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95-672: The Medieval Warm Period ( MWP ), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly , was a time of warm climate in the North Atlantic region that lasted from about 950 CE to about 1250 CE . Climate proxy records show peak warmth occurred at different times for different regions, which indicate that the MWP was not a globally uniform event. Some refer to
190-544: A La Niña -like configuration, but the data are insufficient to show how lake levels varied from year to year or what climatic conditions elsewhere in Australia were like. A 1979 study from the University of Waikato found, Temperatures derived from an O/O profile through a stalagmite found in a New Zealand cave ( 40°40′S 172°26′E / 40.67°S 172.43°E / -40.67; 172.43 ) suggested
285-570: A biome classification, as climate is a major influence on life in a region. One of the most used is the Köppen climate classification scheme first developed in 1899. There are several ways to classify climates into similar regimes. Originally, climes were defined in Ancient Greece to describe the weather depending upon a location's latitude. Modern climate classification methods can be broadly divided into genetic methods, which focus on
380-549: A high stand during the MWP. When human populations returned to the region, they encountered a land altered by climate change and had to reestablish ports. In the Iberian Central Range, there was elevated lake productivity and soil erosion, along with frequent intense runoff events. In Chesapeake Bay (now in Maryland and Virginia , United States ), researchers found large temperature excursions (changes from
475-596: A slippery slope scenario in his style guide that, "if we do end by casting aside the AD/BC convention, almost certainly some will argue that we ought to cast aside as well the conventional numbering system [that is, the method of numbering years] itself, given its Christian basis." Some Christians are offended by the removal of the reference to Jesus, including the Southern Baptist Convention . The abbreviation BCE, just as with BC, always follows
570-526: A 30-year period. A 30-year period is used as it is long enough to filter out any interannual variation or anomalies such as El Niño–Southern Oscillation , but also short enough to be able to show longer climatic trends." The WMO originated from the International Meteorological Organization which set up a technical commission for climatology in 1929. At its 1934 Wiesbaden meeting, the technical commission designated
665-419: A few global datasets exist. Global climate models can be dynamically or statistically downscaled to regional climate models to analyze impacts of climate change on a local scale. Examples are ICON or mechanistically downscaled data such as CHELSA (Climatologies at high resolution for the earth's land surface areas). The most talked-about applications of these models in recent years have been their use to infer
760-510: A gradual withdrawal, which was caused mainly by economic factors such as increased availability of farms in Scandinavian countries. Substantial glacial retreat in southern Europe was experienced during the MWP. While several smaller glaciers experienced complete deglaciation, larger glaciers in the region survived and now provide insight into the region's climate history. In addition to warming induced glacial melt, sedimentary records reveal
855-486: A location is affected by its latitude , longitude , terrain , altitude , land use and nearby water bodies and their currents. Climates can be classified according to the average and typical variables, most commonly temperature and precipitation . The most widely used classification scheme is the Köppen climate classification . The Thornthwaite system , in use since 1948, incorporates evapotranspiration along with temperature and precipitation information and
950-626: A matter of convenience. There is so much interaction between people of different faiths and cultures – different civilizations, if you like – that some shared way of reckoning time is a necessity. And so the Christian Era has become the Common Era. Adena K. Berkowitz, in her application to argue before the United States Supreme Court , opted to use BCE and CE because, "Given the multicultural society that we live in,
1045-539: A notably warm climate in many parts of the world, that lasted a few centuries around 1000–1200 CE , and was followed by a decline of temperature levels till between around 1500–1700 CE the coldest phase since the last ice age occurred. The era of warmer temperatures became known as the Medieval Warm Period and the subsequent cold period the Little Ice Age (LIA). However, the view that
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#17327722637551140-715: A period of 138 years in which the traditional BC/AD dating notation was used. BCE/CE is used by the College Board in its history tests, and by the Norton Anthology of English Literature . Others have taken a different approach. The US-based History Channel uses BCE/CE notation in articles on non-Christian religious topics such as Jerusalem and Judaism . The 2006 style guide for the Episcopal Diocese Maryland Church News says that BCE and CE should be used. In June 2006, in
