Query: Tree-rings diverge from temperature after 1960

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Climate <=SEP=> Climate is the statistics of weather , usually over a 30-year interval . It is measured by assessing the patterns of variation in temperature , humidity , atmospheric pressure , wind , precipitation , atmospheric particle count and other meteorological variables in a given region over long periods of time . Climate differs from weather , in that weather only describes the short-term conditions of these variables in a given region .   A region 's climate is generated by the climate system , which has five components : atmosphere , hydrosphere , cryosphere , lithosphere , and biosphere .   The climate of a location is affected by its latitude , terrain , and altitude , as well as nearby water bodies and their currents . Climates can be classified according to the average and the typical ranges of different variables , most commonly temperature and precipitation . The most commonly used classification scheme was the Köppen climate classification . The Thornthwaite system , in use since 1948 , incorporates evapotranspiration along with temperature and precipitation information and is used in studying biological diversity and how climate change affects it . 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 . Since direct observations of climate are not available before the 19th century , paleoclimates are inferred from proxy variables that 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 from a variety of factors ; recent warming is discussed in global warming . Global warming results in redistributions . For example , `` a 3 ° C change in mean annual temperature corresponds to a shift in isotherms of approximately 300 -- 400 km in latitude ( in the temperate zone ) or 500 m in elevation . Therefore , species are expected to move upwards in elevation or towards the poles in latitude in response to shifting climate zones '' .

Global temperature record <=SEP=> The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time.  The most detailed information exists since 1850, when methodical thermometer-based records began.  There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch.  Older time periods are studied by paleoclimatology.

Sun <=SEP=> The Sun is the star at the center of the Solar System . It is a nearly perfect sphere of hot plasma , with internal convective motion that generates a magnetic field via a dynamo process . It is by far the most important source of energy for life on Earth . Its diameter is about 109 times that of Earth , and its mass is about 330,000 times that of Earth , accounting for about 99.86 % of the total mass of the Solar System .  About three quarters of the Sun 's mass consists of hydrogen ( ~ 73 % ) ; the rest is mostly helium ( ~ 25 % ) , with much smaller quantities of heavier elements , including oxygen , carbon , neon , and iron .   The Sun is a G-type main-sequence star ( G2V ) based on its spectral class . As such , it is informally referred to as a yellow dwarf . It formed approximately 4.6 billionAll numbers in this article are short scale . One billion is 109 , or 1,000,000,000 . years ago from the gravitational collapse of matter within a region of a large molecular cloud . Most of this matter gathered in the center , whereas the rest flattened into an orbiting disk that became the Solar System . The central mass became so hot and dense that it eventually initiated nuclear fusion in its core . It is thought that almost all stars form by this process .   The Sun is roughly middle-aged ; it has not changed dramatically for more than four billion years , and will remain fairly stable for more than another five billion years . After hydrogen fusion in its core has diminished to the point at which it is no longer in hydrostatic equilibrium , the core of the Sun will experience a marked increase in density and temperature while its outer layers expand to eventually become a red giant . It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus , and render Earth uninhabitable .   The enormous effect of the Sun on Earth has been recognized since prehistoric times , and the Sun has been regarded by some cultures as a deity . The synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar , which is the predominant calendar in use today .

Temperature record of the past 1000 years <=SEP=> For information on the description of the Medieval Warm Period and Little Ice Age in various IPCC reports see MWP and LIA in IPCC reportsThe temperature record of the past 1,000 years is reconstructed using data from climate proxy records in conjunction with the modern instrumental temperature record which only covers the last 150 years at a global scale . Large-scale reconstructions covering part or all of the 1st millennium and 2nd millennium have shown that recent temperatures are exceptional : the Intergovernmental Panel on Climate Change Fourth Assessment Report of 2007 concluded that `` Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely '' the highest in at least the past 1,300 years . '' The curve shown in graphs of these reconstructions is widely known as the hockey stick graph because of the sharp increase in temperatures during the last century . As of 2010 this broad pattern was supported by more than two dozen reconstructions , using various statistical methods and combinations of proxy records , with variations in how flat the pre-20th-century `` shaft '' appears . Sparseness of proxy records results in considerable uncertainty for earlier periods .   Individual proxy records , such as tree ring widths and densities used in dendroclimatology , are calibrated against the instrumental record for the period of overlap . Networks of such records are used to reconstruct past temperatures for regions : tree ring proxies have been used to reconstruct Northern Hemisphere extratropical temperatures ( within the tropics trees do not form rings ) but are confined to land areas and are scarce in the Southern Hemisphere which is largely ocean . Wider coverage is provided by multiproxy reconstructions , incorporating proxies such as lake sediments , ice cores and corals which are found in different regions , and using statistical methods to relate these sparser proxies to the greater numbers of tree ring records . The `` Composite Plus Scaling '' ( CPS ) method is widely used for large-scale multiproxy reconstructions of hemispheric or global average temperatures ; this is complemented by Climate Field Reconstruction ( CFR ) methods which show how climate patterns have developed over large spatial areas , making the reconstruction useful for investigating natural variability and long-term oscillations as well as for comparisons with patterns produced by climate models .   During the 1,900 years before the 20th century , it is likely that the next warmest period was from 950 to 1100 , with peaks at different times in different regions . This has been called the Medieval Warm Period , and some evidence suggests widespread cooler conditions during a period around the 17th century known as the Little Ice Age . In the hockey stick controversy , contrarians have asserted that the Medieval Warm Period was warmer than at present , and have disputed the data and methods of climate reconstructions .