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Study Finds Volcanic Eruptions Impacted Global Hydroclimate

The eruption column of Mount Pinatubo on June 12, 1991, three days before the climactic eruption
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The eruption column of Mount Pinatubo on June 12, 1991, three days before the climactic eruption

A new study finds major volcanic eruptions significantly impacted the global hydroclimate. Those effects at times persisted for more than a decade and included abnormally dry conditions in tropical Africa, Central Asia and the Middle East as well as wet conditions in South America.

The study – published in the Proceedings of the National Academy of Sciences – involved the work of two researchers at the University at Albany. WAMC's Jim Levulis spoke with Ernesto Tejedor of the school’s Department of Atmospheric and Environmental Sciences about the work.

Tejedor: This study started with a very general question, right? We imagined what will happen to the world, how would the world be impacted immediately and what would the impact be over the next decade if there is a very large volcanic eruption occurring tomorrow? So we asked that question to start this study. To do so, we had to look into the past, into the last millennium where there have been very large volcanic eruptions. We know that because we had a very large eruption in 1991, which was Mount Pinatubo in Philippines. And that time, we already had satellite information to see how the volcanic ashes went into the stratosphere, and then they were distributed around the globe very quickly. And we knew, because we had instrumental data available, that aerosols make like a layer that reflect the solar radiation. And so that reflection was sending back into space. So the effect on the air was one of cooling. So we knew that from the instrumental data, but Mount Pinatuba was not large enough to address the very large impact that this eruption could have. So we went into the past and looked into these very, very large volcanic eruptions to see what were the impacts in the long term, and in also the immediate impacts. So our main finding is one is the impacts of future volcanic eruptions will be superimposed on anthropogenic climate change in the future. But future climate change scenarios conventionally do not include volcanic forcings. Because we don't know when, where and in what form they will occur. So this inevitably means that there could be surprises in store to which we currently have no strategy. So that since our paper highlights that these two prices could potentially be severe and more persistent than previously thought, because we found that the impacts of these very large volcanic eruptions will be changing how the precipitation system works around the world, and not only for the immediate year after the eruption, but even for a decade. Planning for some places that will mean severe droughts, for example. And the second angle that this study has, is that I don't know if you know about the new engineering solutions to combat climate change. One of them is solar radiation management. That is commonly view as one of the new engineering strategies because they use volcanic eruptions as natural analogs. And so our paper showed that such strategies might come with risks of unintended changes in precipitation throughout the world. And that could last for a decade or longer. That will last much more than previously thought.

Levulis: So taking what this study has found, as you just detailed, how can the data be utilized to prepare for future volcanic eruptions?

Tejedor: There is no perfect result because we are studying it with proxy records and with models. In this case, we use the last millennium product. And this is a new product that combines it's called paleo data simulation product, and it combines natural archives such as tree rings, coral records, that can tell us how the climate of the past works. We combine that with climate models. So to have an idea of how the system works and how the system has worked in the past, also to learn about the future. So these reconstructions are not perfect. So, they have uncertainties. So, when we have our results, our results also have uncertainties. But we can certainly take the changes that we see that will happen in the future or if we have a very large volcanic eruption tomorrow, we can go to the places where these larger changes will happen and start taking precautions because, for example, we know with our results, that these past eruptions caused severe drying in tropical Africa and across Central Asia and the Middle East, they induce significantly wetter conditions over Oceania and the South American monsoon region. Here in the [United] States, we found also that the region of California will also have severe drying. Then if you ask me how they these regions can be prepared, this is tricky because it all depends on their socio-economic state, because for example, California since they have been under severe drought during this these years, and in the past day, they have been preparing for these events for a while and they have the means to do so. But there are other regions that they don't have the resources to be prepared for such an event. If they have a lot of things going on already in terms of drought or hunger or wars, these will be another risk to put on top of their already long list.

Levulis: Finally, I feel like a lot of people know how earthquakes are measured on the Richter scale. What measurements are used to determine the size of a volcanic eruption?

Tejedor: Well that there are different measurements and those are taken into account according to different things. One is the volcanic explosivity index and that would be one of the most common that is used. And it tells you the measurement of the explosiveness of the volcanic eruption, the volume of the products and the eruption cloud, how high it reaches into the atmosphere. And so it goes from zero to eight.

Jim is WAMC’s Associate News Director and hosts WAMC's flagship news programs: Midday Magazine, Northeast Report and Northeast Report Late Edition. Email: jlevulis@wamc.org
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