Year Without a Summer? Not this Time.

You may have heard about the Year Without the Summer, 1816, when severe climate anomalies linked to the eruption of Indonesia’s Mt Tambora provoked widespread famine, the westward expansion of the United States, the invention of the bicycle, and Frankenstein. So epic, so influential: Tales of the dramatic climate impacts of that fateful year got me wondering whether the activity around Eyjafjallajökull would affect more than air traffic. For better or for worse, it turns out that, in this case, the answer is probably not.

Which is not to say that volcanic eruptions don’t regularly affect the global climate. Indeed, as recently as 1991, the eruption of the Philippines’ Mt Pinatubo injected ash particles and sulfur-rich gases into the atmosphere, producing a haze of sulfuric acid  that gradually spread throughout the stratosphere. As a result, the amount of sunlight that reached the Earth dropped by 10%; this reduced average temperatures by 0.9–1.1 °F in the northern hemisphere and 0.7 °F across the globe.

Eyjafjallajökull is not expected to have the effect of either Pinatubo or Tambora, however. First of all, the current eruption is nowhere near the size that would be required to affect the climate system. Eyjafjallajökull’s first explosion, which took place March 20, earned a 1 on the Volcanic Explosivity Index (VEI); the more recent flare-up will rate a 2 or 3. Meanwhile, Mt Tambora’s 1815 eruption scored a 7 on the VEI, making it 10,000 times more powerful than what we’re currently observing. Also, as of April 14, Eyjafjallajökull had emitted 0.004 megatons of SO2, as compared to an estimated 24500 megatons for Mt Tambora in 1815.

The relatively modest size of the eruption also means that Eyjafjallajökull’s gasses have not penetrated the upper atmosphere. Indeed, the gas, dust, and debris that have been spewed into the atmosphere over the last couple weeks have only reached about 12,000 feet above sea level, well below the 30,000-feet threshold that would reduce temperatures. At this height, Eyjafjallajökull’s gasses are expected to rain out of the atmosphere in a week.

The location of Eyjafjallajökull also matters. The Mt Tambora eruption had a great impact on the environment partly because it was so close to the equator. Air in the upper atmosphere flows from the equator to the poles, meaning Mt Tambora’s gases easily spread their way around the entire globe. This won’t be the case in Iceland, even if Eyjafjallajökull’s gasses penetrated the upper atmosphere, because of its northern latitude.

All of this means that unless the Eyjafjallajökull eruption were to grow dramatically in size, we’re unlikely to get anything like Frankenstein or the bicycle out of it. Of course, there is still a chance that the indirect effects of Eyjafjallajökull will impact the climate.

For instance, Europe’s downed planes mean that Eyjafjallajökull may have a positive (that is, negative) effect on greenhouse gas emissions, despite the fact that the volcano itself is emitting nominal levels of CO2. There’s also the issue of contrails, shown to affect the climate after the air-traffic stop associated with 9/11. The recent eruption may also have given people the added incentive they needed to start using teleconferencing and online meetings to communicate rather than traveling. So in the end who knows? Eyjafjallajökull may end up affecting our climate after all.