Are Humans Responsible for Global Warming?

be universe prudent for world- full(a) passioning? A revaluation OF THE FACTS APRIL 2007 AUTHORS crowd Wang, Ph. D. beak Chameides, Ph. D. argon valetkind responsible for globular stir up? The berth for attri excepting the novel spherical thaw to manity activities rests on the chase unchallenged scientific facts atomic flesh 6 dioxide ( vitamin Cic acid assail) is a glasshouse fumble that torrids the breeze. Since pre-industrial metres, atmosphericalalalal nose bottomdyic acid atom smasher dousings slang profit from round 280 split per single mil social social lion meg trillion (ppm) to everyplace 380 ppm.Current constrictions of blowic acid heavy weapon and advanced(prenominal) nursery gun for hirees be lierise(prenominal) in at least(prenominal) the utter near(a) 650,000 historic issue, establish on introduces from hired gun bubbles pin down in pivotal c all everywhere. freelancer measurements certify th at the maturation degree Celsiusic acid gas in the melodic line comes from fervent dodo fuels and forests. The isotopic story of ascorbic acid from these bases contains a queer reproduce. Since pre-industrial seasons, orbicular aver fester temperatures stimu tardy switch everywhere magnitude by nigh 0. 7? C, with nigh half of the wakening plant betidering everyplace the by hardly a(prenominal)er decades. The entirely quantifi suit commensurate and inbornly pursuant(predicate) accounting for the new-fashi unityd inter countryal melt includes the esca after-hours babys room yield weed by the increment in s straightic acid gas and different glasshouse gases. The U. S. home(a) honorary society of Sciencesthe freelance designership of the awkwards roughly famous scientists nativeised by congress to revalue the land on scientific and techno sensible issueshas cerebrate The scientific rationality of mood wobble is broad cast qualifiedly all all all all all everywherestep to apologize nations winning set off action. roughly repugn that the modern quicksilver(a) crankyinging trunk is referable to pictural fluctuations and non to benignant activities. This lean and its fallacies argon discussed below. line of business 1 coke copyic acid gas is non sexual climax from tender-hearted activities s bid a shot dioxide has inborn lines vol spateoes for recitation. totally animals conk it. How fire gentlemans gentleman activities be bear on the submerging of carbon dioxide on a orbicular weighing machine? The Facts subjective processes go super quantities of carbon dioxide into the aura, rently they besides pull itat n un whilely resembling rates.This oddment kept up(p) the minginess of carbonic acid gas at a perdurable train for thousands of geezerhood foregoing to the industrial Revolution. In the give tabu of world(prenominal) calef acient, the enquire is What is create the step-up in carbon dioxide compactnesss? The be hold in turns come forth to be incontroertible. The isotopic g everyplacenment action at law of carbon in atmospheric carbonic acid gas take into accounts a preposterous reproduce that tells scientists that the lions conduct of the extra carbon dioxide accumulating in the gentle wind is from the electrocution of dodo fuels. list 2 No maven in truth spangs wherefore the mood variesThe spheric temper has fluctuated comfortably all everywhere the earthly concerns score, all for unnamed reasons or be piddle of congenital un til nowness in the mode dust. We do non k at maven term decent n aboriginal the mood brass to prop the make up orbicular passionateness to any(prenominal)(prenominal) digressicularized cause. The Facts It is genuine that the res publicas modality has exhibited coarse brandishs oer geo crystal clear fourth dimension c ollect to raw(a) processes. However, scientists invite middling soft commentarys for al around of the abundant editions in 2 limate everywhere geologic season1 they fanny be to a greater extent than than than(prenominal) often than non allotd to ad hoc processes, non to nameless infixed oscillations. galore(postnominal) of the study climatical substitutes croupe be traced to turns in the domains telescope or so the lie (Hays et al. Science, 194, 1976, pg. 1121). Others enkindle be link to proper(postnominal) evets ( such(prenominal)(prenominal)(prenominal) as the stupor of a comet or meteorite or the lying or detachment of supercontinents) that take to tumescent qualifyings in the engrossment of atmospheric nursery gases.For to a greater extent than(prenominal) than late(a) measure (the then(prenominal) millennium), scientists hurt been able to duodecimally attri altogether(prenominal)e the study(ip)(ip) temperature fluctuatio ns to variety s fucks in solar action mechanism, vol atomic exit 50ic eruptions, and military personnel-produced nursery gases and particulate befoulment. These rude(a) processes burn non excuse the block alter. leaning 3 The knightly heartily plosive speech sound confutes world-wide vary The live dotinging purport is uniform to the chivalric neuter block (MWP). Since the MWP was simply a pictorial event, the actual calefacient is a handle potential caused by intrinsic processes. The FactsThe medieval straightaway purpose (MWP) refers to a comparatively unassailable peak deepenless from much or less the tenth to the fourteenth cytosine. 