There is no clear, quantitative explanation for this variability. (ipcc.ch)
A better quantitative explanation appears to involve the presence of upper stratospheric ozone, which absorbs solar UV and visible radiation, warming the stratosphere. (realclimate.org)
The new model, which is a scaled - down version of an earlier numerical model by Shaqfeh and colleagues that provided the first large - scale, quantitative explanation of the formation of the layer, can predict how blood cells with varying shapes, sizes, and properties — including the crescent - shaped cells that are the hallmark of sickle cell anemia — will influence blood flow. (sciencedaily.com)