93-721: The Komadugu Gana River or Misau River is a river in the Chad Basin in northeastern Nigeria that joins the Yobe River at Damasak , in the Mobbar Local Government Area of Borno State . It rises north of Bauchi . According to a 2011 report by the International Union for Conservation of Nature , the water flow of the river no longer reaches the Yobe . The 8,500-year-old Dufuna canoe
186-536: A defined part of the river, wetland or lake, and fishers from elsewhere must seek permission and pay a fee to use this area. The governments only enforced rules and regulations to a limited extent. Fishery management practices vary. For example, on the Katagum river in Jigawa State , Nigeria, a village will have a water management council that collects a portion of each fisherman's catch and redistributes it among
279-479: A feedback or internal climate process, greenhouse gases emitted from volcanoes are typically classified as external by climatologists. Greenhouse gases, such as CO 2 , methane and nitrous oxide , heat the climate system by trapping infrared light. Volcanoes are also part of the extended carbon cycle . Over very long (geological) time periods, they release carbon dioxide from the Earth's crust and mantle, counteracting
372-629: A land-based equivalent, competing theories exist concerning effects on climatic temperatures, for example contrasting the Iris hypothesis and CLAW hypothesis . A change in the type, distribution and coverage of vegetation may occur given a change in the climate. Some changes in climate may result in increased precipitation and warmth, resulting in improved plant growth and the subsequent sequestration of airborne CO 2 . Though an increase in CO 2 may benefit plants, some factors can diminish this increase. If there
465-605: A new climate. Rapid or large climate change can cause mass extinctions when creatures are stretched too far to be able to adapt. Collapses of past civilizations such as the Maya may be related to cycles of precipitation, especially drought, that in this example also correlates to the Western Hemisphere Warm Pool . Around 70 000 years ago the Toba supervolcano eruption created an especially cold period during
558-473: A particular year, there is an energy imbalance and extra heat can be absorbed by the oceans. Due to climate inertia , this signal can be 'stored' in the ocean and be expressed as variability on longer time scales than the original weather disturbances. If the weather disturbances are completely random, occurring as white noise , the inertia of glaciers or oceans can transform this into climate changes where longer-duration oscillations are also larger oscillations,
651-531: A period of anthropogenic global warming . In a larger timeframe, the Earth is emerging from the latest ice age, cooling from the Holocene climatic optimum and warming from the " Little Ice Age ", which means that climate has been constantly changing over the last 15,000 years or so. During warm periods, temperature fluctuations are often of a lesser amplitude. The Pleistocene period, dominated by repeated glaciations , developed out of more stable conditions in
744-404: A phenomenon called red noise . Many climate changes have a random aspect and a cyclical aspect. This behavior is dubbed stochastic resonance . Half of the 2021 Nobel prize on physics was awarded for this work to Klaus Hasselmann jointly with Syukuro Manabe for related work on climate modelling . While Giorgio Parisi who with collaborators introduced the concept of stochastic resonance
837-474: A region constitute the region's climate. Such changes can be the result of "internal variability", when natural processes inherent to the various parts of the climate system alter the distribution of energy. Examples include variability in ocean basins such as the Pacific decadal oscillation and Atlantic multidecadal oscillation . Climate variability can also result from external forcing , when events outside of
930-586: A region will lead to earlier flowering and fruiting times, driving a change in the timing of life cycles of dependent organisms. Conversely, cold will cause plant bio-cycles to lag. Larger, faster or more radical changes, however, may result in vegetation stress, rapid plant loss and desertification in certain circumstances. An example of this occurred during the Carboniferous Rainforest Collapse (CRC), an extinction event 300 million years ago. At this time vast rainforests covered
1023-530: A role. The US Geological Survey estimates are that volcanic emissions are at a much lower level than the effects of current human activities, which generate 100–300 times the amount of carbon dioxide emitted by volcanoes. The annual amount put out by human activities may be greater than the amount released by supereruptions , the most recent of which was the Toba eruption in Indonesia 74,000 years ago. Slight variations in Earth's motion lead to changes in
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#17327719366941116-422: A scale of more than 1 year are the ones that inject over 100,000 tons of SO 2 into the stratosphere . This is due to the optical properties of SO 2 and sulfate aerosols, which strongly absorb or scatter solar radiation, creating a global layer of sulfuric acid haze. On average, such eruptions occur several times per century, and cause cooling (by partially blocking the transmission of solar radiation to
