Generally
Eclectic
Chronological History of Earth and Its Climate
| Time | Event |
|---|---|
| 5 billion years ago | Planet earth formed. The sun's luminosity was 70 to 75 percent of current levels, and has been increasing every since. The "faint sun" paradox is based on the weaker sun giving rise to a generally warmer climate in earth's early years, compared with the present. Earth's surface was likely liquid, and the atmosphere a mixture of toxins until about 3.8 billion years ago. Then, continents began to form. |
| 3.5 billion years | Primitive forms of life emerged. The first recognizable bacteria appear in 3.5 billion year old rocks. |
| 3.5-2.8 billion years ago | The first plants to use photosynthesis appeared. The plants began to draw carbon dioxide from the atmosphere and released oxygen. Carbon dioxide in the atmosphere was 100,000 parts per million (compared to current levels of 385 parts per million), and oxygen levels were negligible (compared with current levels of 210,000 parts per million.) Anaerobic organisms dominated. |
| 2.8 billion years ago | Global glaciation (Snowball Earth) may have occurred. |
| 2.5 billion years ago | Through the development of chlorophyll and photosynthetic organisms, the atmosphere had evolved from one with abundant carbon dioxide and limited oxygen to one rich in oxygen with limited carbon dioxide. The greenhouse character of the atmosphere was reduced. |
| 2.4 to 2.2 billion years ago | Global glaciation (Snowball Earth) may have occurred. |
| 1 billion years ago | Multicellular plants (red and green algae) appeared. |
| 800 to 550 million years ago | Snowball or slush ball earth may have occurred, with at least two and perhaps five major glaciation episodes. The frigid climate appears to have approached the equator. With significant reflection of the sun's energy into space from the snow and ice, what stopped partial glaciation from becoming everlasting? The leading hypothesis is that the glaciation and cold temperatures stopped a number of removal processes of carbon dioxide from the atmosphere, allowing carbon dioxide levels to build up from volcanic activity and to warm the atmosphere. The ice ages may have changed the chemistry of the oceans, from one which had oxygen rich waters within a few metres of the surface because of the oxygen in the atmosphere and anoxic deeper waters rich in hydrogen sulphide, to one in which oxygen penetrated the depths of the oceans. The new ocean chemistry may have set the stage for the evolution of animals. |
| 575 million years ago | Multicellular animals first appeared in the fossil record. Animals evolved rapidly in the early Cambrian period from 542 million years ago to 520 million years ago. Darwin was puzzled by the rapid rise of animals during this period. His theories about the the origins of species maintained that evolution was a gradual process. The rapid evolution of animals in this period is known as "Darwin's Dilemma". Recent evidence suggests that animals may have emerged 800 billion years ago. |
| 490 million years ago | A mass extinction event marked the end of the Cambrian period and beginning of the Ordovician period. Theories about the cause of the extinction event include glaciation and depletion of oxygen in marine waters. |
| 430 million years ago | A mass extinction event marked the end of the Ordovician period and the beginning of the Silurian period. At the time, most complex multicellular organisms lived in the sea. From 80 to 85 percent of known marine species disappeared, as did 25 percent of families. The most commonly accepted theory is that the extinction was triggered by the onset of a long ice age, after a long, stable period of greenhouse conditions. The event was preceded by a fall in atmospheric carbon dioxide. In addition, through plate tectonics, a super continent(Gondwana) drifted over the South Pole. Ice caps formed and receded in up to five pulses. Ice cap formation locked up water from the ocean, and the melting ice caps released water to the ocean. This caused sea levels to rise and fall. Vast shallow intra-continental seas withdrew. This eliminated many ecological niches. Then the niches returned but with diminished populations. Then they disappeared again with the next pulse of glaciation, eliminating biological diversity at each change. In addition, temperature changes from greenhouse to ice house conditions eliminated species that could not adapt. |
