query: Earth’s mean temperature over the last 2,000 years shows two previous periods when temperatures were warmer than they are now; from 1–200 A.D., an epoch called the Roman Warm Period, and more recently the Medieval Warm Period from 900–1100 A.D.

positive: Medieval Warm Period The Medieval Warm Period ( MWP ) , Medieval Climate Optimum , or Medieval Climatic Anomaly was a time of warm climate in the North Atlantic region that may also have been related to other climate events around the world during that time , including China and other areas , lasting from about 950 to 1250 . It was followed by a cooler period in the North Atlantic and elsewhere termed the Little Ice Age . Some refer to the event as the Medieval Climatic Anomaly as this term emphasizes that effects other than temperature were important .   Despite uncertainties , especially for the period prior to 1600 for which data are scarce , the warmest period of the last 2,000 years prior to the 20th century in the Northern Hemisphere very likely occurred between 950 and 1100 . Proxy records show peak warmth occurred at different times for different regions , indicating that the Medieval Warm Period was not a time of globally uniform change . Temperatures in some regions matched or exceeded recent temperatures in these regions , but globally the Medieval Warm Period was cooler than recent global temperatures .   Possible causes of the Medieval Warm Period include increased solar activity , decreased volcanic activity , and changes to ocean circulation .

negative: Global warming hiatus A global warming hiatus , also sometimes referred to as a global warming pause or a global warming slowdown , is a period of relatively little change in globally averaged surface temperatures . In the current episode of global warming many such 15-year periods appear in the surface temperature record , along with robust evidence of the long-term warming trend ; climate is classically averaged over 30-year periods .   Publicity has surrounded claims of a global warming hiatus during the period 1998 -- 2013 . The exceptionally warm El Niño year of 1998 was an outlier from the continuing temperature trend , and so subsequent annual temperatures gave the appearance of a hiatus : by January 2006 , it appeared to some that global warming had stopped or paused . A 2009 study showed that decades without warming were not exceptional , and in 2011 a study showed that if allowances were made for known variability , the rising temperature trend continued unabated . There was increased public interest in 2013 in the run-up to publication of the IPCC Fifth Assessment Report , and despite concerns that a 15-year period was too short to determine a meaningful trend , the IPCC included a section on a hiatus , which it defined as a much smaller increasing linear trend over the 15 years from 1998 to 2012 , than over the 60 years from 1951 to 2012 . Various studies examined possible causes of the short-term slowdown . Even though the overall climate system has continued to accumulate energy due to Earth 's positive energy budget , the available temperature readings at the Earth 's surface indicate slower rates of increase in surface warming than in the prior decade . Since measurements at the top of the atmosphere show that Earth is receiving more energy than it is radiating back into space , the retained energy should be producing warming in the Earth 's climate system .   Research reported in July 2015 on an updated NOAA dataset casts doubt on the existence of a hiatus , and it finds no indication of a slowdown even in earlier years . Scientists working on other datasets welcomed this study , though they have expressed the view that the recent warming trend was less than in previous periods of the same length . Subsequently , a detailed study supports the conclusion that warming is continuing , but it also find there was less warming between 2001 and 2010 than climate models had predicted , and that this slowdown might be attributed to short-term variations in the Pacific decadal oscillation ( PDO ) , which was negative during that period . Another review finds `` no substantive evidence '' of a pause in global warming . A statistical study of global temperature data since 1970 concludes that the term ` hiatus ' or ` pause ' is not justified .   Independent of these discussions about data and measurements for earlier years , 2015 turned out to be much warmer than any of the earlier years , already before El Niño conditions started . The warmth of 2015 largely ended any remaining scientific credibility of claims that the supposed `` hiatus '' since 1998 had any significance for the long-term warming trend . In January 2017 , a study published in the journal Science Advances cast further doubt on the existence of a recent pause , with more evidence that ocean temperatures have been underestimated . An April 2017 study found the data consistent with a steady warming trend globally since the 1970s , with fluctuations within the expected range of short term variability .

negative: Holocene climatic optimum The Holocene Climate Optimum ( HCO ) was a warm period during roughly the interval 9,000 to 5,000 years BP . This event has also been known by many other names , including : Hypsithermal , Altithermal , Climatic Optimum , Holocene Optimum , Holocene Thermal Maximum , and Holocene Megathermal .   This warm period was followed by a gradual decline until about two millennia ago .  For other temperature fluctuations see : Temperature record  For other past climate fluctuation see : Paleoclimatology  For the pollen zone and Blytt-Sernander period associated with the climate optimum , see : Atlantic ( period )

negative: Temperature record of the past 1000 years 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 .

negative: Cool tropics paradox The cool tropics paradox refers to an apparent difference between modeled estimates of tropical temperatures during warm , ice-free periods of the Cretaceous and Eocene , and the colder temperatures which proxies suggested were present . The long-standing paradox was resolved when novel proxy derived temperatures showed significantly warmer tropics during past greenhouse climates . The low-gradient problem , i.e. the very warm polar regions with respect to present day , is still an issue for state-of-the-art climate models .

negative: Younger Dryas The Younger Dryas is a geological period from c. 12,900 to c. 11,700 calendar years ago ( BP ) . It is named after an indicator genus , the alpine-tundra wildflower Dryas octopetala . Leaves of Dryas octopetala are occasionally abundant in the Late Glacial , often minerogenic-rich , like the lake sediments of Scandinavian lakes . The Younger Dryas saw a sharp decline in temperature over most of the northern hemisphere , at the end of the Pleistocene epoch , immediately before the current warmer Holocene . It was the most recent and longest of several interruptions to the gradual warming of the Earth 's climate since the severe Last Glacial Maximum , c. 27,000 to 24,000 calendar years BP . The change was relatively sudden , taking place in decades , and resulted in a decline of 2 to 6 degrees Celsius , advances of glaciers and drier conditions , over much of the temperate northern hemisphere . It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation , which transports warm water from the equator towards the North Pole , and which in turn is thought to have been caused by an influx of fresh cold water from North America into the Atlantic . The Younger Dryas was a period of climatic change , but the effects were complex and variable . In the southern hemisphere , and some areas of the north such as southeastern North America , there was a slight warming .   The presence of a distinct cold period at the end of the Late Glacial interval has been known for a long time . Paleobotanical and lithostratigraphic studies of Swedish and Danish bog and lake sites , e.g. the Allerød clay pit in Denmark , first recognized and described the Younger Dryas .   The Younger Dryas is the youngest and longest of three stadials that resulted from typically abrupt climatic changes that took place over the last 16,000 calendar years . Within the Blytt-Sernander classification of north European climatic phases , the prefix ` Younger ' refers to the recognition that this original ` Dryas ' period was preceded by a warmer stage , the Allerød oscillation , which in turn was preceded by the Older Dryas around 14,000 calendar years BP . This is not securely dated , and estimates vary by 400 years , but it is generally accepted that it lasted around 200 years . In northern Scotland the glaciers were thicker and more extensive than during the Younger Dryas . The Older Dryas , in turn , is preceded by another warmer stage , the Bølling oscillation that separates it from a third and even older stadial . This stadial is often , but not always , known as the Oldest Dryas . The Oldest Dryas occurred approximately 1,770 calendar years before the Younger Dryas and lasted about 400 calendar years . According to the GISP2 ice core from Greenland , the Oldest Dryas occurred between about 15,070 and 14,670 calendar years BP .   In Ireland , the Younger Dryas has also been known as the Nahanagan Stadial , while in Great Britain it has been called the Loch Lomond Stadial . In the Greenland Summit ice core chronology , the Younger Dryas corresponds to Greenland Stadial 1 ( GS-1 ) . The preceding Allerød warm period ( interstadial ) is subdivided into three events : Greenland Interstadial-1c to 1a ( GI-1c to GI-1a ) .

negative: Paleocene–Eocene Thermal Maximum The Paleocene -- Eocene Thermal Maximum ( PETM ) , alternatively ( ETM1 ) , and formerly known as the `` Initial Eocene '' or '' '' was a time period with more than 8 ° C warmer global average temperature than today . This climate event began at the time boundary between the Paleocene and Eocene geological epochs . The exact age and duration of the event is uncertain but it is estimated to have occurred around 55.5 million years ago .   The associated period of massive carbon injection into the atmosphere has been estimated to have lasted no longer than 20,000 years . The entire warm period lasted for about 200,000 years . Global temperatures increased by 5 -- 8 ° C . The carbon dioxide was likely released in two pulses , the first lasting less than 2,000 years . Such a repeated carbon release is in line with current global warming . A main difference is that during the Paleocene -- Eocene Thermal Maximum , the planet was essentially ice-free .   The onset of the Paleocene -- Eocene Thermal Maximum has been linked to an initial 5 ° C temperature rise and to extreme changes in Earth 's carbon cycle . The period is marked by a prominent negative excursion in carbon stable isotope records from around the globe ; more specifically , there was a large decrease in 13C/12C ratio of marine and terrestrial carbonates and organic carbon .   Stratigraphic sections of rock from this period reveal numerous other changes . Fossil records for many organisms show major turnovers . For example , in the marine realm , a mass extinction of benthic foraminifera , a global expansion of subtropical dinoflagellates , and an appearance of excursion , planktic foraminifera and calcareous nanofossils all occurred during the beginning stages of PETM . On land , modern mammal orders ( including primates ) suddenly appear in Europe and in North America . Sediment deposition changed significantly at many outcrops and in many drill cores spanning this time interval .   At least since 1997 , the Paleocene -- Eocene Thermal Maximum has become a focal point of considerable geoscience research because it probably provides the best past analog by which to understand impacts of global climate warming and of massive carbon input to the ocean and atmosphere , including ocean acidification . Although it is now widely accepted that the PETM represents a `` case study '' for global warming and massive carbon input to Earth 's surface , the cause , details and overall significance of the event remain perplexing .