1209-540: Is a third, much lower, aquifer in Bima Sandstones that lies at a depth of 2,700 to 4,600 metres (8,900 to 15,100 ft). Both the current and historical areas of the basin and the mega-basin contain concentrations of fossils. Fossil-fuels deposits in the area are estimated to exceed a trillion barrels of reserves. The Lake Chad Basin Commission was established in 1964 by Cameroon, Chad, Niger and Nigeria,
1302-427: Is an environmental change such as drought, increased CO 2 concentrations will not benefit the plant. So even though climate change does increase CO 2 emissions, plants will often not use this increase as other environmental stresses put pressure on them. However, sequestration of CO 2 is expected to affect the rate of many natural cycles like plant litter decomposition rates. A gradual increase in warmth in
1395-419: Is caused by human activity, as opposed to changes in climate that may have resulted as part of Earth's natural processes. Global warming became the dominant popular term in 1988, but within scientific journals global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing greenhouse gas levels affect. A related term, climatic change ,
1488-635: Is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions. Factors that can shape climate are called climate forcings or "forcing mechanisms". These include processes such as variations in solar radiation , variations in the Earth's orbit, variations in the albedo or reflectivity of the continents, atmosphere, and oceans, mountain-building and continental drift and changes in greenhouse gas concentrations. External forcing can be either anthropogenic (e.g. increased emissions of greenhouse gases and dust) or natural (e.g., changes in solar output,
1581-589: Is fed by the Yedseram River and Ngadda River , which join to form an 80 square kilometres (31 sq mi) swamp to the southwest of the lake. There is not any significant water flow from the swamp to the lake. The Central African Republic (CAR) contains the sources of the rivers Chari and Logone , which flow north into the lake. The volume of water entering Chad annually from the CAR has decreased from about 33 cubic kilometres (7.9 cu mi) before
1674-508: Is in the air and the temperature, but also by the amount of aerosols in the air such as dust. Globally, more dust is available if there are many regions with dry soils, little vegetation and strong winds. Paleoclimatology is the study of changes in climate through the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data preserved within things such as rocks, sediments, ice sheets, tree rings, corals, shells, and microfossils. It then uses
1767-465: Is made of Precambrian bedrock covered by more than 3,600 metres (11,800 ft) of sedimentary deposits. The basin may have resulted from the intersection of an "Aïr-Chad Trough" running NW-SE and a "Tibesti-Cameroon Trough" running NE-SW. That is, the two deepest parts are an extension of the Benue Trough that runs northeast to the margin of the basin, and another extension running from below
1860-431: Is released from the ocean. The exchange of CO 2 between the air and the ocean can also be impacted by further aspects of climatic change. These and other self-reinforcing processes allow small changes in Earth's motion to have a large effect on climate. The Sun is the predominant source of energy input to the Earth's climate system . Other sources include geothermal energy from the Earth's core, tidal energy from
1953-458: Is strongly seasonal than will several smaller continents or islands . It has been postulated that ionized particles known as cosmic rays could impact cloud cover and thereby the climate. As the sun shields the Earth from these particles, changes in solar activity were hypothesized to influence climate indirectly as well. To test the hypothesis, CERN designed the CLOUD experiment , which showed
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#17327719366942046-530: Is the atmospheric cooling after a volcanic eruption, when volcanic ash reflects sunlight. Thermal expansion of ocean water after atmospheric warming is slow, and can take thousands of years. A combination is also possible, e.g., sudden loss of albedo in the Arctic Ocean as sea ice melts, followed by more gradual thermal expansion of the water. Climate variability can also occur due to internal processes. Internal unforced processes often involve changes in
2139-545: Is very slight in the north of the basin, increasing to 1,200 millimetres (47 in) in the south. As late as 2000, the basin has remained home to large populations of wildlife. In the Sahel these include antelopes such as the addax and dama gazelle , and in the savanna there are korrigum and red-fronted gazelle . The black crowned crane and other waterbirds are found in the wetlands. There are populations of elephants , giraffes , and lions . The western black rhinoceros