| 400 million years ago | There was a substantial increase in plant life during the Devonian period. Land plants underwent a hugely significant phase of evolution. Their maximum height reached 30 metres at the end of the period, because of the evolution of advanced vascular systems. These systems permitted the growth of complex branching and rooting systems. The development of seeds permitted reproduction and dispersal in areas which were not waterlogged, allowing plants to colonize previously inhospitable inland and upland areas. These two factors combined to greatly magnify the role of plants on the global scale. This led to the first forests. These tall trees required deep rooting systems to acquire water and nutrients, and provide anchorage. The rooting systems broke up the upper layers of bedrock, creating a deep layer of soil, which would have been on the order of metres thick. Early Devonian plants could penetrate no more than a couple of centimetres. |
| 360 million years ago | The Devonian mass extinction event occurred. Eighty to eighty-five percent of known marine species disappeared, along with 19 percent of families. The leading theories suggest that changes in sea level and ocean anoxia, possibly triggered by global cooling or oceanic volcanism, were responsible. The breakdown of rock into soil facilitated the chemical weathering, which allowed nutrients to flow into rivers and oceans, causing eutrophication and subsequent anoxia in the oceans. |
| 340 to 260 million years ago | This was a period of major glaciation. The maximum was from 300 to 280 million years ago. Coal deposits in Western Europe and North America formed, perhaps by organic debris accumulating in swamps whose water levels rose and fell with the advance and retreat of ice ages. Deposits probably formed in fresh and brackish low-lying coastal waters. |
| 253-247 million years ago | The Permian mass extinction event occurred. This was the Earth's most severe extinction event, with up to 96 percent of all marine species and 70 percent of terrestrial vertebrate species becoming extinct. It is the only known mass extinction of insects. Fifty-seven percent of all families and eighty-three percent of all genera were killed off. The likely cause of the mass extinction event was the cascading effect of several catastrophes. About 251 million years ago, there were massive flood basalt eruptions in Siberia. They covered 200,000 square kilometers with lava. The eruptions threw ash, dust and acid aerosols into the atmosphere, blocking sunlight and disrupting photosynthesis both on land and in the upper layers of the seas, and causing food chains to collapse. Acid rain may have killed land plants and mollusks and planktonic organisms which build calcium carbonate shells. The eruptions would also have emitted carbon dioxide, causing global warming. The basalt lava erupted or intruded into carbonate rocks and into sediments which were in the process of forming large coal beds, both of which would have emitted large additional amounts of carbon dioxide, leading to stronger global warming after the dust and aerosols settled. There is evidence indicating that there was a massive release of methane from methane clathrates. These are methane molecules trapped in cages of water molecules at the right combination of pressure and temperature in permafrost and continental margins. As global temperatures increased by about 6 degrees Celsius near the equator at this time, the conditions were right for a massive release of methane clathrates. There is evidence that the oceans became anoxic (severely deficient in oxygen) towards the end of the Permian, devastating marine life. Possibly, the reduced difference in water temperatures between the poles and the equator slowed or stopped ocean circulation systems, reducing the mixing of oxygen in the ocean and leading to anoxia. A severe anoxic event could have allowed bacteria which produce hydrogen sulphide to become the dominant force in oceanic ecosystems, causing massive emissions of hydrogen sulfide which poisoned plant and animal life on both land and sea, as well as severely weakening the ozone layer, exposing much of the life that remained to fatal levels of ultra-violet radiation. Plate tectonics produced the super continent Pangaea, surrounded by the super ocean Panthalassa. This structure decreased shallow aquatic environments, the most productive part of the seas. It would also have affected both oceanic circulation and atmospheric weather patterns, creating seasonal monsoons near the coasts and an arid climate in the vast continental interior. |
| 251-65 million years ago | After the Permian mass extinction event, life returned slowly, and included the emergence of reptiles. |
