Ice age on earth. What was the last ice age on earth? A new ice age will begin

We are in the grip of autumn and it is getting colder. Are we heading towards an ice age, one reader wonders.

The fleeting Danish summer is over. The leaves are falling from the trees, the birds are flying south, it is getting darker and, of course, colder too.

Our reader Lars Petersen from Copenhagen has started preparing for the cold days. And he wants to know how seriously he needs to prepare.

"When does the next one start? glacial period? I learned that glacial and interglacial periods follow each other regularly. Since we are living in an interglacial period, it is logical to assume that the next ice age is ahead of us, isn’t it?” - he writes in a letter to the section “Ask Science” (Spørg Videnskaben).

We at the editorial office shudder at the thought of the cold winter that awaits us at the end of autumn. We, too, would love to know if we are on the verge of an ice age.

The next ice age is still a long way off

Therefore, we addressed Sune Olander Rasmussen, a lecturer at the Center for Fundamental Research on Ice and Climate at the University of Copenhagen.

Sune Rasmussen studies cold and obtains information about past weather by storming Greenland glaciers and icebergs. In addition, he can use his knowledge to act as an "ice age predictor."

“In order for an ice age to occur, several conditions must coincide. We cannot predict exactly when the ice age will begin, but even if humanity had no further influence on the climate, our forecast is that the conditions for it will develop in 40 to 50 thousand years at best,” Sune Rasmussen reassures us.

Since we're talking to an "ice age predictor" anyway, we might as well get some more information about what "conditions" we're talking about to help us understand a little more about what an ice age actually is.

This is what an ice age is

Sune Rasmussen says that during the last ice age the average temperature on earth was several degrees lower than today, and that the climate at higher latitudes was colder.

Much of the northern hemisphere was covered by massive ice sheets. For example, Scandinavia, Canada and some other parts of North America were covered with a three-kilometer ice shell.

The enormous weight of the ice sheet pressed the earth's crust a kilometer into the Earth.

Ice ages are longer than interglacials

However, 19 thousand years ago changes in climate began to occur.

This meant that the Earth gradually became warmer, and over the next 7,000 years freed itself from the cold grip of the Ice Age. After this, the interglacial period began, in which we now find ourselves.

Context

New ice age? Not soon

The New York Times 06/10/2004

glacial period

Ukrainian Truth 12/25/2006 In Greenland, the last remnants of the shell came off very abruptly 11,700 years ago, or to be precise, 11,715 years ago. This is evidenced by research by Sune Rasmussen and his colleagues.

This means that 11,715 years have passed since the last ice age, and this is a completely normal length of an interglacial.

“It's funny that we usually think of the Ice Age as an 'event', when in fact it's just the opposite. The average ice age lasts 100 thousand years, while the interglacial lasts from 10 to 30 thousand years. That is, the Earth is more often in an ice age than vice versa.”

“The last couple of interglacial periods only lasted about 10,000 years, which explains the widespread but erroneous belief that our current interglacial period is coming to an end,” says Sune Rasmussen.

Three factors influence the possibility of an ice age

The fact that the Earth will plunge into a new ice age in 40-50 thousand years depends on the fact that there are slight variations in the Earth's orbit around the Sun. The variations determine how much sunlight reaches which latitudes, thereby influencing how warm or cold it is.

This discovery was made by Serbian geophysicist Milutin Milankovic almost 100 years ago, and is therefore known as the Milankovitch Cycles.

Milankovitch cycles are:

1. The Earth’s orbit around the Sun, which changes cyclically approximately once every 100,000 years. The orbit changes from almost circular to more elliptical, and then back again. Because of this, the distance to the Sun changes. The further the Earth is from the Sun, the less solar radiation our planet receives. In addition, when the shape of the orbit changes, the length of the seasons also changes.

2. The tilt of the earth's axis, which varies between 22 and 24.5 degrees relative to the orbit around the Sun. This cycle spans approximately 41,000 years. 22 or 24.5 degrees does not seem to be such a significant difference, but the tilt of the axis greatly affects the severity of the different seasons. The more the Earth is tilted, the greater the difference between winter and summer. The Earth's axial tilt is currently 23.5 and decreasing, meaning the differences between winter and summer will decrease over the next thousands of years.

3. The direction of the earth's axis relative to space. The direction changes cyclically with a period of 26 thousand years.

“The combination of these three factors determines whether there are prerequisites for the onset of an ice age. It is almost impossible to imagine how these three factors interact, but using mathematical models we can calculate how much solar radiation certain latitudes receive at certain times of the year, have received in the past and will receive in the future,” says Sune Rasmussen.

Snow in summer leads to ice age

Temperatures in summer play a particularly important role in this context.