2232-495: The 1815 eruption of Mount Tambora causing the Year Without a Summer . At a larger scale—a few times every 50 million to 100 million years—the eruption of large igneous provinces brings large quantities of igneous rock from the mantle and lithosphere to the Earth's surface. Carbon dioxide in the rock is then released into the atmosphere. Small eruptions, with injections of less than 0.1 Mt of sulfur dioxide into
2325-486: The Antarctic ice sheet , can be used to show a link between temperature and global sea level variations. The air trapped in bubbles in the ice can also reveal the CO 2 variations of the atmosphere from the distant past, well before modern environmental influences. The study of these ice cores has been a significant indicator of the changes in CO 2 over many millennia, and continues to provide valuable information about
2418-580: The Atlantic and Pacific Oceans. This strongly affected the ocean dynamics of what is now the Gulf Stream and may have led to Northern Hemisphere ice cover. During the Carboniferous period, about 300 to 360 million years ago, plate tectonics may have triggered large-scale storage of carbon and increased glaciation . Geologic evidence points to a "megamonsoonal" circulation pattern during
2511-478: The Congo Basin via a canal 2,400 kilometres (1,500 mi) long, but major political, technical, and economic challenges would have to be overcome to make this practical. Humans have lived in the inner Chad Basin from at least eight thousand years ago, and were engaging in agriculture and livestock management around the lake by 1000 BC. Permanent villages were established to the south of the lake by 500 BC at
2604-582: The Late Cretaceous (100.5–66 Ma ). These sediments seem to be considerably thicker towards the northeast. Boreholes under Maiduguri have found marine sediments 400 metres (1,300 ft) deep, lying over continental sediments 600 metres (2,000 ft) deep. The sea seems to have retreated from the western part of the basin in the Turonian (93.5–89.3 Ma). In the Maastrichtian (72.1–66 Ma)
2697-621: The Miocene and Pliocene climate . Holocene climate has been relatively stable. All of these changes complicate the task of looking for cyclical behavior in the climate. Positive feedback , negative feedback , and ecological inertia from the land-ocean-atmosphere system often attenuate or reverse smaller effects, whether from orbital forcings, solar variations or changes in concentrations of greenhouse gases. Certain feedbacks involving processes such as clouds are also uncertain; for contrails , natural cirrus clouds, oceanic dimethyl sulfide and
2790-626: The 12th century. The Kanem empire went into decline, shrank, and during the 14th century was defeated by Bilala invaders from the Lake Fitri region. The Kanuri people commanded by the Sayfuwa migrated to the west and south of the lake, where they established the Bornu Empire . By the late 16th century the Bornu empire had expanded and recaptured the parts of Kanem that had been conquered by
2883-806: The 1970s to 17 cubic kilometres (4.1 cu mi) during the 1980s. A further 3 cubic kilometres (0.72 cu mi) to 7 cubic kilometres (1.7 cu mi) of water annually flows from Cameroon into Chad via the Logone River. The Chari-Logone system accounts for about 95% of the water entering Lake Chad. The basin in the Nigerian section contains an upper aquifer of Early Pleistocene alluvial deposits that are often covered by recent sand dunes, varying in thickness from 15 to 100 metres (49 to 328 ft). It consists of interbedded sands, clays and silts, with discontinuous clay lenses. The aquifer recharges from run-off and rainfall. The local people access
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2976-556: The 1970s. Historical climatology is the study of historical changes in climate and their effect on human history and development. The primary sources include written records such as sagas , chronicles , maps and local history literature as well as pictorial representations such as paintings , drawings and even rock art . Climate variability in the recent past may be derived from changes in settlement and agricultural patterns. Archaeological evidence, oral history and historical documents can offer insights into past changes in
3069-464: The 6,000 square kilometres (2,300 sq mi) Hadejia-Nguru wetlands . They converge to form the Yobe , which defines the border between Niger and Nigeria for 300 kilometres (190 mi), flowing into Lake Chad. About .5 cubic kilometres (0.12 cu mi) of water reaches Lake Chad annually. Construction of upstream dams and growth in irrigation have reduced water flow, and the floodplains are drying. The Yedseram - Ngadda sub-basin further south
3162-684: The African continent, with an area of about 2,434,000 square kilometres (940,000 sq mi). It is surrounded by mountains. The Aïr Mountains and the Termit Massif in Niger form the western boundary. To the northwest, in Algeria, are the Tassili n'Ajjer mountains, including the 2,158 metres (7,080 ft) Jebel Azao . The Tibesti Mountains to the north of the basin include Emi Koussi ,
3255-691: The Bilala. Satellite states of Bornu included the Sultanate of Damagaram in the west and Baguirmi to the southeast of Lake Chad. The Tunjur people initiated the Wadai Empire to the east of Bornu during the 16th century. During the 17th century, the Maba people revolted and established a Muslim dynasty. At first, Wadai paid tribute to Bornu and Durfur, but by the 18th century Wadai was fully independent and had become an aggressor against its neighbors. To
