What changes have the climate experienced in human history? How does every climate change affect animals, plants and humans on earth?

Climate and human civilization: a brief historical review

From the third chapter of Earth-Ecology and Human Spirit on the verge of imbalance.

Al Gore (United States)

Unbalanced Earth Ecology and Human Spirit

Al Gore's The Earth in Balance.

Edited and published by China Publishing House.

From the year of 18 16, which is called "a year without summer", a large-scale crop failure triggered a "food riot" in almost every country in Europe, which inspired the revolutionary passion that swept across the European continent for three years. When the French government collapsed, the conservative Duke Richelieu was invited to form a new government. In many cities, crime spreads like a plague, which is unprecedented. Governments all over the world are trying to maintain social order. The Swiss are almost overwhelmed by the wave of criminal activities. Even the number of suicides has risen sharply, and many women have been executed for infanticide.

Historians say "beggars are like bees" blocking roads and begging from passers-by. 18 17 years, a traveler passing by Burgundy described it in this way, which is quite representative: "There are many beggars, but now the number has soared; At every stop, groups of women, children and the elderly gather around the carriage. " Another traveler who came to Burgundy from the British Isles added that although there are many beggars here, "there are definitely not as many tourists surrounded by Ireland". In Switzerland, witnesses said that a large number of beggars crowded the roads like an army. Their eyes are full of despair. In the words of local chronicler R. Zoellick, "their cheeks are pale because of the dead."

Some countries are afraid of revolution and send troops to control the growing population in need of food. An unprecedented wave of arson swept almost all countries. 18 19 In the summer, the first ominous anti-Semitic riot in modern German history broke out in the Bavarian town of Wü rzburg. Hunger and revolutionary passion aggravated the tension and anger, causing riots to spread throughout Germany and northward to Amsterdam and Copenhagen.

Europe has just recovered from the Napoleonic Wars and has undergone many changes. No one knows that the direct cause of this disaster and social unrest is the change of the earth's atmospheric composition, which is the result of a series of unusual eruptions of Tambora volcano on Sombawa Island in Indonesia in the spring of 18 15. Scientists estimate that about 10000 people died when the volcano erupted, and in the following months, nearly 82000 people died of hunger and disease. The most serious impact on other parts of the world will not be felt until a year later, when volcanic dust injected into the air will diffuse the whole atmosphere, greatly reducing the sunlight projected on the earth's surface, leading to a drop in temperature.

In New England, it usually snows in June of 18 16, and there is frost all summer. The Old Lunar Calendar is very popular. Due to a printing error, the almanac predicted that it would snow in July 18 16- but it was correct. From Ireland to the Baltic countries via Britain, it rained almost continuously from May to 65438+1October. The disturbance of climate model accurately predicted the social consequences: crop failure, food riots and social collapse from the British Isles to Europe. Historian J.D. Post called it "the most serious crisis of existence in the western world".

The climate change that led to this crisis lasted less than three years, probably because the substances injected into the atmosphere by volcanoes fell down in a short time. Therefore, even the largest volcanic eruption involving the whole world, its lasting impact will generally not exceed one to two years. For example, the eruption of Mount Pinatubo in the Philippines in 199 1 had a great impact on the whole world, but it was short-lived, cooling the earth a little, temporarily buffering the huge heat generated by human society and temporarily accelerating the depletion of the ozone layer.

The long-term effects of large-scale volcanic eruptions recorded in history have three important effects on human beings. First of all, it shows that human civilization depends to a great extent on the usually stable climate since 10000. Secondly, it shows that the tragedy that attacks one part of the world may be caused by climate change in another corner of the distant world. Thirdly, it shows the destructive results caused by man-made sudden and huge changes in the climate model of the earth's sphere.

The ancients knew very little about things beyond the local boundaries and could not understand the causal relationship between volcanic eruptions on the other side of the earth and local climate changes. But in recent years, detailed weather records from Greenland and Antarctic ice cores have been able to determine the dates of major volcanic eruptions since ancient times. Scientists have also obtained evidence from tree rings, geology and archaeology, and made a detailed analysis of the literature on climate change in ancient society, combining these situations with the current records. In particular, PICC China has a climate record of 36 centuries ago.

