That reduction in sunlight brought about bitter cold weather across the northern hemisphere. The winter of 1784 was the coldest ever seen in New England and in Europe. New Jersey was buried under feet of snow. The Mississippi River froze all the way down to New Orleans! Ice was reported in the Gulf of Mexico. Historical records show that similar conditions existed during the following winter.

Other eruptions have caused similar consequences. Mount Tambora in Indonesia erupted with cataclysmic force in April of 1815, the largest eruption in over 1,600 years. It also came during a time of very low solar activity, known as the “Dalton Minimum.” The following year was called “The Year Without a Summer.” During early June of 1815, a foot of snow fell on Quebec City. In July and August, lake and river ice were observed as far south as Pennsylvania. Frost killed crops across New England with a resulting famine. During the brutal winter of 1816/17, the temperature fell to -32 in New York City.

Mount Pinatubo exploded in June of 1991, after four centuries of sleep. The resultant cloud of volcanic ash in the stratosphere pounded the global temperature down a full one degree Fahrenheit by 1993. Record snowfall buried the Mid-Atlantic states and southern New England during the winter of 1993/94. Those same records were shattered just two years later in the winter of 1995/96 from the effects of the reduced sunlight.

If Eyjafjallajokull induces an eruption of Katla, that event alone could force global temperatures down for 3 to 5 years. But there is much more at work here.

We have just exited the longest and deepest solar minimum in nearly 100 years. During this minimum, the Sun had the greatest number of spotless days (days where there were no sunspots on the face of the sun) since the early 1800s. The solar cycle is usually about 11 years from minimum to minimum — this past cycle 23 lasted 12.7 years. The long length of a solar cycle has been shown to have significant short term climate significance. Australian solar researcher Dr. David Archibald has shown that for every one year increase in the solar cycle length, there is a half-degree Celsius drop in the global temperature in the next cycle.

Using that relationship, we could expect a global temperature drop of one degree Fahrenheit by 2020. That alone would wipe out all of the warming of the last 150 years.

And there is yet a third player in this potential global temperature plunge.

Since autumn of 2009, we have been under the influence of a moderately strong El Nino. El Nino is a warming of the water in the Pacific Ocean along the equator from South America to the international dateline. El Nino’s warm water adds vast amounts of heat and humidity to the atmosphere. The result is a warmer Earth and greatly altered weather patterns around the world. The current El Nino is predicted to fade out this summer, and frequently after an El Nino we see the development of La Nina, the colder sister of El Nino. La Nina’s cooler waters along the equatorial Pacific act to cool the Earth’s temperature.

The stage could soon be set for a confluence of cold-inducing forces. A La Nina, a weaker sun, and a possible major eruption in Iceland could plunge the Earth into a period of bitter cold not seen for two hundred years.

Forecasts of natural phenomena are notoriously difficult. However, a unique set of natural circumstances have a chance to unify into a formidable triad. All eyes will be on Iceland to see if Katla awakens from its long sleep, and if it does, the theory of man-made global warming will be handed yet another crushing blow.