So advanced that it is difficult to even imagine what such people might do. Get it wrong and attempts to control one aspect with devices such as Mr. Carroll's proposed Southern Oscillation damper could cause unforeseen and dire effects. Don't try this at home, kids, not without a spare planet. That's the way humans have done business for millennia, and barring drastic genetic and social engineering, that's the way it will continue to be done for millennia to come. Move the people out of the floodplains, stop using fossil fuels, stop polluting the environment, start using birth control and suddenly a big part of the reason for weather control on our home planet disappears.
Humans are ambitious monkeys who like to fool with things.
Descending in elevation, the heat dissipating efficiency of our bloodstreams would not be enough to prevent our brainpans from exploding. On ascent, our minds would have to generate energy like a furnace. The Krebs cycle does not transport energy anywhere near fast enough for this. This violates a basic tenet of evolutionary theory, that random mutations produce distinct phenotypes, only some of which are beneficial, many of which have null impact and most of which are downright harmful. Ironically, this is diametrically opposed to the stated Darwinistic view of the story.