Unfortunately, gutting the industrial output of the planet by 50% isn't in the cards, except by global war. That is how we got rid of industrial over-capacity last time ;-(
I'm pretty sure that a global war would have the factories working overtime and war tends to not be very environmentally-friendly overall. So, that's not a solution, much less a good one.
And cutting industrial output by 50% right off the bat is unfeasibly large even if it could be implemented.
But there are other options. Phasing out coal/oil/natural gas in favor of green energy sources (solar, wind, hydro, thermal), family planning (slow down global population growth in an ethical way), innovations in fuel efficiency, the ever-decreasing costs of solar panels, etc. Despite all the bad news, progress has been made in the fight against global warming, just in a piecemeal way.
Even simple stuff like mass transit/carpooling, going easy on the thermostat, replacing incandescent light bulbs with more energy-efficient LED bulbs, and keeping your car's tires pumped up helps.
Ideally, such efforts buy enough time for new technologies to hit the market to further improve the situation. We just have to put forth the effort to keep a bad situation from growing worse and weather the storm until it dies down.
That or humanity could go extinct, victims of our own shortsightedness. I dunno about you guys, but that first option sounds a lot better to me.