Science

sun, sunspot, solar flare, solar activity
AP/NASA/ESA
After weeks without observing a sunspot,
one emerges on Sept. 23, 2008

Will the Sun’s Decreased Activity Mean Another Little Ice Age?

May 08, 2009 05:30 PM
by Haley A. Lovett
The sun may be heading into a century-long period of low activity, like the Maunder Minimum of the 17th century, but global warming may prevent another Little Ice Age.

Sun Is Getting Dimmer, Less Active

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Sunspots, the sources of solar activity such as solar flares, had a slow year in 2008, only being observed on about 25 percent of days. But 2009 might be even less active. At the beginning of April NASA reported that sunspots had only been observed on 12 out of the 90 days of the year thus far. In 2008 the sun saw it’s quietest year since 1913, but 2009 might bring even less activity.

Since 1996 the sun’s brightness has dimmed .02 percent at wavelengths visible to the human eye; ultra violet wavelengths have dimmed 6 percent. Solar wind seems to have dropped 20 percent in that same time period, and radio emissions recorded by NASA are down as well.

The sun normally goes through 11-year cycles of activity. The bottom of the activity cycle was 2008, and 2013 is supposed to be the year of maximum activity this sun cycle. But according to New Scientist, the sun also experiences longer high and low cycles that last much longer periods of time, and it is thought that we are currently in a high cycle that has lasted almost 80 years. Scientists in Greenland analyzed the isotopes that were trapped in ancient ice to chart high cycles from the last 10,000 years. They estimate that we may reach a low by 2020.

Opinion: What would a cooler sun mean for Earth?

Although a decline in solar activity might mean fewer dangers from solar flares, there are drawbacks to a less active sun.

New Scientist points out that decreased solar winds would allow more harmful cosmic rays to make it into the solar system, and astronauts would be in greater danger of getting cancer or other complications if exposed to those rays. The Kansas City Star suggests that if the debated correlation between clouds on Earth and cosmic rays turns out to be true, a less active sun might create fewer clouds on Earth, which could mean we’d lose the protective blocking and the warming effect of clouds.

As for an overall cooling of the Earth, some scientists say that it is possible. Nigel Weiss told New Scientist that overall cooling would be less than 1 degree Fahrenheit. Weiss and at least two other scientists, astrophysicists Angela Speck and Adrian Merlott, note that any change in temperature due to a decrease in sun activity would be small in comparison to the potential climate change from global warming. “My worry,” Merlott told the Kansas City Star,” is that it will lower temperatures and cause people to think it’s OK to burn all that coal and oil.”

Background: The Little Ice Age

As scientists continue to debate weather the Sun is entering a period of long-term low activity, many can’t help but think of the Maunder Minimum in the 17th century.

During the “Little Ice Age” that lasted from the 1400s to the early 1700s, sea ice increased, glaciers grew, and Greenland was cut off due to ice. One theory is that low solar activity caused a decrease in circulation on Earth (and thus less warm air was circulated to the poles) that led to the lower temperatures near the northern pole. According to NASA, the coldest part of that period was between 1645 and 1715, and was mainly due to inactivity from the sun. Scientists at the time only recorded 50 sunspots in 30 years.

One study of the Maunder Minimum by a group from NASA’s Goddard Institute for Space Studies found that while global temperatures changed very little, temperatures in regions such as North America and Europe changed quite dramatically.

Related Topics: The danger of coronal mass ejection

Solar activity is most often seen near the North Pole as the aurora borealis, but a flare from the sun can sometimes be harmful, and not just a pretty sight. At times the sun emits a huge ball of plasma all at once, traveling at incredible speeds, this is called a coronal mass ejection. If this ball of plasma were to hit the earth, it could affect satellites as well as power grids. Some scientists worry that a very large, fast coronal mass ejection could be powerful enough to destroy life as we know it.
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