3348-620: The British sphere. Parfait-Louis Monteil was given charge of an expedition to discover where this line actually ran. On 9 April 1892 he reached Kukawa on the shore of the lake. During the next twenty years a large part of the Chad Basin was incorporated by treaty or by force into French West Africa . On 2 June 1909 the Wadai capital of Abéché was occupied by the French. The remainder of
3441-525: The Chad Basin became increasingly linked to the Muslim countries. Trade and improved agricultural techniques enabled more sophisticated societies, resulting in the early kingdoms of the Kanem Empire , the Wadai Empire , and the Sultanate of Bagirmi . Kanem developed during the 8th century in the region to the north and east of Lake Chad. The Sayfuwa dynasty that ruled this kingdom had adopted Islam by
3534-626: The Chad Basin. The population is growing rapidly. Ethnic groups include Kanuri , Maba , Buduma , Hausa , Kanembu , Kotoko , Bagger, Haddad , Kuri , Fulani and Manga . The largest cities are Kano and Maiduguri in Nigeria , Maroua in Cameroon , N'Djamena in Chad and Diffa in Niger . The main economic activities are farming, herding and fishing. At least 40% of the rural population of
3627-423: The Earth's orbit, volcano eruptions). There are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. There are also key thresholds which when exceeded can produce rapid or irreversible change. Some parts of the climate system, such as the oceans and ice caps, respond more slowly in reaction to climate forcings, while others respond more quickly. An example of fast change
3720-461: The Earth's surface) for a period of several years. Although volcanoes are technically part of the lithosphere, which itself is part of the climate system, the IPCC explicitly defines volcanism as an external forcing agent. Notable eruptions in the historical records are the 1991 eruption of Mount Pinatubo which lowered global temperatures by about 0.5 °C (0.9 °F) for up to three years, and
3813-516: The Moon and heat from the decay of radioactive compounds. Both long term variations in solar intensity are known to affect global climate. Solar output varies on shorter time scales, including the 11-year solar cycle and longer-term modulations . Correlation between sunspots and climate and tenuous at best. Three to four billion years ago , the Sun emitted only 75% as much power as it does today. If
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3906-475: The advance and retreat of the Sahara , and for their appearance in the stratigraphic record . During the glacial cycles, there was a high correlation between CO 2 concentrations and temperatures. Early studies indicated that CO 2 concentrations lagged temperatures, but it has become clear that this is not always the case. When ocean temperatures increase, the solubility of CO 2 decreases so that it
3999-499: The atmospheric composition had been the same as today, liquid water should not have existed on the Earth's surface. However, there is evidence for the presence of water on the early Earth, in the Hadean and Archean eons, leading to what is known as the faint young Sun paradox . Hypothesized solutions to this paradox include a vastly different atmosphere, with much higher concentrations of greenhouse gases than currently exist. Over
4092-399: The basin is impoverished and experiences chronic food shortages. Crop production based on rain is possible only in the southern belt. Flood recession agriculture is practiced around Lake Chad and in the riverine wetlands. Nomadic herders migrate with their animals into the grasslands of the northern part of the basin for a few weeks during each brief rainy season, where they intensively graze
4185-660: The basin is separated by a watershed from the Niger River , and to the south it is separated by a basement dome from the Benue River . Further east, watersheds separate it from the Congo Basin and the river Nile . The lowest part of the basin is not Lake Chad, but the Bodélé Depression , at a distance of 480 kilometres (300 mi) to the northeast of the lake. The Bodélé Depression is just 155 metres (509 ft) above sea level in its deepest portion, while
4278-645: The basin was divided by the British in Nigeria who captured Kano in 1903, and the Germans in Kameroun. The countries of the basin regained their independence between 1956 and 1962, retaining the colonial administrative boundaries. The area is badly affected by the Boko Haram insurgency , which began in 2009 and is centred on Borno State in northeastern Nigeria. As of 2011, more than 30 million people lived in
4371-512: The climate system's components produce changes within the system. Examples include changes in solar output and volcanism . Climate variability has consequences for sea level changes, plant life, and mass extinctions; it also affects human societies. Climate variability is the term to describe variations in the mean state and other characteristics of climate (such as chances or possibility of extreme weather, etc.) "on all spatial and temporal scales beyond that of individual weather events." Some of