negative: Pliocene climate During the Pliocene epoch ( 5.3 Ma to 2.6 Ma ) climate became cooler and drier , and seasonal , similar to modern climates .   The global average temperature in the mid-Pliocene ( 3.3 Ma -- 3 Ma ) was 2 -- 3 ° C higher than today , global sea level 25m higher and the northern hemisphere ice sheet was ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma .  The formation of an Arctic ice cap is signaled by an abrupt shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic and North Pacific ocean beds . Mid-latitude glaciation was probably underway before the end of the epoch . The global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas .   During the Pliocene the earth climate system response shifted from a period of high frequency-low amplitude oscillation dominated by the 41,000-year period of Earth 's obliquity to one of low-frequency , high-amplitude oscillation dominated by the 100,000-year period of the orbital eccentricity characteristic of the Pleistocene glacial-interglacial cycles .   The equatorial pacific ocean sea surface temperature gradient was considerably lower than it is today , mean sea surface temperature in the east were substantially warmer than today but similar in the west , this condition has been described as a permanent El Niño state or El Padre

negative: Marine isotope stage Marine isotope stages ( MIS ) , marine oxygen-isotope stages , or oxygen isotope stages ( OIS ) , are alternating warm and cool periods in the Earth 's paleoclimate , deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples . Working backwards from the present , which is MIS 1 in the scale , stages with even numbers have high levels of oxygen-18 and represent cold glacial periods , while the odd-numbered stages are troughs in the oxygen-18 figures , representing warm interglacial intervals . The data are derived from pollen and foraminifera ( plankton ) remains in drilled marine sediment cores , sapropels , and other data that reflect historic climate ; these are called proxies .   The MIS timescale was developed from the pioneering work of Cesare Emiliani in the 1950s , and is now widely used in archaeology and other fields to express dating in the Quaternary period ( the last 2.6 million years ) , as well as providing the fullest and best data for that period for paleoclimatology or the study of the early climate of the Earth , representing `` the standard to which we correlate other Quaternary climate records '' . Emiliani 's work in turn depended on Harold Urey 's prediction in a paper of 1947 that the ratio between oxygen-18 and oxygen-16 isotopes in calcite , the main chemical component of the shells and other hard parts of a wide range of marine organisms , should vary depending on the prevailing water temperature in which the calcite was formed .   Over 100 stages have been identified , going currently back some 6 million years , and the scale may in future reach back up to 15 mya . Some stages , in particular MIS 5 , are divided into sub-stages , such as `` MIS 5a '' , with 5 a , c , and e being warm and b and d cold . A numeric system for referring to `` horizons '' ( events rather than periods ) may also be used , with for example MIS 5.5 representing the peak point of MIS 5e , and 5.51 , 5.52 etc. representing the peaks and troughs of the record at a still more detailed level . For more recent periods , increasingly precise resolution of timing continues to be developed .

negative: Polar forests of the Cretaceous Cretaceous polar forests were temperate forests that grew at polar latitudes during the final period of the Mesozoic Era , known as the Cretaceous Period 145 -- 66 Ma . During this period , global average temperature was about 10 C-change higher and carbon dioxide ( CO2 ) levels were approximately 1000 parts per million ( ppm ) , 2.5 times the current concentration in Earth 's atmosphere . The abundance of atmospheric carbon dioxide had a very significant impact on global climate and Earth 's natural systems as its concentration is considered one of the main factors in the development of a pronounced greenhouse Earth during the Cretaceous with a very low average global temperature gradient . As a consequence , high paleolatitudes in both hemispheres were much warmer than at present . This temperature gradient was partly responsible for the lack of continental ice sheets in polar regions .   As a response to elevated global temperatures , the Earth 's hydrologic cycle was significantly enhanced due to greater volume of moisture evaporation from the surface of the ocean . In turn , the absolute sea level during this time period stood at elevations much higher than the present level . Continental encroachment of seawater formed widespread shallow seas , including expanses of epeiric seas .   An increase in surface area between shallow , warm epeiric seawater and the atmosphere permits higher evaporation rates and more precipitation at various latitudes , producing a more temperate global climate . A widespread temperate climate also had significant effects on high latitude ecosystems .

negative: 2013 heatwave in Ireland and the United Kingdom The 2013 heat wave in the United Kingdom and Ireland was a period of unusually hot weather primarily in July 2013 , with isolated warm days in June and August . A prolonged high pressure system over Britain and Ireland caused higher than average temperatures for 19 consecutive days in July , reaching 33.5 ° C at Heathrow and Northolt . Following a brief period of cooler weather at the end of July , temperatures temporarily rose again , peaking at 34.1 ° C on 1 August in the United Kingdom , the warmest the country had seen since July 2006 , and 31.0 ° C in Ireland . At 19 days , the July heatwave was the longest continuous period of hot weather in the UK since August 1997 .   However , in the general sense , Britain did not have an overall exceptional summer ; the country experienced cool low pressure systems brought by an unseasonably low latitude by the jet stream for the 6 summers previous , which made the summer of 2013 more `` welcome '' and feel warmer than other summers . The historical records suggests `` Using the CET record ( for June , July & August ) , the average temperature by that measure was 16.3 degC ( Provisional ) : neither June nor August was exceptionally warm , so this value does not ` rate ' too highly when set against other very warm summer seasons . '' With June being a cool month and August being an Average month , in terms of temperatures the English Central summer temperature ended up being on the average side set up against previous summers since the CET series began in 1659 .

negative: Flandrian interglacial The Flandrian interglacial or stage is the name given by geologists and archaeologists in the British Isles to the first , and so far only , stage of the Holocene epoch ( the present geological period ) , covering the period from around 12,000 years ago , at the end of the last glacial period to the present day . As such , it is in practice identical in span to the Holocene . Present climatological theory ( based on analysis of Milankovitch cycles ) forecasts that the present Flandrian climate should decline in temperature towards a global climate similar to that of the ice age . Less orbital eccentricity may have the effect of moderating this temperature downturn .   The Flandrian began as the relatively short-lived Younger Dryas climate downturn came to an end . This formed the last gasp of the Devensian glaciation , the final stage of the Pleistocene epoch and is traditionally seen as the latest warm interglacial in a series that has been occurring throughout the Quaternary geological period .   The first part of the Flandrian , known as the Younger Atlantic , was a period of fairly rapid sea level rise , known as the Flandrian transgression and associated with the melting of the Fenno-Scandian , Scottish , Laurentide and Cordilleran glaciers .   Fjords were formed during the Flandrian transgression when U-shaped glaciated valleys were inundated with water .

negative: Sea surface temperature Sea surface temperature ( SST ) is the water temperature close to the ocean 's surface . The exact meaning of surface varies according to the measurement method used , but it is between 1 mm and 20 m below the sea surface . Air masses in the Earth 's atmosphere are highly modified by sea surface temperatures within a short distance of the shore . Localized areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass . Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth 's oceans . Tropical cyclones can also cause a cool wake , due to turbulent mixing of the upper 30 m of the ocean . SST changes diurnally , like the air above it , but to a lesser degree . There is less SST variation on breezy days than on calm days . In addition , ocean currents such as the Atlantic Multidecadal Oscillation ( AMO ) , can effect SST 's on multi-decadal time scales , a major impact results from the global thermohaline circulation , which affects average SST significantly throughout most of the world 's oceans .   Coastal SSTs can cause offshore winds to generate upwelling , which can significantly cool or warm nearby landmasses , but shallower waters over a continental shelf are often warmer . Onshore winds can cause a considerable warm-up even in areas where upwelling is fairly constant , such as the northwest coast of South America . Its values are important within numerical weather prediction as the SST influences the atmosphere above , such as in the formation of sea breezes and sea fog . It is also used to calibrate measurements from weather satellites .

negative: Biber-Danube interglacial The Biber-Danube interglacial ( Biber-Donau-Interglazial ) or Biber-Danube warm period ( Biber-Donau-Warmzeit ) is the oldest named warm period of the Pleistocene epoch in the Alps . It falls between the Biber and Danube glaciations .

