"At the equator, it's hot and so the air rises, and as it does so it cools, which lowers the amount of water it can hold below the amount that is actually in it, causing rain, thunderstorms, etc. The resulting drier air eventually returns to the earth's surface around 30o north and south of the equator - this is the Hadley cell and the dry descending air is the cause of deserts at around those latitudes."
"Similarly at the poles it is very cold, causing sinking air, and driving a similar polar cell which requires air to be lifted up at around 60o north and south of the equator. In between there is a Ferrell cell which moves air northward at the surface and southward high up. All three of these cells essentially serve to move heat from the equator (where the sun shines the most} to the poles (where it shines the least)."
"High up at the boundaries of the cells, air of quite different origins with large pressure and temperature differences meets. These differences drive strong winds, which you'd think would flow in a north south direction, but instead the rotation of the earth (Coriolis force) bends them around so that you end up with very rapid zonal (latitudinal) winds - the jet streams - occurring at high altitude."
The video above is an easy to understand show and tell about the jet stream and its big chaotic-looking meanders named Rossby Waves (also known as planetary waves). Rossby Waves have a massive effect on the weather. If the jet stream gets stuck - the Rossby waves stop or slow down - it can lead to weather extremes - one place may have flooding as rain continues for weeks or months, while another place may have drought as it stays sunny and dry there for an extended period.
The paper explains how the loss of Arctic sea ice means that the Arctic ocean absorbs a lot more sunlight in the late summer and fall, which it then gives back to the atmosphere in the winter. Because the atmosphere is then warmer than it used to be as a result, it is thicker and this in turn will cause the Rossby waves to move more slowly and become bigger and loopier.
This group of atmospheric interactions is another in a series of climate developments which were not projected by climate science or climate models. For example in the relevant section of the IPCC AR4 there is no discussion of the possibility that Rossby Waves might slow down and cause more extreme weather events. As The Mud Report has been trying to show recently that the climate system is far more complex than climate science is currently able to model. It seems, therefore, to be only common sense that we be cautious. But humans seem to have selectively bred out a 'common sense gene', in it's place we've selected for a 'gimme more gene'.