Scientists combined the records from tree rings and ice cores with the historical materials left by China historians, showing the devastating impact of the largest volcanic eruption in history: santorini volcano, 70 miles north of Crete, erupted around 1600 BC, and its power was1000 times that of the famous Indonesian Krakato volcano in 883. The influence of volcanic eruption in santorini on the climate will probably lead to the sudden disappearance of Minoan civilization which ruled the eastern Mediterranean for thousands of years in the Bronze Age in the near future. Some historians believe that the disappearance of Crete civilization is the basis for Plato to describe the disappearance of Atlantis in one day in his fable. )

Five centuries later, between 1 150 BC and 1 136 BC, the Hukla III volcano in Iceland erupted, throwing millions of tons of dust and particles into the atmosphere. According to the original bamboo slips preserved in China, at the same time, "there is dust and rain here". Another China writer said, "It rained for ten days. The rain is gray. " The third man said, "it snowed in June, and the snow was more than a foot deep ... frost killed five kinds of cereal crops ... fiber crops could not mature ... and it rained heavily." Archaeologists have also found evidence of the devastating consequences of the western world in the same period. Scottish archaeologists assert that during the same period, 90% of the population in Scotland and northern England disappeared. Moreover, soil analysis shows that extreme rainstorm and low temperature forced agricultural cultivation to stop temporarily.

Around 209 BC, people thought that this was a big eruption of Icelandic volcano, and evidence was found in the depths of the ice and snow layer covering Greenland and the Irish oak tree rings damaged by frost. Sima Qian, a historian in China, said that two years later, "crops failed" and no one knew the reason. China historian Ban Gu wrote in Hanshu that two years later, half of the population was starved to death by the Great Famine, and the phenomenon of "man eating man" appeared. The emperor lifted the ban on selling children. During this period, according to the chronicles of China, in 208 BC, "the stars could not be seen for three months".

Roman poets recorded the famous eruption of Mount Etna in Sicily in 42 BC, but only recently did historians read the newly translated version, linking this eruption with the disastrous weather changes that affected China. Ban Gu described it as "the sun is obscured", saying that crops failed and food prices rose by 10 times. Referring to the order issued that summer, he said, "Many farmers worked hard to cultivate the land and weed, but found nothing. They are suffering from famine and there is no way to save them. "

Surprisingly, the slight weather change caused by volcanic eruption also played an important role in the French Revolution, an important event in modern history. In his pioneering climate history, The Age of Banquet, The Age of Famine, E.R. Raduri described in detail the terrible scene of crop death and poor harvest in France six years before the 1789 revolution, which was extremely cold in 1788- 1789. That year, the brewing of wine was "a complete failure".

The best report about the weather in those years came from B. Franklin, who happened to be in France from 1776 to 12. 1may 784, he wrote:

1783 In the summer months, the sunshine should be strongest in the north, but parts of Europe and North America are always shrouded in fog. This fog is persistent and dry, and sunlight can't disperse it like wet fog rising from water. Sunlight is so weak when it passes through the fog that it can't even light a piece of paper when it is focused with a convex lens. Of course, the effect of global warming in summer is greatly weakened. So the surface of the earth is close to freezing point, and the snow stays on the ground without melting, and it accumulates more and more. Perhaps 1783- 1784 is much colder in winter than in many years.

Franklin keenly concluded, "The cause of this worldwide fog is still uncertain ... perhaps it is the huge amount of smoke and dust that continued to erupt all summer in Hekla volcano, Iceland, or it may be that the smoke and dust from another volcano (Skatwind Portar-Jokul) rose from the sea near Iceland and spread with the wind. These are still unclear. " What he didn't know was that, except for the volcanic eruption in Iceland, the shallow volcanic eruption in Japan was the most violent in history later that year, and nine times out of ten it was the cause of the unusually cold year in the middle of 65438+80' s, which led to crop failure and social unrest before the French Revolution. And this revolution has played a decisive role in reshaping modern society.

Of course, the role of climate in the formation of human history is extremely complicated, and climate historians often argue about the extent to which climate can be regarded as decisive. Climate is always intertwined with social, political and economic factors, and we have traditionally viewed history mainly from these factors. However, according to detailed evidence, some drastic climate changes are extremely important, even leading factors that cause people's emotions and attitudes before political upheaval, such as the huge climate-induced disasters from 18 16 to 18 19, which led to political turmoil in Europe. 1783 to/. However, it is also clear that climate change is only one of the reasons for these events. The official history ignores the climate factor, but it can't be suddenly said that it is the only factor.

In any case, the impact of climate change on human social, political and economic stability is enormous. If we can consider that the extent to which human beings have changed the global climate may be much deeper and faster than at any time in history, we may be more suitable to deal with the problem by carefully studying the lessons provided by nature.

