Tuesday, October 22, 2013

New paper finds solar UV varies up to 100% during solar cycles, confirms solar amplification mechanism

A paper published today in Atmospheric Chemistry and Physics notes that solar UV radiation can vary up to 100% during solar cycles, that it is "well accepted" these large changes in UV significantly affect stratospheric ozone production, and thereby act as a solar amplification mechanism on temperatures. 

The IPCC dismisses the role of the Sun in climate change by only modelling the tiny changes of the Total Solar Irradiance [TSI], while ignoring the large changes of up to 100% in the most energetic portion of the solar spectrum, the ultraviolet [UV] region. The UV spectrum also penetrates the deepest of any portion of the solar spectrum into the oceans [up to 100 meters] to heat the bulk of the oceans, unlike longwave infrared radiation from greenhouse gases, which can only penetrate a few millionths of one meter to cause evaporative cooling of the ocean 'skin' surface. 

From the Introduction to the paper:

The Sun is the primary source of energy to the Earth’s atmosphere, so it is essential to understand the influence that solar flux variations may have on the climate system. This can be studied by investigating the effect of 11 yr solar flux variations on the atmosphere. Although total solar irradiance (TSI) shows only a small variation ( 0.1% per solar cycle), significant (up to 100 %) variations are observed in the ultraviolet (UV) region of the solar spectrum. In a “top-down” mechanism, these UV changes are thought to modify middle atmospheric (lower mesospheric and stratospheric) O3 [ozone] production, thereby indirectly altering background temperatures (for a review see Gray et al., 2010). These temperature changes can then modulate upward propagating planetary waves, and amplify the solar signal in stratospheric O3 and temperatures. The temperature changes will also affect the rates of chemical reactions which control ozone. This mechanism has been well accepted.

Atmos. Chem. Phys., 13, 10113-10123, 2013

S. S. Dhomse1, M. P. Chipperfield1, W. Feng1, W. T. Ball2, Y. C. Unruh2, J. D. Haigh2, N. A. Krivova3, S. K. Solanki3,4, and A. K. Smith5
1School of Earth and Environment, University of Leeds, Leeds, UK
2Physics Department, Blackett Laboratory, Imperial College London, London, UK
3Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany
4School of Space Research, Kyung Hee University, Yongin, Gyeonggi, South Korea
5National Center for Atmospheric Research, Boulder, CO, USA

Abstract. Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (1996–2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O3 using three different solar flux data sets (SORCE, NRL-SSI and SATIRE-S). Simulated O3 changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O3 anomalies from all solar flux data sets show good agreement with the observations, despite the different flux variations. The off-line CTM reproduces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere, which is due to realistic dynamical changes in our simulations. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux data sets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O3changes during 2001–2010.


  1. If TSI is almost constant and UV varies by 100%, the intensity of some longer wavelength must vary inversely with UV.

    Can anyone comment?

    1. True, would have to vary inversely most likely with the ~40% of the solar spectrum in the infrared, which does not affect ozone production and which does not penetrate the ocean surface.

  2. The sun is very sultry and we must avoid its ultry-violet rays.

    kim H/t Noel C. and Plum's Orchard. Another wave for Erl Happ.

  3. http://www.clim-past-discuss.net/9/6179/2013/cpd-9-6179-2013.pdf

  4. http://iopscience.iop.org/1748-9326/5/3/034008/pdf/1748-9326_5_3_034008.pdf