negative: Wibjörn Karlén Wibjörn Karlén ( born 26 August 1937 in Kristine , Kopparberg County , Sweden ) , Ph.D. , is a professor emeritus of physical geography and quaternary geology at Stockholm University , Sweden .   In an article which describes Karlén as a paleoclimatologist , he is quoted as saying : `` One of the big problems with trying to determine long-term temperature changes , is that weather records only go back to about 1860 . By relying on statistical reconstruction of the last 1000 years , using only the temperature patterns of the last 140 years instead of actual temperature readings , the IPCC report and Summary missed both a major cooling period as well as a significant warming trend during that millennium . '' Karlén has also criticized the mainstream media for `` spreading the exaggerated views of a human impact on climate . '' He was also named in a 2007 minority report of the U.S. Senate Environment and Public Works Committee as one of 400 `` prominent scientists '' who were said to dispute global warming . In 2010 , he predicted that natural climate changes , caused to a large degree by the sun 's activity , would more likely make the climate colder than warmer in the next decades .   He is a contributing author to the Fraser Institute 2007 Independent Summary for Policymakers .   Karlén is a member of the Royal Swedish Academy of Sciences .

negative: Climate of Moscow Moscow has a humid continental climate ( Köppen climate classification Dfb ) with warm , sometimes hot , somewhat humid summers and long , cold winters .  Typical high temperatures in the warm months of June , July and August are around 23 ° C , but during heat waves , which can occur anytime from May to September , daytime temperature highs often top 30 ° C for sometimes one or two weeks . In the winter , temperatures normally drop to approximately -10 ° C , though there can be periods of warmth with temperatures rising above 0 ° C. Summer lasts from mid-May to the beginning of September . Winter lasts from the beginning of November to the end of March .

negative: Deglaciation Deglaciation describes the transition from full glacial conditions during ice ages , to warm interglacials , characterized by global warming and sea level rise due to change in continental ice volume ( IPCC AR5 ) . Thus , it refers to the retreat of a glacier , an ice sheet or frozen surface layer , and the resulting exposure of the Earth 's surface . The decline of the cryosphere due to ablation can occur on any scale from global to localized to a particular glacier . After the Last Glacial Maximum ( ca. 21k years ago ) , the last deglaciation begun , which lasted until the early Holocene .   The previous deglaciation took place between approximately 22ka until 11.5 ka . This occurred when there was an annual mean atmospheric temperature on the earth that increased by roughly 5 ° C , which was also accompanied by regional high-latitude warming that exceeded 10 ° C . This was also followed by noteworthy deep-sea and tropical-se warming , between about 1-2 ° C ( deep-sea ) and 2-4 ° C ( tropical sea ) . Not only did this warming occur , but the global hydrological budget also experienced noticeable changes and regional precipitation patters changed . As a result of all of this , the worlds main ice sheets , including the ones located in Eurasia , North America and parts of the Antarctic Ice Sheets melted . As a consequence , sea levels rose roughly 120 metres ) . These processes did not occur steadily , and they also did not occur at the same time .

negative: March 2012 North American heat wave In March 2012 , one of the greatest heat waves was observed in many regions of North America . Very warm air pushed northward west of the Great Lakes region , and subsequently spread eastward . The intense poleward air mass movement was propelled by an unusually intense low level southerly jet that stretched from Louisiana to western Wisconsin . Once this warm surge inundated the area , a remarkably prolonged period of record setting temperatures ensued .   NOAA 's National Climate Data Center reported that over 7,000 daily record high temperatures were tied or broken from 1 March through 27 March . In some places the temperature exceeded 86 ° F ( 30 ° C ) . For instance , in Grand Rapids , Michigan , the highest temperature recorded was 87 ° F on March 21 ; in Chicago a high of 87 ° F was also recorded on that same day . Records were broken in unusual ways . Chicago , for example , saw temperatures above 80 ° F every day between March 14 -- 18 , breaking records on all five days . Chicago would go on to record eight days at or above 80 ° F during the month , with many suburban areas recording an additional day in the 80s on March 19 ( that day , the city only tied its record high of 78 ° F ) . In context , the National Weather Service 's Chicago branch noted that Chicago typically averages only one day in the 80 's in April . And only once in 140 years of weather observations has April produced as many 80 ° F days as this March . In Traverse City , Michigan one day began with a low temperature ( 67 ° F ) higher than the previous record high for the day .   Temperature records across much of southern Canada also were shattered . Some of the most impressive readings came from Nova Scotia on March 22 , when the mercury climbed to 30.0 C at a climate station in Lake Major , making it the highest March temperature recorded in Nova Scotia , and the third highest March temperature recorded in Canada . That same day , the temperature hit 29.2 C at Western Head , Nova Scotia . The heat reached as far east as Cape Breton Island , with the temperature climbing to 24.0 C at Sydney , Nova Scotia on March 22 , a place historically surrounded by ice-jammed waters , frigid winds , and snow in March . The week of March 18 also set record temperatures in Manitoba and much of Ontario as well as into the Maritime Provinces . Non-severe thunderstorms were reported on the evening hours of March 21 , through to the early morning hours March 22 into northern Ontario .   In addition , NCEP/NCAR Reanalysis data show that the atmospheric pattern was so persistent that much of the Midwest and Northeast , and up into Ontario , had temperature departures over periods of several days to a week or more of magnitudes which would be unusual even for a single day . Averaged over the seven-day period from March 16 to March 22 inclusive , nearly the entire area of the Midwest and Northeast U.S. and most of Ontario and Quebec had temperatures 10 ° C ( 18 ° F ) or more above the 1981-2010 average . Even more dramatically , most of Iowa and Minnesota , all of Wisconsin and Michigan , and most of southeastern Ontario had seven-day mean temperatures more than 15 ° C ( 27 ° F ) above the climatological average for the same period .   An 84 ° F high at Madison , WI in early March was 43 ° F above average and followed an overnight low of 60 ° F , 35 degrees above normal the daily high being more than seven standard deviations above the mean . The absolute temperature and departure statistically would be equivalent to a mid-July high at that station in excess of 125 ° F or more ; the highest temperature recorded there was 107 ° at least once during the heat waves of the middle 1930s .   This mild warm spell brought out spring peepers in northern Ontario on 23 March , which are usually not heard until mid-to-late April , or sometimes early May .   The warm weather was also responsible for several early-season tornado touchdowns , such as the EF3 that struck Dexter , Michigan , near Ann Arbor .

negative: Older Dryas The Older Dryas was a stadial ( cold ) period between the Bølling and Allerød interstadials ( warmer phases ) approximately 14,000 years ago ( BP ) , towards the end of the Pleistocene epoch . Its age is not well defined , with estimates varying by 400 years , but its duration is agreed to have been around two centuries . The gradual warming since the last glacial maximum 27-24 ,000 years BP has been interrupted by two cold spells , the Older Dryas having been followed by the Younger Dryas ( c. 12,900-11 ,650 BP ) . In northern Scotland the glaciers were thicker and deeper during the Older than the succeeding Younger Dryas , and there is no evidence of human occupation of Britain . In north-west Europe an earlier Oldest Dryas is also recognised . They are named after an indicator genus , the arctic and alpine plant Dryas , the remains of which are found in higher concentrations in deposits from colder periods .   The Older Dryas was a variable cold , dry Blytt-Sernander period , observed in climatological evidence in only some regions , depending on latitude . In regions where it is not observed , the Bølling-Allerød is considered a single interstadial ( warm ) period . Evidence of the Older Dryas is strongest in northern Eurasia , particularly part of North Europe roughly equivalent to Pollen zone Ic .

negative: Pliocene The Pliocene ( -LSB- pronˈplaɪəˌsiːn -RSB- also Pleiocene ) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP . It is the second and youngest epoch of the Neogene Period in the Cenozoic Era . The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch . Prior to the 2009 revision of the geologic time scale , which placed the four most recent major glaciations entirely within the Pleistocene , the Pliocene also included the Gelasian stage , which lasted from 2.588 to 1.806 million years ago , and is now included in the Pleistocene .   As with other older geologic periods , the geological strata that define the start and end are well identified but the exact dates of the start and end of the epoch are slightly uncertain . The boundaries defining the Pliocene are not set at an easily identified worldwide event but rather at regional boundaries between the warmer Miocene and the relatively cooler Pliocene . The upper boundary was set at the start of the Pleistocene glaciations .

negative: Polar amplification Polar amplification is the phenomenon that any change in the net radiation balance ( for example greenhouse intensification ) tends to produce a larger change in temperature near the poles than the planetary average . On a planet with an atmosphere that can restrict longwave radiation to space ( a greenhouse effect ) , surface temperatures will be warmer than a simple planetary equilibrium temperature calculation would predict . Where the atmosphere or an extensive ocean is able to convect heat polewards , the poles will be warmer and equatorial regions cooler than their local net radiation balances would predict .   In the extreme , the planet Venus is thought to have experienced a very large increase in greenhouse effect over its lifetime , so much so that its poles have warmed sufficiently to render its surface temperature effectively isothermal ( no difference between poles and equator ) . On Earth , water vapor and trace gasses provide a lesser greenhouse effect , and the atmosphere and extensive oceans provide efficient poleward heat transport . Both palaeoclimate changes and recent global warming changes have exhibited strong polar amplification , as described below .