Apart from causing famine and political turmoil, the great impact of climate change on mankind is large-scale migration, from one geographical area to another. The arrival of human beings in North and South America is one of the biggest migrations in history, and this migration is the direct result of climate change. About 20,000 years ago, during the last ice age, a lot of seawater froze, and the sea level was about 300 feet lower than it is now. Most of the seabed we now call the continental shelf is exposed on land, and some shallow straits such as Bering Strait and Carpentaria Bay have become land bridges. People who are now called Australian aborigines, and Asian nomads who are now called American aborigines in North America and Indians or aborigines in South America all migrated along the route of the land bridge. 10000 years ago, when the glaciers subsided and the sea level rose again, Native Americans and Australians were trapped in the New World. At the same time, the temperature rose, and the global climate became a new model, which has been maintained until now.

In fact, it profoundly influenced the ice age in North and South America and cultivated the primitive roots of human civilization. Cave painting represents the earliest known literature and image data, which appeared 17000 years ago. This is the place where human beings seek warm refuge in the worst and coldest Millennium.

Most historians believe that the continuous glacial period and warm interglacial period from 654.38 billion years ago to 40,000 years ago provided the initial impetus for the development of social organizations. Archaeological and anthropological records show that every time the glaciers recede, the population of primitive races in Eurasia becomes denser and the culture develops more.

From 8000 BC to 7000 BC, the climatic conditions were generally good, glaciers melted and retreated to their present positions, and agricultural surplus appeared in Mesopotamia. The trade of these surplus agricultural products created conditions for the emergence of money, the application of masonry technology in the earliest communities and the development of art and handicrafts. For example, Jericho, the oldest known city, was established in this period, and Europe in this period has just begun to recover from the Ice Age.

Later, smaller but still obvious climate fluctuations shaped more complex social forms. Some historians believe that in the fertile valleys of Tigris, Euphrates and Nile, the earliest appearance of highly organized society was caused by an important climate change about 3000 years ago. A new climate model-characterized by drought for most of the year and flooding every year-forces human communities to concentrate in river valleys. The tasks of preserving and distributing the flooded river water for irrigation, collecting the annual grain harvest and distributing food all need to properly set up the basic functions of human society. According to the Bible, Yue Se warned Pharaoh to prepare seven bad years after seven good years, which reflected that human beings began to realize that they were very vulnerable when climate patterns changed. After Yue Se explained the ecological significance of Pharaoh's dream, Pharaoh appointed Yue Se to check the preparations for the evil year. His decision reflects the firm attitude of human beings to master the ability to predict climate and respond to climate change.

However, the role of climate in human development is even more fundamental. This has become more and more clear. Anthropologists, evolutionary biologists and climate experts, such as E.S. Vrba, F.E. grina, R.G. Crane and D. Pulby, recently combined the history of climate change with anthropological events and reached a new consensus that human evolution itself was formed by the drastic changes in global climate patterns in the past 6 million years. W.K. Stevens said: "Scientists are outlining the important role of climate and ecology in shaping human evolution. Papers have emerged like a flood. "

The important period of global climate cooling, which happened gradually more than 5 million years ago, is consistent with the appearance of the earliest human being called Australopithecus. According to the opinions of many scientists, this is because at least one arboreal ape has adapted to the disappearance of forest environment, learned to look for food on the ground and walk on two legs, so that their hands (which have evolved into branches) can freely hold and carry food and articles, and some articles have later become tools.

About 2.5 million years ago, the more serious and sudden second global cooling explained the evolutionary factors and produced a new advanced branch, Australopithecus robustus. This branch was eventually replaced by "human genus". The Anthropocene appeared after four relatively short (from a geological point of view) and severe ice ages about 654.38 million years ago, just before the last ice age. This incredible ecological change has added a new function to the brain to adapt to the rapidly changing climate conditions. The new discovery linking the emergence of modern people with global climate change has solved one aspect of the mystery of human origin, and at least provided a missing link in evolutionary history from the ecological point of view. Then, 40,000 years ago, the so-called cultural prosperity caused by the proliferation of tools and decorations coincided with an unusually warm Millennium in Europe.

There were some obvious ups and downs during the larger glacial and interglacial periods. These ups and downs are small compared with the ice age or man-made warm period that can be expected now, but they have great influence on human society.

