Joe Pappalardo at Popular Mechanics has a fascinating article on the possible (probable?) result of an extended solar minimum such as that which we are experiencing: global cooling:
Every day, scientists hoping to see an increase in solar activity train their instruments at the sun as it crosses the sky. This is no idle academic pursuit: A lull in solar action could potentially drive the planet’s temperature down, or even prompt a mini Ice Age.
Woah! I wonder if Joe has heard about the overwhelming scientific consensus that denies such a result? Maybe I should sic James Hansen on him…
For millennia, thermonuclear forces inside the star have followed a regular rhythm, causing its magnetic field to peak and ebb, on average, every 11 years. Space weathermen are watching for telltale increases in sunspots, which would signal the start of a new cycle, predicted to have started last March and expected to peak in 2012. “When the sun’s active, it’s a little bit brighter,” explains Ken Tapping, a solar researcher and project director for Canada’s National Research Council.
So far, Tapping reports no change in the magnetic field strength, as measured by radio telescopes. On the more positive side, last month NASA reported a small, earth-sized sunspot with a magnetic field pointing in the opposite direction from those in the previous cycle; qualities that designate the spot as a signal of a new upturn in activity. At the solar maximum, scientists expect to see between 75 and 150 such sunspots per day.
Tapping oversees the operation of a 60-year-old radio telescope that he calls a “stethoscope for the sun.” Recent magnetic field readings are as low as he’s ever seen, he says, and he’s worked with the instrument for more than 25 years. If the sun remains this quiet for another a year or two, it may indicate the star has entered a downturn that, if history is any precedent, could trigger a planetary cold spell that could bring massive snowfall and severe weather to the Northern Hemisphere.
The last such solar funk corresponded with a period of bitter cold that began around 1650 and lasted, with intermittent spikes of warming, until 1715. While there were competing causes for the climatic shift—including the Black Death’s depopulation of tree-cutting Europeans and, more substantially, increased volcanic activity spewing ash into the atmosphere—the sun’s lethargy likely had something to do with it.
Of course, no mention of greenhouse gases.
Just how much influence the sun has on global temperatures has been the subject of sometimes acrimonious debate. While an upswing in solar activity may cause a warming trend, it was discounted in the mid-1990s as the sole driver of current climate change. And for anyone hoping that a solar downswing might bail us out of our current dilemma: Solar influence on climate is slight compared to the impact of man-made greenhouse gases, a National Academy of Sciences report concluded in 1995.
Ah, there it is! So what we have is a contest between global warming due to greenhouse gases, and global cooling due to solar dimming.
Its a dilemma as to what to wish for. Global cooling such as the Little Ice Age would have been a technological challenge to modern 21st Century agriculture, technology and energy resources. What’s there to worry about with global warming? Deserts like the Sahara shrinking is a bad thing to be avoided…like the Plague?
This letter was written to the Greene County Daily:
Each morning I turn on my computer and check to see how the sun is doing. Lately I am greeted with the message “The sun is blank - no sunspots.”
We are at the verge of the next sunspot cycle, solar cycle 24. How intense will this cycle be? Why is this question important? Because the sun is a major force controlling natural climate change on Earth.
Our Milky Way galaxy is awash with cosmic rays. These are high speed charged particles that originate from exploding stars. Because they are charged, their travel is strongly influenced by magnetic fields. Our sun produces a magnetic field that extends to the edges of our solar system. This field deflects many of the cosmic rays away from Earth. But when the sun goes quiet (minimal sunspots), this field collapses inward allowing cosmic rays to penetrate deeper into our solar system. As a result, far greater numbers collide with Earth and penetrate down into the lower atmosphere where they ionize small particles of moisture (humidity) forming them into water droplets that become clouds. Low level clouds reflect sunlight back into space. A large increase in Earth’s cloud cover produce a global drop in temperature.
Some scientist feel they have developed sufficient understanding to predict the intensity of future sunspot cycles. A Solar Cycle 24 Prediction Panel was hosted on 25 April 2007 with officials from NOAA, NASA, ISES and other agencies. They issued a consensus statement which came to the conclusion that the next solar cycle could be severe, peaking at around 140 International Sunspot Numbers (Ri) or moderate, at around 90 Ri. But a few scientist disagree. A number of well regarded solar physicists are predicting the next solar cycle will be far weaker than the last one.
It’s worth pointing out that even NASA is having second thoughts about this, as I pointed out earlier.
A paper by David C. Archibald published in Energy and Environment in 2006 forecasted a low intensity solar cycle with a peak Ri of approximately 50. A few scientist have even claimed that we might be headed into another Solar Minimum. For the past few months, the actual sunspot numbers have been below NOAA’s lower predicted threshold, approaching zero.
And they have continued to be near zero.
Actually the streak of “spotless days” was recently broken when a single, tiny spot appeared and then disappeared after only a few hours. Nevertheless, September and October had the lowest sunspot counts since the last low before Solar Cycle 23:
This blog was setup by me to collate news on solar physics, predictions of future solar activity and possible correlations between solar activity and the Earth’s climate of the past.
I don’t come to any firm conclusions about the effect of solar variation on the climate of the Earth. I am merely reporting what I see.