negative: Waalian interglacial The Waalian interglacial ( Waal-Warmzeit or Waal-Interglazial ) ( Zagwijn , 1960 ) was an interglacial in northern Europe that lasted from about 1.45 million to 1.20 million years ago . It thus lies entirely within the Old Pleistocene and is thus part of the Cenozoic . Its name is derived from a major branch of the Rhine delta , the Waal . The Waal warm period could correspond temporally to the Danube-Gunz interglacial of the northern Alpine Foreland .   The warm period lies wholly within the Matuyama epoch , in which the earth 's magnetic field , with a few exceptions , had a different polarity from that today : the magnetic north pole ( actually corresponding to the magnetic south ) lay near the geographic south pole .

negative: Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages : the Langhian and Serravallian stages . The Middle Miocene is preceded by the Early Miocene .   The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma ( million years ago ) . During this period , a sharp drop in global temperatures took place . This event is known as the Middle Miocene Climate Transition .   For the purposes of establishing European Land Mammal Ages this sub-epoch is equivalent to the Astaracian age .

negative: Global cooling Global cooling was a conjecture during the 1970s of imminent cooling of the Earth 's surface and atmosphere culminating in a period of extensive glaciation . This hypothesis had little support in the scientific community , but gained temporary popular attention due to a combination of a slight downward trend of temperatures from the 1940s to the early 1970s and press reports that did not accurately reflect the full scope of the scientific climate literature , which showed a larger and faster-growing body of literature projecting future warming due to greenhouse gas emissions . The current scientific opinion on climate change is that the Earth has not durably cooled , but underwent global warming throughout the 20th century .

negative: Temperature record For extreme records instead of records as a set of data , see List of weather records   The 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 .

negative: El Niño–Southern Oscillation El Niño -- Southern Oscillation ( ENSO ) is an irregularly periodical variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean , affecting much of the tropics and subtropics . The warming phase is known as El Niño and the cooling phase as La Niña . Southern Oscillation is the accompanying atmospheric component , coupled with the sea temperature change : El Niño is accompanied with high , and La Niña with low air surface pressure in the tropical western Pacific . The two periods last several months each ( typically occur every few years ) and their effects vary in intensity .   The two phases relate to the Walker circulation , discovered by Gilbert Walker during the early twentieth century . The Walker circulation is caused by the pressure gradient force that results from a high pressure system over the eastern Pacific Ocean , and a low pressure system over Indonesia . When the Walker circulation weakens or reverses , an El Niño results , causing the ocean surface to be warmer than average , as upwelling of cold water occurs less or not at all . An especially strong Walker circulation causes a La Niña , resulting in cooler ocean temperatures due to increased upwelling .   Mechanisms that cause the oscillation remain under study . The extremes of this climate pattern 's oscillations cause extreme weather ( such as floods and droughts ) in many regions of the world . Developing countries dependent upon agriculture and fishing , particularly those bordering the Pacific Ocean , are the most affected .

negative: Kumud Kumud is a tribal area in Fujairah , United Arab Emirates .   Kumud is almost totally mountainous . The weather is seasonal , although it is warm most of the year . The months from October to March are generally regarded as the coolest , with daytime temperatures averaging around 25 C and rarely venturing above 30 C . The winter period also coincides with the rainy season . Rainfall is higher than the rest of the UAE because of the effect of the Hajar mountains and the easterly winds bringing with them water-laden clouds off the warm Gulf of Oman in the Indian Ocean . The temperatures climb above 40 C degrees in the summer .

negative: Leon County Pleistocene coastal terraces Leon County Pleistocene coastal terraces and shorelines were the geologic result of warming and cooling periods in what is now Leon County , Florida during the Pleistocene epoch .

negative: Pacific decadal oscillation The Pacific Decadal Oscillation ( PDO ) is a robust , recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin . The PDO is detected as warm or cool surface waters in the Pacific Ocean , north of 20 ° N. Over the past century , the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales ( meaning time periods of a few years to as much as time periods of multiple decades ) . There is evidence of reversals in the prevailing polarity ( meaning changes in cool surface waters versus warm surface waters within the region ) of the oscillation occurring around 1925 , 1947 , and 1977 ; the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean . This climate pattern also affects coastal sea and continental surface air temperatures from Alaska to California .   During a `` warm '' , or `` positive '' , phase , the west Pacific becomes cooler and part of the eastern ocean warms ; during a `` cool '' or `` negative '' phase , the opposite pattern occurs . The Pacific Decadal Oscillation was named by Steven R. Hare , who noticed it while studying salmon production pattern results in 1997 .   The Pacific Decadal Oscillation index is the leading empirical orthogonal function ( EOF ) of monthly sea surface temperature anomalies ( SST-A ) over the North Pacific ( poleward of 20 ° N ) after the global average sea surface temperature has been removed . This PDO index is the standardized principal component time series . A PDO ` signal ' has been reconstructed to 1661 through tree-ring chronologies in the Baja California area .

negative: Attribution of recent climate change Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent climate changes on Earth , commonly known as ` global warming ' . The effort has focused on changes observed during the period of instrumental temperature record , when records are most reliable ; particularly in the last 50 years , when human activity has grown fastest and observations of the troposphere have become available . The dominant mechanisms are anthropogenic , i.e. , the result of human activity . They are :  increasing atmospheric concentrations of greenhouse gases  global changes to land surface , such as deforestation  increasing atmospheric concentrations of aerosols .   There are also natural mechanisms for variation including climate oscillations , changes in solar activity , and volcanic activity .   According to the Intergovernmental Panel on Climate Change ( IPCC ) , it is `` extremely likely '' that human influence was the dominant cause of global warming between 1951 and 2010 . The IPCC defines `` extremely likely '' as indicating a probability of 95 to 100 % , based on an expert assessment of all the available evidence .   Multiple lines of evidence support attribution of recent climate change to human activities :  A basic physical understanding of the climate system : greenhouse gas concentrations have increased and their warming properties are well-established .  Historical estimates of past climate changes suggest that the recent changes in global surface temperature are unusual .  Computer-based climate models are unable to replicate the observed warming unless human greenhouse gas emissions are included .  Natural forces alone ( such as solar and volcanic activity ) can not explain the observed warming .   The IPCC 's attribution of recent global warming to human activities is a view shared by the scientific community , and is also supported by 196 other scientific organizations worldwide ( see also : scientific opinion on climate change ) .

negative: Global cooling (disambiguation) Global cooling was a 1970s conjecture about global climate change .   Global cooling may also refer to :  In general , one of the means by which Earth can undergo climate change  Climate change denial , including contrarian views about global warming in the 20th and 21st centuries  Cooling periods on the multimillion-year scale in the geologic temperature record  Geophysical global cooling , a conjecture about the formation of natural features that was made obsolete by the theory of plate tectonics  Little Ice Age , a period from the 16th to 19th centuries characterized by cooling and coincident with below average sunspots frequency

negative: Color temperature The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source . Color temperature is a characteristic of visible light that has important applications in lighting , photography , videography , publishing , manufacturing , astrophysics , horticulture , and other fields . In practice , color temperature is meaningful only for light sources that do in fact correspond somewhat closely to the radiation of some black body , i.e. , those on a line from reddish/orange via yellow and more or less white to blueish white ; it does not make sense to speak of the color temperature of , e.g. , a green or a purple light . Color temperature is conventionally expressed in kelvins , using the symbol K , a unit of measure for absolute temperature .   Color temperatures over 5000 K are called `` cool colors '' ( bluish white ) , while lower color temperatures ( 2700 -- 3000 K ) are called `` warm colors '' ( yellowish white through red ) . `` Warm '' in this context is an analogy to radiated heat flux of traditional incandescent lighting rather than temperature . The spectral peak of warm-coloured light is closer to infrared , and most natural warm-coloured light sources emit significant infrared radiation . The fact that `` warm '' lighting in this sense actually has a `` cooler '' color temperature often leads to confusion .

negative: Regional effects of global warming Regional effects of global warming are long-term significant changes in the expected patterns of average weather of a specific region due to global warming . The world average temperature is rising due to the greenhouse effect caused by increasing levels of greenhouse gases , especially carbon dioxide . When the global temperature changes , the changes in climate are not expected to be uniform across the Earth . In particular , land areas change more quickly than oceans , and northern high latitudes change more quickly than the tropics , and the margins of biome regions change faster than do their cores .   Regional effects of global warming vary in nature . Some are the result of a generalised global change , such as rising temperature , resulting in local effects , such as melting ice . In other cases , a change may be related to a change in a particular ocean current or weather system . In such cases , the regional effect may be disproportionate and will not necessarily follow the global trend . The increasing temperatures from greenhouse gases have been causing sea levels to rise for many years .   There are three major ways in which global warming will make changes to regional climate : melting or forming ice , changing the hydrological cycle ( of evaporation and precipitation ) and changing currents in the oceans and air flows in the atmosphere . The coast can also be considered a region , and will suffer severe impacts from sea level rise .


