Bob,
No I wouldn't do any sprays. The spraying in Las Vegas/Phoenix/ in strictly for show,and to cool folks walking by.It isn't essential,and it doesn't add anything in respect to growing plants.Those places are so hot/dry in the summertime ,and the spray is so fine that it doesn't even make it to the ground.
I would run underground lines from the "house's" exhaust pipe(or better yet a collector/settling basin).Run them directly to the tree.You would have to do it carefully,so you don't have to add any electric pump.Heck-lots of folks go to health clubs-if you need a pump, use a man driven one-get some free exercise.
Long term Climate Prediction Science is a lot less developed than Chemistry/Physics.It is even waaaaay behind the Biologic sciences.Medical science is fairly new-50-150 years depending on your point of view-and there are plenty of examples of very bright people being very,very wrong.Ulcer treatment is one prominent example.From 1955-1985 1,000,000's of high risk operations were done for ulcers.It wasn't until about 1990 that the correct treatment was accepted-antibiotics for H. pylori.Suitable antibiotics were available from 1950 on(maybe earlier since it might have been sensitive to the earliest penicllins initially).
There were plenty of studies done showing that these surgeries(cutting the vagus nerve,and bypassing the bottom of the stomach) were "good."In hindsight they were BS,but the best and brightest accepted them at the time.Of course,and new disease-GERD- immediately sprung up to use the meds-acid suppressors of one sort or another- that had been developed to treat the ulcers.The low fat/high carb diet is another example of science by polling.
Smart folks can be dead wrong. The weather science folks have a lot of suggestive numbers, but since they can't do experiments we won't know for sure for several hundred years.
On the bright side, conservation-energy efficiency-alternative energy-water conservation are win win situations that can produce jobs that can't be outsourced(someone has to actually install insulation,solar panels).Using power plant CO2 to increase plant growth is another idea being worked on.
We'll see(well,we will be dead, but...)
Charlie
PS-Better warming than cooling if we are forced to choose one.