4464-548: The climate. Changes in climate have been linked to the rise and the collapse of various civilizations. Various archives of past climate are present in rocks, trees and fossils. From these archives, indirect measures of climate, so-called proxies, can be derived. Quantification of climatological variation of precipitation in prior centuries and epochs is less complete but approximated using proxies such as marine sediments, ice cores, cave stalagmites, and tree rings. Stress, too little precipitation or unsuitable temperatures, can alter
4557-593: The climate. Other changes, including Heinrich events , Dansgaard–Oeschger events and the Younger Dryas , however, illustrate how glacial variations may also influence climate without the orbital forcing . During the Last Glacial Maximum , some 25,000 years ago, sea levels were roughly 130 m lower than today. The deglaciation afterwards was characterized by rapid sea level change. In the early Pliocene , global temperatures were 1–2˚C warmer than
4650-405: The climate. The hypothesis is that soot released by large-scale fires blocks a significant fraction of sunlight for as much as a year, leading to a sharp drop in temperatures for a few years. This possible event is described as nuclear winter . Humans' use of land impact how much sunlight the surface reflects and the concentration of dust. Cloud formation is not only influenced by how much water
4743-481: The continents determines the geometry of the oceans and therefore influences patterns of ocean circulation. The locations of the seas are important in controlling the transfer of heat and moisture across the globe, and therefore, in determining global climate. A recent example of tectonic control on ocean circulation is the formation of the Isthmus of Panama about 5 million years ago, which shut off direct mixing between
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#17327719366944836-461: The differences between ancient and modern atmospheric conditions. The O/ O ratio in calcite and ice core samples used to deduce ocean temperature in the distant past is an example of a temperature proxy method. The remnants of plants, and specifically pollen, are also used to study climatic change. Plant distributions vary under different climate conditions. Different groups of plants have pollen with distinctive shapes and surface textures, and since
4929-426: The distribution of energy in the ocean and atmosphere, for instance, changes in the thermohaline circulation . Climatic changes due to internal variability sometimes occur in cycles or oscillations. For other types of natural climatic change, we cannot predict when it happens; the change is called random or stochastic . From a climate perspective, the weather can be considered random. If there are little clouds in
5022-589: The effect of cosmic rays is too weak to influence climate noticeably. Evidence exists that the Chicxulub asteroid impact some 66 million years ago had severely affected the Earth's climate. Large quantities of sulfate aerosols were kicked up into the atmosphere, decreasing global temperatures by up to 26 °C and producing sub-freezing temperatures for a period of 3–16 years. The recovery time for this event took more than 30 years. The large-scale use of nuclear weapons has also been investigated for its impact on
5115-417: The equatorial region of Europe and America. Climate change devastated these tropical rainforests, abruptly fragmenting the habitat into isolated 'islands' and causing the extinction of many plant and animal species. One of the most important ways animals can deal with climatic change is migration to warmer or colder regions. On a longer timescale, evolution makes ecosystems including animals better adapted to
5208-431: The evolution of a glacier in a particular season. The most significant climate processes since the middle to late Pliocene (approximately 3 million years ago) are the glacial and interglacial cycles. The present interglacial period (the Holocene ) has lasted about 11,700 years. Shaped by orbital variations , responses such as the rise and fall of continental ice sheets and significant sea-level changes helped create
5301-441: The extensive lineage of beetles whose genetic makeup has not altered significantly over the millennia, knowledge of the present climatic range of the different species, and the age of the sediments in which remains are found, past climatic conditions may be inferred. One difficulty in detecting climate cycles is that the Earth's climate has been changing in non-cyclic ways over most paleoclimatological timescales. Currently we are in
5394-413: The following approximately 4 billion years, the energy output of the Sun increased. Over the next five billion years, the Sun's ultimate death as it becomes a red giant and then a white dwarf will have large effects on climate, with the red giant phase possibly ending any life on Earth that survives until that time. The volcanic eruptions considered to be large enough to affect the Earth's climate on
