trees are natures air conditioners but you have a hard time convincing people of that. I read somewhere that a mature cottonwood tree has as much cooling power (transpiration IIRC) as 500 room air conditioners. Also homes USED to be built to take advantage of convection cooling, heat sinks and prevailing winds. I had one house that was built in 1921 that on all but the very hottest of southern days could be kept cool by adjustment of windows and doors.
Aaron