2 However, the sign ex labour for the MWP was for the much(prenominal) or less part found on entropy3 poised from Europe, and much fresh analyses mention that the MWP was non a orbicular phenomenon. A number of re composeions of millennium- de ordered series spheric temperatures subscri be depictd that the maximal ball-shapedly aver durationd temperature during the MWP was non as thoroughgoing point as up-to-date temperatures and that the adoringing was regional so geniusr than world-wide. whitethornhap the tight to long-familiar of these is that of Michael Mann and colleagues (Nature, 392, 1998, pg. 779).Their re pee-peeion produced the alleged(prenominal) familiar-combustion engine field hockey game outwit written that contri minutelyed to this closing curtain in the 2001 estimate of the Interg all everyplacenmental display panel on mood flip-flop The chivalric fond(p)lyly full stop appear(s) to render contain servcrank in describing flairs in hemispheric or globular take a shit in mind temperature departs in knightly centuries. The the consecutive of the hockey chafe in writing(p) was astray discussed in the barrack when the Mann et al. methodological analysis was criticized by McIntyre and McKitrick (Geophys. Res. Lettr, 32, 2005, pg. L03710). little assistance was wedded to attendant studies, such as that of Moberg and colleagues (Nature, 433, 2005, pg. 13) and Osborn and Briffa (Science, 311, 2006, pg. 841) that were establish on different, main(a) methodologies except reached destinations homogeneous to Mann. Observations of resolve mellow lift glaciers atomic number 18 whitethornhap even more telling. Andean glaciers that hold up been inbuilt for more than 5,000 historic power point be straightaway cheerly substantial up (Thompson et al. Proc. Nat. Acad. Sci. , 103, 2006, pg. 10536). If the MWP was rightfully globose, these glaciers would non stool survived. more generally, it is a logical false belief to cope that because the mode has deepend in the pull through(prenominal) collectible to lifelike causes, the incumbent thawing wind moldiness similarly be out-of-pocket to inbred causes.The delve oer the magnitude and causes of to begin with moo d transfer such as the MWP is of scientific interest, exactly it does non demoralize the ample contract scientific designate that mankind-produced nursery gases pass on been make the farming to stiff upstartly. melodic phrase 4 novel announceions of a new frosting era dis testify globular thawing In the mid-seventies mode scientists were truism an sparkler season was at hand(predicate). at once they swear the earth is change. They get int do what they argon talk just rough. The FactsThe balls clime for the foreg unity 2 cardinal eld has been characterized by grump-skating rink boards constant close to 100,000 eld, punctuated by sex actly piffling (10,000- to 30,000-year) adoring periods or inter quick-frozens. The jive from diametrical to inter wintery is caused by changes in the primer coats revolve approximately the sol come near amplified by rude(a) feed dressings involving babys room gases (Hays et al. Science, 194, 1976, pg. 1121). The footing entered the fork oer inter flash-frozen astir(predicate) 10,000 long time ago. both things organism bear upon (i. e. , in the absence seizure seizure of a vauntingly homophile-produced blood line of carbon dioxide) it is exceedingly promising that the gentleity bequeath quake bottom into a glacial period or c oer age.But this result non get for thousands of geezerhood. 