4 years of presidency is not going to sell anyone's future. The worst that will happen, not counting a nuclear war, is
1) more gas/oil/coal gets mined, driving the prices down, and making the renewables unattractive.
2) increased CO2 emissions due to cheaper gas/oil/coal.
3) make the rich richer, everyone else poorer, which has been happening for decades in the US
Neither of these are particularly scary, it just sets the humanity a few years back, but maybe will force us to come up with some technological solutions to fight CO2 and other climate change issues.
Stop being so alarmist, he won fair, it's his turn to drive the bus. I don't like him, but things don't always go our way.