The lingering cool temperatures being experience by much of North America has weather forecasters wondering if we are entering a new Little Ice Age—a reference to the prolonged period of cold weather that afflicted the world for centuries and didn't end until just prior to the American Civil War. From historical records, scientists have found a strong correlation between low sunspot activity and a cooling climate. At the end of May, an international panel of experts led by NOAA and sponsored by NASA released a new prediction for the next solar cycle: Solar Cycle 24 will be one of the weakest in recent memory. Are we about to start a new Little Ice Age?

According to the report, Solar Cycle 24 will peak in May 2013 with a sunspot count well below average. “If our prediction is correct, Solar Cycle 24 will have a peak sunspot number of 90, the lowest of any cycle since 1928 when Solar Cycle 16 peaked at 78,” says panel chairman Doug Biesecker of the NOAA Space Weather Prediction Center. This does not mean that we won't feel the results of renewed solar storm activity here on Earth.

“Even a below-average cycle is capable of producing severe space weather,” points out Biesecker. “The great geomagnetic storm of 1859, for instance, occurred during a solar cycle of about the same size we’re predicting for 2013.” A recent report by the National Academy of Sciences found that if a storm similar to the 1859 disturbance—known as the “Carrington Event” after astronomer Richard Carrington who observed the associated solar flare—occurred today, it could cause $1 to 2 trillion in damages to society's high-tech infrastructure and require four to ten years for complete recovery. Reportedly, the 1859 storm electrified transmission cables, set fires in telegraph offices, and produced Northern Lights so bright that people could read newspapers by their glow.

As we reported in Chapter 10 of The Resilient Earth, the most interesting feature of sunspots is that their number increases and decreases in a regular rhythm over about a decade. This regular cycle was first noticed by the German astronomer Samuel Heinrich Schwabe in 1843. This has become known as the solar magnetic activity cycle, or sunspot cycle. The number of sunspots in each cycle is not constant; there have been periods where many sunspots were observed, and others when sunspots seem to disappear altogether. Sightings from China, Korea and Japan between 28 BC and 1743 AD averaged only six sunspots per year. None were observed between 1639 and 1700, a period know as the Maunder Minimum.

The period from roughly 1300 to 1850 is known as the “Little Ice Age,” a period characterized by unusually long and cold winters. Some confine the Little Ice Age to approximately the 16^th century to the mid 19^th century, but it is generally agreed that there were three temperature minima, occurring around 1650, 1770, and 1850. Each minima separated by slight warming intervals. These periods coincides closely with times of solar inactivity, with some of the worst weather occurring squarely during the Maunder Minimum.

The Maunder Minimum is named after the English astronomer Edward W. Maunder (1851-1928). From studying historical records of sunspot counts, called the sunspot number, Maunder discovered that sunspots were virtually absent during this period, and disappeared altogether during the decade starting in 1670. Astronomers observed only about 50 sunspots during the 70 year period from 1645 to 1715. Normal sunspot activity would have produced 40,000 to 50,000 sunspots.

Already in the midst of the Little Ice Age's colder than average climate, Europe and North America went into a deep freeze: alpine glaciers extended over valley farmland, sea ice crept south from the Arctic, and the famous canals in the Netherlands froze regularly—an event that is rare today. In London, ice festivals were held on the frozen Themes and in New York City people could walk to Manhattan and Staten Island on the ice. On the down side, crops failed and many died of the cold.

In 1991, a pair of Danish meteorologists published a paper in which they pointed out a remarkably strong correlation between the length of the solar activity cycle and the global mean temperature in the northern hemisphere. Not all activity cycles are the same length, with longer cycles of 12-14 years duration seeming to indicate cooler global temperatures than shorter 9-10 year cycles. It is difficult to assess the effect of recent solar cycles on global climate, let alone those from the Maunder minimum, because of the relatively short time span for which detailed observations exist. Climate data for the past 100 years are spotty enough, climate records become sparse to nonexistent when looking back more than a century.

The correlation between temperature and sunspot activity has been commented on before on this site (see “Scientists Discover The Sun Does Affect Earth's Climate”), so I will not go into great detail about it here. However, it is interesting to note that a comparison of sea surface temperature and the number of observed sunspots over the past 150 years or so yeilds an astoundingly close match—much closer than the correlation between CO₂ and temperature.

Scientists are not sure how solar activity and space weather are linked to climate here on Earth. They do know that the last time sunspots all but disappeared for an extended period of time our planet experienced a dramatic downswing in temperature. Right now, the solar cycle is in a valley—the deepest of the past century. In 2008 and 2009, the sun set modern records for low sunspot counts, weak solar wind, and low solar irradiance.

There are variations in the 11 year cycle and other cycles of longer duration also seem to be at work here. Naturally, scientists have tried to predict the changing activity of the sun by examining the historical records and, more recently, using computer models. This is not to say that the predictions are always correct, no one correctly predicted the current ebb in solar activity. “In our professional careers, we've never seen anything quite like it,” said Dean Pesnell of the Goddard Space Flight Cente. “Solar minimum has lasted far beyond the date we predicted in 2007.”

“It turns out that none of our models were totally correct," admited Pesnell, NASA's lead representative on the prediction panel. “The sun is behaving in an unexpected and very interesting way.” Though the face of the sun is not as blemish free as it was a few months ago, the latest images from SOHO show sunspot activity is picking up a bit. But the current level of activity is still quite low. In fact, the sun has gone more than two years without a significant solar flare. What does this portend for the weather here on planet Earth?

According to expert long-range forecaster Joe Bastardi, areas from the northern Plains into the Northeast will have a “year without a summer.” This is a reference to the year 1816, also known as the Poverty Year, during which severe and abnormally cold summer weather destroyed crops in Northern Europe, the American Northeast and eastern Canada. According to Bastardi the jet stream is displaced abnormally southward this spring, which is suppressing the number of thunderstorms that can form. The ones that do form in areas of the Ohio Valley and West are forming in places with very cold temperatures, which can lead to thunderstorms more electrically active than normal.

Despite claims by global warming activists that rising temperatures are extending growing seasons around the world, the opposite seems to be happening this year. Cool weather has pushed growth of Western Canada's wheat and barley crop at least 10 days behind schedule, according to the Canadian Wheat Board. “You're pushing development into a period with better likelihood of getting a frost,” said Bruce Burnett, director of weather and market analysis for the Canadian Wheat Board. “It's not particularly what we need at this moment. It's just too cool.”

Proving that this isn't only a Northern Hemisphere phenomenon, Brazil may cut this year’s corn output forecast for a third consecutive time, as a frost in several states caused more crop damage. According to Silvio Porto, agriculture policy director, corn growers may harvest less than the 49.9 million metric tons forecast previously announced as frost struck Parana and Mato Grosso do Sul states in the past two weeks. “It’s a worrying situation as corn has already suffered with a severe drought,” Porto said. “Still, it’s too early to know the size of the damage.”

New record cold temperatures have been seen in a number of locations around the world, marking this as one of the coldest springs in years. With reports of late season frost and snow falls, some are already forecasting a very cool summer. Not trying to sound alarmist or start any rumors but scientists' best conjecture regarding the conditions that signal the start of a new glacial period are cool, cloudy summers. Is this the beginning of Little Ice Age II, the sequel? If so, we will look back fondly on the time we were all so concerned about global warming. Remember, in the words of SF author Orson Scott Card, “'global warming' is just another term for 'good weather.'”

Be safe, enjoy the interglacial and stay skeptical.