query: Humans survived past climate changes

positive: Paleolithic The Paleolithic -LSB- ˌpæliːəˈlɪθᵻk -RSB- age is a prehistoric period of human history distinguished by the development of the most primitive stone tools and covers roughly 95 % of human technological prehistory . It extends from the earliest known use of stone tools , probably by Homo habilis initially , 2.6 million years ago , to the end of the Pleistocene around 10,000 BP .   The Paleolithic era is followed by the Mesolithic . The date of the Paleolithic -- Mesolithic boundary may vary by locality as much as several thousand years .   During the Paleolithic period , humans grouped together in small societies such as bands , and subsisted by gathering plants and fishing , hunting or scavenging wild animals . The Paleolithic is characterized by the use of knapped stone tools , although at the time humans also used wood and bone tools . Other organic commodities were adapted for use as tools , including leather and vegetable fibers ; however , due to their nature , these have not been preserved to any great degree . Surviving artifacts of the Paleolithic era are known as paleoliths .   About 50,000 years ago , there was a marked increase in the diversity of artifacts . For the first time in Africa , bone artifacts and the first art appear in the archaeological record . The first evidence of human fishing is also noted , from artifacts in places such as Blombos cave in South Africa . Firstly among the artifacts of Africa , archaeologists found they could differentiate and classify those of less than 50,000 years into many different categories , such as projectile points , engraving tools , knife blades , and drilling and piercing tools . The new technology generated a population explosion of modern humans which is believed to have led to the extinction of the Neanderthals .   Humankind gradually evolved from early members of the genus Homo -- such as Homo habilis , who used simple stone tools -- into fully behaviorally and anatomically modern humans ( Homo sapiens sapiens ) during the Paleolithic era . During the end of the Paleolithic , specifically the Middle and or Upper Paleolithic , humans began to produce the earliest works of art and engage in religious and spiritual behavior such as burial and ritual . The climate during the Paleolithic consisted of a set of glacial and interglacial periods in which the climate periodically fluctuated between warm and cool temperatures . Archaeological and genetic data suggest that the source populations of Paleolithic humans survived in sparsely wooded areas and dispersed through areas of high primary productivity while avoiding dense forest cover .   By BP , the first humans set foot in Australia . By BP , humans lived at 61 ° N latitude in Europe . By BP , Japan was reached , and by BP humans were present in Siberia , above the Arctic Circle . At the end of the Upper Paleolithic , a group of humans crossed Beringia and quickly expanded throughout the Americas .   The term `` Paleolithic '' was coined by archaeologist John Lubbock in 1865 . It derives from Greek : παλαιός , palaios , `` old '' ; and λίθος , lithos , `` stone '' , meaning `` old age of the stone '' or `` Old Stone Age '' .

positive: Holocene extinction The Holocene extinction , otherwise referred to as the Sixth extinction or Anthropocene extinction , is the ongoing extinction event of species during the present Holocene epoch , mainly due to human activity . The large number of extinctions spans numerous families of plants and animals , including mammals , birds , amphibians , reptiles and arthropods . With widespread degradation of highly biodiverse habitats such as coral reefs and rainforest , as well as other areas , the vast majority of these extinctions is thought to be undocumented . According to the species-area theory , and based on upper-bound estimating , the present rate of extinction may be up to 140,000 species per year , making it the greatest loss of biodiversity since the Cretaceous -- Paleogene extinction event .   The Holocene extinction includes the disappearance of large land animals known as megafauna , starting at the end of the last Ice Age . Megafauna outside of the African continent , which did not evolve alongside humans , proved highly sensitive to the introduction of new predation , and many died out shortly after early humans began spreading and hunting across the Earth ( additionally , many African species have also gone extinct in the Holocene ) . These extinctions , occurring near the Pleistocene -- Holocene boundary , are sometimes referred to as the Quaternary extinction event .   The arrival of humans on different continents coincides with megafaunal extinction . The most popular theory is that human overhunting of species added to existing stress conditions . Although there is debate regarding how much human predation affected their decline , certain population declines have been directly correlated with human activity , such as the extinction events of New Zealand and Hawaii . Aside from humans , climate change may have been a driving factor in the megafaunal extinctions , especially at the end of the Quaternary .   The ecology of humanity has been noted as being that of an unprecedented `` global superpredator '' that regularly preys on the adults of other apex predators and has worldwide effects on food webs . Extinctions of species have occurred on every land mass and ocean , with many famous examples within Africa , Asia , Europe , Australia , North and South America , and on smaller islands . Overall , the Holocene extinction can be characterized by the human impact on the environment . The Holocene extinction continues into the 21st century , with meat consumption , overfishing , ocean acidification and the amphibian crisis being a few broader examples of an almost universal , cosmopolitan decline in biodiversity . A ballooning human population along with profligate consumption are considered to be the primary drivers of this rapid decline .

positive: Quaternary extinction event The Quaternary period saw the extinctions of numerous predominantly larger , especially megafaunal , species , many of which occurred during the transition from the Pleistocene to the Holocene epoch . However , this extinction wave did not stop at the end of the Pleistocene , but continued , especially on isolated islands , in human-caused extinctions , although there is debate as to whether these should be considered separate events or part of the same event . Among the main causes hypothesized by paleontologists are natural climate change and overkill by humans , who appeared during the Middle Pleistocene and migrated to many regions of the world during the Late Pleistocene and Holocene . A variant of the latter possibility is the second-order predation hypothesis , which focuses more on the indirect damage caused by overcompetition with nonhuman predators . The spread of disease is also discussed as a possible reason .

positive: Little Ice Age The Little Ice Age ( LIA ) was a period of cooling that occurred after the Medieval Warm Period . Although it was not a true ice age , the term was introduced into scientific literature by François E. Matthes in 1939 . It has been conventionally defined as a period extending from the 16th to the 19th centuries , but some experts prefer an alternative timespan from about 1300 to about 1850 . Climatologists and historians working with local records no longer expect to agree on either the start or end dates of the period , which varied according to local conditions .   The NASA Earth Observatory notes three particularly cold intervals : one beginning about 1650 , another about 1770 , and the last in 1850 , all separated by intervals of slight warming . The Intergovernmental Panel on Climate Change Third Assessment Report considered the timing and areas affected by the Little Ice Age suggested largely-independent regional climate changes rather than a globally-synchronous increased glaciation . At most , there was modest cooling of the Northern Hemisphere during the period .   Several causes have been proposed : cyclical lows in solar radiation , heightened volcanic activity , changes in the ocean circulation , variations in Earth 's orbit and axial tilt ( orbital forcing ) , inherent variability in global climate , and decreases in the human population .

negative: Michael Schlesinger Dr. Michael Earl Schlesinger ( born February 23 , 1943 ) is a Professor of Atmospheric Sciences and director of the Climate Research Group at the University of Illinois at Urbana-Champaign . He received his Ph.D. ( meteorology ) in 1976 from the University of California , Los Angeles .   Michael Schlesinger is an expert in the modeling , simulation and analysis of climate and climate change , with interests in simulating and understanding the climates of the geologic past and possible future climates resulting from increased concentrations of greenhouse gases and human-made aerosols .   He has been instrumental in developing a range of simple and complex climate models , which have been used by the Intergovernmental Panel on Climate Change and the Energy Modeling Forum . His research currently focuses on : ( 1 ) simulating and understanding the effects on climate of a human-induced melting of the Greenland ice sheet ; ( 2 ) simulating and understanding the coupled climate-chemistry system , including the influences of the Sun - both irradiance and energetic electron precipitation - and volcanoes ; ( 3 ) understanding and reducing the uncertainty in the estimation of climate sensitivity and climate feedbacks ; and ( 4 ) performing integrative assessment of climate change , including further development of the robust adaptive decision strategy for mitigating and adapting to human-induced climate change .   He is known for his work on oscillations in the global climate system , on estimating the climate sensitivity , and on seasonal climate change .   He has edited four books , most recently Human-induced climate change : An interdisciplinary assessment . He regularly appears in the media .

negative: Michael O'Connell (botanist) Michael O'Connell , Professor of Botany , National University of Ireland , Galway .   O'Connell is a member of the Palaeoenvironmental Research Unit , and a member of the Environmental Protection Agency . His area of interests include past environments , past climate change , long-term human impact , as well as lat-glacial and Holocene environments .

negative: Climate change in Nevada Climate change in Nevada has been measured over the last century , with the average temperature in Elko , Nevada increasing by 0.6 F-change , and precipitation increasing by up to 20 % in many parts of the state . These past trends may or may not continue into the future .

negative: Human Rights and Climate Change Human Rights and Climate Change is a conceptual and legal framework under which international human rights and their relationship to global warming are studied , analyzed , and addressed . The framework has been employed by governments , United Nations organs , intergovernmental and non-governmental organizations , human rights and environmental advocates , and academics to guide national and international policy on climate change under the United Nations Framework Convention on Climate Change ( UNFCCC ) and the core international human rights instruments .   Human rights and climate change analysis focuses on the anticipated consequences to humans associated with global environmental phenomena including sea level rise , desertification , temperature increases , extreme weather events , and changes in precipitation , as well as adaptation and mitigation measures taken by governments in response to those phenomena that may involve human rights or related legal protections .

