Dealing with Climate Deniers: Solar Variation 101

Global warming: a cause for the pause

After decades of intensifying warming, the rise in Earth's surface temperatures has slowed since the late 1990s— a seemingly mysterious pause used by climate science skeptics to argue that global warming isn't real.

But the mystery had a simple answer: the warming didn't go away. Instead, researchers found that much of ittook place in deep oceans, which are now warming 15 times faster than in the previous 10,000 years. (Anequatorial Pacific cooling trend also appears to have offset planetary warming trends, but it's expected to end soon.) The pause, it seems, is only a blip.

Changes in solar brightness are too weak to explain recent climate change. - See more on Solar Variation

There is a lot of misinformation fog around the climate change issues, and most of it is being generated directly by the carbon-fuel corporations that fear a carbon-tax and future regulations to cap carbon-emissions or reparations for carbon pollution. Dealing with these climate change deniers is a full time job, they like to use normal variations in data to cast doubt on the general hypothesis that human actions are having a profound change on the Earths climate, and thus irreparably damaging our biosphere, including mass extinctions and potentially a global catastrophe.

One climate denier brought up some scientific data he claimed proved that the Earth was actually cooling rather than warming. He was listening to right-wing radio and learned that Solar Radiation has been declining over the last decade, according to the National Solar Observatory. But this information, when understood properly isn't enough to account for the massive warming trend across the planet, the melting of glaciers and tundra, or the warming of the seas. 

Both long-term and short-term variations in solar activity are hypothesized to affect global climate, but it has proven extremely challenging to directly quantify the link between solar variation and the earth's climate. The topic continues to be a subject of active study.

The Sun's radiation tends to vary over an 11 year sun-spot cycle due to a periodic flipping of the Sun's magnetic poles. Due to the plasma like fluid of compressed hydrogen and helium that makes up most of the Sun's mass, the magnetic field apparently winds faster at the Sun's equator than at its poles. Over an eleven year cycle, the magnetic fields get twisted up and eventually become chaotic, causing a peak in sun-spots, which are essentially solar storms on the surface of the Sun caused by magnetic effects. Each sun-spot is caused by holes in the plasma surface, and indicates mass ejections, and increases in cosmic rays, including "hard particles" and high energy radiation.

Other solar cycles may have climate effects over long periods of geologic time, but generally the Earth's climate is more greatly affected by other astronomic events such as the Earth's precession which causes ice to accumulate in the Northern Hemisphere over a 26,000 year cycle. 

Direct irradiance measurements at the top of the atmosphere have only been available during the last three cycles and are based on a composite of many different observing satellites. However, the correlation between irradiance measurements and other proxies of solar activity make it reasonable to estimate past solar activity over long periods of time.

Although we have been experiencing slightly lower solar irradiance over the last 11-year solar cycle, then over the last two for which we have good scientific data from satellites and observatories, the variation is extremely small. The Sun generally produces about 1366 watts per square meter (perpendicular to the Sun's surface at the radius of the Earth's orbit ~93,000,000 miles), but over the last decade that number had decreased by about one watt per meter square (about 0.1%).

The point of all this data is that while we still don't know enough about the Sun's radiation to predict the solar weather patterns and how they will effect the Earth's climate, as we collect more accurate data over time we get see that "over the past 20 years, all the trends in the Sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures." In other words, the Earth is warming while the Sun has been dimmer than normal. So, the Sun is not causing global warming. 
What's more frighting is that, since humans have greatly increased global particulate pollution, both from carbon fuels (like China's smog problem) and from industrial farming techniques (slash and burn, forest fires, and plowing), we should have experienced a general decline in world temperatures due to this particulate 'sun-screen' in the upper atmosphere. Thus, if we clean our air quality up, we could see a dramatic increase in solar radiation at sea-level, which would be trapped by green-house gasses, like methane, water-vapor, and carbon-dioxide. If this happens, and Solar radiation returns to normal levels, we could see a serious spike in global temperatures. 

The mission of the National Solar Observatory is to advance knowledge of the Sun, both as an astronomical object and as the dominant external influence on Earth, by providing forefront observational opportunities to the research community. The mission includes the operation of cutting edge facilities, the continued development of advanced instrumentation both in-house and through partnerships, conducting solar research, and educational and public outreach. The National Solar Observatory is operated by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation, for the benefit of the astronomical community.