from TheWatchers Website
The luminosity of our own sun varies a 0.1% over the course of the 11-year solar cycle. Even these negligible variations can have a significant effect on terrestrial climate.
According to Greg Kopp of the Laboratory for Atmospheric and Space Physics at the University of Colorado, pointed out that while the variations in luminosity over the 11-year solar cycle amount to only a tenth of a percent (0.1%) of the sun’s total output, such a small fraction is still important.
Even typical short-term variations of 0.1% in incident irradiance exceed all other energy sources (such as natural radioactivity in Earth’s core) combined. The sun’s extreme ultraviolet (EUV) radiation peaks during the years around solar maximum.
This can strongly affect the
chemistry and thermal structure of the upper atmosphere.
show ~0.1 percent variations with solar activity on 11-year and shorter timescales.
These data have been corrected for calibration offsets
between the various instruments used to measure TSI.
Greg Kopp, University of Colorado.)
NRC had to assemble dozens of multi-disciplinary experts from fields of,
...at a single workshop.
According to Charles Jackman of
the Goddard Space Flight Center, nitrogen oxides (NOx) created by
solar energetic particles and cosmic rays in the stratosphere can
reduce ozone levels by a few percent. Ozone absorbs UV radiation, so
less ozone means that more UV rays from the sun could reach the
lower atmosphere and Earth’s surface.
The cooling of the polar
associated with loss of ozone increases the horizontal temperature
gradient near the
tropopause. This alters the flux of angular
momentum by mid-latitude eddies. Solar activity felt in the upper
atmosphere can, through a complicated series of influences, push
surface storm tracks off course.
Gerald Meehl of the National Center for Atmospheric Research (NCAR) presented persuasive evidence that solar variability is leaving an imprint on climate, especially in the Pacific.
According to the report, when researchers look at sea surface temperature data during sunspot peak years, the tropical Pacific shows a pronounced La Niña-like pattern, with a cooling of almost 1°C in the equatorial eastern Pacific.
The equatorial central Pacific is
generally cooler, the runoff from rivers in Peru is reduced, and
drier conditions affect the western USA.
Meehl, J.M. Arblaster, K. Matthes, F. Sassi, and H. van Loon/AAAS)
Scientists also discovered signs of enhanced precipitation in the Pacific Inter-Tropical Convergence Zone (ITCZ ) and South Pacific Convergence Zone (SPCZ) as well as above-normal sea-level pressure in the mid-latitude North and South Pacific, correlated with peaks in the sunspot cycle.
According to Raymond Bradley of
UMass, the regional rainfall seems to be more affected than
temperature. IPCC and previous NRC reports concluded that solar
variability is not the cause of global warming over the last 50
Researchers question how the relatively
small fluctuations of the 11-year solar cycle can produce the
magnitude of the observed climate signals in the tropical Pacific.
Supercomputer models of climate showed that not only “top-down” but
also “bottom-up” mechanisms involving atmosphere-ocean interactions
are required to amplify solar forcing at the surface of the Pacific.
Matt Penn and William Livingston of the National Solar Observatory predict that by the time Solar Cycle 25 arrives, magnetic fields on the sun will be so weak that few if any sunspots will be formed.
Independent lines of
research involving helio-seismology and surface polar fields tend to
support their conclusion.
about every six months, track the rising level of solar activity
since the mission first began to produce consistent images in May, 2010.
The period of solar maximum is expected in 2013.
The images were taken in the 171 Angstrom wavelength of extreme ultraviolet light.
The solar disk is dotted by the dark cores of sunspots and splashed with bright magnetic froth known as faculae.
Planned radiometric imaging will map the
surface of the sun and reveal the contributions of each to the sun’s
luminosity, especially the faculae. A radiometric imager, deployed
on some future space observatory, would allow researchers to develop
the understanding they need to project the sun-climate link into a
future of prolonged spotlessness.
A better long-term record of the sun’s irradiance might be encoded in the rocks and sediments of the Moon or Mars.