No one would argue for having no electricity in times of low wind and solar. The short term solution would be to use natural gas power plants to fill the gaps. If they ran only in those situations, the 90% of CO2 reduction could still be achieved. Of course, we need to expand storage solutions and with internationally coupled grids, those times become even shorter, as the weather variations tend to even out.
This is glib assertion. You might explain how the economics of this would be accomplished country by country. Earlier this year the UK was without significant wind power for nine days. Well, in absence of fossil fuel, that would indeed be personal sacrifice - Old Testament style.