To be fair, 90% of the population lives within 45 degrees of the equator. If we're talking about global energy solutions for CO2 reduction, we can go a long way just by focusing on what works in these areas of the globe.
The article does also point out that hydro/wind are going to be important at higher latitudes in winter, but they also acknowledge that they don't account for seasonal variation in demand. That's the biggest flaw I can find in the analysis.
FWIW: I'm down in a mild arid climate at 35N, and yeah, 90% of our winter days are nearly sunny, even when the lows are in the teens. It's a different world for sure.
Make energy so expensive that people have to move away or burn their old house.
Most everyone else? Only about two percent of the Earths population live above the 55th parallel. There’s a big gulf between that and the ‘subtropics’.
I don’t disagree that solar/battery isn’t the answer for 100% of power needs, let alone 100% of heating needs, but if we got to even 50% we’d be in a lot better situation than we are now.
handwavy argument. Yes, in the (sub)tropics the argument is even stronger pro-PV, not the least because it'll give you the opposite of heating - aircon - for free right when you need it. And considering summer heatwaves as have been seen the last few years "way north", that benefit will extend that way even if you wouldn't bother considering letting it "assist", if not fully replace, your heating. That said though, for 50° polewards and above, if you wanted to use PV in winter orient the panels vertically. If you can clad your too floor with shiplap larch so you can with PV panels. Given the price of timber ... there's a plan.
(only saying handwaving goes both ways)