Milanković realized that for there to be a prerequisite for the onset of an ice age, summers in the northern hemisphere must be cold.

If winters are snowy and much of the northern hemisphere is covered in snow, then temperatures and the number of hours of sunshine in the summer determine whether snow is allowed to remain throughout the summer.

“If the snow does not melt in the summer, then little sunlight penetrates into the Earth. The rest is reflected back into space by a snow-white blanket. This exacerbates the cooling that began due to a change in the Earth’s orbit around the Sun,” says Sune Rasmussen.

“Further cooling brings even more snow, which further reduces the amount of heat absorbed, and so on, until the ice age begins,” he continues.

Likewise, a period of hot summers causes the Ice Age to end. Then the hot sun melts the ice enough so that sunlight can once again hit dark surfaces like soil or sea, which absorb it and warm the Earth.

People are delaying the next ice age

Another factor that matters for the possibility of an ice age is the amount of carbon dioxide in the atmosphere.

Just as snow reflecting light enhances ice formation or speeds up its melting, a rise in atmospheric carbon dioxide from 180 ppm to 280 ppm (parts per million) helped bring the Earth out of the last ice age.

However, since industrialization began, people have been constantly increasing the proportion of carbon dioxide, so that now it is almost 400 ppm.

“It took nature 7,000 years to raise the share of carbon dioxide by 100 ppm after the end of the Ice Age. Humans managed to do the same thing in just 150 years. This has major implications for whether the Earth could enter a new ice age. This is a very significant influence, which not only means that an ice age cannot begin at the moment,” says Sune Rasmussen.

We thank Lars Petersen for good question and send a winter gray T-shirt to Copenhagen. We also thank Sune Rasmussen for his good answer.

We also encourage our readers to send more scientific questions to [email protected].

Did you know?

Scientists always talk about an ice age only in the northern hemisphere of the planet. The reason is that there is too little land in the southern hemisphere to support a massive layer of snow and ice.

Excluding Antarctica, the entire southern part of the southern hemisphere is covered with water, which does not provide good conditions for the formation of a thick ice shell.

InoSMI materials contain assessments exclusively of foreign media and do not reflect the position of the InoSMI editorial staff.

NASA has taken pictures that show: The Little Ice Age on Earth is coming soon, possibly starting as early as 2019! Is this true or a horror story from scientists? Let's figure it out.

Are we on the verge of the end of the world?

In Russia in 2019, winter is truly Russian, with heavy snowfalls and low temperatures. Is this the norm, or is the cold winter a harbinger of a more serious cataclysm? NASA images of the sun show that in a few years the Earth may be experiencing a Little Ice Age!

Photos of the sun usually show dark spots on the sun. These relatively large spots disappeared.

Scientists predict a Little Ice Age on Earth

Some researchers come to the conclusion that the disappearance of spots is an indicator of a decrease in solar activity. Therefore, scientists predict a “Little Ice Age” for the current year 2019.

Where did the sunspots go?

This event is recorded by NASA for the fourth time this year, when the surface of the star turns out to be clean, without spots. It has been observed that solar activity is falling much faster over the past 10,000 years.

According to meteorologist Paul Dorian, this could lead to an ice age. "Weak solar activity over a longer period of time has a cooling effect on the troposphere, which is the lowest layer of Earth's atmosphere in which we all live."

Similarly, Valentina Zharkova, a professor at the British University of Northumbria, is convinced that an ice age will occur on Earth between 2010 and 2050: “I trust our research, based on excellent mathematical calculations and data.”

The last "Little Ice Age" was in the 17th century

The sunspots disappear and it looks like a pendulum moving back and forth. The same thing happens with the eleven-year solar cycle, as scientists explain. The last time spots disappeared at such a rate was in the 17th century.

At that time, the waters of London's Thames were covered with ice, and throughout Europe people were dying from lack of food because crops failed everywhere due to the cold. This period of low temperatures is called a “small one-time.”

Scientists have long suspected that low solar activity is one of the reasons for the onset of the Little Ice Age. But physicists still cannot explain how exactly it arises.

Many historical researchers have concluded that the Little Ice Age in the 17th century was the cause of the Time of Troubles in Russia. The appearance of numerous robbers is also associated with severe cold weather and crop failures in Rus'. So, for example, on the Don, at that time, they ruled

The next one is still far away

We put this question to Suna RASMUSSEN, a lecturer at the Center for Basic Research on Ice and Climate at the University of Copenhagen, who studies cold and obtains information about past weather by drilling into Greenland glaciers and icebergs. In addition, he can use his knowledge to act as an ice age predictor.

“IN ORDER FOR AN ICE AGE TO OCCUR, SEVERAL CONDITIONS MUST COINCIDE. We cannot predict exactly when the ice age will begin, but even if humanity did not influence the climate, our forecast is that the conditions for it will develop in 40-50 thousand years at best,” reassures Sune Rasmussen.

