I'm going to go out on a limb and make a prediction: We will have summer weather in the Northeast next year.
This may seem obvious, but for a while I had my doubts. This year's volcanic eruptions, first in Iceland and more recently in Indonesia, reminded me of the 1991 eruption of Mount Pinatubo in the Philippines. Like Eyjafjallajokull in Iceland and Mount Merapi in Indonesia, Mount Pinatubo spewed clouds of ash high into the air, disrupting air traffic.
The summer of 1992, following the Pinatubo eruption, was ridiculously cold. In New York City the average monthly temperatures from March through June that year were all one to two degrees below normal. In July, the average temperature was 2.5 degrees colder than usual. My young daughters hardly had a chance to use our apartment building's swimming pool. The beaches we frequented in New Jersey and southern New England were pretty useless, too. Eventually my wife and I decided to make a last-minute trip to Florida just so we could find some water warm enough to jump into.
I remember thinking at the time that we were experiencing a scaled-down version of what the Year Without a Summer must have been like. That summer, in 1816, low temperatures and late frosts killed crops throughout northern Europe, the northeastern United States and eastern Canada. Snow fell in June in Albany and Quebec City. Rivers and lakes froze as far south as Pennsylvania. Scientists today believe the main cause of that cold weather was the eruption of Indonesia’s Mount Tambora in 1815.
So it was not without reason that I started to worry that the summer of 2011 might be a cold one.
Fortunately, it seems unlikely that the 2010 eruptions of Eyjafjallajokull and Merapi will have the same climatic effects as the 1815 eruption of Tambora, or even the 1991 eruption of Pinatubo.
The power of volcanic eruptions is measured by the Volcanic Explosivity Index (VEI), which is to volcanoes what the Richter scale is to earthquakes. The VEI takes into consideration the volume of debris produced by an eruption and the height reached by that debris.
Both Iceland's Eyjafjallajokull and Indonesia’s Merapi were fours on the VEI. The largest known eruptions are eights, and each one-number increase along the scale indicates a ten times larger eruption. A category four, or “cataclysmic” eruption, is one that tosses between 0.1 cubic kilometer and 1 cubic kilometer of debris into the sky. Eruptions of this force generally occur about once every 10 years. It was, therefore, unusual that we had two such eruptions this year.
However, despite this coincidence, even two category four eruptions will probably not be enough to have any effect on the weather. The 1980 eruption of Mount St. Helens in Washington was a category five, or “paroxysmal” eruption. The eruption of Mount Vesuvius that destroyed Pompeii was in the same category. Yet Mount St. Helens had no marked weather effects. The 1982 eruption of El Chich√≥n in Mexico was also a category five, and also had no notable effect on the weather.
The 1992 eruption of Pinatubo was a category six, or “colossal” eruption, 100 times bigger than either Eyjafjallajokull or Merapi. Pinatubo was in the same category as Indonesia's 1883 disaster at Krakatoa. Krakatoa and Pinatubo were both followed by cool periods, but even an eruption the size of Pinatubo may not have been big enough to fully account for the cold weather in the Northeast during the summer of 1992. In August of that year, Dr. Alan Robock, a University of Maryland climatologist, told The New York Times he thought the cold spell had more to do with local weather patterns than with any global trend caused by the volcano. Even as the Northeast put up with its disappointingly mild summer, the Pacific Northwest suffered through months of unusually high temperatures.
Mount Tambora, which is more universally agreed to have caused the cold spell that followed it, was a category seven. It was the most powerful eruption in recorded history. To classify as a category seven “super-colossal” eruption, a volcano must produce at least 100 cubic kilometers of debris. The second most recent category seven eruption was at Lake Taupo, in around 180 AD.
In other words, compared to the kinds of volcanoes that cause global cooling, this year’s eruptions were pipsqueaks.
So if you want to find snow in Northeastern city squares next July, I recommend you seek out a vendor with a pushcart and settle for snow cones in lieu of snowballs. You may want to get a couple of them. Summer heat can be tough, and next year looks like it will be no exception.