UV Radiation - One of the Climate Drivers?

TSI or Total Solar Irradiance is often displayed as the posterboy for the AGW crowd. Their tired argument states that with only .1% variance in TSI over the solar cycle TSI cannot have a measurable impact on the Earth's climate, and is not responsible for any rise in global temperatures.

But wait...there is more than just TSI emanating from our Sun.Graph updated to Aug 11, 2010.

Even if TSI had no variance in output it could still be modulated by cloud cover, something the IPCC aligned scientists forget to include in their models, some suggest greater lower level cloud cover will shield our oceans from heat uptake. Outside of this the Sun does more than just provide heat, it provides the solar wind of charged particles which include magnetic properties that shield our planet, as well as the all important UV rays which are now gaining prominence in climate research. There is said to be a 2 fold effect, our ozone layer is maintained by solar UV production and is currently at a very low level, also there is speculation that UV radiation has a warming effect on the higher atmosphere which can permeate to the troposphere with changes to pressure cells that can alter the also important cloud makeup. Add to this the Svensmark effect which is a direct result of the solar wind speed strength, and we start to see a few variables that might make up part of the big picture.

Lately via the Layman's count I have been watching the solar wind speed and how it varies from solar sunspot activity. I will also be watching the UV metrics over SC24. In particular I will be graphing the EUV (extreme UV 26-34nm) that has variations much larger than TSI over the solar cycle. EUV is thought to be a product of faculae or plage regions which are brighter areas present around sunspots or indeed existing without sunspots. In the graph below I have compared the SIDC sunspot count with the EUV readings taken from the CELIAS/SEM experiment on the SOHO satellite. While the plots roughly follow each other there are distinct times when they are not in sync.

Click on the graphs for a full size view....above graph updated to 26th Feb 2010. SIDC figures updated at end of month.

The Layman's Count does not go back far enough for a comparison like this and the SIDC count probably represents a better marker for solar activity. The Layman's count is about comparing the current predicted grand minimum with the previous.

A recent report from NCAR that studies the effect of differnet ozone levels states:

"Top Down – Bottom up

In order for such reinforcement to take place many small wheels have to interdigitate. The initial process runs from the top downwards: increased solar radiation leads to more ozone and higher temperatures in the stratosphere. “The ultraviolet radiation share varies much more strongly than the other shares in the spectrum, i.e. by five to eight per cent, and that forms more ozone” explains Katja Matthes. As a result, especially the tropical stratosphere becomes warmer, which in turn leads to changed atmospheric circulation. Thus, the interrelated typical precipitation patterns in the tropics are also displaced.

The second process takes place in the opposite way: the higher solar activity leads to more evaporation in the cloud free areas. With the trade winds the increased amounts of moisture are transported to the equator, where they lead to stronger precipitation, lower water temperatures in the East Pacific and reduced cloud formation, which in turn allows for increased evaporation. Katja Matthes: “It is this positive back coupling that strengthens the process”. With this it is possible to explain the respective measurements and observations on the Earth’s surface."

Full story here: http://wattsupwiththat.com/2009/08/27/ncar-spots-the-transistor-effect-small-solar-activity-fluctuations-amplify-to-larger-climate-influences/#more-10339

Fligge and Solanki write:

"Solar irradiance variations are known to exhibit a strongwavelength dependence, with the amount of variability increasing towards shorter wavelengths (Lean 1991, Solanki & Unruh 1998). The integrated spectrum (total solar irradiance) changes by roughly 0.1% over the solar cycle. The same amount of variability is found for the visible wave-lengths where most of the solar radiative output occurs. Variations at UV and shorter wavelengths, however, exceed those at visible by orders of magnitude. Since solar UV radiation controls the amount of stratospheric ozone these variations have been proposed as a significant driver of changes of the terrestrial climate system (Haigh 1996)."

They also suggest the EUV under 300nm varies by the greatest amount over the cycle.

http://www.astro.phys.ethz.ch/papers/fligge/GL10884W01.pdf

Unruh et al report on EUV related to faculae here with reference to the higher variation of UV over the cycle:  

http://www.astro.phys.ethz.ch/papers/fligge/GL10884W01.pdf

NASA writes on the topic: http://earthobservatory.nasa.gov/Features/SORCE/sorce_04.php

Some more interesting reading on Ozone here: http://www.heliogenic.net/?cat=45

and here: http://wattsupwiththat.com/2009/03/26/galactic-cosmic-rays-may-be-responsible-for-the-antarctic-ozone-hole/#more-6560

A new report by Robert Hodges and Jim Elsner expands on the UV/climate connection. Some interesting references to a 16% UV variation during solar flare activity (I knew I had seen the 16% figure previously) and also the polar vortex influences. Nicola Scafetta's new paper is also mentioned. http://icecap.us/images/uploads/Warming_Due_To_Ultraviolet_Effects_Through_Ozone_Chemistry.pdf

Low EUV causes the Thermosphere to collapse: http://wattsupwiththat.com/2010/07/15/earths-thermosphere-collapses-film-at-11/