Since we're talking to an "ice age predictor" anyway, we can get some more information, find out what conditions we're talking about, so we can understand a little more about what an ice age actually is.

Sune Rasmussen says that during the last ice age, the average temperature on Earth was several degrees lower than today, and the climate at higher latitudes was colder. Much of the northern hemisphere was covered by massive ice sheets. For example, Scandinavia, Canada and some other parts of North America were covered with a three-kilometer ice shell. The enormous weight of the ice sheet pressed the earth's crust a kilometer into the Earth.

19 thousand years ago changes in climate began to occur. This meant that the Earth gradually became warmer and, over the next 7,000 years, freed itself from the cold grip of the Ice Age. After this, the interglacial period began, in which we now find ourselves.

In Greenland, the last remnants of the shell came off very abruptly 11,700 years ago, or 11,715 years ago to be more precise. This is evidenced by research by Sune Rasmussen and his colleagues. This means that 11,715 years have passed since the last ice age, and this is a completely normal length of the interglacial period.

“It’s funny that we usually consider the ice age as an event, although in fact it’s just the opposite. The average ice age lasts 100 thousand years, while the interglacial lasts from 10 to 30 thousand years. That is, the Earth is more often in an ice age, than vice versa."

"The last two interglacial periods only lasted about 10,000 years, which explains the widespread but erroneous belief that our current interglacial period is coming to an end," says Sune Rasmussen.

THAT THE EARTH WILL SUCCEED INTO A NEW ICE AGE IN 40-50 THOUSAND YEARS, depends on the fact that the Earth's orbit around the Sun has slight variations. The variations determine how much sunlight reaches which latitudes, thereby influencing how warm or cold it is. This discovery was made by Serbian geophysicist Milutin Milankovic almost 100 years ago, and is therefore known as the Milankovitch Cycles.

Milankovitch cycles are:

1. The Earth's orbit around the Sun changes cyclically approximately every 100,000 years. The orbit changes from almost circular to more elliptical, and then vice versa. Because of this, the distance to the Sun changes. The further the Earth is from the Sun, the less solar radiation our planet receives. In addition, when the shape of the orbit changes, the length of the seasons also changes.

2. The tilt of the Earth's axis, which varies between 22 and 24.5 degrees relative to the orbit around the Sun. This cycle spans approximately 41,000 years. 22 or 24.5 degrees does not seem to be such a significant difference, but the tilt of the axis greatly affects the severity of the different seasons. The more the Earth is tilted, the greater the difference between winter and summer. The Earth's axial tilt is currently 23.5 and decreasing, meaning the differences between winter and summer will decrease over the next thousands of years.

3. The direction of the earth's axis relative to space. The direction changes cyclically with a period of 26 thousand years.

"The combination of these three factors determines whether there are preconditions for the onset of an ice age. It is almost impossible to imagine how these three factors interact, but using mathematical models we can calculate how much solar radiation certain latitudes receive at certain times of the year, and also received at past and will receive in the future,” says Sune Rasmussen.

Temperatures in summer play a particularly important role in this context. Milanković realized that a prerequisite for the onset of the ice age was cold summers in the northern hemisphere.

IF WINTERS ARE SNOWY AND MOST OF THE NORTHERN HEMISPHERE covered with snow, the temperatures and hours of sunshine in the summer determine whether the snow will be allowed to remain throughout the summer. “If the snow does not melt in the summer, little sunlight penetrates into the ground. The rest is reflected back into space by a snow-white blanket. This exacerbates the cooling that began due to a change in the Earth’s orbit around the Sun,” says Sune Rasmussen. “Further cooling brings even more snow, which further reduces the amount of heat absorbed, and so on until the ice age begins.”

Likewise, a period of hot summers causes the Ice Age to end. Then the hot sun melts the ice enough so that sunlight can once again hit surfaces like soil or sea, which absorb it and warm the Earth.

Another factor that matters for the possibility of an ice age is the amount of carbon dioxide in the atmosphere.

However, since industrialization began, people have been constantly increasing the proportion of carbon dioxide, so that now it is almost 400 ppm.

“It took nature 7,000 years to raise the carbon dioxide content by 100 ppm after the end of the ice age. Humans managed to do the same in just 150 years. This is important in terms of whether the Earth will be able to enter a new ice age, and means not only that an ice age cannot begin at the moment,” says Sune Rasmussen.

With the exception of Antarctica, the entire southern part of the southern hemisphere is covered with water, which does not provide good conditions for the formation of a thick ice shell.

