What impact will Tonga's 30-year-old volcanic eruption have on the world?

Source: Global Times

The violent eruption of the Hong Aha Apai Island Volcano in the South Pacific island nation of Tonga on the 15th was called "the largest volcanic eruption in 30 years", and the volcanic ash cloud that was instantly spewed out broke through the top of the troposphere and formed an umbrella-shaped cloud with a diameter of nearly 500 kilometers. This violent volcanic eruption shocked the world, what impact will it have on the world?

Satellite image of an undersea volcanic eruption in Tonga. Image source Visual China

From Mt. Fuji to Yellowstone, the world's volcanoes are in turmoil?

After the violent eruption of Aha Apay Island in Tongahun, global attention to volcanic activity has risen again, and the claim that "there are more signs of activity in Mt. Fuji in Japan, and there may be an outbreak in the near future" has spread widely on social media. Will the eruption of the Tonga volcano really cause volcanoes in other parts of the world to follow suit?

First of all, judging from the scale of this eruption of Tonga Volcano, although quite amazing, it is not yet a supervolcano. Heather Handley, a volcanologist at Monash University in Australia, said the energy released by the eruption was quite powerful, judging by the height of the ash rush to the top of the troposphere. Since the eruption has not yet completely ended, the outside world can only roughly calculate its volcanic eruption index (VEI) of about 4-5, which is the strongest volcanic eruption since the eruption of Mount Pinatubo (VEI-6) in the Philippines in 1991, but it is far from the 1815 Indonesian eruption of Mount Tambora (VEI-7), which caused the "summerless year". Experts say Tonga's volcano produces an eruption of this magnitude about once every 1,000 years.

South Korean media recently said that monitoring data show that the magma activity energy of Mt. Fuji in Japan has increased, and the number of fire vents has increased by nearly 6 times. Some American netizens are anxious and afraid about whether the Yellowstone supervolcano will erupt. But experts interviewed by the Global Times said that although the shock wave of the Tonga volcano eruption spread throughout the atmosphere and the tsunami spread throughout the Pacific Ocean, it is too much to say that the Tonga volcanic eruption can drive the global volcano. In general, violent volcanic eruptions are similar to earthquakes and may cause abnormal activity in the same geological belt, but Tonga Volcano belongs to different volcanic groups from Mount Fuji in Japan and Yellowstone in the United States, and the distance is thousands or even tens of thousands of kilometers, so the correlation between them is very small.

But that doesn't mean these volcanoes are completely unrelated to each other. According to the Washington Post, they are all located in the Pacific Ring of Volcanoes. The latter runs from the southern tip of South America, along the west coast of North America, through the Bering Strait, down through Japan and all the way to New Zealand. "The Pacific Ring of Fires, which is more than 40,000 kilometers long, is where the Pacific plate collides with the squeeze of many surrounding geological tectonic plates. According to the U.S. Geological Survey, about 75 percent of the world's active volcanoes are concentrated here. "The Tonga volcano has actually been active, with the last major eruption in 2014. According to reports, the volcano is at the boundary of the squeeze of the Pacific Plate and the Indian Ocean Plate, and the southwest Pacific Plate moves up to the Arc of Tonga-Kmadeke Island at a rate of up to 24 centimeters per year, which is one of the fastest moving plates in the world. Since 1902, there have been more than 20 major and mega earthquakes here.

In recent years, large-scale earthquakes and volcanoes have been reported worldwide, leading to speculation about whether the Earth has entered an active period of crustal movement. At present, the scientific community has no clear conclusions about this. According to the Scientific American website, because the time span of the active period of crustal movement is large, it is difficult to conclude that it has entered the active period of crustal movement based on only a few years of data. It is also believed that because of the increase in scientific observation methods and media communication capabilities, the illusion of "large-scale volcanoes and earthquakes" has been generated, but in fact, they have been happening all the time.

Can volcanoes solve global warming?

After the eruption of the Tonga volcano, the West is particularly concerned about "whether it will change the global climate", and even "benefiting from the volcanic eruption can offset the impact of global warming and reduce the pressure of emission reduction".

Will volcanic eruptions really affect the global climate? Historical large-scale volcanic eruptions do have such an effect. The eruption of Mount Naki in Iceland in 1783 caused an unusually cold winter climate in Europe from 1783 to 1784; the eruption of Mount Tambora in Indonesia in 1815 caused a serious climatic disaster, the average global temperature dropped by about 0.4 degrees to 0.7 degrees in the following year after the eruption, and many parts of the northern hemisphere suffered a "summerless year"; in 1991, the Pinatubo volcano in the Philippines erupted, injecting a large amount of aerosol into the stratosphere, and the global average temperature dropped by about 0.5 degrees a few months later...

