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Ice age

An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and greenhouse periods during which there are no glaciers on the planet. Earth is currently in the ice age called Quaternary glaciation. Individual pulses of cold climate within an ice age are termed glacial periods (glacials, glaciations, glacial stages, stadials, stades, or colloquially, ice ages), and intermittent warm periods within an ice age are called interglacials or interstadials.

In glaciology, the term ice age is defined by the presence of extensive ice sheets in the northern and southern hemispheres. By this definition, the current Holocene period is an interglacial period of an ice age. The accumulation of anthropogenic greenhouse gases is projected to delay the next glacial period.

History of research
In 1742, Pierre Martel (1706–1767), an engineer and geographer living in Geneva, visited the valley of Chamonix in the Alps of Savoy. Two years later he published an account of his journey. He reported that the inhabitants of that valley attributed the dispersal of erratic boulders to the glaciers, saying that they had once extended much farther. Later similar explanations were reported from other regions of the Alps. In 1815 the carpenter and chamois hunter Jean-Pierre Perraudin (1767–1858) explained erratic boulders in the Val de Bagnes in the Swiss canton of Valais as being due to glaciers previously extending further. An unknown woodcutter from Meiringen in the Bernese Oberland advocated a similar idea in a discussion with the Swiss-German geologist Jean de Charpentier (1786–1855) in 1834. Comparable explanations are also known from the Val de Ferret in the Valais and the Seeland in western Switzerland and in Goethe's scientific work. Such explanations could also be found in other parts of the world. When the Bavarian naturalist Ernst von Bibra (1806–1878) visited the Chilean Andes in 1849–1850, the natives attributed fossil moraines to the former action of glaciers.

Meanwhile, European scholars had begun to wonder what had caused the dispersal of erratic material. From the middle of the 18th century, some discussed ice as a means of transport. The Swedish mining expert Daniel Tilas (1712–1772) was, in 1742, the first person to suggest drifting sea ice was a cause of the presence of erratic boulders in the Scandinavian and Baltic regions. In 1795, the Scottish philosopher and gentleman naturalist, James Hutton (1726–1797), explained erratic boulders in the Alps by the action of glaciers. Two decades later, in 1818, the Swedish botanist Göran Wahlenberg (1780–1851) published his theory of a glaciation of the Scandinavian peninsula. He regarded glaciation as a regional phenomenon.

Only a few years later, the Danish-Norwegian geologist Jens Esmark (1762–1839) argued for a sequence of worldwide ice ages. In a paper published in 1824, Esmark proposed changes in climate as the cause of those glaciations. He attempted to show that they originated from changes in Earth's orbit. Esmark discovered the similarity between moraines near Haukalivatnet lake near sea level in Rogaland and moraines at branches of Jostedalsbreen. Esmark's discovery were later attributed to or appropriated by Theodor Kjerulf and Louis Agassiz.

During the following years, Esmark's ideas were discussed and taken over in parts by Swedish, Scottish and German scientists. At the University of Edinburgh Robert Jameson (1774–1854) seemed to be relatively open to Esmark's ideas, as reviewed by Norwegian professor of glaciology Bjørn G. Andersen (1992). Jameson's remarks about ancient glaciers in Scotland were most probably prompted by Esmark. In Germany, Albrecht Reinhard Bernhardi (1797–1849), a geologist and professor of forestry at an academy in Dreissigacker (since incorporated in the southern Thuringian city of Meiningen), adopted Esmark's theory. In a paper published in 1832, Bernhardi speculated about the polar ice caps once reaching as far as the temperate zones of the globe.

In Val de Bagnes, a valley in the Swiss Alps, there was a long-held local belief that the valley had once been covered deep in ice, and in 1815 a local chamois hunter called Jean-Pierre Perraudin attempted to convert the geologist Jean de Charpentier to the idea, pointing to deep striations in the rocks and giant erratic boulders as evidence. Charpentier held the general view that these signs were caused by vast floods, and he rejected Perraudin's theory as absurd. In 1818 the engineer Ignatz Venetz joined Perraudin and Charpentier to examine a proglacial lake above the valley created by an ice dam as a result of the 1815 eruption of Mount Tambora, which threatened to cause a catastrophic flood when the dam broke. Perraudin attempted unsuccessfully to convert his companions to his theory, but when the dam finally broke, there were only minor erratics and no striations, and Venetz concluded that Perraudin was right and that only ice could have caused such major results. In 1821 he read a prize-winning paper on the theory to the Swiss Society, but it was not published until Charpentier, who had also become converted, published it with his own more widely read paper in 1834.

In the meantime, the German botanist Karl Friedrich Schimper (1803–1867) was studying mosses which were growing on erratic boulders in the alpine upland of Bavaria. He began to wonder where such masses of stone had come from. During the summer of 1835 he made some excursions to the Bavarian Alps. Schimper came to the conclusion that ice must have been the means of transport for the boulders in the alpine upland. In the winter of 1835–36 he held some lectures in Munich. Schimper then assumed that there must have been global times of obliteration ("Verödungszeiten") with a cold climate and frozen water. Schimper spent the summer months of 1836 at Devens, near Bex, in the Swiss Alps with his former university friend Louis Agassiz (1801–1873) and Jean de Charpentier. Schimper, Charpentier and possibly Venetz convinced Agassiz that there had been a time of glaciation. During the winter of 1836–37, Agassiz and Schimper developed the theory of a sequence of glaciations. They mainly drew upon the preceding works of Venetz, Charpentier and on their own fieldwork. Agassiz appears to have been already familiar with Bernhardi's paper at that time. At the beginning of 1837, Schimper coined the term "ice age" ("Eiszeit") for the period of the glaciers. In July 1837 Agassiz presented their synthesis before the annual meeting of the Swiss Society for Natural Research at Neuchâtel. The audience was very critical, and some were opposed to the new theory because it contradicted the established opinions on climatic history. Most contemporary scientists thought that Earth had been gradually cooling down since its birth as a molten globe.

In order to persuade the skeptics, Agassiz embarked on geological fieldwork. He published his book Study on Glaciers ("Études sur les glaciers") in 1840. Charpentier was put out by this, as he had also been preparing a book about the glaciation of the Alps. Charpentier felt that Agassiz should have given him precedence as it was he who had introduced Agassiz to in-depth glacial research. As a result of personal quarrels, Agassiz had also omitted any mention of Schimper in his book.

It took several decades before the ice age theory was fully accepted by scientists. This happened on an international scale in the second half of the 1870s, following the work of James Croll, including the publication of Climate and Time, in Their Geological Relations in 1875, which provided a credible explanation for the causes of ice ages.

Evidence
There are three main types of evidence for ice ages: geological, chemical, and paleontological.

Geological evidence for ice ages comes in various forms, including rock scouring and scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites and glacial erratics. Successive glaciations tend to distort and erase the geological evidence for earlier glaciations, making it difficult to interpret. Furthermore, this evidence was difficult to date exactly; early theories assumed that the glacials were short compared to the long interglacials. The advent of sediment and ice cores revealed the true situation: glacials are long, interglacials short. It took some time for the current theory to be worked out.

The chemical evidence mainly consists of variations in the ratios of isotopes in fossils present in sediments and sedimentary rocks and ocean sediment cores. For the most recent glacial periods, ice cores provide climate proxies, both from the ice itself and from atmospheric samples provided by included bubbles of air. Because water containing lighter isotopes has a lower heat of evaporation, its proportion decreases with warmer conditions. This allows a temperature record to be constructed. This evidence can be confounded, however, by other factors recorded by isotope ratios.

The paleontological evidence consists of changes in the geographical distribution of fossils. During a glacial period, cold-adapted organisms spread into lower latitudes, and organisms that prefer warmer conditions become extinct or retreat into lower latitudes. This evidence is also difficult to interpret because it requires:
 * 1) sequences of sediments covering a long period of time, over a wide range of latitudes and which are easily correlated;
 * 2) ancient organisms which survive for several million years without change and whose temperature preferences are easily diagnosed; and
 * 3) the finding of the relevant fossils.

Despite the difficulties, analysis of ice core and ocean sediment cores has provided a credible record of glacials and interglacials over the past few million years. These also confirm the linkage between ice ages and continental crust phenomena such as glacial moraines, drumlins, and glacial erratics. Hence the continental crust phenomena are accepted as good evidence of earlier ice ages when they are found in layers created much earlier than the time range for which ice cores and ocean sediment cores are available.

Major ice ages
There have been at least five major ice ages in Earth's history (the Huronian, Cryogenian, Andean-Saharan, late Paleozoic, and the latest Quaternary Ice Age). Outside these ages, Earth was previously thought to have been ice-free even in high latitudes; such periods are known as greenhouse periods. However, other studies dispute this, finding evidence of occasional glaciations at high latitudes even during apparent greenhouse periods.

Rocks from the earliest well-established ice age, called the Huronian, have been dated to around 2.4 to 2.1 billion years ago during the early Proterozoic Eon. Several hundreds of kilometers of the Huronian Supergroup are exposed 10 to 100 km north of the north shore of Lake Huron, extending from near Sault Ste. Marie to Sudbury, northeast of Lake Huron, with giant layers of now-lithified till beds, dropstones, varves, outwash, and scoured basement rocks. Correlative Huronian deposits have been found near Marquette, Michigan, and correlation has been made with Paleoproterozoic glacial deposits from Western Australia. The Huronian ice age was caused by the elimination of atmospheric methane, a greenhouse gas, during the Great Oxygenation Event.

The next well-documented ice age, and probably the most severe of the last billion years, occurred from 720 to 630 million years ago (the Cryogenian period) and may have produced a Snowball Earth in which glacial ice sheets reached the equator, possibly being ended by the accumulation of greenhouse gases such as produced by volcanoes. "The presence of ice on the continents and pack ice on the oceans would inhibit both silicate weathering and photosynthesis, which are the two major sinks for at present." It has been suggested that the end of this ice age was responsible for the subsequent Ediacaran and Cambrian explosion, though this model is recent and controversial.