Christian SEGREN, Videnskab, Denmark

Whether you're traveling through the Swiss Alps or the Canadian Rockies, you'll soon notice a huge amount of scattered rock. Some are as large as houses and often lie in river valleys, although they are obviously too large to be moved by even the worst floods. Similar erratic boulders can be found at mid-latitudes around the world, although they may be hidden by vegetation or layers of soil.

DISCOVERY OF THE ICE AGE

Wandering scientists of the 18th century, who laid the foundations of geography and geology, considered the appearance of these boulders mysterious, but local folklore preserved the truth about their origin. Swiss peasants told visitors that a long time ago they were abandoned by huge melting glaciers that once were at the bottom of the valley.

Scientists were initially skeptical, but as other evidence emerged of the glacial origins of the fossilized rocks, most accepted this explanation for the nature of the boulders in the Swiss Alps. But some have dared to suggest that a larger glaciation once spread from the poles to both hemispheres.

Mineralogist Jene Esmarck in 1824 put forward a theory confirming a series of global cold snaps, and German botanist Karl Friedrich Schimper in 1837 proposed the term “ice age” to describe such phenomena, but this theory received recognition only several decades later.

ABOUT TERMINOLOGY

Ice ages are periods of cooling lasting hundreds of millions of years during which extensive continental ice sheets and sediments are formed. Ice ages are defined as ice ages that last tens of millions of years. Ice ages consist of ice ages - glaciations (glacials), alternating with interglacials (interglacials).

Today, the term "Ice Age" often mistakenly refers to the last Ice Age, which lasted 100,000 years and ended about 12,000 years ago. It is known for large, cold-adapted mammals such as woolly mammoths and rhinoceroses, cave bears and saber-tooth tigers. However, it would be wrong to regard this era as entirely unfavorable. As the world's main water reserves disappeared under ice, the planet experienced colder but drier weather with lower sea levels. This ideal conditions for the resettlement of our ancestors from African lands around the world.

CHRONOLOGY

Our current climate is just an interglacial break in the ice age, which may resume in about 20,000 years (unless artificial stimulus is introduced). Before the threat of global warming was discovered, many people considered cooling to be the greatest threat to civilization.

The most significant glaciation of the Earth, right up to the equator, was characterized by the Cryogenian period (850-630 million years ago) of the Late Proterozoic glacial era. According to the Snowball Earth hypothesis, during this era our planet was completely covered with ice. During the Paleozoic Ice Age (460-230 million years ago), glaciations were shorter and less widespread. The modern Cenozoic glacial era began relatively recently - 65 million years ago. It ends with the Quaternary Ice Age (2.6 million years ago - present).

The Earth has probably gone through more ice ages, but the geological record of the Precambrian era has been almost completely destroyed by slow but irreversible changes to its surface.

CAUSES AND CONSEQUENCES

At first glance, it seems that there is no pattern in the onset of ice ages, so geologists have long argued about their causes. They are probably caused by certain conditions interacting with each other.

One of the most significant factors is continental drift. This is a gradual displacement of lithospheric plates over tens of millions of years.

If the alignment of the continents blocks warm ocean currents from the equator to the poles, ice sheets begin to form. This usually occurs if a large land mass is located over a pole or polar waters surrounded by nearby continents.

In the Quaternary Ice Age, these conditions correspond to Antarctica and the land-surrounded Arctic Ocean. During the major Cryogenian Ice Age, a large supercontinent became trapped near the Earth's equator, but the effect was the same. Once formed, ice sheets accelerate global cooling by reflecting solar heat and light into space.

Another important factor is the level of greenhouse gases in the atmosphere. One of the ice ages of the Paleozoic Ice Age may have been caused by the presence of large Antarctic land masses and the spread of land plants, which replaced large amounts of carbon dioxide in the Earth's atmosphere with oxygen, negating this thermal effect. Another theory is that the major stages of mountain building led to increased precipitation and accelerated processes such as chemical weathering, which also removed carbon dioxide from the atmosphere.

SENSITIVE EARTH

The described processes occur over millions of years, but there are also short-term phenomena. These days, most geoscientists recognize the important role of variations in the Earth's orbit around the Sun, known as Milankovitch cycles. As other processes have put the Earth in difficult conditions, it has become extremely sensitive to the level of radiation it receives from the Sun depending on the cycle.

In each ice age, there were likely even shorter-term events that could not be tracked. Only two of them are known for sure: the medieval climatic optimum in the X-XIII centuries. and the Little Ice Age in the XIV-XIX centuries.

The Little Ice Age is often associated with a decline in solar activity. There is evidence that changes in the amount of solar energy have a significant impact on the Earth in the last few hundred million years, but as with Milankovitch cycles, it is possible that their short-term effects may be magnified if the planet's climate has already begun to change.