Sun and Solar
Nature: Quiet Sun enters new sunspot cycle Nature 459, 152 (2009) | doi:10.1038/459152f
After a prolonged lull in activity, sunspots, and their associated solar storms, are on the rise again.
According to a panel of scientists led by the US Space Weather Prediction Center, part of the National Oceanic and Atmospheric Administration, a minimum in sunspot activity was passed in December 2008. In a consensus forecast on 8 May, the researchers said a new cycle of solar storms would peak in May 2013. But judging by the historical record, the recent persistence of a quiet Sun suggests that sunspot activity at this peak will be the weakest since the solar maximum of 1928.
Ecologist – 2009-02-06: New studies disprove cosmic ray and solar influence theories of global warming
Get into an argument with a climate change sceptic, and sooner or later they’ll trot out the old arguments about it being all due to cosmic rays, or the sun.
Now, two new studies will help you set them straight. An international group of scientists writing in the journal Atmospheric Chemistry and Physics investigated the hypothesis that a reduction in the amount of cosmic radiation hitting the earth reduces the size and number of cloud droplets, which leads to more sunlight reaching the earth’s surface and consequent temperature rise.
Using satellite data, the researchers looked at what happened to cloud droplet size, water content, and depth during so-called ‘Forbush decrease’ events – periods in which the intensity of rays hitting the earth decreases by up to 30 per cent. They could find no statistically significant association between the Forbush events and any of the cloud factors they studied.
See also Kristjánsson, J. E., Stjern, C. W., Stordal, F., Fjæraa, A. M., Myhre, G., and Jónasson, K.:
Cosmic rays, cloud condensation nuclei and clouds – a reassessment using MODIS data , Atmos. Chem. Phys., 8, 7373-7387, 2008.
… Averaging the results from the 22 Forbush decrease events that were considered, no statistically significant correlations were found between any of the four cloud parameters and GCR, when autocorrelations were taken into account.
Carnegie Mellon, Pittsburgh – 2009-05-11: No link has been found between cloud cover, cosmic rays and global warming
With the U.S. Congress beginning to consider regulations on greenhouse gases, a troubling hypothesis about how the sun may impact global warming is finally laid to rest.
Carnegie Mellon University‘s Peter Adams along with Jeff Pierce from Dalhousie University in Halifax, Canada, have developed a model to test a controversial hypothesis that says changes in the sun are causing global warming.
The hypothesis they tested was that increased solar activity reduces cloudiness by changing cosmic rays. So, when clouds decrease, more sunlight is let in, causing the earth to warm. Some climate change skeptics have tried to use this hypothesis to suggest that greenhouse gases may not be the global warming culprits that most scientists agree they are.
In research published in Geophysical Research Letters, and highlighted in the May 1 edition of Science Magazine, Adams and Pierce report the first atmospheric simulations of changes in atmospheric ions and particle formation resulting from variations in the sun and cosmic rays. They find that changes in the concentration of particles that affect clouds are 100 times too small to affect the climate.
“Until now, proponents of this hypothesis could assert that the sun may be causing global warming because no one had a computer model to really test the claims,” said Adams, a professor of civil and environmental engineering at Carnegie Mellon.
“The basic problem with the hypothesis is that solar variations probably change new particle formation rates by less than 30 percent in the atmosphere. Also, these particles are extremely small and need to grow before they can affect clouds. Most do not survive to do so,” Adams said.
Despite remaining questions, Adams and Pierce feel confident that this hypothesis should be laid to rest. “No computer simulation of something as complex as the atmosphere will ever be perfect,” Adams said. “Proponents of the cosmic ray hypothesis will probably try to question these results, but the effect is so weak in our model that it is hard for us to see this basic result changing.”
Can cosmic rays affect cloud condensation nuclei by altering new particle formation rates? , Geophys. Res. Lett., 36, L09820, doi:10.1029/2009GL037946
Although controversial, many observations have suggested that low-level cloud cover correlates with the cosmic ray flux. Because galactic cosmic rays have likely decreased in intensity over the last century, this hypothesis, if true, could partly explain 20th century warming, thereby upsetting the consensus view that greenhouse-gas forcing has caused most of the warming. The “ion-aerosol clear-air” hypothesis suggests that increased cosmic rays cause increases in new-particle formation, cloud condensation nuclei concentrations (CCN), and cloud cover. In this paper, we present the first calculations of the magnitude of the ion-aerosol clear-air mechanism using a general circulation model with online aerosol microphysics. In our simulations, changes in CCN from changes in cosmic rays during a solar cycle are two orders of magnitude too small to account for the observed changes in cloud properties; consequently, we conclude that the hypothesized effect is too small to play a significant role in current climate change.
Physorg 2006-12-22: Scientists Predict Big Solar Cycle
Evidence is mounting: the next solar cycle is going to be a big one. Solar cycle 24, due to peak in 2010 or 2011 [now projected for 2013]“looks like its going to be one of the most intense cycles since record-keeping began almost 400 years ago,” says solar physicist David Hathaway of the Marshall Space Flight Center. He and colleague Robert Wilson presented this conclusion last week at the American Geophysical Union meeting in San Francisco.
Their forecast is based on historical records of geomagnetic storms. … Hathaway and Wilson looked at records of geomagnetic activity stretching back almost 150 years and noticed something useful:. “The amount of geomagnetic activity now tells us what the solar cycle is going to be like 6 to 8 years in the future,” says Hathaway. A picture is worth a thousand words: