"NEIL DEGRASSE TYSON:" "Oncetherewasaworld notsoverydifferent fromourown." "Therewereoccasional naturalcatastrophes, massivevolcaniceruptions and,everyonceina while, anasteroidwouldcome barrelingoutof theblue todosomedamage." "Butforthefirst billionyearsor so , itwould'veseemed likea paradise." "Thisiswhatwethink theplanetVenus mighthavelookedlikewhen  oursolarsystemwas young." "Thenthingsstarted togohorriblywrong." "¶ ¶" "¶ ¶" "¶ ¶" "¶ ¶" "DEGRASSE TYSON:" "The planet Venus, which once may have seemed like a heaven, turned into a kind of hell." "The difference between the two can be a delicate balance, far more delicate than you might imagine." "Once things began to unravel, there was no way back." "This is what Venus, our nearest planetary neighbor, looks like today." "Venus'soceansarelonggone ." "Thesurfaceis hotter thana broilingoven, hotenoughto meltlead." "Why?" "Youmightthink it'sbecauseVenus is30%closertotheSun thantheEarthis,  butthat'snotthe reason." "Venusiscompletely covered by clouds of sulfuric acid that keep almost all the sunlight from reaching the surface." "That ought to make Venus much colder than the Earth." "So why is Venus scorching hot?" "It's because the small amount of sunlight that trickles in through the clouds to reach the surface can't get back out again." "The flow of energy is blocked by a dense atmosphere of carbon dioxide." "That carbon dioxide gas-- or CO2 for short-- acts like a smothering blanket to keep the heat in." "No one is burning coal or driving big gas-guzzlers on Venus." "Nature can destroy an environment without any help from intelligent life." "Venus is in the grip of a runaway greenhouse effect." "Whydoesit looklike we'reinsideabowl?" "It'sdueto theintense atmosphericpressure." "That'sthewreckofVenera13." "In1982,thescientists andengineers ofwhatwasthen theSovietUnion successfullylanded thisspacecrafton Venus." "Theymanaged tokeepit refrigerated forovertwohours, soitcouldphotograph itssurroundings... andtransmittheimages backtoEarth beforetheonboardelectronics werefried." "VenusandEarthstartedout withaboutthesameamount of carbon, but the two worlds were propelled along radically different paths, and carbon was the decisive element in both stories." "On Venus, it's almost all in the form of gas-- carbon dioxide-- in the atmosphere." "Most of the carbon on Earth has been stored for eons in solid vaults of carbonate rock, like this one, part of a chain that forms the celebrated White Cliffs of Dover, right on the English Channel." "What titan built this wonder of the world?" "Acreatureathousandtimes smallerthanapinhead." "Trillionsofthem." "One-celledalgae." "Volcanoes supply carbon dioxide to the atmosphere, and the oceans slowly absorb it." "Working over the course of millions of years, the microscopic algae harvested the carbon dioxide and turned it into these tiny shells." "They accumulated in thick deposits of chalk, or limestone, on the ocean floor." "Later, the restless Earth pushed up the seafloor and carved out these massive cliffs." "Other marine creatures took in carbon dioxide to build enormous coral reefs." "And the oceans converted dissolved CO2 into limestone even without any help from life." "As a result, only a trace amount was left as a gas in Earth's atmosphere." "Not even three-hundredths of one percent." "Think of it-- fewer than three molecules out of every ten thousand." "Andyet,it makes thecriticaldifference betweena barrenwasteland anda gardenof lifeonEarth." "WithnoCO2atall,  theEarthwouldbefrozen." "Andwithtwiceasmany , we'restilltalking aboutonlysixmolecules outoftenthousand." "Thingswouldget uncomfortablyhot andcauseus  someseriousproblems... butneveras hotasVenus;" "notevenclose." "Thatplanetlost itsoceanto space billionsofyearsago ." "Withoutanocean, ithadno waytocaptureCO2 fromtheatmosphere andstoreit as amineral." "TheCO2fromeruptingvolcanoes justcontinuedto buildup." "Today,thatatmosphere is90timesheavierthan ours ." "Almostallof it is  heat-trappingcarbondioxide." "That'swhyVenusis sucha ferociousinferno sohostileto life." "TheEarth, instunningcontrast, isalive." "It breathes... but very slowly." "A single breath takes a whole year." "The forests contain most of Earth's life, and most forests are in the Northern Hemisphere." "When spring comes to the north, the forests inhale carbon dioxide from the air and grow, turning the land green." "The amount of CO2 in the atmosphere goes down." "When fall comes and the plants drop their leaves, they decay, exhaling the carbon dioxide back into the atmosphere." "The same thing happens in the Southern Hemisphere at the opposite time of the year." "But the Southern Hemisphere is mostly ocean." "So it's the forests of the north that control the annual changes in the global CO2." "The Earth has been breathing like this for tens of millions of years." "But nobody noticed until 1958, when an oceanographer named Charles David Keeling devised a way to accurately measure the amount of carbon dioxide in the atmosphere." "Keeling discovered the Earth's exquisite respiration." "But he also discovered something shocking-- a rapid rise, unprecedented in human history, in the overall level of CO2, one that has continued ever since." "It's a striking departure from the CO2 levels that prevailed during the rise of agriculture and civilization." "In fact, the Earth has seen nothing like it for three million years." "How can we be so sure?" "Theevidenceis written inwater." "DEGRASSE TYSON:" "The Earth keeps adetaileddiary written in the snows of yesteryear." "Climate scientists have drilled ice cores from the depths of glaciers in Greenland and Antarctica." "Theicelayershaveancientair trappedinsidethem." "We can read the unbroken record of Earth's atmosphere that extends back over the last 800,000 years." "In all that time, the amount of carbon dioxide in the air never rose above three-hundredths of one percent." "That is, until the turn of the 20th century." "And it's been going up steadily and rapidly ever since." "It's now more than 40% higher than before the Industrial Revolution." "By burning coal, oil and gas, our civilization is exhaling carbon dioxide much faster than Earth can absorb it." "So CO2 is building up in the atmosphere." "The planet is heating up." "Every warm object radiates a kind of light we can't see with the naked eye-- thermal infrared light." "We all glow with invisible heat radiation, even in the dark." "This is what the Earth looks like in the infrared." "You're seeing the planet's own body heat." "Incominglight fromtheSunhitsthesurface." "TheEarthabsorbsmuch ofthatenergy, whichheatstheplanetup andmakesthesurfaceglow  ininfraredlight." "Butthecarbondioxide intheatmosphere absorbsmostof thatoutgoing heatradiation, sendingmuchof it  rightbackto thesurface." "Thismakestheplanet evenwarmer." "That'sallthereis tothegreenhouseeffect." "It'sbasicphysics, justbookkeeping oftheenergyflow." "There'snothing controversialaboutit ." "Ifwedidn'thaveanycarbon dioxideinouratmosphere, theEarthwouldjustbe agreatbigsnowball, andwewouldn'tbehere ." "So, a little greenhouse effect is a good thing." "But a big one can destabilize the climate and wreck our way of life." "All right... but how do we know that we're the problem?" "Maybe the Earth itself is causing the rise in CO2." "Maybe it has nothing to do with the coal and oil we burn." "Maybe it's those damn volcanoes." "(deep rumbling)" "Every few years, Mount Etna, in Sicily, blows its stack." "Each big eruption sends millions of tons of CO2 into the atmosphere." "Now, combine that with the output ofalltheothervolcanic activityontheplanet." "Let'stakethelargest scientificestimate-- about500milliontons ofvolcanicCO2 enteringtheatmosphere everyear." "Soundslikealot ,right?" "Butthat'snoteventwopercent ofthe30 billiontonsofCO2 thatourcivilization iscrankingouteveryyear ." "And,funnything, themeasuredincreaseinCO2 intheatmosphere tallieswiththeknownamount we'redumpingthere byburningcoal,oil and gas ." "Volcanic CO2 has a distinct signature-- it's slightly heavier than the kind produced by burning fossil fuels." "We can tell the difference between the two when we examine them at the atomic level." "It's clear that the increased CO2 in the air is not from