What is going on with Earth's longwave energy imbalance?

[johnbbahm]

TL;DR Summary

Recorded increase in Outbound Longwave Radiation (OLR) since year 2000.

Observational Assessment of Changes in Earth’s Energy Imbalance Since 2000: 2024

Satellite observations from the Clouds and the Earth’s Radiant Energy System show that Earth’s energy imbalance has doubled from 0.5 ± 0.2 Wm−2 during the first 10 years of this century to 1.0 ± 0.2 Wm−2 during the past decade. The increase is the result of a 0.9 ± 0.3 Wm−2 increase absorbed solar radiation (ASR) that is partially offset by a 0.4 ± 0.25 Wm−2 increase in outgoing longwave radiation (OLR).

Added greenhouse gases are supposed to be decreasing the OLR.

 

[olivermsun]

If the ASR from effective albedo, etc., decreases more than the OLR increases (a natural negative feedback due to the Stefan-Boltzmann relationship) then you still have a net positive energy imbalance, hence net warming.

 

[johnbbahm]

I thought of that also, but for it to be feedback, it has to be feedback from some earlier warming input.
The earlier warming input would have to be forced by an energy imbalance, but if the OLR is increasing,
it cannot be added greenhouse gases that caused the forcing, as their forcing would show up as reduced OLR.

 

[olivermsun]

Say a “unit” of greenhouse gas forcing temporarily decreases OLR and causes temperatures to rise. Eventually OLR has to catch up and counteract the earlier imbalance; else the system would keep warming indefinitely.

In the real climate system, there are additional positive feedbacks that amplify the “original” radiative imbalance, and hence the OLR has to make up for them as well. That’s why the OLR at later times is not just the same as original but actually larger even though the original forcing initially caused a decrease in OLR.

 

[johnbbahm]

Say a “unit” of greenhouse gas forcing temporarily decreases OLR and causes temperatures to rise. Eventually OLR has to catch up and counteract the earlier imbalance; else the system would keep warming indefinitely.

In the real climate system, there are additional positive feedbacks that amplify the “original” radiative imbalance, and hence the OLR has to make up for them as well. That’s why the OLR at later times is not just the same as original but actually larger even though the original forcing initially caused a decrease in OLR.

From the data it is difficult to see if any positive forcing happened at all, in the longwave spectrum. Without the initial perturbation, there would not be anything to feedback upon.