Yes albedo feedback is widely accepted as positive feedback. It causes faster rate of rise but do you see acceleration with 'continued high fossil fuel emissions'?
A really fast feedback like water vapour feedback increases the rate immediately so with "continued high fossil fuel emissions" you wouldn't expect to see acceleration.
I believe I understand you now. But my very limited understanding of the mechanics involved are that loss of albedo from summer sea ice leads to increased warming of the oceans, and (at least potentially) more water vapour. Thus the three seem connected to me. AbruptSLR's post confirms that the oceans are warming significantly, though the rate of increase appears to be linear not to have changed since about 1990 (or maybe earlier).
I guess I don't have much to offer in terms of intelligent discussion at this point. I definitely agree that the arctic temp anomaly graph I posted could be read as a point acceleration with two lines; but I think it could also be read as showing an increase in rate of change beginning at about 2013 (on the black, annual line only), which could make the graph begin to appear more like continuous acceleration.
Maybe someone can get ahold of Hansen and ask him for clarification on what he thinks the cause of this apparent acceleration would be? Or else we'll just have to wait until he decides to clarify...
I did read that a "change of just 1% to the Earth's albedo has a radiative effect of 3.4 Wm-2, comparable to the forcing from a doubling of carbon dioxide"
https://www.skepticalscience.com/earth-albedo-effect-intermediate.htmNo idea where the number comes from unfortunately.
But I did some quick math. Surface Area of the Earth is 510,064,472 km2. 1% change would be 5,100,644.72 km2.
The 2000-2009 avg. for summer minimum sea ice in the arctic drops 968,139 km2 from the 79-99 avg (almost .2%).
The 2010-2018 avg drops 2,040,500 km2 from the 79-99 avg (~0.4% change in earth surface) giving, 1.36 Wm-2 difference
See the graph I've attached.
Of course it probably doesn't work like that (with a linear relationship to the amount of forcing), and I do know that this doesn't account for what the rest of the earth’s albedo change was during that time, and that the change in albedo would only be during a few summer months...
Still I wanted to offer up these back of the envelope calculations, since if I’m lucky enough to receive any criticism, it will be quite the education for me and probably some other lurkers.
I must say, I dont understand the reasoning behind Hansen's graph. The minimums are compared with the latest reading, which is closer to the linear trend than then minimums (or course - since the minimums are below the trend and max are above... And we are currently in between). So drawing lines from the minimums to that end point will show steepening lines even if the minimums stay the same distance between the linear trend line.
....
Edit: If the latest data point IS a minimum, and therefore a minimum higher than the others, that's surely just one point and not particularly evidence of a trend surely. Connecting those other points to this one still doesnt look valid scientifically.
Yes, the last point is a minimum. You're right that it's not a valid scientific argument, but if you were expecting acceleration to begin appearing out of the noise, then it is one small piece of evidence that is suggestive that this has begun. Obviously Hansen has been expecting this, and he has enough credibility that it's worth noting, if nothing else (he famously -- and boldly -- announced that the signal of warming had appeared out of the noise in the late 80s). Though I wish he had explained himself more completely.