Solar irradiance

[morganism]

Long IR re-emittance forcing from open arctic

http://m.phys.org/news/2014-11-berkeley-lab-scientists-driver-arctic.html

In the Arctic, the simulations found that open oceans hold more far-infrared energy than sea ice, resulting in warmer oceans, melting sea ice, and a 2-degree Celsius increase in the polar climate after only a 25-year run.

[wili]

That seems rather...significant, morg. Do you read the last phrase to mean that they found that there is a 2 C increase in polar temps above current models, or in net heating over that period?

[jai mitchell]

it means that when they used the new far infrared emissivity values for open ocean and ice that it turned into an additional positive feedback that would produce an increase in regional warming by 2C over 25 years in the models.  This would lead to earlier ice free conditions and slower winter ice reformation after ice-free conditions.

[crandles]

http://www.globalwarmingart.com/images/7/7c/Atmospheric_Transmission.png

show there is substantial earth emissions in the 15-30 micrometer range. That seems surprisingly close to the atmospheric window which I would have thought would have been well studied.

Ocean emissivity gets down to 0.85 in this range per fig 3 of the paper.
http://www.pnas.org/content/early/2014/10/29/1413640111.full.pdf

2K sounds a lot but I assume they have just switched on the effect. In reality the effect is always there not switched on when we discover it. In modelling it takes hundreds of years to get the ocean in balance with new atmosphere. So perhaps 2K (as a maximum change and some areas having negative change) in first 25 years isn’t that surprising. What is more important is what happens when ocean has been fully spun up to be in balance with the atmosphere and then is forced with our ff burning experiment. Will the modelled Arctic then respond differently? Will it be less reluctant to plunge to seasonally ice free or will there just be less ice in the model to start but still be reluctant to make such plunges?

Any thoughts?

William Connolley replied

And if I were dumping this into a model I'd ramp it up to the limit of what could be possible, just to get something you could see in the model. The real effect, if it pans out, could be much smaller. Plus as you say there could be spin-up effects.