Sahara Went From Green to Sand in a Flash

I am not a climate change denier, I would call myself a climate change confirmer because climate change is always happening. And really I wonder what caused Sahara to go dry? Was it industry? Humans back then have only just learned about metallurgy. But the Sahara went from lush savannah with lakes into a desert we know today within like 100 years. So why is the change of climate today such a problem that needs to be stopped? Can the current warm period be stopped?