The Andean-Saharan occurred from 460 to 420 million years ago, during the Late Ordovician and the Silurian period. The evolution of land plants at the onset of the Devonian period caused a long term increase in planetary oxygen levels and reduction of levels, which resulted in the late Paleozoic icehouse. Its former name, the Karoo glaciation, was named after the glacial tills found in the Karoo region of South Africa. There were extensive polar ice caps at intervals from 360 to 260 million years ago in South Africa during the Carboniferous and early Permian periods. Correlatives are known from Argentina, also in the center of the ancient supercontinent Gondwanaland.

Although the Mesozoic Era retained a greenhouse climate over its timespan and was previously assumed to have been entirely glaciation-free, more recent studies suggest that brief periods of glaciation occurred in both hemispheres during the Early Cretaceous. Geologic and palaeoclimatological records suggest the existence of glacial periods during the Valanginian, Hauterivian, and Aptian stages of the Early Cretaceous. Ice-rafted glacial dropstones indicate that in the Northern Hemisphere, ice sheets may have extended as far south as the Iberian Peninsula during the Hauterivian and Aptian. Although ice sheets largely disappeared from Earth for the rest of the period (potential reports from the Turonian, otherwise the warmest period of the Phanerozoic, are disputed), ice sheets and associated sea ice appear to have briefly returned to Antarctica near the very end of the Maastrichtian just prior to the Cretaceous-Paleogene extinction event.

The Quaternary Glaciation / Quaternary Ice Age started about 2.58 million years ago at the beginning of the Quaternary Period when the spread of ice sheets in the Northern Hemisphere began. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods, glacials or glacial advances, and interglacial periods, interglacials or glacial retreats. Earth is currently in an interglacial, and the last glacial period ended about 11,700 years ago. All that remains of the continental ice sheets are the Greenland and Antarctic ice sheets and smaller glaciers such as on Baffin Island.

The definition of the Quaternary as beginning 2.58 Ma is based on the formation of the Arctic ice cap. The Antarctic ice sheet began to form earlier, at about 34 Ma, in the mid-Cenozoic (Eocene-Oligocene Boundary). The term Late Cenozoic Ice Age is used to include this early phase.

Ice ages can be further divided by location and time; for example, the names Riss (180,000–130,000 years bp) and Würm (70,000–10,000 years bp) refer specifically to glaciation in the Alpine region. The maximum extent of the ice is not maintained for the full interval. The scouring action of each glaciation tends to remove most of the evidence of prior ice sheets almost completely, except in regions where the later sheet does not achieve full coverage.

Glacials and interglacials

Within the current glaciation, more temperate and more severe periods have occurred. The colder periods are called glacial periods, the warmer periods interglacials, such as the Eemian Stage. There is evidence that similar glacial cycles occurred in previous glaciations, including the Andean-Saharan and the late Paleozoic ice house. The glacial cycles of the late Paleozoic ice house are likely responsible for the deposition of cyclothems.

Glacials are characterized by cooler and drier climates over most of Earth and large land and sea ice masses extending outward from the poles. Mountain glaciers in otherwise unglaciated areas extend to lower elevations due to a lower snow line. Sea levels drop due to the removal of large volumes of water above sea level in the icecaps. There is evidence that ocean circulation patterns are disrupted by glaciations. The glacials and interglacials coincide with changes in orbital forcing of climate due to Milankovitch cycles, which are periodic changes in Earth's orbit and the tilt of Earth's rotational axis.

Earth has been in an interglacial period known as the Holocene for around 11,700 years, and an article in Nature in 2004 argues that it might be most analogous to a previous interglacial that lasted 28,000 years. Predicted changes in orbital forcing suggest that the next glacial period would begin at least 50,000 years from now. Moreover, anthropogenic forcing from increased greenhouse gases is estimated to potentially outweigh the orbital forcing of the Milankovitch cycles for hundreds of thousands of years.

Feedback processes
Each glacial period is subject to positive feedback which makes it more severe, and negative feedback which mitigates and (in all cases so far) eventually ends it.

Positive
An important form of feedback is provided by Earth's albedo, which is how much of the sun's energy is reflected rather than absorbed by Earth. Ice and snow increase Earth's albedo, while forests reduce its albedo. When the air temperature decreases, ice and snow fields grow, and they reduce forest cover. This continues until competition with a negative feedback mechanism forces the system to an equilibrium.

One theory is that when glaciers form, two things happen: the ice grinds rocks into dust, and the land becomes dry and arid. This allows winds to transport iron rich dust into the open ocean, where it acts as a fertilizer that causes massive algal blooms that pulls large amounts of out of the atmosphere. This in turn makes it even colder and causes the glaciers to grow more.

In 1956, Ewing and Donn hypothesized that an ice-free Arctic Ocean leads to increased snowfall at high latitudes. When low-temperature ice covers the Arctic Ocean there is little evaporation or sublimation and the polar regions are quite dry in terms of precipitation, comparable to the amount found in mid-latitude deserts. This low precipitation allows high-latitude snowfalls to melt during the summer. An ice-free Arctic Ocean absorbs solar radiation during the long summer days, and evaporates more water into the Arctic atmosphere. With higher precipitation, portions of this snow may not melt during the summer and so glacial ice can form at lower altitudes and more southerly latitudes, reducing the temperatures over land by increased albedo as noted above. Furthermore, under this hypothesis the lack of oceanic pack ice allows increased exchange of waters between the Arctic and the North Atlantic Oceans, warming the Arctic and cooling the North Atlantic. (Current projected consequences of global warming include a brief ice-free Arctic Ocean period by 2050.) Additional fresh water flowing into the North Atlantic during a warming cycle may also reduce the global ocean water circulation. Such a reduction (by reducing the effects of the Gulf Stream) would have a cooling effect on northern Europe, which in turn would lead to increased low-latitude snow retention during the summer. It has also been suggested that during an extensive glacial, glaciers may move through the Gulf of Saint Lawrence, extending into the North Atlantic Ocean far enough to block the Gulf Stream.

Negative
Ice sheets that form during glaciations erode the land beneath them. This can reduce the land area above sea level and thus diminish the amount of space on which ice sheets can form. This mitigates the albedo feedback, as does the rise in sea level that accompanies the reduced area of ice sheets, since open ocean has a lower albedo than land.

Another negative feedback mechanism is the increased aridity occurring with glacial maxima, which reduces the precipitation available to maintain glaciation. The glacial retreat induced by this or any other process can be amplified by similar inverse positive feedbacks as for glacial advances.

According to research published in Nature Geoscience, human emissions of carbon dioxide (CO2) will defer the next glacial period. Researchers used data on Earth's orbit to find the historical warm interglacial period that looks most like the current one and from this have predicted that the next glacial period would usually begin within 1,500 years. They go on to predict that emissions have been so high that it will not.

Causes
The causes of ice ages are not fully understood for either the large-scale ice age periods or the smaller ebb and flow of glacial–interglacial periods within an ice age. The consensus is that several factors are important: atmospheric composition, such as the concentrations of carbon dioxide and methane (the specific levels of the previously mentioned gases are now able to be seen with the new ice core samples from the European Project for Ice Coring in Antarctica (EPICA) Dome C in Antarctica over the past 800,000 years); changes in Earth's orbit around the Sun known as Milankovitch cycles; the motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic crust on Earth's surface, which affect wind and ocean currents; variations in solar output; the orbital dynamics of the Earth–Moon system; the impact of relatively large meteorites and volcanism including eruptions of supervolcanoes.

Some of these factors influence each other. For example, changes in Earth's atmospheric composition (especially the concentrations of greenhouse gases) may alter the climate, while climate change itself can change the atmospheric composition (for example by changing the rate at which weathering removes ).

Maureen Raymo, William Ruddiman and others propose that the Tibetan and Colorado Plateaus are immense "scrubbers" with a capacity to remove enough  from the global atmosphere to be a significant causal factor of the 40 million year Cenozoic Cooling trend. They further claim that approximately half of their uplift (and "scrubbing" capacity) occurred in the past 10 million years.

Changes in Earth's atmosphere
There is evidence that greenhouse gas levels fell at the start of ice ages and rose during the retreat of the ice sheets, but it is difficult to establish cause and effect (see the notes above on the role of weathering). Greenhouse gas levels may also have been affected by other factors which have been proposed as causes of ice ages, such as the movement of continents and volcanism.

The Snowball Earth hypothesis maintains that the severe freezing in the late Proterozoic was ended by an increase in levels in the atmosphere, mainly from volcanoes, and some supporters of Snowball Earth argue that it was caused in the first place by a reduction in atmospheric. The hypothesis also warns of future Snowball Earths.

In 2009, further evidence was provided that changes in solar insolation provide the initial trigger for Earth to warm after an Ice Age, with secondary factors like increases in greenhouse gases accounting for the magnitude of the change.

Position of the continents
The geological record appears to show that ice ages start when the continents are in positions which block or reduce the flow of warm water from the equator to the poles and thus allow ice sheets to form. The ice sheets increase Earth's reflectivity and thus reduce the absorption of solar radiation. With less radiation absorbed the atmosphere cools; the cooling allows the ice sheets to grow, which further increases reflectivity in a positive feedback loop. The ice age continues until the reduction in weathering causes an increase in the greenhouse effect.

There are three main contributors from the layout of the continents that obstruct the movement of warm water to the poles:
 * A continent sits on top of a pole, as Antarctica does today.
 * A polar sea is almost land-locked, as the Arctic Ocean is today.
 * A supercontinent covers most of the equator, as Rodinia did during the Cryogenian period.

Since today's Earth has a continent over the South Pole and an almost land-locked ocean over the North Pole, geologists believe that Earth will continue to experience glacial periods in the geologically near future.

