Sure, it’s all relative I guess (relative levels of apocalypse 
which all seemed a bit of a theme here lately, e.g. see the thread Lokantara, at the End of the Earth 
). The James Lovelock scenario I mentioned above was a kind of worst-case (and a pretty grim one at that). Though probably not the end of all life as such and probably humans would continue too (though perhaps rather a bit less of them). That certainly doesn’t seem to be as imminent as Lovelock previously painted 10 or 15 years ago.
We are, I suppose, whether we want to or not, part of a huge ongoing atmospheric CO2 science experiment. We might quite possibly still get to the same Loveockian place eventually (quite a lot of unknowns in these models though).
TBH I think we are mostly just playing around the edges at this point by thinking about augmenting fossil fuels with a percentage of renewables. Up to about 30% seems the sweet spot for renewables; with moderate subsidies they are still somewhat competitive to a point. That all might slow the overall progression down a bit, but we’ll probably still end up in the same place the way we are going.
Things get a lot trickier when one is talking about really substantially decreasing CO2 emissions (I’ve had something of an interest in the question). A really nice (and free) numbers book on this is David MacKay’s Sustainable Energy - Without the Hot Air. He gives figures on just how much we’d have to scale up renewables if we wanted to depend on them entirely. From perhaps a typical 25% contribution to total electricity in many European countries, you’d want many multiples of that. As a rough estimate, you’d probably want to triple electricity production to cover many of the other things currently needing fossil fuels, so needing even to start with at least 12 times the current number of renewables.
I guess that’s possible. In my country, there doesn’t tend to be a lot of intense sunshine (more often soft rain) but there’s no shortage of wind on the Atlantic Coast! We’d need multiples of present numbers of wind turbines though.
Then there’s the storage problem. Feeding directly into the grid is, as I’ve said, something of a sweet spot for renewables. Grid instability means there’s a limit to that. If you one is really not going to have a fossil fuel based grid, then you need long-term storage. IMO power-to-gas is about the most feasible approach (there are methods with higher efficiencies but that don’t scale). In that, you take electricity produced by renewables and use it to produce synthetic natural gas (methane). That then is storable conventionally in huge quantities for long periods (much as standard fossil fuels are). You can then burn that much later in a conventional gas turbine to produce more electricity (or even power vehicles or industrial processes). Months or years of a backup supply are possible. The problem with that is efficiency. At the moment, you’d be doing well to get 40% efficiency (60% of the original electrical energy lost in the process). However, the Germans are doing a lot of research on this. I think some research was claiming a turnaround efficiency of over 60%. But again this inefficiency in storage means an even greater amount of renewables are needed to compensate (perhaps we might need 20 times rather than a dozen times the current renewable levels).
That’s probably not feasible for a densely populated country like Germany (though a fairly sparsely populated one like Ireland might be able to do it with a lot of wind turbines) so they’d still have to import a lot of their energy.
People have seriously proposed building huge solar arrays in the Sahara and having power lines carry this over to Europe. However, the figures are that one would need to cover an area there the size of Germany in solar panels to get enough power for Europe in general!
MacKay in the book tends to think that nuclear is probably the most feasible option. I’d agree with that. It’s certainly not without its issues though! And if it was adopted as a wide-scale solution, then one probably would have to use fast breeder reactors (tricky enough technically but they can extract 50-100 times more energy from the same uranium and basically eat up most of the nasty byproducts from more conventional single-run lower efficiency fission). The UK have been toying with building one of these to eat up substantial stocks of plutonium they have left over from the cold war.
My guess is that only a fraction of the above will happen in the medium term (nuclear is too unpopular and adoption of renewables on a really large-scale comes with many problems too). Going by human nature, we’ll most likely bumble along for another 30 to 40 years with moderate efforts and then maybe get really worried and start to panic and try to implement some of the above in a rush. Hopefully, our atmospheric system tends a bit more to the robust side of predictions. Or perhaps, practical fusion will at some stage suddenly be no longer 20 years away but now! We can but hope.