1235-484: A period of increased flooding, coinciding with the MWP, in eastern Europe that is attributed to enhanced precipitation from a positive phase NAO. Other impacts of climate change can be less apparent such as a changing landscape. Preceding the MWP, a coastal region in western Sardinia was abandoned by the Romans. The coastal area was able to substantially expand into the lagoon without the influence of human populations and
1330-576: A regional instead of global framing of climate variability in the preindustrial Common Era to aid in understanding. Lloyd D. Keigwin's 1996 study of radiocarbon -dated box core data from marine sediments in the Sargasso Sea found that its sea surface temperature was approximately 1 °C (1.8 °F) cooler approximately 400 years ago, during the LIA , and 1700 years ago, and was approximately 1 °C (1.8 °F) warmer 1000 years ago, during
1425-466: A stable oxygen (δ O) and carbon (δ C) isotope record at a decadal resolution from the Roman Warm Period to the MWP and the LIA . Patterson et al. conclude that the summer temperature stayed high but winter temperature decreased after the initial settlement of Iceland. The Mann et al. study found warmth exceeding 1961–1990 levels in southern Greenland and parts of North America during
1520-421: A time spanning from months to millions of years. Some of the meteorological variables that are commonly measured are temperature , humidity , atmospheric pressure , wind , and precipitation . In a broader sense, climate is the state of the components of the climate system , including the atmosphere , hydrosphere , cryosphere , lithosphere and biosphere and the interactions between them. The climate of
1615-649: A warm and humid MWP from 1,158 to 647 BP. Pollen from Madhya Pradesh dated to the MWP provides further direct evidence for increased monsoonal precipitation. Multi-proxy records from Pookode Lake in Kerala also reflect the warmth of the MWP. Sea surface temperatures in the Arabian Sea increased during the MWP, owing to a strong monsoon. During the MWP, the Arabian Sea exhibited heightened biological productivity. The Arabian Peninsula , already extremely arid in
1710-403: A wider sense is the state, including a statistical description, of the climate system." The World Meteorological Organization (WMO) describes " climate normals " as "reference points used by climatologists to compare current climatological trends to that of the past or what is considered typical. A climate normal is defined as the arithmetic average of a climate element (e.g. temperature) over
1805-480: Is a direct reference to Jesus as Lord . Proponents of the Common Era notation assert that the use of BCE/CE shows sensitivity to those who use the same year numbering system as the one that originated with and is currently used by Christians , but who are not themselves Christian. Former United Nations Secretary-General Kofi Annan has argued: [T]he Christian calendar no longer belongs exclusively to Christians. People of all faiths have taken to using it simply as
1900-562: Is as follows: "Climate in a narrow sense is usually defined as the "average weather", or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in
1995-535: Is called the early Medieval Warm Period while MWP-II is called the conventional Medieval Warm Period. In 1965, Hubert Lamb , one of the first paleoclimatologists , published research based on data from botany , historical document research, and meteorology, combined with records indicating prevailing temperature and rainfall in England around 1200 CE and around 1600 CE . He proposed, evidence has been accumulating in many fields of investigation pointing to
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#17327722637552090-462: Is discussed in terms of global warming , which results in redistributions of biota . For example, as climate scientist Lesley Ann Hughes has written: "a 3 °C [5 °F] change in mean annual temperature corresponds to a shift in isotherms of approximately 300–400 km [190–250 mi] in latitude (in the temperate zone) or 500 m [1,600 ft] in elevation. Therefore, species are expected to move upwards in elevation or towards
2185-485: Is in particularly common use in Nepal in order to disambiguate dates from the local calendar, Bikram or Vikram Sambat. Disambiguation is needed because the era of the local calendar is quite close to the Common Era. In 2002, an advisory panel for the religious education syllabus for England and Wales recommended introducing BCE/CE dates to schools, and by 2018 some local education authorities were using them. In 2018,
2280-511: Is insufficient on its own to explain the MWP and that an external forcing had to be one of the causes. The MWP is generally thought to have occurred from about 950 CE to about 1250 CE , during the European Middle Ages . Some researchers divide the MWP into two phases: MWP-I, which began around 450 CE and ended around 900 CE , and MWP-II, which lasted from about 1000 CE to about 1300 CE ; MWP-I