For example, the climate change from 500 BC to 400 BC, the so-called sub-Atlantic deterioration period, led to changes in wind and temperature distribution and low temperatures throughout Europe. It is generally believed that these changes prompted the end of the Bronze Age in the North and stimulated the Germanic invasion from Scandinavia to Southeast Europe. Less than a century later, the wave of immigrants continued to push to the southeast, which is probably not just a coincidence. It was during this period that Macedonians conquered Greece. Immediately after the next generation, around 300 BC, the whole world began to warm up. During this period, Alexander the Great conquered the "known world" and spread Greek civilization to the whole Mediterranean and its surrounding areas.

During this relatively warm period, the mountain passes in the Alps, which originally separated Italy from the rest of Europe, became unobstructed, which stimulated Rome's imperial ambitions accordingly. At the same time, some mountain passes in Asia were also unblocked, which promoted the spread of Chinese civilization and the opening of the Silk Road. About 750 years later, the end of this warm period coincides with the last era of the Roman Empire. Among the many explanations for the decline and fall of Rome, climate historians added one: between 450 and 500 AD, the global climate pattern suddenly changed, which led to a cold and persistent drought in Central Europe, which may have triggered a large-scale immigration tide that was later called alien invasion.

In the16th century, India completely abandoned the then capital, Fatpur Sikrae, which happened after the southwest monsoon mode suddenly changed and deprived the city of water. The residents of this city have been forced to move to other places, which is just a repeat of what has happened in the Indian subcontinent. In fact, one of the precedents for the collapse of the empire, mainly caused by climate change, appeared 24 centuries ago, just a few hundred miles west of Sikrae in Fatpur. For thousands of years before 1900 BC, the great Indus civilization flourished in today's northwest India and Pakistan. Then, all of a sudden, when the polar cold air, as described by climate historians, moved south to Canada, the climate pattern around the Indus River changed. Places that used to be big cities and settlements were buried under sand dunes in the Rajputana desert, and residents were forced to move elsewhere. According to the analysis of climate historians, in the14th century, there was a similar collapse of Mali civilization in West Africa.

And the mysterious Mycenae. Mycenae originated from Minos, the hometown of King Agamemnon in Homer's epic. After the exquisite Mycenae culture ruled the Aegean Sea for more than two centuries, Mycenae suddenly disappeared in 1200 BC. Historians and archaeologists speculate that a country invaded from the north and found evidence that Mycenae fled to the south and east. But the reason for the sudden collapse of Mycenae culture has always been a mystery. However, modern climate analysis provides an interesting evidence: just before the disappearance of Mycenae civilization, the wind direction and temperature patterns affecting Europe, the Mediterranean, North Africa and the Middle East changed dramatically, which suddenly changed the rainfall law on which Mycenae depended. The new climate model still sends water vapor from the west through the Mediterranean, but it moves south to low latitudes, so that rainfall is concentrated on the west side of the Peloponnesian marginal mountains. Mycenae is located on the east side of the mountain range, so severe drought continued, rivers and wells dried up, crops died, and finally residents were forced to leave.

Some climate historians also believe that the change of the same group of Mediterranean weather patterns was the chief culprit of the catastrophic flood in the Hungarian plain, which led to the March of all ethnic groups from the Balkans across the Bosphorus in the Bronze Age. These large numbers of immigrants from Armenia and other nationalities caused the collapse of Hittite civilization in Asia Minor around 1200 BC, stimulated the great migration to Cyprus, Syria, Palestine and Egypt, and played a destructive role politically and militarily. Records of this event can be found everywhere in the Old Testament. Another part of the same group of immigrants turned from the Hungarian plain to the southwest, crossed the mountain pass, entered Italy, became the later Serus, and the cultural seeds sown later evolved into Roman civilization.

In the western hemisphere, a new analysis of global climate records may explain the mysterious rise and fall of ancient Mayan culture. From about 250 to 300 AD, Mayan culture flourished in the Yucatan Peninsula in southern Mexico and Central America. For unknown reasons, Mayan culture suddenly declined around 950, which caused a heated debate among archaeologists and historians. The Mayans built a magical city, with exquisite underground storage rooms and large buildings of the same size as other parts of the world at the same time. These buildings include complex observatories, where Mayan astronomers calculate the exact dates of the solar year and the lunar month. They know the exact orbit of Venus, and they can predict solar and lunar eclipses. Their mathematicians independently acquired the mathematical concept of zero. However, such a huge and complex culture suddenly came to an end. For some reason, the city was abandoned instead of destroyed. The production of exquisite pottery and sculpture, the construction of monuments and temples all stopped suddenly, all kinds of records, calendars and characters also stopped suddenly, and the population of ceremony centers and villages decreased sharply. All this happened between 50 and 100. Scientists have put forward all kinds of theories, from fratricidal violence and social disintegration to hurricanes and earthquakes, the exhaustion of soil fertility, the thirst for water, the survival competition of savanna and overpopulation.