Some scientists believe that the Himalayas are a major factor in the current ice age, because these mountains have increased Earth's total rainfall and therefore the rate at which carbon dioxide is washed out of the atmosphere, decreasing the greenhouse effect. The Himalayas' formation started about 70 million years ago when the Indo-Australian Plate collided with the Eurasian Plate, and the Himalayas are still rising by about 5 mm per year because the Indo-Australian plate is still moving at 67 mm/year. The history of the Himalayas broadly fits the long-term decrease in Earth's average temperature since the mid-Eocene, 40 million years ago.

Fluctuations in ocean currents
Another important contribution to ancient climate regimes is the variation of ocean currents, which are modified by continent position, sea levels and salinity, as well as other factors. They have the ability to cool (e.g. aiding the creation of Antarctic ice) and the ability to warm (e.g. giving the British Isles a temperate as opposed to a boreal climate). The closing of the Isthmus of Panama about 3 million years ago may have ushered in the present period of strong glaciation over North America by ending the exchange of water between the tropical Atlantic and Pacific Oceans.

Analyses suggest that ocean current fluctuations can adequately account for recent glacial oscillations. During the last glacial period the sea-level fluctuated 20–30 m as water was sequestered, primarily in the Northern Hemisphere ice sheets. When ice collected and the sea level dropped sufficiently, flow through the Bering Strait (the narrow strait between Siberia and Alaska is about 50 m deep today) was reduced, resulting in increased flow from the North Atlantic. This realigned the thermohaline circulation in the Atlantic, increasing heat transport into the Arctic, which melted the polar ice accumulation and reduced other continental ice sheets. The release of water raised sea levels again, restoring the ingress of colder water from the Pacific with an accompanying shift to northern hemisphere ice accumulation.

According to a study published in Nature in 2021, all glacial periods of ice ages over the last 1.5 million years were associated with northward shifts of melting Antarctic icebergs which changed ocean circulation patterns, leading to more CO2 being pulled out of the atmosphere. The authors suggest that this process may be disrupted in the future as the Southern Ocean will become too warm for the icebergs to travel far enough to trigger these changes.

Uplift of the Tibetan plateau
Matthias Kuhle's geological theory of Ice Age development was suggested by the existence of an ice sheet covering the Tibetan Plateau during the Ice Ages (Last Glacial Maximum?). According to Kuhle, the plate-tectonic uplift of Tibet past the snow-line has led to a surface of c. 2,400,000 square kilometres (930,000 sq mi) changing from bare land to ice with a 70% greater albedo. The reflection of energy into space resulted in a global cooling, triggering the Pleistocene Ice Age. Because this highland is at a subtropical latitude, with 4 to 5 times the insolation of high-latitude areas, what would be Earth's strongest heating surface has turned into a cooling surface.

Kuhle explains the interglacial periods by the 100,000-year cycle of radiation changes due to variations in Earth's orbit. This comparatively insignificant warming, when combined with the lowering of the Nordic inland ice areas and Tibet due to the weight of the superimposed ice-load, has led to the repeated complete thawing of the inland ice areas.

Variations in Earth's orbit
The Milankovitch cycles are a set of cyclic variations in characteristics of Earth's orbit around the Sun. Each cycle has a different length, so at some times their effects reinforce each other and at other times they (partially) cancel each other.

There is strong evidence that the Milankovitch cycles affect the occurrence of glacial and interglacial periods within an ice age. The present ice age is the most studied and best understood, particularly the last 400,000 years, since this is the period covered by ice cores that record atmospheric composition and proxies for temperature and ice volume. Within this period, the match of glacial/interglacial frequencies to the Milanković orbital forcing periods is so close that orbital forcing is generally accepted. The combined effects of the changing distance to the Sun, the precession of Earth's axis, and the changing tilt of Earth's axis redistribute the sunlight received by Earth. Of particular importance are changes in the tilt of Earth's axis, which affect the intensity of seasons. For example, the amount of solar influx in July at 65 degrees north latitude varies by as much as 22% (from 450 W/m2 to 550 W/m2). It is widely believed that ice sheets advance when summers become too cool to melt all of the accumulated snowfall from the previous winter. Some believe that the strength of the orbital forcing is too small to trigger glaciations, but feedback mechanisms like may explain this mismatch.

While Milankovitch forcing predicts that cyclic changes in Earth's orbital elements can be expressed in the glaciation record, additional explanations are necessary to explain which cycles are observed to be most important in the timing of glacial–interglacial periods. In particular, during the last 800,000 years, the dominant period of glacial–interglacial oscillation has been 100,000 years, which corresponds to changes in Earth's orbital eccentricity and orbital inclination. Yet this is by far the weakest of the three frequencies predicted by Milankovitch. During the period 3.0–0.8 million years ago, the dominant pattern of glaciation corresponded to the 41,000-year period of changes in Earth's obliquity (tilt of the axis). The reasons for dominance of one frequency versus another are poorly understood and an active area of current research, but the answer probably relates to some form of resonance in Earth's climate system. Recent work suggests that the 100K year cycle dominates due to increased southern-pole sea-ice increasing total solar reflectivity.

The "traditional" Milankovitch explanation struggles to explain the dominance of the 100,000-year cycle over the last 8 cycles. Richard A. Muller, Gordon J. F. MacDonald,  and others have pointed out that those calculations are for a two-dimensional orbit of Earth but the three-dimensional orbit also has a 100,000-year cycle of orbital inclination. They proposed that these variations in orbital inclination lead to variations in insolation, as Earth moves in and out of known dust bands in the solar system. Although this is a different mechanism to the traditional view, the "predicted" periods over the last 400,000 years are nearly the same. The Muller and MacDonald theory, in turn, has been challenged by Jose Antonio Rial.

William Ruddiman has suggested a model that explains the 100,000-year cycle by the modulating effect of eccentricity (weak 100,000-year cycle) on precession (26,000-year cycle) combined with greenhouse gas feedbacks in the 41,000- and 26,000-year cycles. Yet another theory has been advanced by Peter Huybers who argued that the 41,000-year cycle has always been dominant, but that Earth has entered a mode of climate behavior where only the second or third cycle triggers an ice age. This would imply that the 100,000-year periodicity is really an illusion created by averaging together cycles lasting 80,000 and 120,000 years. This theory is consistent with a simple empirical multi-state model proposed by Didier Paillard. Paillard suggests that the late Pleistocene glacial cycles can be seen as jumps between three quasi-stable climate states. The jumps are induced by the orbital forcing, while in the early Pleistocene the 41,000-year glacial cycles resulted from jumps between only two climate states. A dynamical model explaining this behavior was proposed by Peter Ditlevsen. This is in support of the suggestion that the late Pleistocene glacial cycles are not due to the weak 100,000-year eccentricity cycle, but a non-linear response to mainly the 41,000-year obliquity cycle.

Variations in the Sun's energy output
There are at least two types of variation in the Sun's energy output:
 * In the very long term, astrophysicists believe that the Sun's output increases by about 7% every one billion years.
 * Shorter-term variations such as sunspot cycles, and longer episodes such as the Maunder Minimum, which occurred during the coldest part of the Little Ice Age.

The long-term increase in the Sun's output cannot be a cause of ice ages.

Volcanism
Volcanic eruptions may have contributed to the inception and/or the end of ice age periods. At times during the paleoclimate, carbon dioxide levels were two or three times greater than today. Volcanoes and movements in continental plates contributed to high amounts of CO2 in the atmosphere. Carbon dioxide from volcanoes probably contributed to periods with highest overall temperatures. One suggested explanation of the Paleocene–Eocene Thermal Maximum is that undersea volcanoes released methane from clathrates and thus caused a large and rapid increase in the greenhouse effect. There appears to be no geological evidence for such eruptions at the right time, but this does not prove they did not happen.

Recent glacial and interglacial phases

The current geological period, the Quaternary, which began about 2.6 million years ago and extends into the present, is marked by warm and cold episodes, cold phases called glacials (Quaternary ice age) lasting about 100,000 years, and warm phases called interglacials lasting 10,000–15,000 years. The last cold episode of the Last Glacial Period ended about 10,000 years ago. Earth is currently in an interglacial period of the Quaternary, called the Holocene.

Glacial stages in North America
The major glacial stages of the current ice age in North America are the Illinoian, Eemian, and Wisconsin glaciation. The use of the Nebraskan, Afton, Kansan, and Yarmouthian stages to subdivide the ice age in North America has been discontinued by Quaternary geologists and geomorphologists. These stages have all been merged into the Pre-Illinoian in the 1980s.

During the most recent North American glaciation, during the latter part of the Last Glacial Maximum (26,000 to 13,300 years ago), ice sheets extended to about 45th parallel north. These sheets were 3 to 4 km thick.

This Wisconsin glaciation left widespread impacts on the North American landscape. The Great Lakes and the Finger Lakes were carved by ice deepening old valleys. Most of the lakes in Minnesota and Wisconsin were gouged out by glaciers and later filled with glacial meltwaters. The old Teays River drainage system was radically altered and largely reshaped into the Ohio River drainage system. Other rivers were dammed and diverted to new channels, such as Niagara Falls, which formed a dramatic waterfall and gorge, when the waterflow encountered a limestone escarpment. Another similar waterfall, at the present Clark Reservation State Park near Syracuse, New York, is now dry.

The area from Long Island to Nantucket, Massachusetts was formed from glacial till, and the plethora of lakes on the Canadian Shield in northern Canada can be almost entirely attributed to the action of the ice. As the ice retreated and the rock dust dried, winds carried the material hundreds of miles, forming beds of loess many dozens of feet thick in the Missouri Valley. Post-glacial rebound continues to reshape the Great Lakes and other areas formerly under the weight of the ice sheets.

The Driftless Area, a portion of western and southwestern Wisconsin along with parts of adjacent Minnesota, Iowa, and Illinois, was not covered by glaciers.