2375-580: Is used in studying biological diversity and how climate change affects it. The major classifications in Thornthwaite's climate classification are microthermal, mesothermal, and megathermal. Finally, the Bergeron and Spatial Synoptic Classification systems focus on the origin of air masses that define the climate of a region. Paleoclimatology is the study of ancient climates. Paleoclimatologists seek to explain climate variations for all parts of
2470-406: Is what you expect, weather is what you get." Over historical time spans, there are a number of nearly constant variables that determine climate, including latitude , altitude, proportion of land to water, and proximity to oceans and mountains. All of these variables change only over periods of millions of years due to processes such as plate tectonics . Other climate determinants are more dynamic:
2565-515: The Gregorian calendar (and its predecessor, the Julian calendar ), the world's most widely used calendar era . Common Era and Before the Common Era are alternatives to the original Anno Domini (AD) and Before Christ (BC) notations used for the same calendar era. The two notation systems are numerically equivalent: "2024 CE" and "AD 2024" each describe the current year; "400 BCE" and "400 BC" are
2660-599: The Gregorian calendar without the AD prefix. As early as 1825, the abbreviation VE (for Vulgar Era) was in use among Jews to denote years in the Western calendar. As of 2005 , Common Era notation has also been in use for Hebrew lessons for more than a century. Jews have also used the term Current Era . Some academics in the fields of theology , education , archaeology and history have adopted CE and BCE notation despite some disagreement. A study conducted in 2014 found that
2755-495: The LIA . Peak temperatures did not rise as to the level of the late 20th century, which were unprecedented in the area during the study period of 1600 years. Ge et al. studied temperatures in China for the past 2000 years and found high uncertainty prior to the 16th century but good consistency over the last 500 years highlighted by the two cold periods, 1620s–1710s and 1800s–1860s, and the 20th-century warming. They also found that
2850-723: The National Trust said it would continue to use BC/AD as its house style. English Heritage explains its era policy thus: "It might seem strange to use a Christian calendar system when referring to British prehistory, but the BC/AD labels are widely used and understood." Some parts of the BBC use BCE/CE, but some presenters have said they will not. As of October 2019, the BBC News style guide has entries for AD and BC, but not for CE or BCE. The style guide for The Guardian says, under
2945-614: The date of birth of Jesus . Since the year numbers are the same, BCE and CE dates should be equally offensive to other religions as BC and AD. Roman Catholic priest and writer on interfaith issues Raimon Panikkar argued that the BCE/CE usage is the less inclusive option since they are still using the Christian calendar numbers and forcing it on other nations. In 1993, the English-language expert Kenneth G. Wilson speculated
Medieval Warm Period - Misplaced Pages Continue
3040-484: The thermohaline circulation of the ocean leads to a 5 °C (9 °F) warming of the northern Atlantic Ocean compared to other ocean basins. Other ocean currents redistribute heat between land and water on a more regional scale. The density and type of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric greenhouse gases (particularly carbon dioxide and methane ) determines
3135-495: The Arctic region and oceans. 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 the variability does not appear to be caused systematically and occurs at random times. Such variability is called random variability or noise . On
3230-596: The BCE/CE notation is not growing at the expense of BC and AD notation in the scholarly literature, and that both notations are used in a relatively stable fashion. In 2011, media reports suggested that the BC/AD notation in Australian school textbooks would be replaced by BCE/CE notation. The change drew opposition from some politicians and church leaders. Weeks after the story broke, the Australian Curriculum, Assessment and Reporting Authority denied
3325-579: The Christian Era, it was sometimes qualified, e.g., "common era of the Incarnation", "common era of the Nativity", or "common era of the birth of Christ". An adapted translation of Common Era into Latin as Era Vulgaris was adopted in the 20th century by some followers of Aleister Crowley , and thus the abbreviation "e.v." or "EV" may sometimes be seen as a replacement for AD. Although Jews have their own Hebrew calendar , they often use
3420-508: The EASM and ENSO are responsible for increased precipitation in the region during the MWP. However, other sites in southern China show aridification and not humidification during the MWP, showing that the MWP's influence was highly spatially heterogeneous. Modelling evidence suggests that EASM strength during the MWP was low in early summer but very high during late summer. In far eastern Russia , continental regions experienced severe floods during