| 205-199 million years ago | There was another mass extinction event. About half of the species known to have been living on Earth at that time went extinct. Several explanations for this event have been suggested, but all have unanswered challenges. The gradual climate change or sea-level fluctuations during the late Triassic period do not explain the suddenness of the extinctions in the marine realm. The massive volcanic eruptions, specifically the flood basalts of the Central Atlantic Magmatic Province (middle of the Atlantic near Brazil),occurred between 202 and 199 million years ago and would have released carbon dioxide (which would have caused warming) or sulfur dioxide (which would have caused cooling). There is some evidence that atmospheric carbon dioxide increased. Warming from rises in carbon dioxide may have led to releases of methane clathrates. |
| 199 to 65 million years ago | There were several minor extinction events. The climate was generally warm, and the dinosaurs were the dominant species on land. |
| 100 million years ago |
Atmospheric concentrations of carbon dioxide have been estimated at 2,000 parts per million. Surface waters around Antarctica were about 15 degrees Celsius. At this time, the vegetation on the peninsula was lush, and there were conifers. The mean annual temperatures has been estimated at 17 to 19 degrees Celsius. |
| 65 million years ago | There was a mass extinction event. The extinction was rapid, and life returned relatively quickly after the extinction event. There are several theories as to cause. The leading theory is an impact of one or more comets or asteroids. This theory is supported by iridium deposits all over the world in sediments formed 65 million years ago. Iridium is rare in the earth's crust, but common in asteroids and comets. The Chicxulub Crater under Chicxulub on the coast of Yucatan, Mexico was formed about this time, and is considered the leading candidate. However, there were other craters formed around this time: the 24-km (15 mi) Boltysh crater in Ukraine, the 20-km (12 mi) Silverpit crater, a suspected impact crater in the North Sea, and the controversial and much bigger 600-km (370 mi) Shiva crater. The asteroid that formed the Chicxulub Crater landed in the ocean and would have caused tsunamis,for which evidence has been found in several locations in the Caribbean and eastern United States; marine sand has been found in locations which were then inland, and vegetation debris and terrestrial rocks in marine sediments have been dated to the time of the impact. The asteroid landed in a bed of gypsum (calcium sulfate), which would have produced a vast sulphur dioxide aerosol. This would have further reduced the sunlight reaching the Earth's surface and then precipitated as acid rain, killing vegetation, plankton and organisms which build shells from calcium carbonate. The blocked sunlight would have inhibited photosynthesis, causing the die off of plants and animals that depend on it.. A pulse of infrared radiation from the reentry of material into the atmosphere after impact would have killed exposed organisms. Global fire storms may have resulted from the heat pulse and the fall of incendiary fragments from the blast back to Earth. Widespread fires would have increased the carbon dioxide content of the atmosphere and caused a temporary greenhouse effect. In addition to impacts, there is clear evidence that sea levels fell prior to the impact. The most likely explanation is that the mid-ocean ridges became less active and therefore sank under their own weight. |
| 65 million years ago to present | The period is known as the Cenozoic era (Age of Mammals). Mammals are almost exclusively warm-blooded, which means they are able to regulate body temperatures by eating food and converting food to heat in order to warm themselves, and by perspiring to cool themselves. They can adapt to warm and cold and can be found in warm and cool climates. |
| 55 million years ago | The Paleocene-Eocene Thermal Maximum occurred. The cause is believed to be a rapid increase in methane in the atmosphere, perhaps through a massive volcanic eruption interacting with methane-containing flood deposits. Average global temperatures increased 4 to 8 degrees Celsius over a few thousand years. Sea surface temperatures in the Arctic may have reached 23 degrees Celsius. There were widespread extinctions in marine and terrestrial eco-systems. The world has been progressively cooling since then. |
| 50 million years ago |
India collided with Asia, creating the Himalayas. The high elevations in the Tibetan plateau may have disrupted wind currents.
