American Elephants


I Really Don’t Know Clouds At All by The Elephant's Child

I learned something new to me. from a comment from Richard Lindzen, MIT Professor of Meteorology, emeritus. The upper level cirrus clouds have a greenhouse effect comparable to water vapor but are mostly ice, not liquid. The upper level cirrus are called Spissatus clouds and are the highest clouds in the atmosphere, forming in the higher tropopause, where most of the water vapor freezes out, or even in the lower stratosphere. Unlike most cirrus clouds, which are generally thin and wispy, Spissatus clouds are dense and opaque, blocking sunlight. They are often found at the top of thunderheads and, due to the shape formed by high altitude winds where they are blocked from rising further, are called anvil clouds.

They are formed at the tropopause because it is there that  thermal inversion occurs – rather than atmosphere being colder with increasing altitude, the atmosphere starts being warmer with increasing altitude.

The tropopause with its temperature inversion separates the troposphere from the stratosphere. The warming of the stratosphere with increasing altitude is from ozone created from oxygen by ultraviolet sunlight. Ozone is not an important greenhouse gas below the stratosphere.

Lindzen has written and produced evidence of what is called the “iris hypothesis.” The testable hypothesis states that increasing temperatures in the tropics, particularly increasing sea surface temperatures (seas cover about 75% of the tropics), will reduce cirrus clouds, reducing the greenhouse effect of these clouds. Independently, Roy Spencer, et al. have used satellite data to support the iris hypothesis. The Climate Establishment strongly disagrees, but there have been additional papers and evidence supporting the hypothesis using satellite observations.

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