The problem is not with the number of human but with our lifestyle...
We've populated large portions of the planet that we really have no business living in without climate controlled indoor environments. HVAC is also a huge energy suck with all the externalities that come along with it. If we were to really want to cut energy use, for example, and climate control had to go we almost certainly couldn't continue to sustain as many people as we have today.
I'm with you, but let's just say it.
People, as a whole, don't want to make the changes we all know would make the world better.
People, as individuals? While there are exceptions, the reality is a classic tragedy of the commons. Individuals generally won't accept a short-term drop in their standard of living while watching their neighbors refuse to do the same.
It is what it is, frankly. We can and will change our lifestyles at the very last possible moment. Let's hope it's enough.
Think of the aboriginals and nomads roaming the deserts and the inuit in the icy north. All before hvac.
And hvac isn't really as much of an energy problem as heating is. Because when hvac is needed it is during a time of abundance of sunlight.
I can't imagine Canada or Europe could support their current population sizes without HVAC, or refrigeration, or pesticides and herbicides.
The list goes on, but in my opinion and understanding there is too strong of a correlation to ignore between those types of modern inventions and population growth.