Last Glacial Period in the semiarid Andes around Aconcagua and Tupungato
A specially interesting climatic change during glacial times has taken place in the semi-arid Andes. Beside the expected cooling down in comparison with the current climate, a significant precipitation change happened here. So, researches in the presently semiarid subtropic Aconcagua-massif (6,962 m) have shown an unexpectedly extensive glacial glaciation of the type "ice stream network". The connected valley glaciers exceeding 100 km in length, flowed down on the East-side of this section of the Andes at 32–34°S and 69–71°W as far as a height of 2,060 m and on the western luff-side still clearly deeper. Where current glaciers scarcely reach 10 km in length, the snowline (ELA) runs at a height of 4,600 m and at that time was lowered to 3,200 m asl, i.e. about 1,400 m. From this follows that—beside of an annual depression of temperature about c. 8.4 °C— here was an increase in precipitation. Accordingly, at glacial times the humid climatic belt that today is situated several latitude degrees further to the S, was shifted much further to the N.

Effects of glaciation
Although the last glacial period ended more than 8,000 years ago, its effects can still be felt today. For example, the moving ice carved out the landscape in Canada (See Canadian Arctic Archipelago), Greenland, northern Eurasia and Antarctica. The erratic boulders, till, drumlins, eskers, fjords, kettle lakes, moraines, cirques, horns, etc., are typical features left behind by the glaciers. The weight of the ice sheets was so great that they deformed Earth's crust and mantle. After the ice sheets melted, the ice-covered land rebounded. Due to the high viscosity of Earth's mantle, the flow of mantle rocks which controls the rebound process is very slow—at a rate of about 1 cm/year near the center of rebound area today.

During glaciation, water was taken from the oceans to form the ice at high latitudes, thus global sea level dropped by about 110 meters, exposing the continental shelves and forming land-bridges between land-masses for animals to migrate. During deglaciation, the melted ice-water returned to the oceans, causing sea level to rise. This process can cause sudden shifts in coastlines and hydration systems resulting in newly submerged lands, emerging lands, collapsed ice dams resulting in salination of lakes, new ice dams creating vast areas of freshwater, and a general alteration in regional weather patterns on a large but temporary scale. It can even cause temporary reglaciation. This type of chaotic pattern of rapidly changing land, ice, saltwater and freshwater has been proposed as the likely model for the Baltic and Scandinavian regions, as well as much of central North America at the end of the last glacial maximum, with the present-day coastlines only being achieved in the last few millennia of prehistory. Also, the effect of elevation on Scandinavia submerged a vast continental plain that had existed under much of what is now the North Sea, connecting the British Isles to Continental Europe.

The redistribution of ice-water on the surface of Earth and the flow of mantle rocks causes changes in the gravitational field as well as changes to the distribution of the moment of inertia of Earth. These changes to the moment of inertia result in a change in the angular velocity, axis, and wobble of Earth's rotation.

The weight of the redistributed surface mass loaded the lithosphere, caused it to flex and also induced stress within Earth. The presence of the glaciers generally suppressed the movement of faults below. During deglaciation, the faults experience accelerated slip triggering earthquakes. Earthquakes triggered near the ice margin may in turn accelerate ice calving and may account for the Heinrich events. As more ice is removed near the ice margin, more intraplate earthquakes are induced and this positive feedback may explain the fast collapse of ice sheets.

In Europe, glacial erosion and isostatic sinking from the weight of ice made the Baltic Sea, which before the Ice Age was all land drained by the Eridanos River.

Future ice ages
A 2015 report by the Past Global Changes Project says simulations show that a new glaciation is unlikely to happen within the next approximately 50,000 years, before the next strong drop in Northern Hemisphere summer insolation occurs "if either atmospheric concentration remains above 300 ppm or cumulative carbon emissions exceed 1000 Pg C" (i.e. 1,000 gigatonnes carbon). "Only for an atmospheric content below the preindustrial level may a glaciation occur within the next 10 ka. ... Given the continued anthropogenic  emissions, glacial inception is very unlikely to occur in the next 50 ka, because the timescale for  and temperature reduction toward unperturbed values in the absence of active removal is very long [IPCC, 2013], and only weak precessional forcing occurs in the next two precessional cycles." (A precessional cycle is around 21,000 years, the time it takes for the perihelion to move all the way around the tropical year.)

Ice ages go through cycles of about 100,000 years, but the next one may well be avoided due to our carbon dioxide emissions.

title: Ice age


text:
Irving Langmuir

Irving Langmuir (January 31, 1881 – August 16, 1957) was an American chemist, physicist, and engineer. He was awarded the Nobel Prize in Chemistry in 1932 for his work in surface chemistry.

Langmuir's most famous publication is the 1919 article "The Arrangement of Electrons in Atoms and Molecules" in which, building on Gilbert N. Lewis's cubical atom theory and Walther Kossel's chemical bonding theory, he outlined his "concentric theory of atomic structure". Langmuir became embroiled in a priority dispute with Lewis over this work; Langmuir's presentation skills were largely responsible for the popularization of the theory, although the credit for the theory itself belongs mostly to Lewis. While at General Electric from 1909 to 1950, Langmuir advanced several fields of physics and chemistry, inventing the gas-filled incandescent lamp and the hydrogen welding technique. The Langmuir Laboratory for Atmospheric Research near Socorro, New Mexico, was named in his honor, as was the American Chemical Society journal for surface science called Langmuir.

Early years
Irving Langmuir was born in Brooklyn, New York, on January 31, 1881. He was the third of the four children of Charles Langmuir and Sadie, Comings. During his childhood, Langmuir's parents encouraged him to carefully observe nature and to keep a detailed record of his various observations. When Irving was eleven, it was discovered that he had poor eyesight. When this problem was corrected, details that had previously eluded him were revealed, and his interest in the complications of nature was heightened.

During his childhood, Langmuir was influenced by his older brother, Arthur Langmuir. Arthur was a research chemist who encouraged Irving to be curious about nature and how things work. Arthur helped Irving set up his first chemistry lab in the corner of his bedroom, and he was content to answer the myriad questions that Irving would pose. Langmuir's hobbies included mountaineering, skiing, piloting his own plane, and classical music. In addition to his professional interest in the politics of atomic energy, he was concerned about wilderness conservation.

Education
Langmuir attended several schools and institutes in America and Paris (1892–1895) before graduating high school from Chestnut Hill Academy (1898), an elite private school located in the affluent Chestnut Hill area in Philadelphia. He graduated with a Bachelor of Science degree in metallurgical engineering (Met.E.) from the Columbia University School of Mines in 1903. He earned his PhD in 1906 under Friedrich Dolezalek in Göttingen, for research done using the "Nernst glower", an electric lamp invented by Nernst. His doctoral thesis was entitled "On the Partial Recombination of Dissolved Gases During Cooling" (Ueber partielle Wiedervereinigung dissociierter Gase im Verlauf einer Abkühlung). He later did postgraduate work in chemistry. Langmuir then taught at Stevens Institute of Technology in Hoboken, New Jersey, until 1909, when he began working at the General Electric research laboratory (Schenectady, New York).

Research

His initial contributions to science came from his study of light bulbs (a continuation of his PhD work). His first major development was the improvement of the diffusion pump, which ultimately led to the invention of the high-vacuum rectifier and amplifier tubes. A year later, he and colleague Lewi Tonks discovered that the lifetime of a tungsten filament could be greatly lengthened by filling the bulb with an inert gas, such as argon, the critical factor (overlooked by other researchers) being the need for extreme cleanliness in all stages of the process. He also discovered that twisting the filament into a tight coil improved its efficiency. These were important developments in the history of the incandescent light bulb. His work in surface chemistry began at this point, when he discovered that molecular hydrogen introduced into a tungsten-filament bulb dissociated into atomic hydrogen and formed a layer one atom thick on the surface of the bulb.

His assistant in vacuum tube research was his cousin William Comings White.

As he continued to study filaments in vacuum and different gas environments, he began to study the emission of charged particles from hot filaments (thermionic emission). He was one of the first scientists to work with plasmas, and he was the first to call these ionized gases by that name because they reminded him of blood plasma. Langmuir and Tonks discovered electron density waves in plasmas that are now known as Langmuir waves.

He introduced the concept of electron temperature and in 1924 invented the diagnostic method for measuring both temperature and density with an electrostatic probe, now called a Langmuir probe and commonly used in plasma physics. The current of a biased probe tip is measured as a function of bias voltage to determine the local plasma temperature and density. He also discovered atomic hydrogen, which he put to use by inventing the atomic hydrogen welding process; the first plasma weld ever made. Plasma welding has since been developed into gas tungsten arc welding.

In 1917, he published a paper on the chemistry of oil films that later became the basis for the award of the 1932 Nobel Prize in chemistry. Langmuir theorized that oils consisting of an aliphatic chain with a hydrophilic end group (perhaps an alcohol or acid) were oriented as a film one molecule thick upon the surface of water, with the hydrophilic group down in the water and the hydrophobic chains clumped together on the surface. The thickness of the film could be easily determined from the known volume and area of the oil, which allowed investigation of the molecular configuration before spectroscopic techniques were available.

Later years
Following World War I Langmuir contributed to atomic theory and the understanding of atomic structure by defining the modern concept of valence shells and isotopes.

Langmuir was president of the Institute of Radio Engineers in 1923.

Based on his work at General Electric, John B. Taylor developed a detector ionizing beams of alkali metals, called nowadays the Langmuir-Taylor detector. In 1927, he was one of the participants of the fifth Solvay Conference on Physics that took place at the International Solvay Institute for Physics in Belgium.

He joined Katharine B. Blodgett to study thin films and surface adsorption. They introduced the concept of a monolayer (a layer of material one molecule thick) and the two-dimensional physics which describe such a surface. In 1932 he received the Nobel Prize in Chemistry "for his discoveries and investigations in surface chemistry."