volcanoes." "What's more, the observed warming is as much as predicted from the measured increase in carbon dioxide." "It's a pretty tight case." "Our fingerprints are all over this one." "How much is 30 billion tons of CO2 per year?" "If you compressed it into solid form, it would occupy about the same volume as the White Cliffs of Dover." "And we're adding that much CO2 to the air every year, relentlessly, year after year." "Unlucky for us, the main waste product of our civilization is not just any substance." "It happens to be the chief climate-regulating gas of our global thermostat, year in, year out." "Too bad CO2 is an invisible gas." "Maybe if we could see it... (car engine starts)" "Ifoureyesweresensitive toCO2-- andperhapsthereare  suchbeingsin thecosmos-- ifwecouldsee all  thatcarbondioxide, thenwewouldovercome thedenial andgraspthemagnitudeof ourimpacton theatmosphere." "But the evidence that the world is getting warmer is all around us." "For starters, let's just check the thermometers." "Weather stations around the world have been keeping reliable temperature records since the 1880s, and NASA has used the data to compile a map tracking the average temperatures around the world through time." "Yellowmeans warmertemperatures thantheaverage, foranyregioninthe1880s ." "Orangemeanshot." "Andredmeanshotter." "Theworldis warmerthanitwas inthe19thcentury." "Backthen,at thegreatestfair  theworldhaseverseen , aforgottengeniusdemonstrated thesolutionto thisproblem." "Comewithme ." "DEGRASSE TYSON:" "Oncetherewasaworld thatwasnottoo hot  andnottoocold." "Itwasjustright." "Thentherecameatime  whenthelifeitsustained begantonotice ourlovelyplanetwas changing." "Andit'snot asifwe didn'tsee itcoming." "Asfarbackas1896 , theSwedishscientist SvanteArrhenius calculated thatdoublingtheamount ofCO2in theatmosphere wouldmelttheArcticice." "Inthe1930s,the American physicistE.O.Hulburt, attheNaval ResearchLaboratory, confirmedthatresult." "Sofar,it wasstill justtheoretical." "Butthen,theEnglishengineer GuyCallendar assembledtheevidencetoshow  thatboththeCO2 and  theaverageglobaltemperature wereactuallyincreasing." "Even now, man may be unwittingly changing the world's climate through the waste products of his civilization." "Duetoourrelease, throughfactories andautomobileseveryyear, ofmorethan sixbilliontons ofcarbondioxide, whichhelpsairabsorbheat  fromtheSun, our atmosphere seems to be getting warmer." "This is bad?" "Well, it's been calculated, a few degrees rise in the Earth's temperature wouldmeltthepolaricecaps." "DEGRASSE TYSON:" "In 1960, CarlSagan'sPhDthesis includedthefirstcalculation oftherunaway greenhouseeffecton Venus." "Thiswaspart ofa career-longinterest intheatmospheresof theplanets,includingour own ." "IntheoriginalCosmosseries, in1980,CarlSaganwarned..." "SAGAN:" "We are releasing vast quantitiesofcarbondioxide, increasing thegreenhouseeffect." "Itmaynottakemuch  todestabilize theEarth'sclimate, toconvertthisheaven, ouronlyhomeinthecosmos, intoa kindof hell." "Since Carl spoke those words, we've burdened the atmosphere of our world with an additional" "400 billion tons of carbon dioxide." "If we don't change our ways, what will the planet be like in our children's future?" "Basedonscientific projections, ifwejustkeep ondoingbusinessasusual, ourkidsarein fora roughride:" "Killerheatwaves, recorddroughts, risingsealevels, massextinctionof species." "Weinheritedabountifulworld madepossible bya relativelystableclimate." "Agriculture andcivilizationflourished forthousandsof years." "Andnow,ourcarelessnessand greedputallofthat atrisk." "Okay, so if we scientists are so good at making these dire, long-term predictions about the climate, how come we're so lousy about predicting the weather?" "Besides, this year, we had a colder winter in my town." "For all us scientists know, we could be in for global cooling." "Here's the difference between weather and climate:" "Weather is what the atmosphere does in the short term-- hour to hour, day to day." "Weather is chaotic, which means that even a microscopic disturbance can lead to large-scale changes." "That's