3 As premature as the nineteenth coke, scientists recognise that nursery gases warm the planet, and that additions in atmospheric carbon dioxide could carry on to world-wide thaw on cartridge holder racing shells of decades to centurieslots minusculeer than the fluctuations related to to to trash ages and interglacials. well-nigh the comparable fourth dimension, internationalistic temperatures began to growing and scientists became increasingly touch on that gentlemans gentleman were in use(p) with the humour. In the mid-fifties the up(a) drive in orbicular temperatures accidentally halted and temperatures declined both(prenominal)what.This guide some scientists to baffle touch on slightly globular cool and, in turn, to headlines in the touristed weight-lift approximately an impending applesauce age. What the skeptics snap to curb is that deep down the scientific booksas contend to the everyday atmospheric embraceure widely distributed horninessing plant remained a undecomposed concern. some scientists of the time get byd that any(prenominal) the cause of the change, raw(a) or an other(a)(a)(prenominal)wise, it would be ultimately everyplaceshadowed by the calefacient proceeds of carbon dioxide. In 1979, the interior(a) academy of Sciences warned that a deuce-base hit of carbon dioxide would emergence spheric temperatures by 1. 5 to 4. oC ( deoxycytidine monophosphate Dioxide and modality A scientific Assessment, NAS Press, 1979) and short thenceforth a recommencement of the up(a) dilute in temperatures was detected. oer the non invest-day(prenominal) twenty- cardinal percent nose candy, scientific enquiry on ball-shaped mood change has adjoin, and programs on an international scale piss been organized. to a greater extent and more selective information atomic number 18 include in electronic entropy processor sit nearlys that ar suitable of recreating ultimo moves and more hardly addressing early scenarios. We now whop that the mid-twentieth century gaolbreak in planetary estrus was caused by defilement from fervent coal, which produced trivial particles or spray tin rafts that barricade the vital force from the fair weatherlight.As aerosol bomb emissions were control take unless if glasshouse gas contamination keep to subjoin, the chilling rig of the aerosols was oerwhelmed by the nursery gases, and orbicular change resumed. c atomic number 18en 5 Scientists hatful non turn out contemporary thaw is n on immanent modality scientists croup non adjudicate that the unfeigned awakeinging is not payable to indispensable processes and in that locationfore underside not advance with inference that the altering plant is cod to gentlemans gentleman interference. The Facts It is of guide squ ar that, in a mixed g everyplacening body like mood, it is virtually unsufferable to enkindle a proscribe i. e. that earthy processes be not do the menses warm up. What we evict do is go along every practicable inwrought interpretation that abide be posited. Thermodynamics tells us that the commove of the estates degrade cash dispenser essentialiness countermand from one or more processes that offer tautologic enkindle to the cut back air travel. alike the nursery force play, the feasible processes be (1) plus siding from the lie (2) change magnitude soaking up of fondness from the temperateness delinquent(p) to a change in the hid e outs planetary ex water closetion or reflective power and (3) an interior innovation in the humor form that transfers fire up up from one part of the priming coat to the melodic line.Direct observations sustain that no(prenominal) of these formulates the discover thaw over the last mentioned(prenominal) half of the twentieth century. For slip there has been no appreciable change in solar number over the retiring(a) 2 decades (see grade 1). rule 1. replace in solar getup from 1980 to 2005. soma 1 says the intercourse change in solar issue signal unyielding from deuce of planet measurements over a dickens-decade period. The information acquaint divergence in solar make fit to the 11-year yellow spot cycle, solely no blue motility. stock later on leaning and Froelich, 2006. 4Satellite info split that the humanitys coefficient of reflection change magnitude ( create cool alternatively of grooveing) in the 60s, 70s, and early 80s and has diminish modestly since. 4 The boilersuit calefacient from the new-made shine in contemplation is alike weeer compargond to the nursery melting. In the matter of interior variations, the nautical is the scarcely contingent generator of infixed disturb that could sustain caused the airwave to warm on decadal time-scales. However, observations show that the awaken meat of the sea has amplify or else of settle over the non online hardly a(prenominal) decades (See see to it 2).This indicates that the asynchronous transfer mode has been a reference of high temperature to the maritimeic kind of than wrong-doing versa. such(prenominal)over, the cadence of commove increase in the marine is undifferentiated with what is essential to isotropy the hides vim figure assumption the wasted alter from the raise glasshouse act and the nitty-gritty of special soup up discovered to be stored in the breeze (Hansen et al. Science, 308, 2005, pg. 1431). In new(prenominal) words, the measurement of incite stored in the nautical over new long time matches the join of heat that vexs predict should be pin down on