Figure 1 The moment of the eruption of the Tonga volcano
Although it has been many days since the eruption of the Tonga volcano on January 15, the impact of the eruption has not ended there, but has a tendency to further expand. Judging from the relevant data, this may be the largest volcanic eruption in the world in nearly 30 years. The eruption seemed to have touched the nerves of the earth, and the "butterfly effect" quickly spread the effects to the whole world.
On January 16, the Washington Post website disclosed that the shock wave caused by the volcanic eruption spread rapidly outward at a speed of near-sound, and the sound of the volcanic eruption was faintly heard in Alaska, nearly 10,000 kilometers away, that is, the "ripples" caused by the atmospheric shock wave spread throughout half the world. In addition, according to the Monitoring of american meteorological satellites, the ash from the eruption has reached an altitude of 40 kilometers, beyond the troposphere and reaching the stratosphere. Due to the specific environment of the stratosphere, these volcanic ash will remain in the atmosphere for several years.
So, what does this mean for the masses? Judging from the recent comprehensive reports of relevant media, the most mentioned thing is whether global grain production will be affected.
▲ Hong Aha Apai Island photographed after the eruption
- Volcanic ash spreads and temperatures drop, triggering crop yield reductions
At this stage, the general view is that due to the spread of volcanic ash in the stratosphere, it will trigger a "particle effect" that obscures the sunlight on the earth, thereby reducing the earth's temperature, and the global temperature reduction will directly affect the growth of global crops and directly affect the yield.
Such cases have indeed happened since recorded. In early April 1815, Mount Tambora, located in the northern part of the Indonesian island of Sumbawa, began to erupt violently and did not largely end until mid-July. Later data modeling shows that the total amount of volcanic ash in this eruption alone is as high as 130 billion tons, and a large amount of volcanic ash enters the troposphere and stratosphere, spreading globally with the atmospheric circulation, and the records show that it is located 1500 kilometers northwest of Tambora Volcano, and the ash height has reached 1 cm thick. It is also affected by the spread of volcanic ash that solar radiation has declined, and the global average temperature has dropped by 0.53 degrees Celsius, for which it is said that "there was no summer in 1816".
▲Temperature conditions in Europe in 1816
In addition, according to the May-August 1816 European barometric pressure map reconstructed by Wigley meteorologists at the University of Norwich, a large amount of volcanic ash did prevent direct sunlight from reaching the ground, which immediately caused the surface pressure in the mid-latitude region of the North Atlantic region to decrease, triggering a fierce westerly wind, bringing cold waves into the European region, resulting in an abnormal drop in temperature in the region. At the same time, rainfall has also increased, and low temperatures and heavy rainfall have directly led to a decline in crop yields in most parts of Europe. According to the statistics of cereal production in some provinces published by the French Minister of the Interior in November 1816, the reduction in cereal production was around 3%-33%. At the same time, relevant data show that in 1817, the price of wheat in 18 provinces in France increased significantly, which also confirmed from the side that France did have a decrease in cereal production in 1816. From the root of the event, the volcanic eruption in 1815 was the culprit.
During the same period, the mainland was also affected by the eruption of Mount Tambora in Indonesia. According to the "Crop Structure Changes in jiaodong Peninsula and climate abrupt changes after 1816" published by mainland scholars in 2009, the sudden change in climate after 1816 led to changes in the crop structure in an area of Jiaodong Peninsula, and traditional drought-saving and moisture-tolerant crops became the main crops, while drought-tolerant traditional grains began to shrink in scale. From this point of view, the eruption of the Indonesian volcano in 1815 alone did cause a decrease in global temperatures, and global cereal production also declined.
▲Production of cocoa beans, a major cash crop in the Philippines, 1990-1997 (Source: Official Statistics of the Philippines published by the Food and Agriculture Organization of the United Nations)
In addition, the 1991 eruption of Mount Pinatubo in the Philippines also had an impact on global temperatures. Although the eruption was much smaller than the Indonesian eruption of 1815, it still ejected at least 20 million tons of sulfur dioxide into the stratosphere, resulting in a 10% reduction in global sunlight. Combined with the data given in "The Impact of Mount Pinatubo on the Large-Scale Climate in 1992" published by mainland researchers, the year after the eruption, that is, in July-September 1992, there was the largest cooling in the world, with an average reduction of 0.6 degrees Celsius. According to the telemetry data of the US Climate Center for the same period, in the summer of 1992, the tropospheric temperature in the middle and high latitudes of the northern hemisphere fell by 1.2 degrees Celsius compared with the same period in 1991. As temperatures have fallen, the yield of cash crops in the Philippines has also fluctuated dramatically. According to official statistics from the Food and Agriculture Organization of the United Nations, the main crop of cacao beans in the Philippines was 9584 tons in 1991, and by the year after the eruption, cocoa bean production fell sharply, at only 7537 tons, a 10% drop, and the production of cocoa beans in the Philippines remained below 8000 tons in the following decade.
