Which debate over global warming are you referring to? There are debates that involve atmospheric chemists that discuss Earth darkening cause and effects.

https://en.m.wikipedia.org/wiki/Albedo

Right, the average person hasn't a clue about albedo, nor do they know why say CO2 and CH4 increase global warming whereas others such as O2 are more benign.

It may help lower the temperature of the debate if they did.

Edit, we're pitching this discussion at the level he has—the lay public. Scientific argument over the minutiae is another matter altogether.

Yeah debates in climate science are about phenomena laypeople don’t even know exist. It’s about how what we observe happens. No one is arguing about what we’re observing, eg global warming.

The important part to understand is timescales. In a day, the Earth does absorb some energy. Of course it does, plants collect it, solar panels collect, the ocean and land collect it. The amount Earth collects is a tiny fraction of what it releases. That collection isn’t permanent though and is slowly released. Within a day, the Earth absorbs some energy, but over a long enough timescale, all of that energy is released again.

The Earth is taking on energy every day from the sun. If we didn’t release it all back, the earth would be warming much much faster. It only remains relatively cool because it releases almost as much as it receives.

Another important note is that long term energy is not only stored as heat on earth. It’s stored as potential energy in the atoms of cells in plants and animals. Think of how cold a gallon of gasoline is, yet how much energy it stores.

For an example think of hot asphalt from a summer day. It gets real hot all day and slowly cools down at night. Sometimes it can be pretty warm to stand on the road even if it’s a cool night.

Within the human timescale, the Earth is retaining some (tiny fraction) of heat. That tiny fraction of heat is a very small window of heat that life can tolerate. It’s not too much and not too little. If the earth were to retain just a tiny bit more, suddenly life can’t tolerate it. On the scale of the universe, the difference between those realities is minuscule, even though it’s enormous to us.

My understanding:

Global warming occurs because the previous equilibrium between incoming and outgoing energy has been broken by changes in the composition of the atmosphere.

So until we reach a new equilibrium long after the atmosphere composition ceases to change, the outgoing energy will be less than the incoming energy.

That’s exactly it. Except that equilibrium will never be reached, it’s more like tending towards a steady state.

Right, better stated than me.

It would help if we could convey this across to the lay public. No doubt, the minutiae is complex and involved and the details will be argued over for years but at the high level it's pretty straightforward.

Seems to me many balk at climate science because the figures seem to magically appear from nowhere—they just pop out of climate scientists' mouths without explanation. A simple understandable explanation might reduce some of the noisy opposition.

The basic principles are simple: stuff goes in from the Sun and the inside of the Earth; stuff goes out through the atmosphere. Greenhouse gases trap stuff in the atmosphere, which results in the accumulation of stuff in the oceans and atmosphere. No need to delve into entropy and free energy here: the concept of heat is enough*.

The details are insanely complex and I would not claim to understand the beginning of it, though.

* the concept of heat is of course horrendous from a scientific point of view and we do use things like enthalpy and entropy in modern thermodynamics. But there’s a reason why heat is used in vulgarisation and introductions. It is intuitive and useful if you don’t dig too far, so perfect to explain things to laymen and 5 years olds.