Even if this was feasible, atmospheric heating from the microwaves interacting with the atmosphere (as well as water vapor and particles in it) would be a real

Even if this was feasible, atmospheric heating from the microwaves interacting with the atmosphere (as well as water vapor and particles in it) would be a real problem. This would be equivalent to the Sun heating the earth+atmosphere on the order of a few percent more than it already does (see below). This seems like a pretty intractable problem with these sorts of plans to beam energy to earth. --- showing my work... Microwaves attenuate in the atmosphere at about 15 dB/km or 3%/km (see http://dspace.mit.edu/bitstream/handle/1721.1/4963/RLE-TR-087-14236979.pdf http://dspace.mit.edu/bitstream/handle/1721.1/4963/RLE-TR-08...). If the signal is losing power, its going somewhere: notably as energy (some converted to heat) into the atmosphere. If you're sending 13 PetaWatts (as indicated in the original link) through 10+ km of atmosphere, that's 3.400 PetaWatts, or 26% of the power, "lost" on the way to earth. All the power that's "lost" is being absorbed by the atmosphere and contributing to atmospheric heating. The earth gets 174 Petawatts of incoming radiation from the Sun (http://en.wikipedia.org/wiki/Solar_energy http://en.wikipedia.org/wiki/Solar_energy), but 30% of that actually gets reflected back, so the Sun heats with 122 PW of incoming solar radiation and this plan would add 3.4 PW, 3% more. Note that I didn't take into account the thinning of the atmosphere or the fact that not all the energy goes into heat (some of it could be absorbed in other ways). However, you still end up with some pretty significant additional heating and having microwaves absorbed by doing things like breaking chemical bonds in the atmosphere probably isn't a great thing either.