negative: Climate justice Climate justice is a term used for framing global warming as an ethical and political issue , rather than one that is purely environmental or physical in nature . This is done by relating the effects of climate change to concepts of justice , particularly environmental justice and social justice and by examining issues such as equality , human rights , collective rights , and the historical responsibilities for climate change . A fundamental proposition of climate justice is that those who are least responsible for climate change suffer its gravest consequences .  Occasionally , the term is also used to mean actual legal action on climate change issues .

negative: Climate ethics Climate ethics is an area of research that focuses on the ethical dimensions of climate change ( also known as global warming ) , and concepts such as climate justice .   Human-induced climate change raises many profound ethical questions , yet many believe that these ethical issues have not been addressed adequately in climate change policy debates or in the scientific and economic literature on climate change ; and that , consequently , ethical questions are being overlooked or obscured in climate negotiations , policies and discussions . It has been pointed out that those most responsible for climate change are not the same people as those most vulnerable to its effects .   Terms such as climate justice and ecological justice ( ` eco justice ' ) are used worldwide , and have been adopted by various groups .

negative: The Hockey Stick and the Climate Wars The Hockey Stick and the Climate Wars : Dispatches from the Front Lines is a 2012 book about climate change by the American climatologist and geophysicist Michael E. Mann . In the book Mann describes how he became a researcher investigating the temperature record of the past 1000 years and was lead author , with Raymond S. Bradley and Malcolm K. Hughes , on the 1999 reconstruction that was the first to be dubbed the hockey stick graph . He concisely explains the basics of climate science including statistical methodology dealing with paleoclimate proxy data , and examines the tactics which opponents of action on climate change use to distort the science and attack the reputations of climate scientists . The book describes both the hockey stick controversy and the broader context of skepticism in science and contrarians rejecting evidence of human influence on climate .   The book was picked by Physics Today books editor Jermey Matthews as one of the five top books of the 49 they had reviewed in 2012 .

negative: Piers Forster Piers Forster is Professor of Physical Climate Change and Director of the Priestley International Centre for Climate at the University of Leeds .  A physicist by training , his research focuses on quantifying the different human causes of climate change and the way the Earth responds . He is best known for his work on radiative forcing , climate sensitivity , contrails and geoengineering . He has contributed heavily to the writing of Intergovernmental Panel on Climate Change reports , including acting as a Lead Author for both the IPCC Fourth Assessment Report and IPCC Fifth Assessment Report .

negative: Copernicus Climate Change Service (C3S) The Copernicus Climate Change Service ( C3S ) is one of the six thematic services provided by the European Union 's Copernicus Programme . The Copernicus Programme is managed by the European Commission and the C3S is implemented by the European Centre for Medium-Range Weather Forecasts ( ECMWF ) and is expected to become operational in 2018 .   The objective of the Copernicus Climate Change Service is to build an EU knowledge base in support of mitigation and adaptation policies for Climate Change and Global Warming . The goal of the operational Climate Change service is to provide reliable information about the current and past state of the climate , the forecasts on a seasonal time scale , and the more likely projections in the coming decades for various scenarios of greenhouse gas emissions and other Climate Change contributors .

negative: Land change modeling Land change models ( LCMs ) describe , project , and explain changes in and the dynamics of land use and land-cover . LCMs are a means of understanding ways that humans are changing the Earth 's surface in the past , present , in forecasting land change into the future .   Land change models are valuable in development policy , helping guide more appropriate decisions for resource management and the natural environment at a variety of scales ranging from a small piece of land to the entire spatial extent . Moreover , developments within land-cover , environmental and socio-economic data ( as well as within technological infrastructures ) have increased opportunities for land change modeling to help support and influence decisions that affect human-environment systems , as national and international attention increasingly focuses on issues of global climate change and sustainability .

negative: Journal of Climate The Journal of Climate is a scientific journal published by the American Meteorological Society .  The journal publishes articles on climate research , in particular those concerned with large-scale atmospheric and oceanic variability , changes in the climate system ( including those caused by human activities ) , and climate simulation and prediction .

negative: Ecological forecasting Ecological forecasting uses knowledge of physics , ecology and physiology to predict how ecosystems will change in the future in response to environmental factors such as climate change . The ultimate goal of the approach is to provide people such as resource managers and designers of marine reserves with information that they can then use to respond , in advance , to future changes , a form of adaptation to global warming .   One of the most important environmental factors for organisms today is global warming . Most physiological processes are affected by temperature , and so even small changes in weather and climate can lead to large changes in the growth , reproduction and survival of animals and plants . The scientific consensus  is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era . These changes are in turn affecting human and natural ecosystems .   One major challenge is to predict where , when and with what magnitude changes are likely to occur so that we can mitigate or at least prepare for them . Ecological forecasting applies existing knowledge of how animals and plants interact with their physical environment to ask how changes in environmental factors might result in changes to the ecosystems as a whole .

negative: Valerie Masson-Delmotte Valerie Masson-Delmotte is a French climate scientist and Research Director at the French Alternative Energies and Atomic Energy Commission , where she works in the Climate and Environment Sciences Laboratory ( LSCE ) . She uses data from past climates to test models of climate change , and has contributed to several IPCC reports .

negative: Tom Wigley Tom Wigley is a climate scientist at the University of Adelaide . He is also affiliated with the University Corporation for Atmospheric Research ( UCAR ) . He was named a fellow of the American Association for the Advancement of Science ( AAAS ) for his major contributions to climate and carbon cycle modeling and to climate data analysis , and because he is `` one of the world 's foremost experts on climate change and one of the most highly cited scientists in the discipline . '' His h-index ( August 2014 ) is 64 , one of the highest in the discipline . He contributed to many of the reports published by the Intergovernmental Panel on Climate Change ( the work of the IPCC , including the contributions of many scientists , was recognised by the joint award of the 2007 Nobel Peace Prize ) .   Wigley was educated as a mathematical physicist and earned his doctorate at the University of Adelaide in Australia . He served as director of the Climatic Research Unit at the University of East Anglia in the United Kingdom from 1978 to 1993 . In 1993 he went on to the National Center for Atmospheric Research in Boulder , Colorado , where he was appointed a senior scientist in 1994 . He subsequently moved to the University of Adelaide where he currently ( 2014 ) holds a Professorial Fellowship .   His published papers include the first paper to demonstrate 20th century warming using both land and marine data , the first paper to include the effects of aerosol cooling on projections of future climate change , the first paper to provide realistic scenarios for the stabilization of atmospheric CO2 , and the first paper to use pattern-based methods to identify a significant human influence on the climate . Wigley has also published a number of highly cited papers in aqueous geochemistry , including a now-standard method for carbon dating of groundwater . Wigley has argued in the popular media that the IPCC has been too optimistic about the prospect of averting harmful climate change by reducing greenhouse emissions through the use of renewable technologies alone , and argued that any realistic portfolio must include significant contributions from nuclear energy . He has also pointed out that `` the human-induced changes that are expected over the next 100 years are much , much greater than any changes that societies experienced in the past . '' In 2013 , with other leading experts , he was co-author of an open letter to policy makers , which stated that `` continued opposition to nuclear power threatens humanity 's ability to avoid dangerous climate change . ''

negative: Climate change denial Climate change denial , or global warming denial , is part of the global warming controversy . It involves denial , dismissal , unwarranted doubt or contrarian views which strongly depart from the scientific opinion on climate change , including the extent to which it is caused by humans , its impacts on nature and human society , or the potential of adaptation to global warming by human actions . Some deniers do endorse the term , but others often prefer the term climate change skepticism , although this is a misnomer for those who deny anthropogenic global warming . In effect , the two terms form a continuous , overlapping range of views , and generally have the same characteristics : both reject , to a greater or lesser extent , mainstream scientific opinion on climate change . Climate change denial can also be implicit , when individuals or social groups accept the science but fail to come to terms with it or to translate their acceptance into action . Several social science studies have analyzed these positions as forms of denialism .   Campaigning to undermine public trust in climate science has been described as a `` denial machine '' of industrial , political and ideological interests , supported by conservative media and skeptical bloggers in manufacturing uncertainty about global warming . In the public debate , phrases such as climate skepticism have frequently been used with the same meaning as climate denialism . The labels are contested : those actively challenging climate science commonly describe themselves as `` skeptics '' , but many do not comply with common standards of scientific skepticism and , regardless of evidence , persistently deny the validity of human caused global warming .   Although scientific opinion on climate change is that human activity is extremely likely to be the primary driver of climate change , the politics of global warming have been affected by climate change denial , hindering efforts to prevent climate change and adapt to the warming climate . Those promoting denial commonly use rhetorical tactics to give the appearance of a scientific controversy where there is none .   Of the world 's countries , the climate change denial industry is most powerful in the United States . Since January 2015 , the United States Senate Committee on Environment and Public Works has been chaired by oil lobbyist and climate change denier Jim Inhofe . Inhofe is notorious for having called climate change `` the greatest hoax ever perpetrated against the American people '' and for having claimed to have debunked the alleged hoax in February 2015 when he brought a snowball with him in the Senate chamber and tossed it across the floor . Organised campaigning to undermine public trust in climate science is associated with conservative economic policies and backed by industrial interests opposed to the regulation of emissions . Climate change denial has been associated with the fossil fuels lobby , the Koch brothers , industry advocates and libertarian think tanks , often in the United States . More than 90 % of papers sceptical on climate change originate from right-wing think tanks .  The total annual income of these climate change counter-movement-organizations is roughly $ 900 million . Between 2002 and 2010 , nearly $ 120 million ( # 77 million ) was anonymously donated via the Donors Trust and Donors Capital Fund to more than 100 organisations seeking to undermine the public perception of the science on climate change . In 2013 the Center for Media and Democracy reported that the State Policy Network ( SPN ) , an umbrella group of 64 U.S. think tanks , had been lobbying on behalf of major corporations and conservative donors to oppose climate change regulation .   Since the late 1970s , oil companies have published research broadly in line with the standard views on global warming . Despite this , oil companies organized a climate change denial campaign to disseminate public disinformation for several decades , a strategy that has been compared to the organized denial of the hazards of tobacco smoking by tobacco companies .

