Articles Tagged "Judith Lean"

Total Irradiance Monitor (TIM)

It’s not often I voice my opinion on climate change without sounding like a tree-hugger or a total kook. However, in this circumstance I had an opportunity to read about some findings that hit home with my own personal thoughts and I figured you might like to know, too.

According to the latest American Astronomical Society Press Release, “Scientists have taken a major step toward accurately determining the amount of energy that the Sun provides to Earth, and how variations in that energy may contribute to climate change. In a new study of laboratory and satellite data, researchers report a lower value of that energy, known as total solar irradiance, than previously measured and demonstrate that the satellite instrument that made the measurement — which has a new optical design and was calibrated in a new way — has significantly improved the accuracy and consistency of such measurements. The new findings give confidence, the researchers say, that other, newer satellites expected to launch starting early this year will measure total solar irradiance with adequate repeatability — and with little enough uncertainty — to help resolve the long-standing question of how significant a contributor solar fluctuations are to the rising average global temperature of the planet.

Figures 1B, 1C and 1D from the paper: The average of three different reported composites (ACRIM, PMOD, and RMIB) adjusted to match the SORCE/TIM absolute scale. The grey shading indicates the standard deviation of the three composites. (c) Irradiance variations estimated from an empirical model that combines the two primary influences of facular brightening and sunspot darkening with their relative proportions determined via regression from direct observations made by SORCE/ TIM. (d) The daily sunspot numbers indicate fluctuating levels of solar activity for the duration of the database.

From a new paper by Dr. Greg Kopp and Dr. Judith Lean, new finding on the solar minimum TSI in 2008

The most probable value of total solar irradiance representative of solar minimum is 1360.8 ± 0.5 W m−2, lower than the canonical value of 1365.4 ± 1.3 W m−2 recommended a decade ago. This new value, measured by SORCE/TIM, is validated by irradiance comparisons to a NIST‐calibrated cryogenic radiometer in the new TSI Radiometer Facility. Uncorrected scattering and diffraction are shown to cause erroneously high readings in non‐TIM instruments.