Solar variation
hideSolar variations are changes in the amount of solar radiation emitted by the Sun. There are periodic components to these variations, the principal one being the 11-year solar cycle (or sunspot cycle), as well as aperiodic fluctuations. Solar activity has been measured via satellites during recent decades and through 'proxy' variables in prior times. Climate scientists are interested in understanding what, if any, effect variations in solar activity have on the Earth. Effects on the earth caused by solar activity are called "solar forcing".
The variations in total solar irradiance remained at or below the threshold of detectability until the satellite era, although the small fraction in ultra-violet wavelengths varies by a few percent. Total solar output is now measured to vary (over the last three 11-year sunspot cycles) by approximately 0.1% or about 1.3 W/m² peak-to-trough during the 11 year sunspot cycle. The amount of solar radiation received at the outer surface of Earth's atmosphere averages 1,366 watts per square meter (W/m²). There are no direct measurements of the longer-term variation and interpretations of proxy measures of variations differ. On the low side North et al. report results suggesting ~ 0.1% variation over the last 2,000 years. Others suggest the change has been ~ 0.2% increase in solar irradiance just since the 17th century. The combination of solar variation and volcanic effects are likely to have contributed to climate change, for example during the Maunder Minimum. Apart from solar brightness variations, more subtle solar magnetic activity influences on climate from cosmic rays or the Sun's ultraviolet radiation cannot be excluded although confirmation is not at hand since physical models for such effects are still too poorly developed.
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News tagged with solar activity
The Sun's Sneaky Variability
Space & Earth / Space Exploration
Oct 28, 2009 |
4.8 / 5 (11) |
5
Every 11 years, the sun undergoes a furious upheaval. Dark sunspots burst forth from beneath the sun's surface. Explosions as powerful as a billion atomic bombs spark intense flares of high-energy radiation. ...
EVE: Measuring the Sun's hidden variability
Space & Earth / Space Exploration
Sep 22, 2009 |
4.1 / 5 (7) |
0
Every 11 years, the sun undergoes a furious upheaval. Dark sunspots burst forth from beneath the sun's surface. Explosions as powerful as a billion atomic bombs spark intense flares of high-energy radiation. ...
Mystery of the Missing Sunspots, Solved?
Space & Earth / Space Exploration
Jun 18, 2009 |
4.7 / 5 (20) |
11
The sun is in the pits of a century-class solar minimum, and sunspots have been puzzlingly scarce for more than two years. Now, for the first time, solar physicists might understand why.
Giant balloon flying high over Atlantic to catch cosmic rays
Space & Earth / Space Exploration
May 21, 2009 |
5 / 5 (3) |
4
(PhysOrg.com) -- University of Delaware researchers in Sweden have launched a giant balloon taller than a football field that is now flying at the edge of space to collect data on cosmic rays -- the most super-charged ...
Scientists: No link cloud coverage and global warming
Space & Earth / Earth Sciences
May 11, 2009 |
4.1 / 5 (89) |
35
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.
Watching solar activity muddle Earth's magnetic field
Space & Earth / Space Exploration
Apr 29, 2009 |
4.5 / 5 (2) |
4
(PhysOrg.com) -- Scientists have found that extreme solar activity drastically compresses the magnetosphere and modifies the composition of ions in near-Earth space. They are now looking to model how these ...
New Sun-Watching Instrument to Monitor Sunlight Fluctuations
Space & Earth / Space Exploration
Mar 23, 2009 |
3.7 / 5 (6) |
3
(PhysOrg.com) -- During the Maunder Minimum, a period of diminished solar activity between 1645 and 1715, sunspots were rare on the face of the sun, sometimes disappearing entirely for months to years. At ...
The sun could be having a 15% or 20% effect on climate change
Space & Earth / Earth Sciences
Jul 18, 2008 |
2.9 / 5 (27) |
11
Global warming is mainly caused by greenhouse gas emissions resulting from human activities; however, current climatic variations may be affected “around 15% or 20%” by solar activity, according to the researcher Manuel Vázquez ...