Chemical weathering of mountains may have removed carbon dioxide from atmosphere. One hypothesis suggests that this event
contributed to a cooling period that began about this time. The surface waters of the Arctic Ocean were fresh, based on evidence of a fresh water fern for a period of about 800,000 years. |
| 40 million years ago | Carbon dioxide levels in the atmosphere were 700 parts per million - considerably higher than current levels of 385 parts per million. |
| 35 million years ago | The Antarctic ice sheet started to form. Global temperatures dropped sharply. The likely cause was the end of a land link between Antarctica and South America. This led to changes in wind patterns and ocean currents. Specifically, a circular current in the Southern Ocean around Antarctica insulated Antarctica from the warmer waters and atmosphere to the north. |
| 24 million years ago | Carbon dioxide levels in the atmosphere were 500 parts per million, compared with 385 parts per million today. |
| 7 million years ago | Glaciers started in the Andes, Alaska, and Greenland. |
| 3.2 million years ago | Tectonic events probably triggered a gradual cooling. North and South America joined together at Panama, closing the connection between the Atlantic and Pacific Oceans. Atlantic currents moved toward the present day Gulf Stream. In addition, the uplift of the Andes, and the western parts of North America occurred. While there has been some continental movement since then, the major elements of the earth's geography (the basic configuration of the continents, the location of mountain ranges, no land link between Antarctica and South America, the closure of the passage between North and South America, effectively separating the Atlantic and Pacific Oceans in this area ) were established at this time. |
| 2.7 million years ago | Northern hemisphere glaciation in Europe and North America glaciation started, and continues to the present, interrupted by relatively short interglacial warm periods such as the one we are currently experiencing. The primary explanatory factors behind the ice age cycles are changes in the earth's tilt, wobble and elliptical orbit,reinforced by feedback systems. When the earth's tilt, wobble and elliptical orbit combine to produce relatively little temperature difference between summer and winter in the northern hemisphere (where most land masses are), snow builds up in winter and stays around longer in the spring and summer. The white colour of the ice and snow reflects more solar energy into space. This lowers temperatures, and reinforces the processes that allow the snow and ice to last longer. Cooler temperatures also reduce water vapour - a greenhouse gas - in the atmosphere. The process continues until the earth's tilt, wobble and elliptical orbit align to create warmer summers and colder winters. The warmer summers reduce the extent and duration of ice coverage, leading to less radiation of solar energy into space and warmer temperatures. The colder winters mean lower snowfalls on the ice caps in winter. |
| 2 million years ago | The species "homo" appeared. The Pliocene period ended. Global temperatures peaked at between 3 and 5 degrees Celsius warmer than today. Under global warming scenarios examined by the Intergovernmental Panel on Climate Change, the earth might experience similar temperatures by 2100. |
| 650,000 years ago | This is the start of the period covered by the Antarctic Ice Core Record of the European Project for Ice Core Drilling. The drilling occurred about 500 kilometres from Vostok. Since this time, carbon dioxide levels have been in the range 180 to 300 parts per million. |
| 440,000 years ago | This is the start of the period covered by the Antarctica Vostok Ice Core, drilled in 1995. |
| 195,000 years ago | The first anatomically modern humans evolved in Africa near the end of the second last interglacial warm period (the Hoxnian Interglacial). |
| 130,000 years ago | The last interglacial warm period (the Eemian Interglacial) before the present one began. During the period, sea levels rose to levels 6 metres higher than today. The coral reefs that make up Mexico's Yucatan Peninsula formed at this time. The earth was about as warm as today. Carbon dioxide levels were at pre industrial levels. Hippos roamed England and parts of Europe. |
| 125,000 years ago | Early modern humans expanded their range in Africa. Later, they began to expand beyond Africa. Fossil remains in the Middle East have been dated between 119,000 and 85,000 years ago, in China between 111,000 and 67,000 years ago, in Australia between 50,000 and 42,000 years ago , in Europe about 35,000 years ago, and in the Americas about 13,400 years ago. |
