If we had energy cheap enough for every human to live at the highest current levels of consumption, wouldn’t we have to do something with the waste heat? Radiator fins on space elevators? Or can we send it out into space from the ground?
All renewable energy (solar, wind, hydro, biofuels) comes from the sun anyway and the only difference if that sunpower goes into 'waste heat' immediately or gets temporarily used for work before turning into the exact same amount of waste heat.
Fossil fuels are releasing energy that was taken from the sun millions of years ago, but the direct heat outcome of burning all that is dwarfed by the greenhouse effect of emitted gasses - small changes to how much Earth radiates into space matter much more than the heat produced by burning that fuel.
The same applies for nuclear, which does generate extra waste heat but it is not significant compared to the greenhouse effect.
We have a long way to go before humanity's heat output is anywhere rivalling the heat the Sun dumps on us. Most of our power generation (except nuclear) is just repurposing the Sun's energy anyways, delaying its conversion into heat so that we can extract work from the process. The same heat is generated with or without our power plants. (Fossil fuels delay for so long that the energy release occurs at a much faster rate than it was gathered, but still insignificant compared to the regular solar energy incident on the Earth).
If GDP is as tightly-coupled to energy use as data suggest, and we presume, say, 4% annual growth rate, then we have a slight issue.
10,000 times is just over 13 doubling periods' worth of growth. And 4% annual growth rate means doubling every 13.3 years, roughly.
In which case, humans would cut into that 10,000-fold margin in slightly over 230 years.
Which suggests that there are in fact limits to growth.
Interestingly, this still overestimates the role of our waste heat for an even simpler reason: much of it was going to be heat anyway. Waste heat generated from fossil fuels is pure extra energy (although that effect is still dwarfed by the greenhouse effect for anything beyond the very local area). Nuclear is effectively net positive on heat as the natural half life of the fuel is far longer then when it is put in a reactor. However, solar energy is by definition part of that 10^17 watts of energy that is going to hit the Earth weather we generated electrons from it or not (Granted, solar panels probably reflect less of that energy back into space). Wind energy is pulling kinetic energy out of the air that would have become heat. Geothermal is taking advantage of heat that was already there (although we accelerate how quickly it reaches the surface). Hydroelectic energy would have become heat once the water finished loosing its potential energy when it reaches sea level.
We just aren't to that point yet.
Modern humans themselves originated only 200 kya.
<https://ui.adsabs.harvard.edu/abs/2014Natur.513..401Z>
<https://www.worldhistory.org/article/1886/origins-of-world-a...>
https://www.sciencealert.com/green-sahara-early-holocene-agr...
We do know that the climate of the Sahara differed and it was grasslands in portions for a time.
But it wasn't farmed (your own article notes that the seeds found were wild), and the processes which re-asserted the pre-existing desert landscape were not human-induced.