negative: Gary Haq Dr. Gary Haq is a Human Ecologist and freelance author , broadcaster and a Senior Researcher at the Stockholm Environment Institute at the University of York . He is an expert in transport and environment , climate change , carbon footprint , behavioural change , carbon and urban air pollution management .   He is author of several reports on climate change , behaviour and lifestyle Greening the Greys : Climate Change and the Over 50s , The Carbon Cost of Christmas and Growing Old in a Changing Climate : Meeting the Challenges of Climate Change and an Ageing Population . During 2006-2008 he coordinated a climate change communication campaign in Yorkshire Climate Talk in collaboration with BBC Radio and York Press .   He has undertaken research and provided policy advice on air quality management in developing countries . He undertook the first comprehensive assessment of air quality management in 20 Asian Cities and developed a Strategic Framework for Air Quality Management in Asian Cities .   He is author of five books : Towards Sustainable Transport Planning , World Transport Policy and Practice , Urban Air Pollution in Asian Cities , Environmentalism Since 1945 , Short Guide to Environmental Policy .   He is author of the environmental blog : A Human Ecologist 's View .

negative: Shobhakar Dhakal Shobhakar Dhakal ( born in Nepal ) is the Head of Department of Energy , Environment and Climate Change at the Asian Institute of Technology , Thailand . His main areas of expertise are energy and climate change policies . Dhakal actively contributes to international and scientific arena . He was the Coordinating Lead Author of the Nobel Prize winning 5th Mitigation Assessment Report written by the Inter-governmental Panel on Climate Change ( released in April 2014 ) for the Chapter on Human Settlements , Infrastructure and Spatial Planning .

negative: Loss and damage The term Loss and damage denotes impacts of climate-related stressors that occur despite efforts to reduce greenhouse gas emissions and adapt to climatic changes . Loss and damage can result from sudden-onset events ( climate disasters , such as cyclones ) as well as slow-onset processes ( such as sea level rise ) . Loss and damage can occur in human systems ( such as livelihoods ) as well as natural systems ( such as biodiversity ) , though the emphasis in research and policy is on human impacts . Within the realm of loss and damage to human systems , a distinction is made between economic losses and non-economic losses . The main difference between the two is that non-economic losses involve things that are not commonly traded in markets .   At the 18th Conference of the Parties meeting of the UNFCCC in 2012 in Doha , Qatar , it took 36 hours of negotiation between 195 nations to arrive at a plan to address loss and damage associated with adverse effects of climate change particularly in countries most vulnerable to climate change . A new website was launched at the conference by the Loss and Damage Vulnerable Countries Initiative . It described its aim as being `` the first dedicated site for news , resources and opinion on the issue of loss and damage associated with the adverse impacts of climate change '' . Examples of types of loss and damage include farmers who can no longer grow crops to eat , or grass to feed cattle , because their soil has become too salty , and fishermen who have lost their livelihoods because rivers have dried up .   In popular press , and in statements by some parties in the climate negotiations , the terms loss and damage is often associated with liability and compensation . This explains why the topic raises heated debates , and tends to widen the divide between developed countries , which are historically responsible for most greenhouse gas emissions , and developing countries that are more vulnerable to impacts of climate change . For vulnerable countries , loss and damage is most of all about recognizing that past and current efforts to avoid dangerous climate change , and that there are limits and constraints to adaptation .   The United Nations Framework Convention on Climate Change has developed a work programme on loss and damage which aims to find ways to address the issue in developing countries that are particularly vulnerable to the adverse effects of climate change . On 12 -- 14 September 2013 , it held a meeting in Fiji to consider how best to address loss and damage from ` slow-onset events ' . These are impacts of climate change that occur over time , such as sea-level rise , rather than in a single , destructive event . Bangladesh is already suffering from loss and damage resulting from sea-level rise , due to its flat terrain in the coastal region .   At the 19th Conference of the Parties meeting of the UNFCCC in 2013 in Warsaw , Poland , the Warsaw International Mechanism for Loss and Damage associated with Climate Change Impacts was established . At the 20th Conference of the Parties in Lima , Peru ( 2014 ) , the work plan of the executive committee of the Warsaw International Mechanism was approved .   The 5th Assessment Report of the Intergovernmental Panel on Climate Change ( IPCC ) , published in 2013-2014 had no separate chapter on loss and damage , but WG2 Chapter 16 about adaptation limits and constraints , is very relevant for people interested in loss and damage . A qualitative data analysis ( QDA ) of what the IPCC 5th Assessment Report has to say about loss and damage surprisingly showed that the term was used much more often in statements about Annex 1 countries ( e.g. US , Australia or European countries ) than in text about non-Annex 1 countries ( most countries in Africa , Asia Latin America and the Pacific ) , which tend to be more vulnerable to impacts of climate change . Whether or not the IPCC 6th Assessment Report will have a chapter on loss and damage has not yet been decided .

negative: Sägistalsee Sägistalsee is a lake in Canton of Berne , Switzerland . Its surface area is 7 ha . The lake 's sediments were studied to determine past climate and human activities .

negative: Regime shift In ecology , regime shifts are large , abrupt , persistent changes in the structure and function of a system . A regime is a characteristic behaviour of a system which is maintained by mutually reinforced processes or feedbacks . Regimes are considered persistent relative to the time period over which the shift occurs . The change of regimes , or the shift , usually occurs when a smooth change in an internal process ( feedback ) or a single disturbance ( external shocks ) triggers a completely different system behavior . Although such non-linear changes have been widely studied in different disciplines ranging from atoms to climate dynamics , regime shifts have gained importance in ecology because they can substantially affect the flow of ecosystem services that societies rely upon , such as provision of food , clean water or climate regulation . Moreover , regime shift occurrence is expected to increase as human influence on the planet increases -- the Anthropocene -- including current trends on human induced climate change and biodiversity loss .

negative: World Climate Research Programme The World Climate Research Programme ( WCRP ) was established in 1980 , under the joint sponsorship of International Council for Science and the World Meteorological Organization , and has also been sponsored by the Intergovernmental Oceanographic Commission of UNESCO since 1993 . It is a component of the World Climate Programme . The objectives of the programme are to develop the fundamental scientific understanding of the physical climate system and climate processes needed to determine to what extent climate can be predicted and the extent of human influence on climate . The programme encompasses studies of the global atmosphere , oceans , sea ice , land ice ( such as glaciers , ice caps and ice sheets ) , and the land surface which together constitute the Earth 's physical climate system .   WCRP activities address issues of scientific uncertainty in the Earth 's climate system including transport and storage of heat by the ocean , the global energy and hydrological cycle , the formation of clouds and their effects on radiative transfer , and the role of the cryosphere in climate . These activities match the scientific priorities identified by the Intergovernmental Panel on Climate Change , and provide the basis for responding to issues raised in the United Nations Framework Convention on Climate Change . WCRP also lays the scientific foundation for meeting the research challenges posed in Agenda 21 . Together with the International Geosphere-Biosphere Programme and the International Human Dimensions of Global Environmental Change Programme , WCRP provides the international framework for scientific cooperation in the study of global climate change .   Scientific guidance for the programme is provided by a Joint Scientific Committee consisting of 18 scientists selected by mutual agreement between the three sponsoring organizations .

negative: Climate Rush Climate Rush is a UK organisation that campaigns on various environmental issues related to climate change . Their website states that , `` We are a diverse group of women and men who are determined to raise awareness of the biggest threat facing humanity today - that of Climate Change '' . The organisation was founded in October 2008 by a group of eleven women , including Tamsin Omond . They have organised various protests using direct action to highlight their cause . They model their actions on those of the suffragettes who campaigned a century ago to gain women the right to vote . Members of the Women 's Institute have campaigned alongside members of the organisation .