5487-483: The four countries that contain parts of Lake Chad. About 20% of the basin, lying in these countries, is termed the Conventional Basin. The Lake Chad Basin Commission manages use of water and other natural resources in this area. Although the lake fluctuates considerably in size from one year to another, the general trend has been for water levels to decrease. There has been a proposal to supply water from
5580-444: The growth rate of trees, which allows scientists to infer climate trends by analyzing the growth rate of tree rings. This branch of science studying this called dendroclimatology . Glaciers leave behind moraines that contain a wealth of material—including organic matter, quartz, and potassium that may be dated—recording the periods in which a glacier advanced and retreated. Analysis of ice in cores drilled from an ice sheet such as
5673-572: The highest mountain in the Sahara at 3,415 metres (11,204 ft). The Ennedi Plateau lies to the northeast, rising to 1,450 metres (4,760 ft). The Ouaddaï highlands lies the east. They include the Marrah Mountains in Darfur at up to 3,088 metres (10,131 ft) in height. The Adamawa Plateau , Jos Plateau , Biu Plateau , and Mandara Mountains lie to the south. To the west
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#17327719366945766-520: The ice age, leading to a possible genetic bottleneck in human populations. Glaciers are considered among the most sensitive indicators of a changing climate. Their size is determined by a mass balance between snow input and melt output. As temperatures increase, glaciers retreat unless snow precipitation increases to make up for the additional melt. Glaciers grow and shrink due both to natural variability and external forcings. Variability in temperature, precipitation and hydrology can strongly determine
5859-414: The ice sheet melts, the resulting water is very low in salt and cold, driving changes in circulation. Life affects climate through its role in the carbon and water cycles and through such mechanisms as albedo , evapotranspiration , cloud formation , and weathering . Examples of how life may have affected past climate include: Whereas greenhouse gases released by the biosphere is often seen as
5952-470: The last glacial period ) show that the circulation in the North Atlantic can change suddenly and substantially, leading to global climate changes, even though the total amount of energy coming into the climate system did not change much. These large changes may have come from so called Heinrich events where internal instability of ice sheets caused huge ice bergs to be released into the ocean. When
6045-591: The north of the basin. During the Holocene , from 11,000 years ago until recently, a giant "Lake Mega-Chad" covered an area of more than 350,000 square kilometres (140,000 sq mi) in the basin. It would have drained to the Atlantic Ocean via the Benue River . Stratigraphic records show that "Mega-Chad" varied in size as the climate changed , with a maximum about 2,300 years ago. The remains of fish and molluscs from this period are found in what are now desert regions. The Chad Basin covers almost 8% of
6138-405: The northeast and east. The basin spans four modern nations, including most of Chad and a large part of Niger , Nigeria and Cameroon . A combination of dams, increased irrigation, climate change , and reduced rainfall are causing water shortages. Lake Chad continues to shrink. The geological basin, which is smaller than the drainage basin, is a Phanerozoic sedimentary basin formed during
6231-486: The nutritious grasses. When the dry season starts they move back south, either to grazing lands around the lakes and floodplains, or to the savannas further to the south. During the period 2000-01, fisheries in the Lake Chad basin provided food and income to more than 10 million people, with a harvest of about 70,000 tons. Fisheries have been managed traditionally by a system where each village has recognized rights over
6324-413: The ocean having hundreds of times more mass than in the atmosphere , and thus very high thermal inertia. For example, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat in the world's oceans. Ocean currents transport a lot of energy from the warm tropical regions to the colder polar regions. Changes occurring around the last ice age (in technical terms,
6417-638: The outer surface of pollen is composed of a very resilient material, they resist decay. Changes in the type of pollen found in different layers of sediment indicate changes in plant communities. These changes are often a sign of a changing climate. As an example, pollen studies have been used to track changing vegetation patterns throughout the Quaternary glaciations and especially since the last glacial maximum . Remains of beetles are common in freshwater and land sediments. Different species of beetles tend to be found under different climatic conditions. Given
6510-772: The plate divergence that opened the South Atlantic Ocean. The basin lies between the West African Craton and Congo Craton , and formed about the same time as the Benue Trough . It covers an area of about 2,335,000 square kilometres (902,000 sq mi). It merges into the Iullemmeden Basin to the west at the Damergou gap between the Aïr and Zinder massifs. The floor of the basin