The only thing that has not been studied is whether the changes in global climate patterns can explain the demise of Maya. However, the historical records of the climate in the Western Hemisphere show that the temperature rose and the climate changed around 950. Just as the Maya collapsed, in the far north, L. ericson crossed the Labrador Sea between Greenland (where his father Eric established a new settlement) and North America by boat and set foot on a new land. He was the first European to set foot on this land and named it Wen Lan.

Thus began the global climate change called the medieval warm period. Although it is regarded as a natural phenomenon in Europe, judging from the arrival of the first Europeans in North America at this time, it is obviously a change in the global climate pattern. Only climate change can explain why they came to North America. Before about 900 AD, the North Atlantic sea route from Scandinavia and Iceland to the new settlement in Greenland was completely frozen and impassable. At the end of the warm period around 1300, the temperature began to drop, and the sea surface froze again, blocking the route. Sporadic sailing to Brunei has stopped, and ships can't return to Iceland from Greenland to replenish soon. A generation later, the last group of immigrants froze to death. Since then, the historical glory of Eriksson's voyage has been concealed by Columbus, a southern European.

So what happened to the climate of Yucatan Peninsula around 950? If the new climate model enables settlements in Greenland and North America to be established (no matter how short the time is), will this model suddenly make the Mayan society in Central America unable to survive? Climate change will cause changes in the distribution of animals and plants, pests will spread from the equator to the north, and rainfall patterns will also change. Will the Maya, who have been growing up in a slightly cooler and pleasant climate, be killed by the terrible tropical sunshine? Climate factors can at least partially solve the mystery of Maya disappearance.

After the warm period, the temperature dropped again at the beginning of14th century, which brought great problems to Europe and Asia. First of all, the sudden and repeated climate change has caused a large amount of moisture to sweep across the vast areas of the British Isles and the European continent from the North Atlantic. In the past 10 years, people in western Europe suffered from crop rot and river flooding, culminating in the great famine from 13 15 to 13 17. G de nangis reported from Rouen and chartres that "poor, haggard men and women came to the church in droves, praying to be rescued from the relentless rain". He added, "We saw a large number of men and women, not only from nearby, but also from five miles away, all barefoot. Many of them are naked except women, and their priests are among them. " That year and the following year, the grain harvest in Europe was completely destroyed. Raduri reported that the summer in 13 16 was "too humid to have good weather for shearing". Years of famine have brought the death toll to an unprecedented peak, but the worst case is the Black Death 30 years later.

Just before the Black Death, four years of bad weather and crop failure caused widespread malnutrition and decreased resistance to diseases, which made some people afraid of the recurrence of the Great Famine. This fear prompted people to import food from Asia Minor, first bringing infected mice to Constantinople, and then to the ports of Messina and Marseille. These mice and the plague they carried swept through western Europe in just two years, causing 1/3 deaths.

The plague itself actually originated in China, and the deceased was first discovered in 1333. The same global weather change that caused continuous rain in Europe also caused an abnormal rainstorm in China, which led to the continuous flooding of the Yellow River. From 1327, the situation is getting worse and worse. By 1332, the biggest flood occurred in the Middle Ages, and it was reported that the death toll at that time was 7 million. Climatologist H. Lamb wrote: "There is no doubt that floods not only force people to migrate, but also force wild animals to find other habitats, including rats carrying plague." His conclusion is: "The Black Death that finally swept the world was the Black Death that occurred in China in 1333." And 1333 was the second year of the Yellow River flood that caused China's corpses everywhere.

The Little Ice Age (1550- 1850) is one of the most important and completely recorded climate fluctuations, and the obvious social changes in Europe are all related to the Little Ice Age. People stay indoors more and keep warm around the suddenly popular fireplace, which has evolved into a new social way. People exchange ideas more around topics like science. Romanticism has gradually emerged in the field of art, and some independent opinions have also appeared in the political field. For some northern Europeans, the new weather conditions are too bad for outdoor activities.

1690 In Aberdeen, Scotland, an Eskimo appeared on the Tang River in a canoe, and people were shocked. The migration of Europeans to Greenland has completely stopped, but the living environment that Eskimos are used to extends southward to the Orkney Islands and northern Scotland.

