In the beginning of 2022, the underwater volcano of Hongahaapai Island in Tonga, an island country in the South Pacific, erupted violently, becoming the largest volcanic eruption in the 21st century so far. A large amount of sulfur dioxide (SO2) and hydrogen sulfide entered the atmosphere with the volcanic eruption. Some netizens worry that this eruption will cause a “year without summer” like Mount Tambora in 1815?
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Regarding the possible climate impact of the volcanic eruption, a reporter from The Paper (www.thepaper.cn) interviewed Gao Chaochao, an associate professor at the School of Environment and Resources of Zhejiang University, whose research direction is global climate change and low-carbon economy. She said, “Based on the currently observed amount of SO2 gas (about 400,000 tons) that the Tonga volcano erupted into the stratosphere this month, it will not have a significant impact on the global climate.” According to overseas research, as of January 17, The Tonga volcanic eruption produced about 400,000 tons of sulfur dioxide into the stratosphere.
Gao Chaochao mainly studies the global and regional climate effects of aerosols, low-carbon pathways for energy use and urbanization, and stratospheric climate engineering mechanisms and impacts. She has published nearly 20 SCI papers in international academic journals such as J. Geophys. Res., one of which was selected as a scientific research highlight by the journal Nature (Research Highlight in Nature, 2006); the other was selected as a scientific research highlight by the American Geophysical Society (Research Spotlight in AGU, , 2014).
Gao Chaochao believes that the potential future climate impact of the Tonga volcano depends first on whether there is a follow-up eruption, and second on the spread of sulfate aerosols, as well as the radiative forcing it produces and other processes in the current climate system (such as the El Niño-Southern Oscillation). ) potential interactions.
According to the United Nations Intergovernmental Panel on Climate Change (IPCC), radiative forcing is a measure of the degree to which a factor alters the balance of incoming and outgoing energy in the Earth-atmosphere system, and it is also an index that reflects the importance in underlying climate change mechanisms. Positive forcing warms the Earth’s surface, while negative forcing cools it.
The pictures before compilation are from the eruption of the submarine volcano in Tonga on January 14 and 15, USGS local time. On January 17, the volcano was again monitored for a major eruption, and the eruption for several days even triggered a tsunami thousands of kilometers away. The Tonga government issued its first disaster report on the 18th, saying that a tsunami as high as 15 meters was triggered by the eruption of an underwater volcano, causing an “unprecedented disaster” to the country.
“Volcanic activity is one of the important natural factors for the construction of the Earth’s climate system, and has had different degrees of impact on the regional or global climate in different periods.” Gao Chaochao told The Paper, “The climate effect of volcanic eruptions mainly depends on the eruption process. The amount of SO2 and H2S gases entering the stratosphere, which form aerosols and cause surface cooling by reflecting solar radiation. Eruption season and geographic location will affect the reflected solar radiation, coupled with the associated dynamics and feedbacks of the climate system. processes that influence the climate effects of volcanic eruptions.”
For the measurement standards of volcanic eruptions, Gao Chaochao mentioned three standards: Volcanic Dust Curtain Index (DVI), Volcanic Explosion Index (VEI), and Atmospheric Optical Depth (AOD) series. She once wrote in a paper: “Lamb was the first to establish the Volcanic Dust Curtain Index (DVI) using data such as historical records, radiation observations, temperature and eruption volume. Newhall et al. and Self et al. The Volcanic Explosion Index (VEI) was established by using 11 characteristic parameters such as destructiveness. Sato et al. used different proxy data such as the volume of volcanic dust curtains, optical properties and satellite observations during 1850-1882, 1882-1979 and 1979-1990, respectively. reconstructed atmospheric optical depth (AOD) sequences of volcanic activity over the past 150 years.”
At the same time, the paper also pointed out that because DVI and Sato sequences use different surrogate data, there is a lack of consistency in time series. However, VEI mainly characterizes geological features such as the intensity of volcanic eruptions, and has a low direct correlation with climatic effects (such as sulfur content in eruptions).