In 1938, Langmuir's scientific interests began to turn to atmospheric science and meteorology. One of his first ventures, although tangentially related, was a refutation of the claim of entomologist Charles H. T. Townsend that the deer botfly flew at speeds of over 800 miles per hour. Langmuir estimated the fly's speed at 25 miles per hour.

After observing windrows of drifting seaweed in the Sargasso Sea he discovered a wind-driven surface circulation in the sea. It is now called the Langmuir circulation.

During World War II, Langmuir and Research Associate Vincent J Schaefer worked on improving naval sonar for submarine detection, and later to develop protective smoke screens and methods for deicing aircraft wings. This research led him to theorize and then demonstrate in the laboratory and in the atmosphere, that the introduction of ice nuclei dry ice and silver iodide into a sufficiently moist cloud of low temperature (supercooled water) could induce precipitation (cloud seeding); though in frequent practice, particularly in Australia and the People's Republic of China, the efficiency of this technique remains controversial today.

In 1953 Langmuir coined the term "pathological science", describing research conducted with accordance to the scientific method, but tainted by unconscious bias or subjective effects. This is in contrast to pseudoscience, which has no pretense of following the scientific method. In his original speech, he presented ESP and flying saucers as examples of pathological science; since then, the label has been applied to polywater and cold fusion.

His house in Schenectady, was designated a National Historic Landmark in 1976.

Personal life
Langmuir was married to Marion Mersereau (1883–1971) in 1912 with whom he adopted two children: Kenneth and Barbara. After a short illness, he died in Woods Hole, Massachusetts from a heart attack on August 16, 1957. His obituary ran on the front page of The New York Times.

On his religious views, Langmuir was an agnostic.

In fiction
According to author Kurt Vonnegut, Langmuir was the inspiration for his fictional scientist Dr. Felix Hoenikker in the novel Cat's Cradle, and the character's invention of ice-nine, a new phase of water ice (similar in name only to Ice IX). Langmuir had worked with Vonnegut's brother, Bernard Vonnegut at General Electric on seeding ice crystals to diminish or increase rain or storms.

Honors

 * Fellow of the American Academy of Arts and Sciences (1918)
 * Member of the United States National Academy of Sciences (1918)
 * Member of the American Philosophical Society (1922)
 * Perkin Medal (1928)
 * Nobel Prize in Chemistry (1932)
 * Franklin Medal (1934)
 * Faraday Medal (1944)
 * John J. Carty Award of the National Academy of Sciences (1950)
 * Mount Langmuir  (elevation 8022 ft / 2445m ) in Alaska is named after him (Chugach National Forest, Copper River, AK)
 * Langmuir College, a residential college at Stony Brook University in H-Quad, named for him in 1970
 * grandson, Roger R Summerhayes, directed/wrote/produced/edited a 57-minute documentary in 1999 called Langmuir's World

Patents

 * Langmuir,, "Incandescent Electric Lamp"
 * Langmuir,, "Electron-discharge apparatus and method of operating the same"
 * Langmuir,, "Method of and apparatus for controlling x-ray tubes"

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Irving Langmuir


text:
Talk:Ice age

Intro: Data provided about the anthropogenic delay in the next ice age is misleading
The last sentence in the intro states "The amount of anthropogenic greenhouse gases emitted into Earth's oceans and atmosphere is predicted to prevent the next glacial period for the next 500,000 years ," but is not supported by the three links provided. The third link does project a 500,000 year delay, but the second posits only a 50,000 year delay. The sentence should be changed to something like: "The amount of anthropogenic greenhouse gases emitted into Earth's oceans and atmosphere is predicted to prevent the next glacial period by 50,000 to 500,000 years ," 184.170.161.43 (talk) 14:13, 3 July 2022 (UTC)

and likely more after

 * The amount of anthropogenic greenhouse gases emitted into Earth's oceans and atmosphere is predicted to delay the next glacial period by between 100,000 and 500,000 years, which otherwise would begin in around 50,000 years, and likely more glacial cycles after.

That last phrase needs rewriting; it looks like an orphaned fragment. Does it mean later glaciations would also be delayed (as seems redundant, if more than one would otherwise be expected within that demi-megayear)? Or that the second future glaciation would be delayed by even longer? Or, on the contrary, that this delay makes a second and third future glaciation more likely? —Tamfang (talk) 19:29, 1 February 2023 (UTC)

I agree. The comment is unclear and I have deleted it. Dudley Miles (talk) 20:51, 1 February 2023 (UTC)

Photo is not correct - the sea during an ice age is about 120m down
Hello, considering this photo

"An artist's impression of ice age Earth at glacial maximum."

there has to be considered that the sea leve during an ice age is 120m lower than we have now.

So this vision should show much more soil and less sea according to the seabed map.

Have a nice day, Michael Palomino

history: http://www.hist-chron.com/index-ENGL.html

Signature: --- 2A02:1210:5295:F000:B5C6:49FA:3183:B9FE (talk) 12:56, 18 July 2023 (UTC)

 * We are in an ice age right now. What? Also, since last time we were out of ice age 2.5 million years ago the sea level was lower. Valery Zapolodov (talk) 16:17, 14 August 2023 (UTC)

Link 35 is broken
Link 35 to a 2004 Scientific American article is broken. 68.193.241.245 (talk) 12:40, 8 February 2024 (UTC)

Inaccuracies
The article says the last interglacial period lasted 28,000 years, and the current interglacial period started 11,700 years ago, but then claims the next ice would start 50,000 years from now if not for human activity. That's not credible. 24.76.102.121 (talk) 01:12, 17 February 2024 (UTC)
 * The estimate for the next ice age is credible but it is just one of many estimates and the text is unclear. I have deleted. Dudley Miles (talk) 10:21, 17 February 2024 (UTC)

title: Talk:Ice age


text:
International Association of Travel Agents Network

The International Airlines Travel Agent Network (IATAN) is a Miami-based trade association in the United States representing the interests of its member companies (airlines) and the U.S. travel distribution network (travel agencies). It is an independent department of the International Air Transport Association (IATA).

In addition, it (along with the IATA) is the body responsible for the standard international codes for airlines, airports, hotels, cities and car rental firms. These codes provide a method to link international travel network with international suppliers.


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Insider trading

Insider trading is the trading of a public company's stock or other securities (such as bonds or stock options) based on material, nonpublic information about the company. In various countries, some kinds of trading based on insider information are illegal. This is because it is seen as unfair to other investors who do not have access to the information, as the investor with insider information could potentially make larger profits than a typical investor could make. The rules governing insider trading are complex and vary significantly from country to country. The extent of enforcement also varies from one country to another. The definition of insider in one jurisdiction can be broad and may cover not only insiders themselves but also any persons related to them, such as brokers, associates, and even family members. A person who becomes aware of non-public information and trades on that basis may be guilty of a crime.

Trading by specific insiders, such as employees, is commonly permitted as long as it does not rely on material information not available to the general public. Many jurisdictions require that such trading be reported so that the transactions can be monitored. In the United States and several other jurisdictions, trading conducted by corporate officers, key employees, directors, or significant shareholders must be reported to the regulator or publicly disclosed, usually within a few business days of the trade. In these cases, insiders in the United States are required to file Form 4 with the U.S. Securities and Exchange Commission (SEC) when buying or selling shares of their own companies. The authors of one study claim that illegal insider trading raises the cost of capital for securities issuers, thus decreasing overall economic growth. Some economists, such as Henry Manne, argued that insider trading should be allowed and could, in fact, benefit markets.

There has long been "considerable academic debate" among business and legal scholars over whether or not insider trading should be illegal. Several arguments against outlawing insider trading have been identified: for example, although insider trading is illegal, most insider trading is never detected by law enforcement, and thus the illegality of insider trading might give the public the potentially misleading impression that "stock market trading is an unrigged game that anyone can play." Some legal analysis has questioned whether insider trading actually harms anyone in the legal sense, since some have questioned whether insider trading causes anyone to suffer an actual "loss" and whether anyone who suffers a loss is owed an actual legal duty by the insiders in question.

Illegal
Rules prohibiting or criminalizing insider trading on material non-public information exist in most jurisdictions around the world (Bhattacharya and Daouk, 2002), but the details and the efforts to enforce them vary considerably. In the United States, Sections 16(b) and 10(b) of the Securities Exchange Act of 1934 directly and indirectly address insider trading. The U.S. Congress enacted this law after the stock market crash of 1929. While the United States is generally viewed as making the most serious efforts to enforce its insider trading laws, the broader scope of the European model legislation provides a stricter framework against illegal insider trading. In the European Union and the United Kingdom, all trading on non-public information is, under the rubric of market abuse, subject at a minimum to civil penalties and possible criminal penalties as well. UK's Financial Conduct Authority has the responsibility to investigate and prosecute insider dealing, defined by the Criminal Justice Act 1993.

Definition of "insider"
In the United States, Canada, Australia, Germany and Romania for mandatory reporting purposes, corporate insiders are defined as a company's officers, directors and any beneficial owners of more than 10% of a class of the company's equity securities. Trades made by these types of insiders in the company's own stock, based on material non-public information, are considered fraudulent since the insiders are violating the fiduciary duty that they owe to the shareholders. The corporate insider, simply by accepting employment, has undertaken a legal obligation to the shareholders to put the shareholders' interests before their own, in matters related to the corporation. When insiders buy or sell based on company-owned information, they are said to be violating their obligation to the shareholders.

For example, illegal insider trading would occur if the chief executive officer of Company A learned (prior to a public announcement) that Company A would be taken over and then bought shares in Company A while knowing that the share price would likely rise. In the United States and many other jurisdictions, "insiders" are not just limited to corporate officials and major shareholders where illegal insider trading is concerned but can include any individual who trades shares based on material non-public information in violation of some duty of trust. This duty may be imputed; for example, in many jurisdictions, in cases where a corporate insider "tips" a friend about non-public information likely to have an effect on the company's share price, the duty the corporate insider owes the company is now imputed to the friend and the friend violates a duty to the company if he trades on the basis of this information.