Due to the failure of cod fishing and poor agricultural harvest, Scots have left their homes after years of disasters. By 169 1, Scots with a population of110 settled in Ulster, Ireland (now called Northern Ireland, which is the closest to Scotland), replacing and expelling the native Irish, which gradually formed a lot of problems and stubborn violence.

In the years after the Scots immigrated, the population of Ireland continued to grow. Historians generally believe that Ireland is a social and political mess. The British rulers made some stupid decisions, and King James VI's decision to promote Scottish immigration was only the beginning. Old land ownership can only produce low-level culture, which in turn encourages early marriage and further population growth. From 1779 to 184 1, the population increased by 172%. According to disraeli's estimation, Ireland is the most densely populated area in Europe. It was a fatal decision to take potato as the only food crop, and then the terrible tragedy of "potato famine" occurred.

At the end of the Little Ice Age, the average temperature rose slightly, which led to rainy and warm climate conditions conducive to the growth of potato Fusarium wilt. Modern laboratory research shows that the epidemic disease attacking Ireland is Phytophthora infection, and the required conditions are: relative humidity above 90%, temperature above 10℃ for at least 12 hours, and potato leaves watering for at least 4 hours. During the Little Ice Age, Ireland began to rely on potatoes for a living, but it was unlikely that such a comprehensive situation would occur at that time. This possibility increased when a new warm atmosphere appeared in the mid-1940s.

This epidemic originated from a new potato variety in Peru. 1843 was first discovered in the northeastern United States, and was discovered in Flanders the following year. By the summer of 1845, its seeds had spread to Ireland. That winter was the warmest winter in Irish memory, and spring was also very warm. The temperature in June is 3 to 4 degrees higher than the average temperature in the same period in the past 100, and the summer is the second hottest summer in 19 century as a whole. To make matters worse, it rained for 64 days in July, August and September, and it rained 24 times in August alone.

Fusarium wilt destroyed the only food crop that determined Ireland's fate. In the next few years, more than 1 10,000 people in Ireland died of hunger or malnutrition-related diseases. The terrible stories of survivors made us realize what hunger means to mankind. 1846 65438+In February, the father of two children in Cork County died of hunger (the mother had already starved to death). According to the investigation report, "people didn't know about it until two children hobbled into Shur village. They cried with hunger, saying that their father had not spoken to them for four days, and it was as cold as a slate. People also saw two other bodies, a mother and a child. They all died of hunger and the bodies were bitten by rats. "

An eyewitness who was published in the newspaper at that time described: "In a cabbage field, I saw the bodies of Barry and her two children buried in thin soil, her hands and feet were completely exposed, and the meat was eaten up by the dog. Two yards away from her head, there was some skin and hair on her head; At first, I thought it was part of a ponytail. I don't need to comment in detail, but I can't help asking: Are we part of Britain? " The practice of planting a single crop instead of multiple plants in a large area is called monoculture. The problem with this practice is that once plant diseases or stress-resistant pests occur, all crops will die, which is difficult to resist. This vulnerability is even more prominent if only a single variety of a single crop is selected. Irish people used to rely on a single variety of potatoes as their only food source, which had the highest yield in the past 300 years. Potato famine reminds us that artificially changing our relationship with nature like monoculture, regardless of climate change, will weaken the ability of society to feed the population. This incident also shows that rapid warming will lead to disaster.

Historically, climate tragedies such as potato famine led to a large number of immigrants to rich countries, especially the United States. Thirty years before the Great Famine, the survival crisis of1816-1817 also stimulated the immigration tide, not only from Europe to the United States, but also from the United States, because the impact of climate change was also felt outside Europe. For example, the history of migration from Maine to the west says: "After the unusually cold and ominous spring of 18 16 and 18 17, the fear of famine became a magical new motive force for migration. Hundreds of people with families sold their houses without thinking about it, left in a hurry and rushed to the distance. " The relationship between the migration tide in Maine and the abnormal climate pattern caused by the eruption of Tambora volcano in1816-18/7 can be confirmed by the following data: 18 18, as soon as the abnormal climate ended, the population of Maine returned to stability. States such as New Hampshire, Vermont, Connecticut and South Carolina also recorded the same situation. An eyewitness wrote: "In the summer of 18 17 ... something like a rout happened."

Perhaps the largest forced migration wave in American history occurred during the "drought and sandstorm" in the early 1930s, when a large number of people abandoned their homes and fled from Kansas, Oklahoma, Texas, parts of New Mexico, Colorado, Nebraska and other plain states. Like the potato famine, the cause of drought and sandstorm is the misuse of land, which makes the land and its people more unbearable to emergencies. In the 1920s, in