Influence of Shiveluch Volcano on Climate Uncertain; A Review of Mount Redoubt Climate Effects

Discussion: The Shiveluch Volcano has been active since 1999. Shiveluch is classified as a volcanic eruption index = 4 on the zero to 9 (VEI) scale. Generally, volcanoes with an eruption index of 3 or 4 are emitting enough fallout into the stratosphere to alter climate although exact influences and duration are usually unique to the latitude of the eruption. The recent Shiveluch eruption easily qualified as a VEI = 4 episode implying influence on climate is likely. The specific influence characteristics and duration of this volcano are not known.

To illustrate what CAN happen, a review of the MAR-JUN 2009 eruption of Mount Redoubt (located east of Anchorage, Alaska) is worth noting. The Mount Redoubt eruption was classified VEI = 3 therefore strong enough to emit fallout into the stratosphere and having a sufficiently lengthy duration to influence climate. The following summer the stratosphere cooled dramatically across Canada and the northern U.S. based on 10 MB height anomalies (Fig. 1). In the troposphere, a polar vortex formed over the Great Lakes region (Fig. 2). The result? The year without a summer as cool temperatures dominated the Intermountain West to Midwest and Northeast U.S. (Fig. 3). Along the southern periphery of the upper trough, persistent heavy showers and thunderstorms rocked the Interior Northwest to the Tennessee Valley to the Northeast Corridor (Fig. 4). Climate forecasts for summer of 2009 were caught off guard by the exceptional cool climate.

Fig: 1-4: Temperature historical ranks by state for March 2023.

Can this happen in 2023? Probably not. Looking at the history of stratosphere/troposphere patterns following major eruptions of Shiveluch there is no apparent consistent reaction. The lack of definable climate reaction may be due to water as expansive downwind of the Kamchatka Peninsula while downwind from Mt. Redout was all land mass. Also, several major eruptions of Shiveluch have taken place during the 1999-2023 active period with no obvious influence on climate. However, the lack of an obvious connection between Shiveluch eruptions and climate patterns does not mean we should not be aware of some sort of development over the next couple months especially if VEI = 4 intensity eruptions continue.