why those ten-day weather forecasts are useless." "A butterfly flaps its wings in Bali, and six weeks later, your outdoor wedding in Maine is ruined." "Climate is the long-term average of the weather, over a number of years." "It's shaped by global forces that alter the energy balance in the atmosphere, such as changes in the Sun, the tilt of the Earth's axis, the amount of sunlight the Earth reflects back to space and the concentration of greenhouse gases in the air." "A change in any of them affects the climate in ways that are broadly predictable." "My friend'd's meandering represents the short-term fluctuations-- that's weather." "It's almost impossible to predict what'll attract his interest next, but not hard to know what the range of his meandering will be, because I'm holding him on a leash." "We can't observe climate directly-- all we see is the weather-- but the average weather, over the course of years, reveals a pattern." "I represent that long-term trend, which is climate." "Keep your eye on the man, not the dog." "Weather is hard to predict, like my friend here, but climate is predictable." "Climate has changed many times in the long history of the Earth but always in response to a global force." "The strongest force driving climate change right now is the increasing CO2 from the burning of fossil fuels, which is trapping more heat from the Sun." "All that additional energy has to go somewhere." "Some of it warms the air." "Most of it ends up in the oceans." "All over the world, the oceans are getting warmer." "It'smostobvious intheArcticOcean andthelandsthatsurroundit." "Okay,sowe 'relosing thesummerseaice  ina place wherehardlyanyoneevergoes ." "WhatdoIcareifthere 's noicearoundthe NorthPole ?" "Iceisthebrightest naturalsurfaceon theEarth, andopenoceanwater isthedarkest." "Icereflectsincomingsunlight backtospace." "Waterabsorbssunlight andgetswarmer, whichmeltsevenmoreice,  whichexposes stillmoreoceansurface toabsorbevenmoresunlight." "Thisiswhatwecall  apositivefeedbackloop." "It'soneof manynatural mechanismsthatmagnify anywarmingcaused byCO2alone." "We're at Drew Point, Alaska, on the edge of the Arctic Ocean." "DEGRASSE TYSON:" "WhenI wasborn,the shoreline wasa milefartherout , anditwasbreakingoffata rateofabout20feet peryear." "Now... it'sbeingeatenaway atabout50 feetper year." "TheArcticOceaniswarming andatan increasingrate." "Soit'sice-free duringmoreof theyear." "Thatleavestheshorehere  moreexposedto erosion fromstorms, whicharealsogetting morepowerful, anothereffect ofclimatechange." "The northern reaches of Alaska, Siberia and Canada are mostly permafrost, groundthathasbeenfrozen year-roundformillennia." "Itcontainslots oforganicmatter, oldleavesandroots fromplants thatgrewthousands ofyearsago." "BecausetheArcticregions arewarmingfaster thananywhereelseonEarth, thepermafrostis thawing anditscontentsare rotting, justlikewhenyou unplug thefreezer." "Thethawingpermafrost isreleasingcarbondioxide andmethane,an evenmore potentgreenhousegas, intotheatmosphere." "Thisismakingthings evenwarmer, anotherexampleof apositive feedbackmechanism." "Theworld'spermafroststores enoughcarbon tomorethandoubletheCO2 intheatmosphere." "At the rate we're going, global warming could release most of it by the end of the century." "We might be tipping the climate past a point of no return into an unpredictable slide." "Okay,theair,the water andtheland areallgettingwarmer, so global warming is really happening." "But maybe it's not our fault." "Maybe it's just nature." "Maybe it's the Sun." "No,it'snotthe Sun ." "We'vebeenmonitoringthe Sun  verycloselyfordecades, andthesolarenergyoutput hasn'tchanged." "What'smore,theEarth iswarmingmoreatnight thanindaytime, andmorein winter thaninsummer." "That'sexactlywhatweexpect fromgreenhousewarming, buttheoppositeofwhat  increasedsolaroutput wouldcause." "It'snowclearbeyond anyreasonabledoubt thatwearechanging theclimate." "TheSunisn'tthe problem." "Butitis thesolution, andwe'veknownthis fora longtime, muchlonger thanyoumightthink." "Paris,September1878." "TheEiffelTowerwon 'tbebuilt foryearsto come." "Witnessone