| 116,000 years ago | This was the start of last ice age. Carbon dioxide levels began to drop. During the ice ages, there were distinct periods of rapid warming and cooling. Greenland temperatures would rise 5 to 6 degrees Celsius within a few decades, and be followed by a period of abrupt cooling. The leading hypothesis is that the variations in the ocean currents. When strong, they would bring warm air to the north Atlantic from the tropics (thus cooling the tropics). Warm air would lead to increased precipitation on the ice sheets that surrounded the north Atlantic. Increased precipitation would cause a build up of ice in the sheets. This would then cause the glaciers to move toward the ocean, dumping fresh water into the North Atlantic several hundred years later. The fresh water would act as a brake on the tropical currents, stopping the flow of warm air to the north Atlantic. In the colder north Atlantic, the flow of fresh water from the ice sheets would fall, allowing the Gulf Stream to shift back to its strong mode. |
| 100,000 years ago | This was the start of the period covered under the Greenland ice core drilled in the 1990s. |
| 25,000 years ago | Mid latitude glaciers started to grow in Bolivia, then started to move north in south America to Peru and Ecuador. |
| 24,000 years ago | The Neanderthals had become extinct. |
| 21,000 years ago | This was the glacial maximum in the most recent ice age in the northern hemisphere. Sea levels were around 130 metres lower than today. Temperatures in unglaciated areas were 5 degrees Celsius below current levels. The Laurentide Ice Sheet extended as far as New York City, Cincinnati and des Moine. The Cordilleran Ice Sheet covered Western Canada and reached into Washington, Montana, and Idaho. The Scandinavian Ice Sheet covered the British Isles, north-eastern Europe, and north-central Siberia. After the glacial maximum, the ice caps began to retreat. |
| 15,000 years ago | At the height of the last ice age, sea levels were sufficiently low that North America and Asia were connected by a land bridge. Alaska's lowlands were free of ice, because there was insufficient precipitation to create an ice cap. In the environment, humans were able to cross from Asia to North America. |
| 14,500 years ago | Sudden warming caused sea levels to rise about 20 metres within 400 years, or one metre every twenty years. |
| 12,800 years ago | The Younger Dryas era, triggered by the emptying of a North America glacier in North America, was a cold period. The cooling may have been limited to the northern hemisphere, because ice cores in the southern hemisphere all showed warming. The period lasted for 1,300 years, then ended abruptly, with a warming of 6 degrees Celsius in a decade. The abrupt cooling and subsequent warming probably resulted from the shut down of the Atlantic currents. The Atlantic currents operate through a process in which warm surface waters flow northward. They cool through contact with the atmosphere. Cooler surface waters sink because they are denser and heavier than the deeper waters, and then flow southward underneath the surface flow to complete the circulation of water. In the Younger Dryas event, when the large amounts of fresh water from rivers and glaciers met the waters flowing northward, they were more buoyant than the salty ocean waters, and prevented the surface water from sinking. This shut down the flow of warm tropical waters into the North Atlantic, causing abrupt cooling. |
| 12,000 years ago | The ice cap started to grow on Mount Kilimanjaro. |
| 9000 years ago | Carbon dioxide levels rose to around 180 parts per million at the glacial maximum to 260 parts per million, and grew only slightly until the start of the industrial revolution (280 parts per million). |
| 8,200 years ago | Ice-age conditions returned to Europe for 350 years, probably triggered by another release of fresh water into the North Atlantic. About 8,500 years ago, Lake Agassiz in central North America experienced its last major draining. The draining was sudden and water flowed into Hudson Bay. The sudden release of fresh water into the North Atlantic may have stopped the thermohaline circulation (Gulf Stream). |
| 8,000 years ago | The ice cap started to grow in the Himalayas. |
| 8,000 years ago | The Storegga land slip in North Sea triggered a massive tsunami. The land slip occurred when a 400 kilometre cliff slumped 2.4 kilometres vertically down a slope to the ocean floor. Evidence suggests that the land slip was caused by the release of methane clathrates - methane molecules trapped in water in particular conditions of pressure and temperature. Ocean temperatures had risen by about 6 degrees Celsius as the Gulf Stream became stronger off Norway following the end of the ice age. The warming caused the release of massive amounts of methane from the sea bed, triggering the tsunami. An analysis of the Greenland ice cores showed a large increase in methane around this time. |
