Climate of earth hypersensitive to sun's ultraviolet strength?

Question

A model study by Soon et al (2000), showed clearly that our atmosphere is hypersensitive to solar ultraviolet outbursts, that changes to CO2 or total solar irradiance were not very important.

This website has images of current solar output in ultraviolet: http://umbra.nascom.nasa.gov/images/latest.html

This can account for extreme climates during the past not linked to Milankovich cycles, volcanos or cosmic collisions. I wanted to find out more about the geologic periods where this might show up so that's my question, what time periods of extreme weather aren't explainable by natural causes?

Answer 1

Also, you have to take into account that the ozone layer (The layer of atmosphere that helps protect us from ultraviolet rays) is thinning, almost to the point of nonexistence in some places.  Over some parts of Australia for instance, it is nearly a sentence to skin cancer to leave the house without skin protection.  Some causes of this are release of CFC's (Chlorofluorocarbons) and specific aerosols into the air.  Neither of these substances are naturally released into the air and are in the atmosphere only because of mankind.

So then logically any extreme weather conditions caused by a thinner ozone layer are the result of unnatural causes.

Answer 2

The Soon blog from 2000 is essentially proposing the cosmic ray theory.  That theory is now dead.  

http://www.realclimate.org/index.php/arc...

The climate may be sensitive to UV through a biological feedback, however.

Paul, V.J. Global warming and cyanobacterial harmful algal blooms. Adv Exp Med Biol. 2008;619:239-57.

There are 87 more papers on this theme if you do a search at PubMed.

Answer 3

As far as I'm aware, all periods of extreme weather are explainable by natural causes, except for the current warm period, which is human caused.