negative: Carbon rift Carbon rift is a theory attributing the input and output of carbon into the environment to human capitalistic systems . This is a derivative of Karl Marx 's concept of metabolic rift . In practical terms , increased commodity production demands that greater levels of carbon dioxide ( or CO2 ) be emitted into the biosphere via fossil fuel consumption . Carbon rift theory states that this ultimately disrupts the natural carbon cycle and that this `` rift '' has adverse effects on nearly every aspect of life . Many of the specifics regarding how this metabolic carbon rift interacts with capitalism are proposed by Brett Clark and Richard York in a 2005 article titled `` Carbon Metabolism : Global capitalism , climate change , and the biospheric rift '' in the journal Theory and Society . Researchers such as Jean P. Sapinski of the University of Oregon claim that , despite increased interest in closing the carbon rift , it is projected that as long as capitalism continues , there is little hope of reducing the rift .   Both deforestation and the emission of greenhouse gases have been linked to increased atmospheric CO2 levels . Carbon rift theory states that these are the result of human production through capitalistic systems . There are proposed solutions to climate change such as geoengineering proposed in the December 2015 Paris Agreement . However , some argue that the capitalist mode of production is at fault for the emission of greenhouse gas and that solutions must be found to this issue before climate change itself can be addressed .   Carbon rift theory , while rarely criticized directly , often indirectly receives criticism regarding the underlying causes of climate change and attributing the stated effects to alternative explanations for climate change , instead of as a result of human activity . Such explanations include the Chaotic Solar System Theory and that increased water vapor is responsible for climate change .

negative: Thin Ice (2013 film) Thin Ice is a 2013 documentary film following geologist Simon Lamb on a search to understand the science behind climate change . This is achieved by traveling the world and meeting a range of scientists , from biologists to physicists , who are investigating the climate . The film 's conclusion emphasises the scientific consensus on human-induced climate change .   The film was a joint initiative between Oxford University and Victoria University of Wellington , and premiered around the world on Earth Day 2012 , and in New Zealand in 2015 .

negative: U.S. Global Change Research Program The United States Global Change Research Program ( USGCRP ) coordinates and integrates federal research on changes in the global environment and their implications for society . The program began as a presidential initiative in 1989 and was codified by Congress through the Global Change Research Act of 1990 ( P.L. 101-606 ) , which called for `` a comprehensive and integrated United States research program which will assist the Nation and the world to understand , assess , predict , and respond to human-induced and natural processes of global change . ''   Thirteen departments and agencies participate in the USGCRP , which was known as the U.S. Climate Change Science Program from 2002 through 2008 . The program is steered by the Subcommittee on Global Change Research under the Committee on Environment , Natural Resources and Sustainability , overseen by the Executive Office of the President , and facilitated by a National Coordination Office .   During the past two decades , the United States , through the USGCRP , has made the world 's largest scientific investment in the areas of climate change and global change research . Since its inception , the USGCRP has supported research and observational activities in collaboration with several other national and international science programs .   These activities led to major advances in several key areas including :  Observing and understanding short - and long-term changes in climate , the ozone layer , and land cover ;  Identifying the impacts of these changes on ecosystems and society ;  Estimating future changes in the physical environment , and vulnerabilities and risks associated with those changes ; and  Providing scientific information to enable effective decision making to address the threats and opportunities posed by climate and global change .   These advances have been documented in numerous assessments commissioned by the program and have played prominent roles in international assessments such as those of the Intergovernmental Panel on Climate Change . Program results and plans are documented in the program 's annual report , Our Changing Planet .

negative: Minister of Environment and Climate Change (Canada) The Minister of Environment and Climate Change ( Ministre de l'Environnement et du Changement Climatique ) is the Minister of the Crown in the Canadian Cabinet who is responsible for overseeing the federal government 's environment department , Environment and Climate Change Canada . The Minister is also responsible for overseeing Parks Canada and the Canadian Environmental Assessment Agency .   Noted environment ministers of the past have included Jack Davis , Roméo LeBlanc , Jean Charest , Stéphane Dion , Sheila Copps , David Anderson and Peter Kent .   Known as the Minister of the Environment until 2015 , the position was given its current name in 2015 upon the creation of the 29th Canadian Ministry .

negative: Media coverage of global warming Media coverage of climate change has had effects on public opinion on climate change, as it mediates the scientific opinion on climate change that the global temperature has increased in recent decades and that the trend is mainly caused by human-induced emissions of greenhouse gases. Almost all scientific bodies of national or international standing agree with this view, although a few organisations hold non-committal positions. Climate change communication research frequently studies the effectiveness of that media.  Some researchers and journalists believe that media coverage of political issues is adequate and fair, while a few feel that it is biased. However, most studies on media coverage of the topic are neither recent nor concerned with coverage of environmental issues. Moreover, they are only rarely concerned specifically with the question of bias.Despite recent trends in increased coverage on climate change, media coverage is not constant, and researchers wonder if the current increase in attention will be sustained.

negative: Land use, land-use change and forestry Land use , land-use change and forestry ( LULUCF ) is defined by the United Nations Climate Change Secretariat as a `` greenhouse gas inventory sector that covers emissions and removals of greenhouse gases resulting from direct human-induced land use , land-use change and forestry activities . ''   LULUCF has impacts on the global carbon cycle and as such , these activities can add or remove carbon dioxide ( or , more generally , carbon ) from the atmosphere , influencing climate . LULUCF has been the subject of two major reports by the Intergovernmental Panel on Climate Change ( IPCC ) . Additionally , land use is of critical importance for biodiversity .

negative: Phil Jones (climatologist) Philip Douglas Jones ( born April 22 , 1952 ) retired from his positions as the Director of the Climatic Research Unit ( CRU ) and as a Professor in the School of Environmental Sciences at the University of East Anglia ( UEA ) at the end of 2016 . Jones was replaced as CRU director by Tim Osborn and has taken up a position as a Professorial Fellow at the UEA from January 2017 .   His research interests include instrumental climate change , palaeoclimatology , detection of climate change and the extension of riverflow records in the UK . He has also published papers on the temperature record of the past 1000 years .   He is known for maintaining a time series of the instrumental temperature record . This work was featured prominently in both the 2001 and 2007 IPCC reports , where he was a contributing author to Chapter 12 , Detection of Climate Change and Attribution of Causes , of the Third Assessment Report and a Coordinating Lead Author of Chapter 3 , Observations : Surface and Atmospheric Climate Change , of the AR4 .

negative: Brian Clegg (writer) Brian Clegg ( born 1955 ) is an English science writer . He is the author of popular science books on topics including light , infinity , quantum entanglement and surviving the impact of climate change , and biographies of Roger Bacon and Eadweard Muybridge .

negative: 350.org 350 . org is an international environmental organization encouraging citizens to action with the belief that publicizing the increasing levels of carbon dioxide will pressure world leaders to address climate change and to reduce levels from 400 parts per million to 350 parts per million . It was founded by author Bill McKibben with the goal of building a global grassroots movement to raise awareness about human-driven climate change , to confront climate change denial , and to cut emissions of carbon dioxide in order to slow the rate of global warming . 350 . org takes its name from the research of Goddard Institute for Space Studies scientist James E. Hansen , who posited in a 2007 paper that 350 parts-per-million ( ppm ) of CO2 in the atmosphere is a safe upper limit to avoid a climate tipping point .

negative: Climate change mitigation Climate change mitigation consists of actions to limit the magnitude or rate of long-term climate change . Climate change mitigation generally involves reductions in human ( anthropogenic ) emissions of greenhouse gases ( GHGs ) . Mitigation may also be achieved by increasing the capacity of carbon sinks , e.g. , through reforestation . Mitigation policies can substantially reduce the risks associated with human-induced global warming .   According to the IPCC 's 2014 assessment report , `` Mitigation is a public good ; climate change is a case of the ` tragedy of the commons . Effective climate change mitigation will not be achieved if each agent ( individual , institution or country ) acts independently in its own selfish interest ( see international cooperation and emissions trading ) , suggesting the need for collective action . Some adaptation actions , on the other hand , have characteristics of a private good as benefits of actions may accrue more directly to the individuals , regions , or countries that undertake them , at least in the short term . Nevertheless , financing such adaptive activities remains an issue , particularly for poor individuals and countries . ''   Examples of mitigation include phasing out fossil fuels by switching to low-carbon energy sources , such as renewable and nuclear energy , and expanding forests and other `` sinks '' to remove greater amounts of carbon dioxide from the atmosphere . Energy efficiency may also play a role , for example , through improving the insulation of buildings . Another approach to climate change mitigation is climate engineering .   Most countries are parties to the United Nations Framework Convention on Climate Change ( UNFCCC ) . The ultimate objective of the UNFCCC is to stabilize atmospheric concentrations of GHGs at a level that would prevent dangerous human interference of the climate system . Scientific analysis can provide information on the impacts of climate change , but deciding which impacts are dangerous requires value judgments .   In 2010 , Parties to the UNFCCC agreed that future global warming should be limited to below 2.0 ° C ( 3.6 ° F ) relative to the pre-industrial level . With the Paris Agreement of 2015 this was confirmed , but was revised with a new target laying down `` parties will do the best '' to achieve warming below 1.5 ° C . The current trajectory of global greenhouse gas emissions does not appear to be consistent with limiting global warming to below 1.5 or 2 ° C . Other mitigation policies have been proposed , some of which are more stringent or modest than the 2 ° C limit .