Liability
Liability for inside trading violations generally cannot be avoided by passing on the information in an "I scratch your back; you scratch mine" or quid pro quo arrangement if the person receiving the information knew or should have known that the information was material non-public information. In the United States, at least one court has indicated that the insider who releases the non-public information must have done so for an improper purpose. In the case of a person who receives the insider information (called the "tippee"), the tippee must also have been aware that the insider released the information for an improper purpose.

One commentator has argued that if Company A's CEO did not trade on undisclosed takeover news, but instead passed the information on to his brother-in-law who traded on it, illegal insider trading would still have occurred (albeit by proxy, by passing it on to a "non-insider" so Company A's CEO would not get his hands dirty).

Misappropriation theory
A newer view of insider trading, the misappropriation theory, is now accepted in U.S. law. It states that anyone who misappropriates material non-public information and trades on that information in any stock may be guilty of insider trading. This can include elucidating material non-public information from an insider with the intention of trading on it or passing it on to someone who will. This theory constitutes the background for the securities regulation that enforces the insider trading. Disgorgement represents ill-gotten gains (or losses avoided) resulting from individuals violating the securities laws. In general in the countries where the insider trading is forbidden, the competent Authority seeks disgorgement to ensure that securities law violators do not profit from their illegal activity. When appropriate, the disgorged funds are returned to the injured investors. Disgorgements can be ordered in either administrative proceedings or civil actions, and the cases can be settled or litigated. Payment of disgorgement can be either completely or partially waived based on the defendant demonstrating an inability to pay. In settled administrative proceedings, Enforcement may recommend, if appropriate, that the disgorgement be waived. There are several approaches in order to quantify the disgorgement; an innovative procedure based on probability theory was defined by Marcello Minenna by directly analyzing the time periods of the involved transactions in the insider trading.

Proof of responsibility
Proving that someone has been responsible for a trade can be difficult because traders may try to hide behind nominees, offshore companies, and other proxies. The Securities and Exchange Commission (SEC) prosecutes over 50 cases each year, with many being settled administratively out of court. The SEC and several stock exchanges actively monitor trading, looking for suspicious activity. The SEC does not have criminal enforcement authority but can refer serious matters to the U.S. Attorney's Office for further investigation and prosecution.

Trading on information in general
In the United States and most non-European jurisdictions, not all trading on non-public information is illegal insider trading. For example, a person in a restaurant who hears the CEO of Company A at the next table tell the CFO that the company's profits will be higher than expected and then buys the stock is not guilty of insider trading—unless he or she had some closer connection to the company or company officers. However, even where the tippee is not himself an insider, where the tippee knows that the information is non-public and the information is paid for, or the tipper receives a benefit for giving it, then in the broader-scope jurisdictions the subsequent trading is illegal.

Notwithstanding, information about a tender offer (usually regarding a merger or acquisition) is held to a higher standard. If this type of information is obtained (directly or indirectly) and there is reason to believe it is nonpublic, there is a duty to disclose it or abstain from trading.

In the United States in addition to civil penalties, the trader may also be subject to criminal prosecution for fraud or where SEC regulations have been broken, the U.S. Department of Justice (DOJ) may be called to conduct an independent parallel investigation. If the DOJ finds criminal wrongdoing, the department may file criminal charges.

Legal
Legal trades by insiders are common, as employees of publicly traded corporations often have stock or stock options. These trades are made public in the United States through Securities and Exchange Commission filings that are also being made available by academic researchers as structured datasets.

U.S. SEC Rule 10b5-1 clarified that the prohibition against insider trading does not require proof that an insider actually used material nonpublic information when conducting a trade; possession of such information alone is sufficient to violate the provision, and the SEC would infer that an insider in possession of material nonpublic information used this information when conducting a trade. However, SEC Rule 10b5-1 also created for insiders an affirmative defense if the insider can demonstrate that the trades conducted on behalf of the insider were conducted as part of a pre-existing contract or written binding plan for trading in the future.

For example, if an insider expects to retire after a specific period of time and, as part of retirement planning, the insider has adopted a written binding plan to sell a specific amount of the company's stock every month for two years, and the insider later comes into possession of material nonpublic information about the company, trades based on the original plan might not constitute prohibited insider trading.

United States law
Until the 21st century and the European Union's market abuse laws, the United States was the leading country in prohibiting insider trading made on the basis of material non-public information. Thomas Newkirk and Melissa Robertson of the SEC summarize the development of US insider trading laws. Insider trading has a base offense level of 8, which puts it in Zone A under the U.S. Sentencing Guidelines. This means that first-time offenders are eligible to receive probation rather than incarceration.

Statutory
U.S. insider trading prohibitions are based on English and American common law prohibitions against fraud. In 1909, well before the Securities Exchange Act was passed, the United States Supreme Court ruled that a corporate director who bought that company's stock when he knew the stock's price was about to increase committed fraud by buying but not disclosing his inside information.

Section 15 of the Securities Act of 1933 contained prohibitions of fraud in the sale of securities, later greatly strengthened by the Securities Exchange Act of 1934.

Section 16(b) of the Securities Exchange Act of 1934 prohibits short-swing profits (from any purchases and sales within any six-month period) made by corporate directors, officers, or stockholders owning more than 10% of a firm's shares. Under Section 10(b) of the 1934 Act, SEC Rule 10b-5, prohibits fraud related to securities trading.

The Insider Trading Sanctions Act of 1984 and the Insider Trading and Securities Fraud Enforcement Act of 1988 place penalties for illegal insider trading as high as three times the amount of profit gained or loss avoided from illegal trading.

SEC regulations
SEC regulation FD ("Fair Disclosure") requires that if a company intentionally discloses material non-public information to one person, it must simultaneously disclose that information to the public at large. In the case of unintentional disclosure of material non-public information to one person, the company must make a public disclosure "promptly".

Insider trading, or similar practices, are also regulated by the SEC under its rules on takeovers and tender offers under the Williams Act.

Court decisions
Much of the development of insider trading law has resulted from court decisions.

In 1909, the Supreme Court of the United States ruled in Strong v. Repide that a director who expects to act in a way that affects the value of shares cannot use that knowledge to acquire shares from those who do not know of the expected action. Even though, in general, ordinary relations between directors and shareholders in a business corporation are not of such a fiduciary nature as to make it the duty of a director to disclose to a shareholder general knowledge regarding the value of the shares of the company before he purchases any from a shareholder, some cases involve special facts that impose such duty.

In 1968, the Second Circuit Court of Appeals advanced a "level playing field" theory of insider trading in SEC v. Texas Gulf Sulphur Co. The court stated that anyone in possession of inside information must either disclose the information or refrain from trading. Officers of the Texas Gulf Sulphur Company had used inside information about the discovery of the Kidd Mine to make profits by buying shares and call options on company stock.

In 1984, the Supreme Court of the United States ruled in the case of Dirks v. Securities and Exchange Commission that tippees (receivers of second-hand information) are liable if they had reason to believe that the tipper had breached a fiduciary duty in disclosing confidential information. One such example would be if the tipper received any personal benefit from the disclosure, thereby breaching his or her duty of loyalty to the company. In Dirks, the "tippee" received confidential information from an insider, a former employee of a company. The reason the insider disclosed the information to the tippee, and the reason the tippee disclosed the information to third parties, was to blow the whistle on massive fraud at the company. As a result of the tippee's efforts the fraud was uncovered, and the company went into bankruptcy. But, while the tippee had given the "inside" information to clients who made profits from the information, the U.S. Supreme Court ruled that the tippee could not be held liable under the federal securities laws—for the simple reason that the insider from whom he received the information was not releasing the information for an improper purpose (a personal benefit), but rather for the purpose of exposing the fraud. The Supreme Court ruled that the tippee could not have been aiding and abetting a securities law violation committed by the insider—for the simple reason that no securities law violation had been committed by the insider.

(In 2019, in the case of United States v. Blaszczak, the U.S. Court of Appeals for the Second Circuit ruled that the “personal-benefit” test announced in Dirks does not apply to Title 18 fraud statutes, such as 18 USC 1348. )

In Dirks, the Supreme Court also defined the concept of "constructive insiders", who are lawyers, investment bankers, and others who receive confidential information from a corporation while providing services to the corporation. Constructive insiders are also liable for insider trading violations if the corporation expects the information to remain confidential, since they acquire the fiduciary duties of the true insider.

The next expansion of insider trading liability came in SEC vs. Materia 745 F.2d 197 (2d Cir. 1984), the case that first introduced the misappropriation theory of liability for insider trading. Materia, a financial printing firm proofreader, and clearly not an insider by any definition, was found to have determined the identity of takeover targets based on proofreading tender offer documents in the course of his employment. After a two-week trial, the district court found him liable for insider trading, and the Second Circuit Court of Appeals affirmed holding that the theft of information from an employer, and the use of that information to purchase or sell securities in another entity, constituted a fraud in connection with the purchase or sale of a securities. The misappropriation theory of insider trading was born, and liability further expanded to encompass a larger group of outsiders.

In United States v. Carpenter (1986) the U.S. Supreme Court cited an earlier ruling while unanimously upholding mail and wire fraud convictions for a defendant who received his information from a journalist rather than from the company itself. The journalist R. Foster Winans was also convicted, on the grounds that he had misappropriated information belonging to his employer, The Wall Street Journal. In that widely publicized case, Winans traded in advance of "Heard on the Street" columns appearing in the Journal.

The Court stated in Carpenter: "It is well established, as a general proposition, that a person who acquires special knowledge or information by virtue of a confidential or fiduciary relationship with another is not free to exploit that knowledge or information for his own personal benefit but must account to his principal for any profits derived therefrom."

However, in upholding the securities fraud (insider trading) convictions, the justices were evenly split.

