Thursday, 2 April 2015

Three Neat Videos.

I've just visited Cryosphere Today, and noticed a new heading 'Arctic Climate Feedbacks'. From the date of the video it references, it's not really new, the Youtube video is dated 22 January 2015. Anyway it led on to three short but impressive TED videos that neatly link together (well I think they do). Each video is only around 5 minutes long.

First off, Lieven Scheire explains the basics of how greenhouse gasses warm the planet, explaining the issue in terms of quantum mechanics.

So that is the stage set, the cause of the global warming of the last several decades, and a good proportion of the warming over the last century.

Then the video that led me to the other two on this page. William Chapman of the University of Illinois Arctic Climate Research Group, who produce Cryosphere Today, explains how the Arctic's sea ice is the canary in the coalmine for climate change. And that it is not only a region of leading effects but how these effects can impact those of us further south.

Chapman also explains how the sea ice makes the Arctic Ocean a region replete with powerful feedbacks, over the last few decades these have been overwhelmingly positive. Even though I doubt the dominance of net positive feedbacks will continue to be as strong, I don't doubt that the overall feedback will remain mainly positive.

Next Victor J Donnay uses a beautifully neat analogy to explain how chaotic behaviour can emerge from a stable system due to changes in boundary conditions, in this case the boundary conditions being the boundary of a pool table.

This video links well with the Chapman video preceding where Chapman explains how the changing pole-equator temperature gradient may be affecting mid latitude weather, that's a case of changes to boundary conditions. But it also works well in another respect, concerning the loss of sea ice.

I've previously stated my opinion that CO2 causes Arctic Sea Ice loss, yet since then I have blogged about research that shows that the volume loss in PIOMAS is driven by the ice-albedo feedback, and I have often mentioned how the thinning of the ice is what has been driving the decline in extent (so I view the volume decline as central to changes in the Arctic Ocean). This might seem like I am guilty of holding two opposed opinions: What caused the loss of volume, the ice-albedo feedback or the increase in CO2?

The opinions and those two options are not mutually exclusive however. In a manner similar to changing the boundaries of the pool table in Donnay's analogy, the increase in CO2 and attendant global warming have changed the boundary conditions for the existence of sea ice. Thus after a trigger point, the export of large amounts of ice through the Fram Strait in the early 1990s, the ice-albedo feedback has been able to take hold because of the changed boundary conditions. To be clear; this is not some issue of physical boundaries like coast or ice edge, it is a change to the thermodynamic bounding conditions that dictate the seasonal cycle of the ice, and the long term survival of sea ice. To find a similar change one has to go back some 7000 years to the Holocene Thermal Maximum when July insolation was 10% larger than at present. Now the change is a similarly externally forced change, that of anthropogenic global warming, of which the largest single driving factor is the increase in CO2 due to fossil fuel burning.

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