6603-606: The present lake to below the Ténéré rift structure to the east of the Aïr massif. The southern part of the basin is underlain by another elongated depression. This runs in an ENE direction and extends from the Yola arm of the Benue trough. At times, parts of the basin were below the sea. In the northeastern part of the Benue Trough where it enters the Chad Basin there are marine sediments from
6696-439: The present temperature, yet sea level was 15–25 meters higher than today. Sea ice plays an important role in Earth's climate as it affects the total amount of sunlight that is reflected away from the Earth. In the past, the Earth's oceans have been almost entirely covered by sea ice on a number of occasions, when the Earth was in a so-called Snowball Earth state, and completely ice-free in periods of warm climate. When there
6789-541: The records to determine the past states of the Earth's various climate regions and its atmospheric system. Direct measurements give a more complete overview of climate variability. Climate changes that occurred after the widespread deployment of measuring devices can be observed directly. Reasonably complete global records of surface temperature are available beginning from the mid-late 19th century. Further observations are derived indirectly from historical documents. Satellite cloud and precipitation data has been available since
6882-607: The seasonal distribution of sunlight reaching the Earth's surface and how it is distributed across the globe. There is very little change to the area-averaged annually averaged sunshine; but there can be strong changes in the geographical and seasonal distribution. The three types of kinematic change are variations in Earth's eccentricity , changes in the tilt angle of Earth's axis of rotation , and precession of Earth's axis. Combined, these produce Milankovitch cycles which affect climate and are notable for their correlation to glacial and interglacial periods , their correlation with
6975-568: The start of the Iron Age . The Chad Basin contained important trade routes to the east and to the north across the Sahara. By the 5th century AD camels were being used for trans-Saharan trade via the Fezzan , or to the east via Darfur , where slaves and ivory were exchanged for salt, horses, glass beads, and, later, firearms. After the Arabs conquered North Africa during the 7th and 8th centuries,
7068-485: The stratosphere, affect the atmosphere only subtly, as temperature changes are comparable with natural variability. However, because smaller eruptions occur at a much higher frequency, they too significantly affect Earth's atmosphere. Over the course of millions of years, the motion of tectonic plates reconfigures global land and ocean areas and generates topography. This can affect both global and local patterns of climate and atmosphere-ocean circulation. The position of
7161-559: The sun and radiates energy to outer space . The balance of incoming and outgoing energy and the passage of the energy through the climate system is Earth's energy budget . When the incoming energy is greater than the outgoing energy, Earth's energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and Earth experiences cooling. The energy moving through Earth's climate system finds expression in weather, varying on geographic scales and time. Long-term averages and variability of weather in
7254-558: The surface of Lake Chad is 275 metres (902 ft) above sea level. The basin spans parts of eight countries. These are: The northern half of the basin is desert, containing the Ténéré desert, Erg of Bilma and Djurab Desert . South of that is the Sahel zone, dry savanna and thorny shrub savanna. The main rivers include riparian forests, flooding savannas and wetland areas. In the far south there are dry forests. Rainfall varies widely from year to year. The amount of annual rainfall
7347-543: The term climate change only refers to those variations that persist for a longer period of time, typically decades or more. Climate change may refer to any time in Earth's history, but the term is now commonly used to describe contemporary climate change, often popularly referred to as global warming. Since the Industrial Revolution , the climate has increasingly been affected by human activities . The climate system receives nearly all of its energy from
7440-431: The time of the supercontinent Pangaea , and climate modeling suggests that the existence of the supercontinent was conducive to the establishment of monsoons. The size of continents is also important. Because of the stabilizing effect of the oceans on temperature, yearly temperature variations are generally lower in coastal areas than they are inland. A larger supercontinent will therefore have more area in which climate
7533-644: The title of the Intergovernmental Panel on Climate Change (IPCC) and the UN Framework Convention on Climate Change (UNFCCC). Climate change is now used as both a technical description of the process, as well as a noun used to describe the problem. On the broadest scale, the rate at which energy is received from the Sun and the rate at which it is lost to space determine the equilibrium temperature and climate of Earth. This energy