3515-459: The EU's Copernicus Climate Change Service, average global air temperature has passed 1.5C of warming the period from February 2023 to January 2024. Climate models use quantitative methods to simulate the interactions and transfer of radiative energy between the atmosphere , oceans , land surface and ice through a series of physics equations. They are used for a variety of purposes, from the study of
3610-477: The Earth as a single point and average outgoing energy. This can be expanded vertically (as in radiative-convective models), or horizontally. Finally, more complex (coupled) atmosphere–ocean– sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange. Common Era Common Era ( CE ) and Before the Common Era ( BCE ) are year notations for
3705-554: The Earth during any given geologic period, beginning with the time of the Earth's formation. Since very few direct observations of climate were available before the 19th century, paleoclimates are inferred from proxy variables . They include non-biotic evidence—such as sediments found in lake beds and ice cores —and biotic evidence—such as tree rings and coral. Climate models are mathematical models of past, present, and future climates. Climate change may occur over long and short timescales due to various factors. Recent warming
3800-495: The Gregorian Calendar as BCE and CE without compromising their own beliefs about the divinity of Jesus of Nazareth." In History Today , Michael Ostling wrote: "BC/AD Dating: In the year of whose Lord? The continuing use of AD and BC is not only factually wrong but also offensive to many who are not Christians." Critics note the fact that there is no difference in the epoch of the two systems—chosen to be close to
3895-523: The Latin term anno aerae nostrae vulgaris may be that in a 1615 book by Johannes Kepler . Kepler uses it again, as ab Anno vulgaris aerae , in a 1616 table of ephemerides , and again, as ab anno vulgaris aerae , in 1617. A 1635 English edition of that book has the title page in English that may be the earliest-found use of Vulgar Era in English. A 1701 book edited by John Le Clerc includes
Medieval Warm Period - Misplaced Pages Continue
3990-711: The MWP and three cool phases, two of which could be related to the LIA . Other research in northeastern Japan showed that there was one warm and humid interval, from 750 to 1200, and two cold and dry intervals, from 1 to 750 and from 1200 to now. The Indian Summer Monsoon (ISM) was also enhanced during the MWP with a temperature driven change to the Atlantic Multi-decadal Oscillation (AMO), bringing more precipitation to India . Vegetation records in Lahaul in Himachal Pradesh confirm
4085-509: The MWP as the Medieval Climatic Anomaly to emphasize that climatic effects other than temperature were also important. The MWP was followed by a regionally cooler period in the North Atlantic and elsewhere, which is sometimes called the Little Ice Age (LIA). Possible causes of the MWP include increased solar activity, decreased volcanic activity, and changes in ocean circulation. Modelling evidence has shown that natural variability
4180-608: The MWP display a strong correlation with the North Atlantic Oscillation (NAO). The Norse colonization of the Americas has been associated with warmer periods. The common theory is that Norsemen took advantage of ice-free seas to colonize areas in Greenland and other outlying lands of the far north. However, a study from Columbia University suggests that Greenland was not colonized in warmer weather, but
4275-618: The MWP in the Southern Ocean lagged the MWP's onset in the North Atlantic by approximately 150 years. A sediment core from the eastern Bransfield Basin, in the Antarctic Peninsula , preserves climatic events from both the LIA and the MWP. The authors noted, "The late Holocene records clearly identify Neoglacial events of the LIA and Medieval Warm Period (MWP)." Some Antarctic regions were atypically cold, but others were atypically warm between 1000 and 1200. Corals in
4370-521: The MWP than during the LIA and 0.65 °C (1.2 °F) warmer than the decades before the study. The MWP has been noted in Chile in a 1500-year lake bed sediment core, as well as in the Eastern Cordillera of Ecuador . A reconstruction, based on ice cores, found that the MWP could be distinguished in tropical South America from about 1050 to 1300 and was followed in the 15th century by
4465-645: The MWP to LIA , was found for northeast and central-east China but not for northwest China and the Tibetan Plateau . During the MWP, the East Asian Summer Monsoon (EASM) was the strongest it has been in the past millennium and was highly sensitive to the El Niño Southern Oscillation (ENSO). The Mu Us Desert witness increased moisture in the MWP. Peat cores from peatland in southeast China suggest changes in
4560-717: The MWP was a global event was challenged by other researchers. The IPCC First Assessment Report of 1990 discussed the: Medieval Warm Period around 1000 CE (which may not have been global) and the Little Ice Age which ended only in the middle to late nineteenth century. It stated that temperatures in the: late tenth to early thirteenth centuries (about 950–1250 CE ) appear to have been exceptionally warm in western Europe, Iceland and Greenland. The IPCC Third Assessment Report from 2001 summarized newer research: evidence does not support globally synchronous periods of anomalous cold or warmth over this time frame, and
