A paper published in Geophysical Research Letters finds another means by which climate models dismiss the role of the Sun in climate change. The paper notes that climate models consider total solar irradiance [TSI], but ignore the large shifts in wavelength distributions during solar cycles. The most energetic wavelengths from the Sun in the UV can vary up to 100% over solar cycles, and have significant effects on climate via stratospheric ozone.
According to the authors, "These findings need to be incorporated into Earth-climate [models] since the solar forcing induced by these differential trends are inherently different from the relatively flat spectral contributions employed in the IPCC assessments."
The authors find periods of low solar activity increase high-energy UV wavelengths, which would increase stratospheric ozone production. This has an inverse effect upon global temperatures, thus acting as a solar amplification mechanism.
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| Figure from another paper showing the inverse relationship between ozone and global temperatures Fig. 1. Time series of annual data of: Land air T anomalies (thin line with dots); CO2 anomalies (squares); Arosa total ozone (dash-dotted line with diamonds) for period 1900–2010. The values of CO2 anomalies are rescaled by the formula: CO2=(measured−mean)/100. The thick continuous curves are smoothed values(11-year and 22-year running averages) of total O3 and land air T. |
Jerald W. Harder, Juan M. Fontenla, Peter Pilewskie, Erik C. Richard, Thomas N. Woods
The Spectral Irradiance Monitor (SIM) on-board the Solar Radiation and Climate Experiment (SORCE) satellite provides the first multi-year continuous measurements of solar spectral irradiance (SSI) variability from 200–2400 nm, accounting for about 97% of the total solar irradiance (TSI). In addition to irradiance modulation from active region passage, the SSI values for wavelengths with a brightness temperature greater than 5770 K show a brightening with decreasing solar activity, whereas those with lower brightness temperatures show a dimming. These results demonstrate that different parts of the solar atmosphere contribute differently to the TSI with the behavior in the deep photospheric layers giving an opposing and nearly compensating trend to that in the upper photospheric and lower chromospheric layers. These findings need to be incorporated into Earth-climate assessments since the solar forcing induced by these differential trends are inherently different from the relatively flat spectral contributions employed in the IPCC assessments.
Notes: 5770 K corresponds to a peak wavelength of 502 nm in the blue portion of the visible spectrum, brightness temperatures higher than 5770 K have a shorter wavelength, e.g. UV wavelengths are at 350 nm and below
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