The main reason why a volcanic eruption causes cooling is that it injects sulfur-containing aerosols into the atmosphere, which enter the stratosphere and help the Earth reflect more sunlight, creating a cooling effect within the atmosphere. However, it should be noted that for this causal relationship to be established, an important factor must also be considered - "magnitude". U.S. satellite monitoring photos show that as of the 16th, the eruption of sulfur dioxide from the Tonga volcano was 420,000 tons. Michael Mann, distinguished professor of atmospheric sciences at Pennsylvania State University, believes that the eruption of Pinatubo Volcano, which caused the global average temperature to drop by 0.5 degrees, eventually released 20 million tons of sulfur dioxide, so to achieve the impact of the previous eruption on temperature drops, "Tonga Volcano needs to emit more sulfur dioxide."

So how big will the impact of the Tonga volcano on China be? In view of the low latitudes of Tonga volcanoes, Zhu Congwen, deputy director and researcher of the Institute of Climate and Climate Change of the Chinese Academy of Meteorological Sciences, said that in the past 100 years, there have been three large-scale low-latitude volcanic eruptions, namely Agung Volcano (March 17, 1963), Elchijom Volcano (April 4, 1982) and Pinatubo Volcano (June 15, 1991). In the winter of the year after their eruption (December to February), temperatures were low in most parts of the mainland except the northeast and Xinjiang. In addition, the occurrence of the La Niña phenomenon also played a cooling role in the winter temperature of the mainland except the Qinghai-Tibet Plateau that year. Zhu Congwen said that volcanic eruptions of this scale will generally have a sustained impact on the global and East Asian climate in the next year or two, with a cooling effect of about 0.3 degrees. For the mainland, volcanic eruptions can weaken the intensity of the following year's East Asian summer winds, which in turn leads to the southward summer rain band of the continent.

Since volcanic eruptions can create the effect of global cooling, can we rely on artificially induced volcanoes to offset the effects of global warming? Chen Ying, a researcher at the Institute of Ecological Civilization of the Chinese Academy of Social Sciences, explicitly objected to this statement on the Internet, "Without the premise of reducing emissions, relying only on SRM (solar radiation intervention, that is, changing the radiation balance of the Earth system at a large scale through artificial methods to cope with global warming) will certainly not solve the problem of climate change." "In addition, this approach will not solve the problem of ocean acidification, which in turn may introduce other risks and uncertainties, such as changing the temperature and precipitation distribution."

Cao Long, a professor in the Department of Atmospheric Sciences at Zhejiang University's School of Earth Sciences, said the currently proposed SRM method includes injecting aerosols into the stratosphere, low-cloud lighting in the ocean, and increasing the albedo of the ocean and land surface. The basic starting point of these methods is to increase the albedo of the Earth-atmosphere system, reduce solar radiation reaching the atmosphere and the ground, and counteract the warming effect caused by the increase in greenhouse gases through short-wave radiation intervention. However, SRM cannot completely offset climate change caused by greenhouse gas increases on a global and regional scale, and there is currently limited understanding of cloud-aerosol radiation processes and microphysical processes, and there is still a lot of uncertainty about the cooling potential of aerosol-based SRM.

Why is volcano warning so hard

The violent volcanic eruption severely damaged Tonga, and the resulting tsunami caused heavy property damage to many places such as Japan. Can you warn of a volcanic eruption in advance?

Nathan Wood, a geographer at the U.S. Geological Survey's Western Geographic Science Center, said predicting volcanic eruptions was "very challenging." He said that while a complex network of seismic stations is being built around the world to monitor earthquakes and estimate average intervals of occurrence, "volcanoes are more difficult to predict." He said that when monitoring land volcanoes, it is convenient to place sensors near the crater. But even so, subject to financial and manpower constraints, most of Earth's terrestrial volcanoes still lack adequate monitoring data. Tonga's eruption is an undersea volcano, and many of the 1,350 active volcanoes that are erupting or may erupt in the future are hidden in the depths of the ocean that we cannot see. "Underwater and even deep-sea monitoring and early warning is far beyond the capabilities of volcanologists." Moreover, the secondary disasters of submarine volcanic eruptions are more serious. For example, on December 22, 2018, Indonesia's "Sons of Krakatoa" volcano only had a small eruption, which did not attract attention at the time, but because of the volcano's large-scale landslides in this eruption, the resulting huge tsunami caused more than 400 deaths.

Liu Jiaqi, an academician of the Chinese Academy of Sciences, called on "at present, there is a lack of global monitoring of submarine volcanoes, which cannot reach the level of accurate prediction." Now that earth science is developing towards deep space, deep earth, and deep sea, volcanoes are closely related to these three aspects, so efforts should be made in these aspects. ”