“VEI is the most used one in the news. Generally, VEI4 or above will attract attention in climate observation and research.” Gao Chaochao explained, “The eruption level of Tonga Volcano in January 2022 is about VEI5. Middle and lower.”
As a submarine volcano, how is the eruption and impact of Tonga volcano different from that of ground volcanoes?
Gao Chaochao said that submarine volcanoes usually trigger tsunamis, so they have an instantaneous impact on the surrounding waters or islands (if they exist), while surface volcanoes, especially mountain volcanoes, are relatively easy to spray gases such as ash and SO2 into the atmosphere at higher altitudes. middle. Under the same volume and material composition, the latter’s climate effect may be more significant.
A large area of Tonga is covered in volcanic ash. The picture is from CNN, taken on January 17, 2022. The high-level introduction. At present, the active volcanic areas in the world are mainly distributed in three belts.
First, there are more than 300 active volcanoes in the Pacific Rim Volcanic Belt, accounting for more than 60% of the world‘s active volcanoes. Among them, there are about 10 in South America, the west coast of Central America and the West Indies; 39 in Alaska and the Aleutians, and about 200 in the western and southwestern Pacific islands.
Second, there are more than 70 active volcanoes in the Mediterranean-Indonesia volcanic belt. Among them, there are 13 along the Mediterranean Sea and more than 60 in Indonesia.
Third, the ridge volcanic belt is mainly distributed in the ridges of the Atlantic, Pacific and Indian Oceans. Among them, there are 22 in the Atlantic Ocean and 22 in Iceland and Jan Mayen.
In this regard, The Paper reporters noticed that there have been several famous volcanic eruptions in history that had a significant and even sustained impact on the global climate. For example, famous scientific journals such as “Live Science” and “Australian Geography” have sorted out the more serious volcanic eruptions in human history.
Among them, the 1815 Tambora volcanic eruption in Indonesia was the most violent in 500 years, and the Volcanic Explosion Index (VEI) reached a rare level of 7 in human history. The world has experienced continued severe temperature drops due to massive emissions of sulphur dioxide, leading to global crop failures and the spread of typhus in Europe. 1816 was therefore called the “Year without Summer” in history.
The crater formed by the eruption of Mount Tambora in 1815. The picture comes from the history of the Associated Press in 1610 BC, the eruption of Thera (Thera) volcano in the Aegean Islands, with a VEI of 7. Geologists believe that Thera volcano in the Aegean Islands erupted in a fraction of a second with an energy equivalent to hundreds of atomic bombs. While there are no written records of the eruption, geologists believe it may have been the most powerful volcanic eruption ever recorded, and it is reasonable to speculate that the large amount of sulfur dioxide the volcanoes pumped into the atmosphere changed the climate, triggering tsunamis and a drop in temperatures .
However, the impact of some historical volcanic eruptions with a VEI of around 6 on the global climate should not be underestimated.
In 450 AD, the Ilopango volcano erupted for the first time, and the VEI was above 6. The eruption killed 100,000 people and displaced more than 400,000. It is thought to be responsible for the cooling of global temperatures between AD 535 and AD 536 and caused crop failures from Rome to China.
In 1600, Huaynaputina erupted, the largest recorded eruption in South America, with a VEI 6 level. The ash from the eruption buried more than 50 square kilometers west of the mountain and is still covered today. The summer following the eruption of the volcano in 1600 was the coldest in 500 years.
In 1783, the Laki volcano in Iceland erupted. The eruption lasted for about 8 months and released about 14.7 cubic kilometers of lava, VEI6. The poisonous gas not only poisoned crops, it also killed 60 percent of Iceland’s grazing livestock. The sulfur dioxide released by the volcano caused acid rain and a drop in global temperatures, causing famine that killed more than 10,000 Icelanders, about a quarter of Iceland’s population at the time.
In 1991, the Pinatubo volcano in the Philippines erupted, the second largest volcanic eruption of the 20th century, with a VEI 6 level. The volcano spewed nearly 20 million tons of sulfur dioxide into the stratosphere, causing global temperatures to plummet.