| 6,000 years ago | Humans numbered 12 million people. About that time, changes in atmospheric methane and carbon dioxide levels beyond those that might have been expected due to natural events. This has led to hypotheses that early humans may have influenced climate by clearing, initiating agricultural, etc. |
| 5,500 years ago | The Sahara Desert turned arid, after the African Humid Period which began 13,000 years ago. |
| 4,200 years ago | Aridification concentrated in the Middle East caused collapse of civilization there. Dust from the area was found in Kilimanjaro, Himalayan and Andean ice cores. |
| 750 to 950 A.D. | Multi-year droughts detected in nearby Caribbean sediments probably caused the collapse of Mayan civilization. |
| 800 to 1300 A.D. | This was the medieval warm period in the northern hemisphere. There were droughts in North America and vineyards in England. The Vikings reached Newfoundland and created settlements around 1,000 A.D. Field crops went up hillsides to elevations not farmed before. Warmth-loving crops moved northward. |
| 1601 A.D. | Europe experienced its coldest winter in hundreds of years, caused presumably by a volcanic eruption in Peruvian Andes. |
| 1600 to 1800 A.D. | This was known as the Little Ice Age, although this is a misnomer. Sunspot activity was low and may have caused a slightly cooler interval compared with before and after. There was slight expansion of Alpine glaciers. Average temperatures changed of 1 to 2 degrees Celsius. The Inuit migrated southward. Glaciers encroached on agricultural land. As the climate cooled, cod populations moved south, and European fishermen followed them to North America. Paintings depicting snow and ice appeared in Europe. An analysis of paintings found skies were cloudier during the Little Ice Age than in other periods. |
| 1800 A.D. | Carbon dioxide levels in the atmosphere were 280 parts per million. |
| 1815 A.D. | The eruption of Mount Tambora on the island Sumbawa in Indonesia put aerosols into the atmosphere and led to 1816 as the ""year without summer"". Snow fell in New England in June and crops in Europe failed. |
| 1979 A.D. | Lake Superior waters were 2.5 degrees Celsius colder than today. The warming since then has been far greater than could be attributed to average air temperatures, and is probably due to less ice cover. |
| 1979 A.D. | The melting of the Greenland ice cap began, as annual summer losses exceeded annual winter gains. |
| 1980s A.D. | The ozone hole over the Antarctic was discovered. |
| 1991 A.D. | Eruption of Mount Pinatubo caused the earth to cool briefly by about 0.5 degrees Celsius. Scientists used the explosion to demonstrate the effects of aerosols. |
| 1995 A.D. | The Larsen A ice shelf in the Antarctic collapsed. |
| 1998 A.D. | This was the year of the strongest el Ni�o on record. |
| 1999 A.D. | This marked the end of the warmest decade in the last 1,000 years. |
| 2000 A.D. | Carbon dioxide concentrations in the atmosphere reached 369 parts per million, perhaps the highest level in the last 650,000 years (based on ice core measurements). |
| 2002 A.D. | The Larsen B ice shelf in the Antarctic collapsed. |
| 2003 A.D. | Europe suffered a massive heat wave, killing 35,000 people. |
| 2004 A.D. | There was the first known hurricane in the South Atlantic. |
| 2005 A.D. | There was a strong el Ni�o. Rains failed in the Amazon, causing drought. There was massive melting of the Siberian permafrost. |
|
2007 A.D. |
Several million tonnes of extra methane entered the atmosphere from unknown sources. The likely source was the Siberia permafrost. Warm temperatures in Siberia may have triggered the release. At times, East Siberia was 7 degrees Celsius warmer than normal during 2007. |
| 2007 A.D. | The area covered by ice in the Arctic Ocean in summer was 23 percent less than the previous record set in 2005 and 39 percent less than the annual average from 1979 to 2000. Causes included clear skies, changes in wind patterns, and unusually warm temperatures. |
| 2009 A.D. | An ice bridge connecting two islands on the Wilkins ice shelf in Antarctica disintegrated, leaving the Wilkins ice shelf vulnerable to collapse. |
| 2009 A.D. | Plumes of gas, primarily methane, were discovered bubbling in the Arctic Ocean west of the Svalbard archipelago in Norway by an expendition led by Graham Westbrook of the University of Birmingham. The west Spitsbergen current flows through the area and has warmed by over 1 degree Celsius in 30 years. The release of methane from the ocean floor has been a predicted consequence of global warming, but this even |
| 2009 A.D. | Carbon dioxide levels in the atmosphere reached 385 parts per million. |