In 1997, the U.S. Supreme Court adopted the misappropriation theory of insider trading in United States v. O'Hagan, 521 U.S. 642, 655 (1997). O'Hagan was a partner in a law firm representing Grand Metropolitan, while it was considering a tender offer for Pillsbury Company. O'Hagan used this inside information by buying call options on Pillsbury stock, resulting in profits of over $4.3 million. O'Hagan claimed that neither he nor his firm owed a fiduciary duty to Pillsbury, so he did not commit fraud by purchasing Pillsbury options.

The Court rejected O'Hagan's arguments and upheld his conviction.

The "misappropriation theory" holds that a person commits fraud "in connection with" a securities transaction and thereby violates 10(b) and Rule 10b-5, when he misappropriates confidential information for securities trading purposes, in breach of a duty owed to the source of the information. Under this theory, a fiduciary's undisclosed, self-serving use of a principal's information to purchase or sell securities, in breach of a duty of loyalty and confidentiality, defrauds the principal of the exclusive use of the information. In lieu of premising liability on a fiduciary relationship between company insider and purchaser or seller of the company's stock, the misappropriation theory premises liability on a fiduciary-turned-trader's deception of those who entrusted him with access to confidential information.

The Court specifically recognized that a corporation's information is its property: "A company's confidential information ... qualifies as property to which the company has a right of exclusive use. The undisclosed misappropriation of such information in violation of a fiduciary duty ... constitutes fraud akin to embezzlement – the fraudulent appropriation to one's own use of the money or goods entrusted to one's care by another."

In 2000, the SEC enacted SEC Rule 10b5-1, which defined trading "on the basis of" inside information as any time a person trades while aware of material nonpublic information. It is no longer a defense for one to say that one would have made the trade anyway. The rule also created an affirmative defense for pre-planned trades.

In Morgan Stanley v. Skowron, 989 F. Supp. 2d 356 (S.D.N.Y. 2013), applying New York's faithless servant doctrine, the court held that a hedge fund's portfolio manager engaging in insider trading in violation of his company's code of conduct, which also required him to report his misconduct, must repay his employer the full $31 million his employer paid him as compensation during his period of faithlessness. The court called the insider trading the "ultimate abuse of a portfolio manager's position". The judge also wrote: "In addition to exposing Morgan Stanley to government investigations and direct financial losses, Skowron's behavior damaged the firm's reputation, a valuable corporate asset."

In 2014, in the case of United States v. Newman, the United States Court of Appeals for the Second Circuit cited the Supreme Court's decision in Dirks, and ruled that for a "tippee" (a person who used information they received from an insider) to be guilty of insider trading, the tippee must have been aware not only that the information was insider information, but must also have been aware that the insider released the information for an improper purpose (such as a personal benefit). The Court concluded that the insider's breach of a fiduciary duty not to release confidential information—in the absence of an improper purpose on the part of the insider—is not enough to impose criminal liability on either the insider or the tippee.

In 2016, in the case of Salman v. United States, the U.S. Supreme Court held that the benefit a tipper must receive as predicate for an insider-trader prosecution of a tippee need not be pecuniary, and that giving a 'gift' of a tip to a family member is presumptively an act for the personal though intangible benefit of the tipper.

By members of Congress
Members of the US Congress are not exempt from the laws that ban insider trading. Because they generally do not have a confidential relationship with the source of the information they receive, however, they do not meet the usual definition of an "insider". House of Representatives rules may however consider congressional insider trading unethical. A 2004 study found that stock sales and purchases by senators outperformed the market by 12.3% per year. Peter Schweizer points out several examples of insider trading by members of Congress, including action taken by Spencer Bachus following a private, behind-the-doors meeting on the evening of September 18, 2008 when Hank Paulson and Ben Bernanke informed members of Congress about the issues due to the financial crisis of 2007–2008, Bachus then shorted stocks the next morning and cashed in his profits within a week. Also attending the same meeting were Senator Dick Durbin and House Speaker John Boehner; the same day (trade effective the next day), Durbin sold mutual-fund shares worth $42,696, and reinvested it all with Warren Buffett. Also the same day (trade effective the next day), Boehner cashed out of an equity mutual fund.

In May 2007, a bill entitled the Stop Trading on Congressional Knowledge Act, or STOCK Act was introduced that would hold congressional and federal employees liable for stock trades they made using information they gained through their jobs and also regulate analysts or political intelligence firms that research government activities. The STOCK Act was enacted on April 4, 2012. As of 2021, in the approximately nine month period up to September 2021, Senate and House members disclosed 4,000 trades worth at least $315 million of stocks and bonds.

Arguments for legalizing
Some economists and legal scholars (such as Henry Manne, Milton Friedman, Thomas Sowell, Daniel Fischel, and Frank H. Easterbrook) have argued that laws against insider trading should be repealed. They claim that insider trading based on material nonpublic information benefits investors, in general, by more quickly introducing new information into the market.

Friedman, laureate of the Nobel Memorial Prize in Economics, said: "You want more insider trading, not less. You want to give the people most likely to have knowledge about deficiencies of the company an incentive to make the public aware of that." Friedman did not believe that the trader should be required to make his trade known to the public, because the buying or selling pressure itself is information for the market.

Other critics argue that insider trading is a victimless act: a willing buyer and a willing seller agree to trade property that the seller rightfully owns, with no prior contract (according to this view) having been made between the parties to refrain from trading if there is asymmetric information. The Atlantic has described the process as "arguably the closest thing that modern finance has to a victimless crime".

Legalization advocates also question why "trading" where one party has more information than the other is legal in other markets, such as real estate, but not in the stock market. For example, if a geologist knows there is a high likelihood of the discovery of petroleum under Farmer Smith's land, he may be entitled to make Smith an offer for the land, and buy it, without first telling Farmer Smith of the geological data.

Advocates of legalization make free speech arguments. Punishment for communicating about a development pertinent to the next day's stock price might seem an act of censorship. If the information being conveyed is proprietary information and the corporate insider has contracted not to expose it, he has no more right to communicate it than he would to tell others about the company's confidential new product designs, formulas, or bank account passwords.

Some authors have used these arguments to propose legalizing insider trading on negative information (but not on positive information). Since negative information is often withheld from the market, trading on such information has a higher value for the market than trading on positive information.

There are very limited laws against "insider trading" in the commodities markets if, for no other reason than that the concept of an "insider" is not immediately analogous to commodities themselves (corn, wheat, steel, etc.). However, analogous activities such as front running are illegal under US commodity and futures trading laws. For example, a commodity broker can be charged with fraud for receiving a large purchase order from a client (one likely to affect the price of that commodity) and then purchasing that commodity before executing the client's order to benefit from the anticipated price increase.

Commercialisation
The advent of the Internet has provided a forum for the commercialisation of trading on insider information. In 2016 a number of dark web sites were identified as marketplaces where such non-public information was bought and sold. At least one such site used bitcoins to avoid currency restrictions and to impede tracking. Such sites also provide a place for soliciting for corporate informants, where non-public information may be used for purposes other than stock trading.

Legal differences among jurisdictions
The US and the UK vary in the way the law is interpreted and applied with regard to insider trading. In the UK, the relevant laws are the Criminal Justice Act 1993, Part V, Schedule 1; the Financial Services and Markets Act 2000, which defines an offence of "market abuse"; and the European Union Regulation No 596/2014. The principle is that it is illegal to trade on the basis of market-sensitive information that is not generally known. This is a much broader scope than under U.S. law. The key differences from U.S. law are that no relationship to either the issuer of the security or the tipster is required; all that is required is that the guilty party traded (or caused trading) whilst having inside information, and there is no scienter requirement under UK law.

Japan enacted its first law against insider trading in 1988. Roderick Seeman said, "Even today many Japanese do not understand why this is illegal. Indeed, previously it was regarded as common sense to make a profit from your knowledge."

In Malta the law follows the European broader scope model. The relevant statute is the Prevention of Financial Markets Abuse Act of 2005, as amended. Earlier acts included the Financial Markets Abuse Act in 2002, and the Insider Dealing and Market Abuse Act of 1994.

The International Organization of Securities Commissions (IOSCO) paper on the "Objectives and Principles of Securities Regulation" (updated to 2003) states that the three objectives of good securities market regulation are investor protection, ensuring that markets are fair, efficient and transparent, and reducing systemic risk.

The discussion of these "Core Principles" state that "investor protection" in this context means "Investors should be protected from misleading, manipulative or fraudulent practices, including insider trading, front running or trading ahead of customers and the misuse of client assets." More than 85 percent of the world's securities and commodities market regulators are members of IOSCO and have signed on to these Core Principles.

The World Bank and International Monetary Fund now use the IOSCO Core Principles in reviewing the financial health of different country's regulatory systems as part of these organization's financial sector assessment program, so laws against insider trading based on non-public information are now expected by the international community. Enforcement of insider trading laws varies widely from country to country, but the vast majority of jurisdictions now outlaw the practice, at least in principle.

Larry Harris claims that differences in the effectiveness with which countries restrict insider trading help to explain the differences in executive compensation among those countries. The US, for example, has much higher CEO salaries than have Japan or Germany, where insider trading is less effectively restrained.

European Union
In 2014, the European Union (EU) adopted legislation (Criminal Sanctions for Market Abuse Directive) that harmonised criminal sanctions for insider dealing. All EU Member States agreed to introduce maximum prison sentences of at least four years for serious cases of market manipulation and insider dealing, and at least two years for improper disclosure of insider information.

Australia
The current Australian legislation arose out of the report of a 1989 parliamentary committee report which recommended removal of the requirement that the trader be 'connected' with the body corporate. This may have weakened the importance of the fiduciary duty rationale and possibly brought new potential offenders within its ambit. In Australia if a person possesses inside information and knows, or ought reasonably to know, that the information is not generally available and is materially price sensitive then the insider must not trade. Nor must she or he procure another to trade and must not tip another. Information will be considered generally available if it consists of readily observable matter or it has been made known to common investors and a reasonable period for it to be disseminated among such investors has elapsed.