4655-477: The MWP while nearby islands experienced less precipitation leading to a decrease in peatland. Pollen data from this region indicates an expansion of warm climate vegetation with an increasing number of broadleaf and decreasing number of coniferous forests. Adhikari and Kumon (2001), investigating sediments in Lake Nakatsuna , in central Japan , found a warm period from 900 to 1200 that corresponded to
4750-557: The MWP, which the study defines as from 950 to 1250, with warmth in some regions exceeding temperatures of the 1990–2010 period. Much of the Northern Hemisphere showed a significant cooling during the LIA , which the study defines as from 1400 to 1700, but Labrador and isolated parts of the United States appeared to be approximately as warm as during the 1961–1990 period. Greenlandic winter oxygen isotope data from
4845-682: The MWP. Using sediment samples from Puerto Rico , the Gulf Coast , and the Atlantic Coast from Florida to New England , Mann et al. found consistent evidence of a peak in North Atlantic tropical cyclone activity during the MWP, which was followed by a subsequent lull in activity. Iceland was first settled between about 865 and 930, during a time believed to be warm enough for sailing and farming. By retrieval and isotope analysis of marine cores and from examination of mollusc growth patterns from Iceland , Patterson et al. reconstructed
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#17327722637554940-565: The Medieval Warm Period to have occurred between [... about 1050–1400 CE ] and to have been 0.75 °C [1.4 °F] warmer than the Current Warm Period. More evidence in New Zealand is from an 1100-year tree-ring record. Climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over
5035-560: The North Atlantic have been noticed. The nature and extent of the MWP has been marked by long-standing controversy over whether it was a global or regional event. In 2019, by using an extended proxy data set, the Pages-2k consortium confirmed that the Medieval Climate Anomaly was not a globally synchronous event. The warmest 51-year period within the MWP did not occur at the same time in different regions. They argue for
5130-625: The United States, the Kentucky State School Board reversed its decision to use BCE and CE in the state's new Program of Studies, leaving education of students about these concepts a matter of local discretion. The use of CE in Jewish scholarship was historically motivated by the desire to avoid the implicit "Our Lord" in the abbreviation AD . Although other aspects of dating systems are based in Christian origins, AD
5225-599: The Western United States. Aridity was more prevalent in the southeastern United States during the MWP than the following LIA, but only slightly; this difference may be statistically insignificant. Droughts in the MWP may have impacted Native American settlements also in the Eastern United States , such as at Cahokia . Review of more recent archaeological research shows that as the search for signs of unusual cultural changes has broadened, some of
5320-462: The amount of solar energy retained by the planet, leading to global warming or global cooling . The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned. Climate classifications are systems that categorize the world's climates. A climate classification may correlate closely with
5415-426: The causes of climate, and empiric methods, which focus on the effects of climate. Examples of genetic classification include methods based on the relative frequency of different air mass types or locations within synoptic weather disturbances. Examples of empiric classifications include climate zones defined by plant hardiness , evapotranspiration, or more generally the Köppen climate classification which
5510-409: The climate became colder and stormier around 1250, their diet steadily shifted towards ocean sources. By around 1300, seal hunting provided over three quarters of their food. By 1350, there was reduced demand for their exports, and trade with Europe fell away. The last document from the settlements dates from 1412, and over the following decades, the remaining Europeans left in what seems to have been
5605-456: The column of the table in which he introduced the new era as " Anni Domini Nostri Jesu Christi " (Of the year of our Lord Jesus Christ]. This way of numbering years became more widespread in Europe with its use by Bede in England in 731. Bede also introduced the practice of dating years before what he supposed was the year of birth of Jesus, without a year zero . In 1422, Portugal became
5700-411: The consequences of increasing greenhouse gases in the atmosphere, primarily carbon dioxide (see greenhouse gas ). These models predict an upward trend in the global mean surface temperature , with the most rapid increase in temperature being projected for the higher latitudes of the Northern Hemisphere. Models can range from relatively simple to quite complex. Simple radiant heat transfer models treat
