Human population growth is set to reach a peak in just two+ decades, and then will start declining for some time. Where we've seen fertility drop below replace

Human population growth is set to reach a peak in just two+ decades, and then will start declining for some time. Where we've seen fertility drop below replacement rate we've also seen that drop be persistent for decades, which means that population declines will accelerate before they arrest (if they arrest). So this is a bit of much ado about nothing. We're not going to exceed low single digits percentage points of the energy reaching the planet from the Sun. Heat dissipation is relatively easy if we use 1% equivalent of Solar energy on Earth: the water cycle can speed up in response to positive forcings and slow down in response to negative forcings. This is why the planet's climate has been so stable in the sense of being a random walk centered on an optimum that supports the sort of life that we have on the planet. Similar observations explain Mars' and Venus' inhospitability: there's not enough atmosphere, much less liquid water on Mars to drive a similar thermostatic system, while Venus' climate is pegged at a maximum, with albedo as high as it can reasonably go, and it can't cool itself significantly with anything like a water cycle.