▲Effects of the eruption of Mount Pinatubo
Therefore, theoretically, if the total amount of volcanic ash from the Tonga eruption is huge, there is reason to believe that it will have an impact on global temperatures, once again causing a decline in global crop production.
- Will a mountain eruption produce La Niña or an El Niño phenomenon?
Two El Niño events occurred in 1982 and 1986, following the eruption of Mount Elchcan in Mexico in 1982 and the eruption of Mount Neva do Trez in Colombia in 1985. If you push the time forward, the eruption of Mount Santiagodo in 1902 and the eruption of Mount Agung in 1963 also occurred after El Niño. This raises doubts that volcanic eruptions may lead to El Niño.
▲The impact of El Niño on the global climate and economy
At the same time, some scientists have put forward different views, such as the 2020 atmospheric scientist Christine Karanpidou of the University of Hawaii at Monoia, who published a study in the journal Science Advances showing that "when volcanic eruptions in the tropics and north of the equator, el Niño occurs; but when volcanoes south of the equator erupt, it is more likely to occur in La Niña." According to this view, Tonga, where the eruption occurred, is located south of the equator, so the probability of La Niña is high. Coincidentally, according to the forecast given by the National Oceanic and Atmospheric Administration, since October last year, the equatorial Middle East Pacific SST has continued to decline, and the world has entered a La Niña state, and a weak to moderate intensity La Niña event has formed in the winter.
While there is disagreement, there is also a consensus that large-scale volcanic eruptions can cause extreme weather phenomena that can affect global crop yields.
According to relevant monitoring data, once the El Niño occurs, the equatorial Pacific region is the most affected, such as Drought in Australia, Indonesia and northeast Brazil, while the rainy sea from the equatorial Central Pacific Ocean to the west coast of South America is predominantly rainy, at this time, the northeast of the continent has a sustained low summer temperature, and most of the area has little precipitation. This harsh climate directly led to crop yield reductions, and the data showed that the total summer grain output in the country in 2016 was 139.26 million tons, a decrease of 1.2% compared with 1.621 million tons in 2015. Among them, cereal production was 128.643 million tons, down 1.2% from 1.572 million tons in 2015.
▲Global wheat production from 2008 to 2018
The emergence of the La Niña phenomenon also has a negative impact on global crop yields. When this phenomenon occurred, rainfall increased significantly in Indonesia, Australia, northeast Brazil, and other places; at this time, the equatorial region of Africa was dominated by drought; during the same period, the continent was prone to cold winters and hot summers, and the total number of tropical cyclones landing on the continent was higher than usual. Affected by La Niña in 2011, total global wheat production was lower than the previous year, and food prices were pushed higher. In addition, according to a warning issued by the Food and Agriculture Organization of the United Nations at the end of last year, la Niña may cause unusually dry weather in Afghanistan in the coming months, and Afghan farmers will usher in a second dry year in 2022, while at least 23 million people face extreme famine this winter.
▲ Precarious Mt. Fuji
Of course, while focusing on the Tonga volcano, we also need to turn our eyes back to us. On the day of the tonga eruption, South Korea's Channel A tv station reported that Japan's Mt. Fuji is also accumulating strength, and through recent surveys, the number of spitfire vents in Mt. Fuji in Japan has increased by nearly 6 times in the short term. This has raised concerns about whether the volcanic eruption in Tonga will trigger a super-large eruption of Mt. Fuji. Once this happens, the global climate, agriculture, and economy will be greatly impacted.
To conclude, only a violent volcanic eruption will affect global food production. According to the ESA Sentinel-5 satellite monitoring estimates, the Tonga volcanic eruption, into the stratosphere of about 400,000 tons of sulfur dioxide, equivalent to 1/50 of the 1991 Philippines Pinatubo eruption, from this point of view, for a short period of time global crop production can remain cautiously optimistic, but all this will depend on whether the Tonga volcanic eruption ends.