5795-557: The context of environmental policy , the term "climate change" often refers only to changes in modern climate, including the rise in average surface temperature known as global warming . In some cases, the term is also used with a presumption of human causation, as in the United Nations Framework Convention on Climate Change (UNFCCC). The UNFCCC uses "climate variability" for non-human caused variations. Earth has undergone periodic climate shifts in
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#17327722637555890-406: The conventional terms of 'Little Ice Age' and 'Medieval Warm Period' are chiefly documented in describing northern hemisphere trends in hemispheric or global mean temperature changes in past centuries. Global temperature records taken from ice cores, tree rings , and lake deposits have shown that the Earth may have been slightly cooler globally (by 0.03 °C or 0.1 °F) than in the early and
5985-489: The date that he believed to be the date of birth of Jesus , was conceived around the year 525 by the Christian monk Dionysius Exiguus . He did this to replace the then dominant Era of Martyrs system, because he did not wish to continue the memory of a tyrant who persecuted Christians. He numbered years from an initial reference date (" epoch "), an event he referred to as the Incarnation of Jesus. Dionysius labeled
6080-583: The dynamics of the weather and climate system to projections of future climate. All climate models balance, or very nearly balance, incoming energy as short wave (including visible) electromagnetic radiation to the Earth with outgoing energy as long wave (infrared) electromagnetic radiation from the Earth. Any imbalance results in a change in the average temperature of the Earth. Climate models are available on different resolutions ranging from >100 km to 1 km. High resolutions in global climate models require significant computational resources, and so only
6175-519: The early 20th century. The phrase "common era", in lower case , also appeared in the 19th century in a "generic" sense, not necessarily to refer to the Christian Era, but to any system of dates in common use throughout a civilization. Thus, "the common era of the Jews", "the common era of the Mahometans", "common era of the world", "the common era of the foundation of Rome". When it did refer to
6270-418: The early patterns (such as violence and health problems) have been found to be more complicated and regionally varied than had been previously thought. Other patterns, such as settlement disruption, deterioration of long-distance trade, and population movements, have been further corroborated. The climate in equatorial eastern Africa has alternated between being drier than today and relatively wet. The climate
6365-428: The entry for CE/BCE: "some people prefer CE (common era, current era, or Christian era) and BCE (before common era, etc.) to AD and BC, which, however, remain our style". In the United States, the use of the BCE/CE notation in textbooks was reported in 2005 to be growing. Some publications have transitioned to using it exclusively. For example, the 2007 World Almanac was the first edition to switch to BCE/CE, ending
6460-453: The first of which was but eight days", and also refers to the common era as a synonym for vulgar era with "the fact that our Lord was born on the 4th year before the vulgar era, called Anno Domini, thus making (for example) the 42d year from his birth to correspond with the 38th of the common era". The Catholic Encyclopedia (1909) in at least one article reports all three terms (Christian, Vulgar, Common Era) being commonly understood by
6555-421: The global temperature and produce an interglacial period. Suggested causes of ice age periods include the positions of the continents , variations in the Earth's orbit, changes in the solar output, and volcanism. However, these naturally caused changes in climate occur on a much slower time scale than the present rate of change which is caused by the emission of greenhouse gases by human activities. According to
6650-485: The grounds that BCE and CE are religiously neutral terms. They have been promoted as more sensitive to non-Christians by not referring to Jesus , the central figure of Christianity , especially via the religious terms " Christ " and Dominus ("Lord") used by the other abbreviations. Nevertheless, its epoch remains the same as that used for the Anno Domini era. The idea of numbering years beginning from
6745-459: The last Western European country to switch to the system begun by Dionysius. The term "Common Era" is traced back in English to its appearance as " Vulgar Era" to distinguish years of the Anno Domini era, which was in popular use, from dates of the regnal year (the year of the reign of a sovereign) typically used in national law. (The word 'vulgar' originally meant 'of the ordinary people', with no derogatory associations. ) The first use of