ofthemostgloriousspectacles theworldhaseverseen ." "Themagnificenthead oftheStatueofLiberty hasjustbeencompleted." "Thousandsofexhibitors fromaroundtheplanet covered66acresofParis withtheirinventions andgoods." "Edison'sfirstpublic demonstrationofthelightbulb willnottakeplace foranotheryear." "There'snosuchthing aselectricalappliances." "Peopledon'tflickswitches andpressbuttons." "It'sa hand-cranked, horse-drawnworld." "That'stheguywecame tosee, theone withthecrazymoustache." "He'sa mathteacher namedAugustinMouchot." "Remember,it's1878." "Thisisaworld litmostlyby gaslight." "Theautomobile isstillyearsaway." "ButMouchot,here, isdazzlingthecrowd withhissolarpower concentrator." "The Sun belongs to all of us!" "Even though it is 150 million kilometers away from us, feel its awesome power!" "My invention concentrates the free energy of the Sun and converts it into mechanical motion." "It can power any kind of machine." "It can produce electricity or run a printing press or make ice on a hot day." "Etvoilà!" "(spectators gasp, chatter)" "(chuckles)" "Think of it, sunlight converted into ice." "You see, my friends, what wonders we can work if we harness the bounteous energy of the Sun." "The world will someday run out of coal, but the magnificent Sun will always be there for us." "Mouchot took home the gold medal from the fair." "But the price of coal tumbled, becoming so cheap that there was no interest in solar energy." "Besides, no one understood, back then, what the true cost was of burning fossil fuel." "Mouchot's research funding was cut off." "35 years later, in the early years of the 20th century, another door opened to an alternative future." "It happened in Egypt, on the banks of the Nile." "DEGRASSE TYSON:" "Memotofuturetimetravelers:" "thiswouldbe  anexcellententrypoint foravertingclimatechange." "Egypt,1913." "That'sFrankShuman ofPhiladelphia." "He'sonlyhad threeyearsof schooling, buthisgeniusfor innovation morethanmakesupforthat." "Beforehewas30, Shuman hadinventedsafetyglass." "Itsusein automobilesand  skylightssavedcountlesslives andmadehimavery rich man,  richenough topursuehisrealpassion, solarenergy." "Shumanledtheteam thatdesignedandbuilt anarray ofsolarenergyconcentrators." "Itcouldpowerasteamengine." "Shumanishoping tousetheSun 'spower toirrigatethedesert andturnit green." "Theofficialinauguration ofShuman'ssolarpowerplant, in1913, wasa dazzlingsuccess." "Hehadinventedapracticalway totaptheSun 'senergy onanindustrialscale, makingsolarenergy evencheaperthancoal." "TheBritish andGermangovernments bothofferedShuman generousfunding todevelophisinvention." "Itwastheidealsource ofabundantpower intropicalregions, whereimportedcoal wasprohibitivelyexpensive." "ButShumanwasdreaming evenbigger." "Ina letter toScientificAmerican, hecalculated thathissolarpowerplants, ifdeployedin an area oftheSaharaDesert only150milesona side , couldsupplyas muchpower asconsumedby all theindustriesof theworld." "Butitwasnot tobe." "Themarketforaliquid fossilfuel,petroleum, wasexplodingforshipping, homeheating, andcarsandtrucks." "Oilwasabundant, cheapereventhancoal, andmucheasiertoget outofthegroundandprocess." "Ittook100men aweek  tofuelashipwith coal , butwithoil, onemancoulddothejob ina singleday." "AyearafterShuman's triumphinthedesert," "WorldWarIbrokeout." "Hissolarcollectors wererecycledintoweapons." "FrankShuman'sdream ofa solar-poweredcivilization wouldhaveto wait anothercentury beforeitwasreborn." "There'sanotherinexhaustible sourceofcleanenergy fortheworld." "Thewindsthemselves aresolarpowered, becauseourstardrives thewindsandthe waves." "Unlikesolarcollectors, windfarmstakeup verylittleland, andnoneat all,ifoffshore, wherethewindsare strongest." "Ifwecouldtap even onepercentof theirpower, we'dhaveenoughenergy torunourcivilization." "And more solar energy falls on Earth in one hour than all the energy our civilization consumes in an entire year." "If we could harness a tiny fraction of the available solar and wind power, we could supply all our energy needs forever, and without adding any carbon to the atmosphere." "It'snottoolate." "There's a future worth fighting