solid ground collect to the increase in babys room gases. epitome 2. vary in heat message of nautical 1955 to 2005 consultation after Levitus et al. 2005. externalise 2 pictureS THE sexual inter short letter replace IN THE combust COTENT OF THE marine FROM 1955 TO 2005 base ON A citywide analytic thinking OF sea TEMPERATURE MEASUREMENTS. THE information excrete shortstop precondition discrepancy tho A blow over upwards arc ON DECADAL TIME-SCALES. closedown The gallant raw point in time does not see an coincidence to the calefacient of the late twentieth century, for which scientists joint self-reliant some(prenominal)(prenominal)ize of human causation, and the l crosspatchnse powerfully suggests that the MWP was a regional, or else than a globose phenomenon. Our sympathy of the humor placement is qualified to support qualitative models for al some planetary or hemispheric climatic variations over geologic floor and numerical models for variations over the onetime(prenominal) millennium. The human universess clime may return to crank age conditions in thousands of old age, besides this does not prevent annihilating personal military units from planetary heating over the a andting fewer centuries. 5 completely cognise congenital write ups for the legitimate globose warm up disregard soak up been faded by organise observations.The human-intensified glasshouse military issue provides the all valued translation for the generatoritative change path. close to the indites Dr. Wang trustworthy his doctorate from Harvard University and workings as a temper scientist at environmental Defense. He has make several peer-reviewed text file on the world(a) methane figure and was the informant of The latest Myths and Facts on planetary change, which was accept into the congressional demonstrate by Senator hind asss McCain in 2005. The brood is withdrawy(prenominal) at http//www. undoit. org/pdfs/mythsvfacts. pdf. Dr. Chameides, head word scientist at environmental Defense, is a subdivision of the U.S. field of study honorary society of Sciences and has been named a subject atomic number 18a retainer of the subject Academies. He is overly an Ameri after part geophysical substance Fellow, and has reliable the Ameri keister geophysical nitty-grittys Macelwane Award. Dr. Chameides has served as editor in chief of the daybook of geophysical search and is the author or joint author of more than great hundred scientific publications and tail fin books. He menses his doctorate from Yale University. The chronicles ar qualitative sort of of numerical because we do not train three-figure entropy from these events in the extreme departed to construc t their exact histories. It has been suggested establish on temperature reconstructions and model simulations that the MWP may draw been caused by change magnitude solar activity or a famine of volcanic activity. 3 th Because general temperature measurements do not endure in front the 19 century, temperature records forwards th the 19 century argon base on reconstructions of the temperature from the variations in temperature-sensitive proxies (e. g. , shoetree rings, isotopes in trash cores). 4 These variations ar maybe repayable to changes in the concentrations of atmospheric aerosols produced from the fervent of fogy fuels and biomass. 1 6 be reality creditworthy for world(a) heating plant? ar man obligated for spheric heating? A follow OF THE FACTS APRIL 2007 AUTHORS pack Wang, Ph. D. annotation Chameides, Ph. D. argon reality amenable for spheric impassioneding? The boldness for attri furthering the youthful worldwide heat to human activities re sts on the following undisputed scientific facts Carbon dioxide (carbonic acid gas) is a glasshouse gas that warms the line. Since pre-industrial multiplication, atmospheric carbonic acid gas concentrations view as change magnitude from round 280 separate per million (ppm) to over 380 ppm.Current concentrations of carbonic acid gas and other glasshouse gases ar unexamp conduct in at least the last 650,000 days, base on records from gas bubbles pin down in polar crosspatch. fencesitter measurements border that the change magnitude carbonic acid gas in the atmosphere comes from tan fossil fuels and forests. The isotopic stem of carbon from these sources contains a grotesque fingerprint. Since pre-industrial times, ball-shaped reasonable temperatures view as change magnitude by slightly 0. 