6840-673: The mean temperature of that time) during the MWP (about 950–1250) and the Little Ice Age (about 1400–1700, with cold periods persisting into the early 20th century), which are possibly related to changes in the strength of North Atlantic thermohaline circulation . Sediments in Piermont Marsh of the lower Hudson Valley show a dry MWP from 800 to 1300. In the Hammock River marsh in Connecticut , salt marshes extended 15 kilometres (9.3 mi) farther westward than they do in
6935-539: The mid-20th century. Palaeoclimatologists developing region-specific climate reconstructions of past centuries conventionally label their coldest interval as "LIA" and their warmest interval as the "MWP". Others follow the convention, and when a significant climate event is found in the "LIA" or "MWP" timeframes, they associate their events to the period. Some "MWP" events are thus wet events or cold events, rather than strictly warm events, particularly in central Antarctica , where climate patterns that are opposite to those of
7030-456: The modern time scale, their observation frequency, their known error, their immediate environment, and their exposure have changed over the years, which must be considered when studying the climate of centuries past. Long-term modern climate records skew towards population centres and affluent countries. Since the 1960s, the launch of satellites allow records to be gathered on a global scale, including areas with little to no human presence, such as
7125-404: The most common atmospheric variables (air temperature, pressure, precipitation and wind), other variables such as humidity, visibility, cloud amount, solar radiation, soil temperature, pan evaporation rate, days with thunder and days with hail are also collected to measure change in climate conditions. The difference between climate and weather is usefully summarized by the popular phrase "Climate
7220-705: The other hand, periodic variability occurs relatively regularly and in distinct modes of variability or climate patterns. There are close correlations between Earth's climate oscillations and astronomical factors ( barycenter changes, solar variation , cosmic ray flux, cloud albedo feedback , Milankovic cycles ), and modes of heat distribution between the ocean-atmosphere climate system. In some cases, current, historical and paleoclimatological natural oscillations may be masked by significant volcanic eruptions , impact events , irregularities in climate proxy data, positive feedback processes or anthropogenic emissions of substances such as greenhouse gases . Over
7315-402: The past state of the climate. It demonstrates periods of stability and periods of change and can indicate whether changes follow patterns such as regular cycles. Details of the modern climate record are known through the taking of measurements from such weather instruments as thermometers , barometers , and anemometers during the past few centuries. The instruments used to study weather over
7410-465: The past, including four major ice ages . These consist of glacial periods where conditions are colder than normal, separated by interglacial periods. The accumulation of snow and ice during a glacial period increases the surface albedo , reflecting more of the Sun's energy into space and maintaining a lower atmospheric temperature. Increases in greenhouse gases , such as by volcanic activity , can increase
7505-496: The phrase "Before Christ according to the Vulgar Æra, 6". The Merriam Webster Dictionary gives 1716 as the date of first use of the term "vulgar era" (which it defines as Christian era). The first published use of "Christian Era" may be the Latin phrase annus aerae christianae on the title page of a 1584 theology book, De Eucharistica controuersia . In 1649, the Latin phrase annus æræ Christianæ appeared in
7600-553: The phrase "before the common era" may be that in a 1770 work that also uses common era and vulgar era as synonyms, in a translation of a book originally written in German. The 1797 edition of the Encyclopædia Britannica uses the terms vulgar era and common era synonymously. In 1835, in his book Living Oracles , Alexander Campbell , wrote: "The vulgar Era, or Anno Domini; the fourth year of Jesus Christ,
7695-508: The poles in latitude in response to shifting climate zones." Climate (from Ancient Greek κλίμα 'inclination') is commonly defined as the weather averaged over a long period. The standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations. The Intergovernmental Panel on Climate Change (IPCC) 2001 glossary definition
7790-455: The present day, was even drier during the MWP. Prolonged drought was a mainstay of the Arabian climate until around 660 BP, when this hyperarid interval was terminated. There is an extreme scarcity of data from Australia for both the MWP and the LIA . However, evidence from wave-built shingle terraces for a permanently-full Lake Eyre during the 9th and the 10th centuries is consistent with
7885-632: The present due to higher sea levels. Prolonged droughts affected many parts of what is now the Western United States , especially eastern California and the west of Great Basin . Alaska experienced three intervals of comparable warmth: 1–300, 850–1200, and since 1800. Knowledge of the MWP in North America has been useful in dating occupancy periods of certain Native American habitation sites, especially in arid parts of
