Sun's brilliance? If you mean the energy output of the Sun, it it nearly constant, at least on a timescale of decades. The 11-year solar cycles involve profound changes in the solar activity - things like sunspots, prominences, coronal mass ejections, the amount of solar wind, etc - but the energy involved in these phenomena is negligible compared to the stable thermal emission of the solar photosphere. The changes on longer timescales - hundreds of years - are less well known.
The sun is a variable star, this puts some prespective from the Whats up with that site that put this into perspective:
It would take about 109 earths to equal the width of the suns diameter (Sun=1.39 million km Earth=12,700 km)
Over 1 million Earths would fit inside the Sun’s volume
The sun has a total luminosity output of 386 YottaWatts
(386,000,000,000,000,000,000,000,000 watts, some background here and here)
The total luminous energy output received by earth from the sun is 174 PETAWATTS (174,000,000,000,000,000) watts.
A 0.1% increase in luminosity dumps an extra 174 trillion watts (174,000,000,000,000) watts into our planetary energy balance.
Data source for graph: http://www1.ncdc.noaa.gov/pub/data/pale ... diance.txt
Note: In the graph above, the low flatline from 1645-1715 is the Maunder Minimum, a period of virtually no sunspots, where the historical reports from the northern hemisphere tell a story of dramatic climate change: harsh winters, cools summers, crop failures, famine and disease.
From the abstract referenced above: “Estimated increases since 1675 are 0.7%, 0.2% and 0.07% in broad ultraviolet, visible/near infrared and infrared spectral bands, with a total irradiance increase of 0.2%. “
So its not just 0.1 %, it is 0.2% which translates to a 348 TeraWatts global irradiance increase.
Now lets put 348 trillion watts into perspective:
Hurricanes: the heat energy released by a hurricanes category 1-5 equals about 50 to 200 trillion watts or about the same amount of energy released by exploding a 10-megaton nuclear bomb every 20 minutes.
Katrina, released about 200 trillion watts over its life cycle.
Now imagine double that amount of extra energy being added to earth’s atmosphere every second by small increases in the suns output that have been documented to exist. That’s what the increase in solar irradiance is doing. Since 1675, after the depths of the Maunder Minimum, we’ve seen an increase in solar irradiance of about 2.5 watts per square meter.
Climate modelers say that the extra CO2 equates to a forcing of about 2 watts per square meter, which totals about 1.12 Petawatt (1,120,000,000,000,000 watts). The problem is, they can’t always recreate that reliably between all of the different models out there, with the positive and negative feedback mechanisms, and other variables involved. There’s disagreement on the total contribution. A lot of it. Nonetheless they seem all to agree that CO2 makes some contribution, and that’s likely true. But compared to the sun, I believe it’s minimal.
Now lets look at us: 13.5 TeraWatts is the average total power consumption of the human world in 2001.
Compared to solar variance, do you think we could change the planets atmospheric energy balance with that if we squeezed all the power we made that year together and radiated it into our atmosphere ?
What is very clear though, when you look at history, and the graph above, is that our earths atmosphere and resulting climate is extremely sensitive to variations in solar output. The sweet center point seems to be about 1365 watts per square meter of irradiance…what we consider as “normal” climate. Take 1.5 watts/sq. meter away, and we get significant cooling, harsh winters, cool summers, and increases in ice and glaciers. Add 1.5 watts,/sq. meter and we get hotter summers, mild winters, and melting of ice and glaciers.
Now irradiance aside, as it’s only one component, there’s also the chnage in the suns dynamic magnetic field and solar wind, which according to Svensmark, which modulates the number of cosmic rays that enter our atmosphere (I think there may be some possible effect also due to modulation of the earth’s magnetic field), which modulates the number of clouds that form, hence changing the net surface irradiance. Plots of changes in the suns magnetic field line up very well with climate change.