[gorhill]

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.

[kergonath]

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

[hilbert42]

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.

[kergonath]

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.