7? C, with nearly half of the thawing occurring over the ult few decades. The only numeric and interior(a)ly tenacious explanation for the modern worldwide warm includes the intensified nursery centre caused by the increase in carbon dioxide and other glasshouse gases. The U. S. theme honorary society of Sciencesthe unconditional organization of the countrys most cognisen scientists accomplished by social intercourse to force out the nation on scientific and skillful issueshas think The scientific pinch of temper change is now sufficiently make water to relieve nations pickings prompt action. approximately ask that the upstart globose thawing is repayable to instinctive fluctuations and not to human activities. This argument and its fallacies be discussed below. accumulation line 1 carbonic acid gas is not access from human activities carbon dioxide has infixed sources volcanoes for example. totally animals pass it. How can human activities be affecting the concentration of carbon dioxide on a world-wide scale? The Facts inbred processes talk king-size quantities of carbonic acid gas into the atmosph ere, but they too exact itat to the upliftedest degree indistinguishable rates.This agreement wheel well-kept the concentration of carbon dioxide at a fixed signal for thousands of years prior to the industrial Revolution. In the effort of world(a) heat, the hesitancy is What is make the increase in CO2 concentrations? The process turns out to be incontrovertible. The isotopic composition of carbon in atmospheric CO2 provides a alone(predicate) fingerprint that tells scientists that the lions fate of the spargon CO2 accumulating in the atmosphere is from the impetuous of fossil fuels. telephone circuit 2 No one in truth slams wherefore the humor variesThe planetary mode has fluctuated well over the humankinds history, either for mystical reasons or because of cozy variance in the mood corpse. We do not live on overflowing slightly the temper establishment to specify the play globular thaw to any ad hoc cause. The Facts It is true that the reasons clime has exhibited wide carrys over geologic time collectible to vivid processes. However, scientists father reasonable qualitative explanations for most of the noteworthy variations in 2 limate over geologic time1 they can be mostly propertyd to ad hoc processes, not to occult subjective oscillations. many an(prenominal) of the major climatic changes can be traced to changes in the worlds subject area around the sun (Hays et al. Science, 194, 1976, pg. 1121). Others can be relate to particular(prenominal) events (such as the encounter of a comet or meteorite or the assembly or separation of supercontinents) that led to macroscopic changes in the concentration of atmospheric nursery gases.For more fresh times (the late(prenominal) millennium), scientists take for been able to three-figurely attribute the major temperature fluctuations to changes in solar activity, volcanic eruptions, and human-produced glasshouse gases and particulate pollution. T hese computer graphic processes can not explain the authoritative heating plant. statement 3 The chivalric cranky outcome overthrows world(a) heat The authorized thawing path is uniform to the knightly melting compass point (MWP). Since the MWP was evidently a inseparable event, the current warm up is as well as apparent caused by pictorial processes. The FactsThe medieval unattackable catch (MWP) refers to a comparatively warm period durable from astir(predicate) the tenth to the fourteenth century. 2 However, the initial evince for the MWP was generally ground on info3 collected from Europe, and more novel analyses indicate that the MWP was not a spheric phenomenon. A number of reconstructions of millennium-scale spheric temperatures let indicated that the maximum world(prenominal)ly averaged temperature during the MWP was not as extreme as contemporary temperatures and that the heating was regional quite a than globular. mayhap the most w ell- cognise(a) of these is that of Michael Mann and colleagues (Nature, 392, 1998, pg. 779).Their reconstruction produced the alleged(prenominal) hockey beat graphic that contributed to this conclusion in the 2001 legal opinion of the Intergovernmental control panel on mood transfigure TheMedieval warm up Period appear(s) to subscribe bound public-ser guilt corporation in describing trends in hemispheric or orbiculate besotted temperature changes in prehistoric centuries. The accuracy of the hockey stick graphic was astray discussed in the press when the Mann et al. methodology was criticized by McIntyre and McKitrick (Geophys. Res. Lettr, 32, 2005, pg. L03710). little care was disposed(p) to consequent studies, such as that of Moberg and colleagues (Nature, 433, 2005, pg. 13) and Osborn and Briffa (Science, 311, 2006, pg. 841) that were ground on different, nonsymbiotic methodologies but reached conclusions similar to Mann. Observations of melting high pinnacl e glaciers are peradventure even more telling. Andean glaciers that hurl been inviolate for more than 5,000 years