for." "How do I know?" "Every one of us comes from a long line of survivors." "Ourspeciesis nothing ifnotadaptive." "Itwasonlybecause ourancestorslearned tothinklong-term, andactaccordingly, thatwe'rehereatall." "We'vehadourbacks tothewallbefore, andwecamethrough toscalenewheights." "Infact,themostmythic humanaccomplishmentsof all cameoutof ourdarkesthour ." "DEGRASSE TYSON:" "Oncetherewasaworld riggedwith60,000 hair-triggerednuclearweapons." "Thecombatantswere thetwomostpowerful countriesonEarth, andtheywerelocked ina deadlyembrace, eachvowingthat theywouldrathersee  everythingwelovedestroyed thansubmit tothewilloftheother ." "WhenI wasthreeyearsold,  thelargestman-made explosionofalltime wasdetonated bytheSovietUnion." "Thatterrorhassubsided, tobereplacedbynewfears ." "Thedangerthatthe 2,000 largestcitieson Earth wouldbereducedtorubble inthespaceofanafternoon isnolongerone ofthem ." "Thenuclearrivalry betweentheUnitedStates andtheSovietUnion hadanotherby-product." "TheApollomissionstotheMoon wereanextension ofthearmsrace thatragedbetweenthem." "Sendingpeople toorbittheEarth orgoto theMoon requiresbig,reliable, powerfulrockets-- preciselythesametechnology youneedto carry anuclearwarhead halfwayaroundtheplanet todestroyyourenemy's largestcities." "PRESIDENT KENNEDY:" "Ibelievethatthisnation shouldcommititself toachievingthegoal, beforethisdecadeisout,  oflandingaman ontheMoon andreturninghimsafely totheEarth." "DEGRASSE TYSON:" "PresidentKennedy's1961speech electrifiedthenation, anditcontainedmuch thatwasremarkablyprophetic-- butnotawordabout ascientificobjective forgoingto theMoon." "Noquestions abouttheMoon'sorigin orthehopeofbringingback samplestoanalyze." "No,theApollomissions wereconceived asa demonstration ofthesuperiorpower andprecision ofourstrategicmissiles." "Buta funnything happenedtous  onourwaytotheMoon." "Welookedhomeward... and discovered another world-- our own." "Forthefirsttime, weinhabitantsof Earth couldstepback andseeit as it reallyis- - oneworld,indivisible, andkindof small inthecosmiccontext." "Whateverthereasonwefirst musteredtheenormousresources required fortheApolloprogram, howevermiredit was inColdWarnationalism andtheinstrumentsofdeath, theinescapablerecognition oftheunity andfragilityof theEarth isitsclear andluminousdividend," "theunexpectedgiftofApollo." "Aprojectconceived indeadlycompetition madeusrecognize ourcommunity." "Whattitanbuilt thiswonderof theworld?" "It was the Ifugao people of the Philippines, working with not much more than their hands." "About 10,000 years ago, our ancestors all over the world took advantage of another form of climate change, the gentler climate of the intermission in the ice age-- they invented agriculture." "They gave up the ceaseless wandering, hunting and gathering that had been their way of life for a million years or so, to settle down and produce food." "They found a way to harvest ten to a hundred times more solar energy than the environment naturally provided for their ancestors." "People all over the world made the difficult transition from nomadic cultures to agricultural ones that used solar energy more efficiently." "It gave rise to civilization." "We stand on the shoulders of those who did the hard work that such a fundamental transformation required." "Now... it's our turn." "Oncetherewasaworld..." "IflifeeverexistedonVenus , itwouldhavehad nochance toavertthehellishdestiny ofthisworld." "Thisrunawaygreenhouseeffect wasunstoppable." "(thunder crashing)" "Once... there was a world ours." "And that world is now." "There are no scientific or technological obstacles to protecting our world and the precious life that it supports." "It all depends... on what we truly value... and if we can summon the will to act." "¶ ¶" "PRESIDENT KENNEDY:" "Butwhy,somesay ,the Moon?" "Whychoosethisasourgoal?" "Andtheymaywellask,  whyclimbthehighestmountain?" "Wechoose togoto theMoon... wechooseto go to theMoon... (applause,cheering)" "...wechooseto go to theMoon inthisdecade anddotheotherthings, notbecausetheyare easy, butbecausetheyare hard." "Captioned by MediaAccessGroupatWGBH  access.wgbh.org"