Heating is accelerating. IF we stop adding greenhouse gases to the air, the heating should stop. It won't go back down without removing massive amounts of CO2, though.
Yes, net zero, which some companies and countries pledged to reach until 2050. Unfortunately it's delusional, because they count on technological fixes being invented in the future and until then it's "business as usual".
Industries like cement, chemical and steel will never be net zero without carbon capture for example.
I feel like this is closer to the truth. Isn't there a theory that theres about a 2 decade lag between the CO2 (or equivalent) being released and the effects of heating?
The atmosphere stores negligible heat (only weather, not climate), but the ocean has a much greater capacity than the atmosphere, for both heat and CO2 (mainly in the form of HCO3-), and it takes a long time (centuries - millenia) to fully mix the ocean. Also it takes ages for icecaps to melt. If you really stop adding CO2, concentration in the atmosphere will go down slowly as it mixes into deeper ocean, but not back to preindustrial, the surface temperature will likewise go down slowly and partially after a slight lag, but ice will keep melting (-> sea-level rises) for a while. Other gases and aerosols make short term response more complex.
There's no rule of thumb that summarises it, but I made an interactive model - here.