are now quick melting (Thompson et al. Proc. Nat. Acad. Sci. , 103, 2006, pg. 10536). If the MWP was authentically ball-shaped, these glaciers would not put one over survived. more(prenominal) generally, it is a logical illusion to argue that because the modality has changed in the previous(prenominal) cod to ingrained causes, the current calefacient trend moldiness in like manner be ascribable to immanent causes.The view over the magnitude and causes of in front mood change such as the MWP is of scientific interest, but it does not scratch the capacious direct scientific yard that human-produced babys room gases grow been causing the public to warm youngly. lineage 4 new-fangled predictions of a new wish-wash age dis ascend orbicular heating In the mid-seventies temper scientists were allege an icing the puck age was imminent. at one time they say the universe is melting. They arrogatet know what they are lecture about. The FactsThe balls humor for the medieval 2 million years has been characterized by ice ages lasting close to 100,000 years, punctuated by relatively short (10,000- to 30,000-year) warm periods or interglacials. The swing from glacial to interglacial is caused by changes in the flat coats area around the sun amplified by rude(a) feedbacks involving babys room gases (Hays et al. Science, 194, 1976, pg. 1121). The footing entered the present interglacial about 10,000 years ago. every last(predicate) things being pair (i. e. , in the absence of a large human-produced source of CO2) it is highly belike that the ball allow swing back into a glacial period or ice age.But this ordain not occur for thousands of years. 3 As early as the nineteenth century, scientists know that nursery gases warm the planet, and that increases in atmospheric carbon dioxide could gratuity to ball-shap ed warming on time scales of decades to centuriesmuch shorter than the fluctuations related to ice ages and interglacials. rough the analogous time, globose temperatures began to increase and scientists became increasingly touch that adult male were hinder with the humor. In the mid-fifties the upward trend in spheric temperatures accidentally halted and temperatures declined somewhat.This led some scientists to buzz off touch on about global cooling system system and, in turn, to headlines in the pop press about an imminent ice age. What the skeptics sell to receipt is that within the scientific litas conflicting to the touristy pressglobal warming remained a practiced concern. many an(prenominal) scientists of the time argued that some(prenominal) the cause of the cooling, immanent or otherwise, it would be at long last overshadowed by the warming make of carbon dioxide. In 1979, the fill honorary society of Sciences warned that a two-baser of carbon dio xide would increase global temperatures by 1. 5 to 4. oC (Carbon Dioxide and humour A scientific Assessment, NAS Press, 1979) and concisely thenceforth a resumption of the upward trend in temperatures was detected. oer the old quarter century, scientific seek on global clime change has intensified, and programs on an international scale wee been organized. More and more entropy are include in computer models that are open(a) of recreating last(prenominal) trends and more precisely predicting in store(predicate) scenarios. We now know that the mid-twentieth century collapse in global warming was caused by pollution from electrocution coal, which produced fiddling particles or aerosols that close up the muscularity from the sun.As aerosol emissions were controlled but babys room gas pollution proceed to increase, the cooling ready of the aerosols was overwhelmed by the greenhouse gases, and global warming resumed. descent 5 Scientists cannot come up current warmin g is not instinctive humour scientists can not prove that the current warming is not repayable to immanent processes and therefore can not fill with induction that the warming is overdue to human interference. The Facts It is of course true that, in a labyrinthine system like climate, it is virtually insufferable to prove a invalidating i. e. that raw(a) processes are not causing the current warming. What we can do is eliminate every possible natural explanation that can be posited. Thermodynamics tells us that the warming of the personifyences pooh-pooh atmosphere must arise from one or more processes that bring supererogatory heat to the swallow atmosphere. to a fault the greenhouse effect, the workable processes are (1) increase produce from the sun (2) increase ducking of heat from the sun due to a change in the existences planetary mirror image or reflective power and (3) an internal variation in the climate system that transfers heat from one part of th e man to the atmosphere.Direct observations strengthen that no(prenominal) of these explains the observe warming over the latter half of the 20th century. For example there has been no appreciable change in solar outturn over the away two decades (see simulacrum 1). blueprint 1. Change in solar payoff from 1980 to 2005. run into 1 shows the relative change in solar fruit situated from two of major planet measurements over a two-decade period. The data show variability in solar output similar to the 11-year yellow spot cycle, but no lay trend. credit subsequently slant and Froelich, 2006. 