7980-595: The rumours and stated that the BC/AD notation would remain, with CE and BCE as an optional suggested learning activity. In 2013, the Canadian Museum of Civilization (now the Canadian Museum of History) in Gatineau (opposite Ottawa ), which had previously switched to BCE/CE, decided to change back to BC/AD in material intended for the public while retaining BCE/CE in academic content. The notation
8075-540: The same year. The expression can be traced back to 1615, when it first appears in a book by Johannes Kepler as the Latin : annus aerae nostrae vulgaris ( year of our common era ), and to 1635 in English as " Vulgar Era". The term "Common Era" can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish religious scholars. Since the late 20th century, BCE and CE have become popular in academic and scientific publications on
8170-489: The thirty-year period from 1901 to 1930 as the reference time frame for climatological standard normals. In 1982, the WMO agreed to update climate normals, and these were subsequently completed on the basis of climate data from 1 January 1961 to 31 December 1990. The 1961–1990 climate normals serve as the baseline reference period. The next set of climate normals to be published by WMO is from 1991 to 2010. Aside from collecting from
8265-417: The title of an English almanac. A 1652 ephemeris may be the first instance found so far of the English use of "Christian Era". The English phrase "Common Era" appears at least as early as 1708, and in a 1715 book on astronomy it is used interchangeably with "Christian Era" and "Vulgar Era". A 1759 history book uses common æra in a generic sense, to refer to "the common era of the Jews". The first use of
8360-497: The traditional Jewish designations – B.C.E. and C.E. – cast a wider net of inclusion." In the World History Encyclopedia , Joshua J. Mark wrote "Non-Christian scholars, especially, embraced [CE and BCE] because they could now communicate more easily with the Christian community. Jewish, Islamic, Hindu and Buddhist scholars could retain their [own] calendar but refer to events using
8455-608: The tropical Pacific Ocean suggest that relatively cool and dry conditions may have persisted early in the millennium, which is consistent with a La Niña -like configuration of the El Niño-Southern Oscillation patterns. In 2013, a study from three US universities was published in Science magazine and showed that the water temperature in the Pacific Ocean was 0.9 °C (1.6 °F) warmer during
8550-479: The variability or average state of the atmosphere over time scales ranging from decades to millions of years. These changes can be caused by processes internal to the Earth , external forces (e.g. variations in sunlight intensity) or human activities, as found recently. Scientists have identified Earth's Energy Imbalance (EEI) to be a fundamental metric of the status of global change. In recent usage, especially in
8645-546: The warming effect in fact lasted for only very briefly. Around 1000 CE the climate was sufficiently warm for the Vikings to journey to Newfoundland and to establish a short-lived outpost there. Around 985, Vikings founded the Eastern and Western Settlements , both near the southern tip of Greenland. In the colony's early stages, they kept cattle, sheep, and goats, with around a quarter of their diet from seafood. After
8740-466: The warming from the 10th to the 14th centuries in some regions might be comparable in magnitude to the warming of the last few decades of the 20th century, which was unprecedented within the past 500 years. Generally, a warming period was identified in China, coinciding with the MWP, using multi-proxy data for temperature. However, the warming was inconsistent across China. Significant temperature change, from
8835-448: The years, the definitions of climate variability and the related term climate change have shifted. While the term climate change now implies change that is both long-term and of human causation, in the 1960s the word climate change was used for what we now describe as climate variability, that is, climatic inconsistencies and anomalies. Climate change is the variation in global or regional climates over time. It reflects changes in
8930-463: Was drier during the MWP (1000–1270). Off the coast of Africa, Isotopic analysis of bones from the Canary Islands' inhabitants during the MWP to LIA transition reveal the region experienced a 5 °C (9.0 °F) decrease in air temperature. Over this period, the diet of inhabitants did not appreciably change, which suggests they were remarkably resilient to climate change . The onset of
9025-533: Was originally designed to identify the climates associated with certain biomes . A common shortcoming of these classification schemes is that they produce distinct boundaries between the zones they define, rather than the gradual transition of climate properties more common in nature. Paleoclimatology is the study of past climate over a great period of the Earth 's history. It uses evidence with different time scales (from decades to millennia) from ice sheets, tree rings, sediments, pollen, coral, and rocks to determine
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