7626-472: The total energy budget of the Earth. A climate oscillation or climate cycle is any recurring cyclical oscillation within global or regional climate . They are quasiperiodic (not perfectly periodic), so a Fourier analysis of the data does not have sharp peaks in the spectrum . Many oscillations on different time-scales have been found or hypothesized: The oceanic aspects of climate variability can generate variability on centennial timescales due to
7719-582: The uptake by sedimentary rocks and other geological carbon dioxide sinks . Since the Industrial Revolution , humanity has been adding to greenhouse gases by emitting CO 2 from fossil fuel combustion, changing land use through deforestation, and has further altered the climate with aerosols (particulate matter in the atmosphere), release of trace gases (e.g. nitrogen oxides, carbon monoxide, or methane). Other factors, including land use, ozone depletion , animal husbandry ( ruminant animals such as cattle produce methane ), and deforestation , also play
7812-412: The variability does not appear to be caused by known systems and occurs at seemingly random times. Such variability is called random variability or noise . On the other hand, periodic variability occurs relatively regularly and in distinct modes of variability or climate patterns. The term climate change is often used to refer specifically to anthropogenic climate change. Anthropogenic climate change
7905-426: The villagers, or sells it and used the proceeds for communal projects. Local governments and traditional authorities are increasingly engaged in rent-seeking , collecting license fees with the help of the police or army. Notes Citations Sources Climate change (general concept) Climate variability includes all the variations in the climate that last longer than individual weather events, whereas
7998-512: The water with hand-dug wells and shallow boreholes, and use it for domestic use, growing vegetables and watering their livestock. Below this aquifer, separated from it by a sequence of grey to bluish-grey clays from the Zanclean , is a second aquifer at a depth of 240 to 380 metres (790 to 1,250 ft). Due to intensive pumping, since the start of the 1980s the water levels in both aquifers has been lowered, and some wells no longer function. There
8091-725: The west of Bornu, by the 15th century the Kingdom of Kano had become the most powerful of the Hausa Kingdoms , with an unstable truce with the Kingdom of Katsina to the north. Both of these states adopted Islam during the 15th and 16th centuries. Both were absorbed into the Sokoto Caliphate during the Fulani War of 1805, which threatened Bornu itself. During the Berlin Conference in 1884-85 Africa
8184-531: The west was non-marine, but the southeast probably was still marine. No marine sediments have been found from the Paleocene (66–56 Ma). For most of the Quaternary , from 2.6 million years ago to the present, the basin seems to have been a huge, well-watered plain, with many rivers and water bodies, probably rich in plant and animal life. Towards the end of this period the climate became drier. Around 20,000-40,000 years ago, eolianite sand dunes began to form in
8277-430: Was awarded the other half but mainly for work on theoretical physics. The ocean and atmosphere can work together to spontaneously generate internal climate variability that can persist for years to decades at a time. These variations can affect global average surface temperature by redistributing heat between the deep ocean and the atmosphere and/or by altering the cloud/water vapor/sea ice distribution which can affect
8370-613: Was discovered during a dig near the river in 1987 in the Fune Local Government Area. Chad Basin The Chad Basin is the largest endorheic basin in Africa, centered approximately on Lake Chad . It has no outlet to the sea and contains large areas of semi-arid desert and savanna . The drainage basin is approximately coterminous with the sedimentary basin of the same name, but extends further to
8463-532: Was divided between the European colonial powers, defining boundaries that are largely intact with the present post-colonial states. On 5 August 1890 the British and French concluded an agreement to define the boundary between French West Africa and what would become Nigeria . A boundary was agreed along a line from Say on the river Niger to Barruwa on Lake Chad, but leaving the Sokoto Caliphate in
8556-488: Was once common but is now extinct. Elephants almost became extinct by the end of the nineteenth century due to European and American demand for ivory, but stocks have since recovered. The seasonal Korama River in the south of Niger does not reach Lake Chad. Nigeria includes two sub-basins that drain into Lake Chad. The Hadejia - Jama'are - Yobe sub-basin in the north contains the Hadejia and Jama'are rivers, which supply
8649-494: Was proposed by the World Meteorological Organization (WMO) in 1966 to encompass all forms of climatic variability on time-scales longer than 10 years, but regardless of cause. During the 1970s, the term climate change replaced climatic change to focus on anthropogenic causes, as it became clear that human activities had a potential to drastically alter the climate. Climate change was incorporated in
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