4Satellite data exhibit that the backgrounds observation increase (causing cooling sooner of warming) in the 60s, 70s, and early 80s and has fall modestly since. 4 The boilers suit warming from the recent decrease in musing is also small compared to the greenhouse warming. In the shimmy of internal variations, the sea is the only viable rootage of internal heat that coul d pitch caused the atmosphere to warm on decadal time-scales. However, observations show that the heat content of the sea has increase instead of reduced over the olden few decades (See ensure 2).This indicates that the atmosphere has been a source of heat to the sea earlier than vice versa. Moreover, the enumerate of heat increase in the ocean is lucid with what is necessitate to balance the creations qualification calculate given over the overindulgence heating from the deepen greenhouse effect and the add of prodigality heat detect to be stored in the atmosphere (Hansen et al. Science, 308, 2005, pg. 1431). In other words, the meter of heat stored in the ocean over recent years matches the metre of heat that models predict should be detain on footing due to the increase in greenhouse gases. figure 2.Change in heat content of ocean 1955 to 2005 stem afterward Levitus et al. 2005. enroll 2 SHOWS THE sexual congress neuter IN THE instigate COTENT OF THE ocean FROM 1955 TO 2005 ground ON A spaciotemporal depth psychology OF ocean TEMPERATURE MEASUREMENTS. THE selective information SHOW rook terminal figure variance solely A work upwardly turn off ON DECADAL TIME-SCALES. terminal The Medieval Warm Period does not play an simile to the warming of the late 20th century, for which scientists leave nonsymbiotic yard of human causation, and the tell apart potently suggests that the MWP was a regional, sort of than a global phenomenon. Our discernment of the climate system is sufficient to provide qualitative models for most global or hemispheric climatic variations over geologic history and denary models for variations over the knightly millennium. The balls climate may return to ice age conditions in thousands of years, but this does not veto destroy cause from global warming over the nigh few centuries. 5 altogether known natural explanations for the current global warming trend give up been eliminated by direct observations.The human-intensified greenhouse effect provides the only numerical explanation for the current warming trend. somewhat the authors Dr. Wang stock his doctorate from Harvard University and work as a climate scientist at environmental Defense. He has publish several peer-reviewed papers on the global methane budget and was the author of The in style(p) Myths and Facts on spheric Warming, which was read into the congressional record by Senator whoremaster McCain in 2005. The distinguish is available at http//www. undoit. org/pdfs/mythsvfacts. pdf. Dr. Chameides, tribal chief scientist at environmental Defense, is a member of the U.S. home(a) honorary society of Sciences and has been named a field confederate of the matter Academies. He is also an American geophysical Union Fellow, and has authorized the American geophysical Unions Macelwane Award. Dr. Chameides has served as editor of the ledger of geophysical interrogation and is the author or coa uthor of more than cxx scientific publications and five books. He legitimate his doctorate from Yale University. The explanations are qualitative instead of quantitative because we do not have quantitative data from these events in the far-flung gone to construct their exact histories. It has been suggested establish on temperature reconstructions and model simulations that the MWP may have been caused by increase solar activity or a shortage of volcanic activity. 3 th Because worldwide temperature measurements do not exist aheadhand the 19 century, temperature records before th the 19 century are base on reconstructions of the temperature from the variations in temperature-sensitive proxies (e. g. , tree rings, isotopes in ice cores). 4 These variations are perhaps due to changes in the concentrations of atmospheric aerosols produced from the zealous of fossil fuels and biomass. 1 6