Burning wood is absolutely a cost on the environment; just ask anyone who grew up in homes heated by firewood. But of course, as you say, the scale is different. Should your example of medieval deforestation have been impermissible for environmental reasons, then? Where should the line be drawn? Who has the authority to draw that line?
No (non-nuclear) renewable technology currently exists that can by itself meet the energy demands of developed world standards of living. I'm not sure if wind and solar alone can even meet a developing country's standard of living. I'd really like it if we could build a thousand new nuclear power plants, but of course, reality is often disappointing and we get things like Germany shutting down its nuclear reactors and burning more coal instead.
No (non-nuclear) renewable technology currently exists that can by itself meet the energy demands of developed world standards of living. I'm not sure if wind and solar alone can even meet a developing country's standard of living. I'd really like it if we could build a thousand new nuclear power plants, but of course, reality is often disappointing and we get things like Germany shutting down its nuclear reactors and burning more coal instead.