Norway
In 2009, a journalist in Nettavisen (Thomas Gulbrandsen) was sentenced to four months in prison for insider trading.

The longest prison sentence in a Norwegian trial where the main charge was insider trading, was for eight years (two suspended) when Alain Angelil was convicted in a district court on December 9, 2011.

United Kingdom
Although insider trading in the UK has been illegal since 1980, it proved difficult to successfully prosecute individuals accused of insider trading. There were a number of notorious cases where individuals were able to escape prosecution. Instead the UK regulators relied on a series of fines to punish market abuses.

These fines were widely perceived as an ineffective deterrent, and there was a statement of intent by the UK regulator (the Financial Services Authority) to use its powers to enforce the legislation (specifically the Financial Services and Markets Act 2000). Between 2009 and 2012 the FSA secured 14 convictions in relation to insider dealing.

United States
Anil Kumar, a senior partner at management consulting firm McKinsey & Company, pleaded guilty in 2010 to insider trading in a "descent from the pinnacle of the business world".

Chip Skowron, a hedge fund co-portfolio manager of FrontPoint Partners LLC's health care funds, was convicted of insider trading in 2011, for which he served five years in prison. He had been tipped off by a consultant to a company that the company was about to make a negative announcement regarding its clinical trial for a drug. At first Skowron denied the charges against him, and his defense attorney said he would plead not guilty, saying "We look forward to responding to the allegations more fully in court at the appropriate time". However, after the consultant charged with tipping him off pleaded guilty, he changed his position, and admitted his guilt.

Rajat Gupta, who had been managing partner of McKinsey & Co. and a director at Goldman Sachs Group Inc. and Procter & Gamble Co., was convicted by a federal jury in 2012 and sentence to two years in prison for leaking inside information to hedge fund manager Raj Rajaratnam who was sentenced to 11 years in prison. The case was prosecuted by the office of United States Attorney for the Southern District of New York Preet Bharara.

Mathew Martoma, former hedge fund trader and portfolio manager at S.A.C. Capital Advisors, was accused of generating possibly the largest single insider trading transaction profit in history at a value of $276 million. He was convicted in February 2014, and is serving a nine-year prison sentence.

With the guilty plea by Perkins Hixon in 2014 for insider trading from 2010 to 2013 while at Evercore Partners, Bharara said in a press release that 250 defendants whom his office had charged since August 2009 had now been convicted.

On December 10, 2014, a federal appeals court overturned the insider trading convictions of two former hedge fund traders, Todd Newman and Anthony Chiasson, based on the "erroneous" instructions given to jurors by the trial judge. The decision was expected to affect the appeal of the separate insider-trading conviction of former SAC Capital portfolio manager Michael Steinberg and the U.S. Attorney and the SEC in 2015 did drop their cases against Steinberg and others.

In 2016, Sean Stewart, a former managing director at Perella Weinberg Partners LP and vice president at JPMorgan Chase, was convicted on allegations he tipped his father on pending health-care deals. The father, Robert Stewart, previously had pleaded guilty but did not testify during his son's trial. It was argued that by way of compensation for the tip, the father had paid more than $10,000 for Sean's wedding photographer.

In 2017, Billy Walters, Las Vegas sports bettor, was convicted of making $40 million on private information of Dallas-based dairy processing company Dean Foods, and sentenced to five years in prison. Walters's source, company director Thomas C. Davis employing a prepaid cell phone and sometimes the code words "Dallas Cowboys" for Dean Foods, helped him from 2008 to 2014 realize profits and avoid losses in the stock, the federal jury found. Golfer Phil Mickelson "was also mentioned during the trial as someone who had traded in Dean Foods shares and once owed nearly $2 million in gambling debts to" Walters. Mickelson "made roughly $1 million trading Dean Foods shares; he agreed to forfeit those profits in a related civil case brought by the Securities and Exchange Commission". Walters appealed the verdict, but in December 2018 his conviction was upheld by the 2nd U.S. Circuit Court of Appeals in Manhattan.

In 2018, David Blaszczak, the "king of political intelligence," Theodore Huber and Robert Olan, two partners at hedge fund Deerfield Management, and Christopher Worrall, an employee at the Centers for Medicare and Medicaid Services (CMS), were convicted for insider trading by the U.S. Attorney's Office in the Southern District of New York. Worrall leaked confidential government information that he stole from CMS to Blaszczak, and Blaszczak passed that information to Huber and Olan, who made $7 million trading securities. The convictions were upheld in 2019 by the Second Circuit, U.S. Court of Appeals in Manhattan; that opinion was vacated by the Supreme Court in 2021, and the Second Circuit is now reconsidering its decision.

In 2023, Terren Peizer was charged with insider trading by the SEC, which alleged that he sold $20 million of Ontrak Inc. stock while he was in possession of material nonpublic negative information. Peizer was the CEO and chairman of Ontrak. In addition, the U.S. Department of Justice announced criminal charges of securities fraud against Peizer, charging that thereby he had avoided $12 million in losses; he was arrested. The case was tried in the U.S. District Court for the Central District of California before U.S. District Judge Dale S. Fischer. He was convicted of all three charges in June 2024, and faces up to 65 years in prison.

Canada
In 2008, police uncovered an insider trading conspiracy involving Bay Street and Wall Street lawyer Gil Cornblum who had worked at Sullivan & Cromwell and was working at Dorsey & Whitney, and a former lawyer, Stan Grmovsek, who were found to have gained over $10 million in illegal profits over a 14-year span. Cornblum committed suicide by jumping from a bridge as he was under investigation and shortly before he was to be arrested but before criminal charges were laid against him, one day before his alleged co-conspirator Grmovsek pled guilty. Grmovsek pleaded guilty to insider trading and was sentenced to 39 months in prison. This was the longest term ever imposed for insider trading in Canada. These crimes were explored in Mark Coakley's 2011 non-fiction book, Tip and Trade.

Kuwait
The U.S. SEC alleged that in 2009 Kuwaiti trader Hazem Al-Braikan engaged in insider trading after misleading the public about possible takeover bids for two companies. Three days after Al-Braikan was sued by the SEC, he was found dead of a gunshot wound to the head in his home in Kuwait City on July 26, 2009, in what Kuwaiti police called a suicide. The SEC later reached a $6.5 million settlement of civil insider trading charges, with his estate and others.

China
The majority of shares in China before 2005 were non-tradeable shares that were not sold on the stock exchange publicly but privately. To make shares more accessible, the China Securities Regulation Commission (CSRC) required the companies to convert the non-tradeable shares into tradeable shares. There was a deadline for companies to convert their shares and the deadline was short, due to this there was a massive amount of exchanges and in the midst of these exchanges many people committed insider trading knowing that the selling of these shares would affect prices. Chinese people did not fear insider trading as much as one may in the United States because there is no possibility of imprisonment. Punishment may include monetary fees or temporary relieving from a position in the company. The Chinese do not view insider trading as a crime worth prison time because generally the person has a clean record and a path of success with references to deter them from being viewed as a criminal. On October 1, 2015, Chinese fund manager Xu Xiang was arrested due to insider trading.

India
Insider trading in India is an offense according to Sections 12A, 15G of the Securities and Exchange Board of India Act, 1992. Insider trading is when one with access to non-public, price-sensitive information about the securities of the company subscribes, buys, sells, or deals, or agrees to do so or counsels another to do so as principal or agent. Price-sensitive information is information that materially affects the value of the securities. The penalty for insider trading is imprisonment, which may extend to five years, and a minimum of five lakh rupees (500,000) to 25 crore rupees (250 million) or three times the profit made, whichever is higher.

The Wall Street Journal, in a 2014 article entitled "Why It's Hard to Catch India's Insider Trading", said that despite a widespread belief that insider trading takes place on a regular basis in India, there were few examples of insider traders being prosecuted in India. One former top regulator said that in India insider trading is deeply rooted and especially rampant because regulators do not have the tools to address it. In the few cases where prosecution has taken place, cases have sometimes taken more than a decade to reach trial, and punishments have been light; and despite SEBI by law having the ability to demand penalties of up to $4 million, the few fines that were levied for insider trading have usually been under $200,000.

Philippines
Under Republic Act 8799 or the Securities Regulation Code, insider trading in the Philippines is illegal.

Brazil
The practice of insider trading is an illegal act under Brazilian law, since it constitutes unfair behavior that threatens the security and equality of legal conditions in the market. Since 2001, the practice is also considered a crime. Law 6,385/1976, as amended by Law 10,303/2001, provided for Article 27-D, which typifies the conduct of "Using relevant information not yet disclosed to the market, of which he is aware and from which he must maintain secrecy, capable of providing, for himself or for others, undue advantage, through trading, on his own behalf or on behalf of a third party, with securities: Penalty - imprisonment, from 1 (one) to 5 (five) years, and a fine of up to 3 (three) times the amount of the illicit advantage obtained as a result of the crime."

The first conviction handed down in Brazil for the practice of the offense of "misuse of privileged information" occurred in 2011, by federal judge Marcelo Costenaro Cavali, of the Sixth Criminal Court of São Paulo. It is the case of the Sadia-Perdigão merger. The former Director of Finance and Investor Relations, Luiz Gonzaga Murat Júnior, was sentenced to one year and nine months in prison in an open regime, replaceable by community service, and the inability to exercise the position of administrator or fiscal councilor of a publicly traded company for the time he serves his sentence, in addition to a fine of R$349,711.53. The then member of the board of directors Romano Ancelmo Fontana Filho was sentenced to prison for one year and five months in an open regime, also replaceable by community service, in addition to not being able to exercise the position of administrator or fiscal councilor of a publicly-held company. He was also fined R$374,940.52.

title: Insider trading