The Earth's energy imbalance has doubled from 0.5 ± 0.2 Wm−2 to 1.0 ± 0.2 Wm−2 since 2000, as reported by the Clouds and the Earth’s Radiant Energy System satellite observations. This increase is attributed to a rise in absorbed solar radiation (ASR) by 0.9 ± 0.3 Wm−2, partially offset by a 0.4 ± 0.25 Wm−2 increase in outgoing longwave radiation (OLR). The dynamics of greenhouse gases suggest that while OLR should decrease, feedback mechanisms and additional positive feedbacks complicate the relationship, leading to a net positive energy imbalance and ongoing warming. The data indicates challenges in identifying any positive forcing in the longwave spectrum without an initial perturbation.
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Added greenhouse gases are supposed to be decreasing the OLR.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).
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.olivermsun said: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.