>>> TURNING NOW TO A FEAT OF SKILL AND BRAVERY IN THE NAME OF SCIENCE.

YOU MAY REMEMBER CLIMBER ALEX HONNOLD FROM THE OSCAR WINNING DOCUMENTARY "FREE SOLO" WHEN HE BECAME THE FIRST PERSON TO SCALE EL CAPITAN IN YOSEMITE NATIONAL PARK WITHOUT ANY ROPES.

NOW IN A NEW NATIONAL GEOGRAPHIC SERIES "ARCTIC ASCENT," HE SETS HIS SIGHTS EVEN HIGHER ON A 4,000 FOOT SEA CLIFF IN GREEN LAND.

THIS TIME HE'S GOT ROPES, BUT HE'S ALSO GOT THE CLIMATE ON HIS MIND, AND HE IS JOINED BY A TEAM OF SCIENTISTS HEADED UP BY GLACIOLOGIST HEIDI SEVESTRE.

HARI SREENIVASAN SPEAKS TO THEM BOTH ABOUT WHAT THEY DISCOVERED.

>> EXPEDITION LEADER ALEX HONNOLD AND GLACIOLOGIST HEIDI SEVESTRE, THANK YOU BOTH FOR JOINING US.

ALEX, LET ME START WITH YOU.

OUR VIEWERS MIGHT REMEMBER YOU STOPPED BY OUR STUDIOS A FEW YEARS AGO WHEN YOU WERE OUT TALKING ABOUT "FREE SOLO," A MOVIE THAT CATALOGED AN EXCRUCIATING AND ANXIETY INDUCING DETAIL YOUR ASCENT ABOVE EL CAPITAN, ONE OF THE MOST FAMOUS ROCK FACES IN THE UNITED STATES.

THIS IS A FILM THAT DOES CATALOG YOU TAKING ON AN ASCENT IN GREENLAND, BUT IT SEEMS LIKE THERE WAS MORE TO IT THAT INTERESTED YOU THAN JUST THE ROCK CLIMBING.

WHY DID YOU DO THIS?

>> THIS EXPEDITION WAS MUCH BROADER IN SCOPE AND IN PURPOSE.

WE WERE IN A REMOTE PART OF EASTERN GREENLAND.

WE WERE THERE DOING SCIENCE WITH HEIDI, WHO IS RUNNING MANY DIFFERENT PROJECTS ALONG OUR JOURNEY.

AND MOSTLY WE WERE JUST EXPLORING THIS INCREDIBLE LANDSCAPE AND SORT OF TELLING A STORY ABOUT WHY GREENLAND AND WHY THE ARCTIC IS SO IMPORTANT FOR COMMUNITY.

>> THE FIRST PICTURE I SAW, IT LOOKED LIKE THE SCARIEST WALL I'VE EVER SEEN.

WE HAVE NO IDEA WHAT THE ROCK WILL BE LIKE.

SO WE'VE ASKED TWO OF THE BEST CLIMBERS IN THE WORLD TO JOIN ME.

AND WE HAVE THE RIGHT HUMAN TO DO MEANINGFUL RESEARCH AS WE GO CLIMBING.

>> NO ONE HAS BEEN HERE FOR ALMOST TWO DECADES.

BECAUSE IT'S REALLY ONE OF THE MOST DANGEROUS ENVIRONMENTS ON EARTH.

>> HEIDI, TELL OUR AUDIENCE WHAT IS THE CONSEQUENCE OF THE MELTING THAT IS HAPPENING IN THE ARCTIC AND IN GREENLAND.

>> THE ARCTIC IS WARMING THREE TO FOUR TIMES FASTER THAN THE REST OF THE WORLD.

AND WE'RE SEEING THE IMPACTS OF CLIMATE CHANGE DAY IN AND DAY OUT IN THAT REGION.

WHEN YOU THINK OF THE ARCTIC, YOU HAVE TO UNDERSTAND THAT THERE IS THIS GIANT ISLAND OF GREENLAND THAT IS MOSTLY COVERED BY ICE.

IF THIS ICE WERE TO MELT AWAY, IT WOULD INCREASE SEA LEVELS GLOBALLY BY UP TO 24 FEET.

SO OUR FUTURE IS DIRECTLY CONNECTED TO THE HEALTH OF THE ARCTIC AND TO THE HEALTH OF THE GREENLAND ICE SHEETS.

>> ALEX, YOU HAVE BEEN INTERESTED IN ENVIRONMENT AND PROTECTING IT AND THINKING ABOUT CLIMATE CHANGE FOR QUITE SOME TIME NOW.

WHEN YOU STARTED OUT ON THIS TREK, EVEN JUST TO GET TO THE FACE YOU'RE GOING THE CLIMB, WHAT DID YOU NOTICE?

>> WELL, TO BE HONEST, IT FOR ME AS A LAYPERSON, AS A NONSCIENTIST, I JUST NOTICED INCREDIBLE GLACIERS, INCREDIBLE MOUNTAINS, INCREDIBLE SCENERY.

AND THAT'S PART OF THE WONDER OF GREENLAND IS THAT IT IS ALMOST LIKE A FANTASY LANDSCAPE.

IT'S JUST INCREDIBLE.

EVERYTHING, THE SCALE IS SO VAST.

I THINK FROM A LAY PERSPECTIVE, IT'S AMAZING.

IT'S BEAUTIFUL.

AND I THINK THAT'S A BIG PART OF WHAT YOU SEE IN THE SHOW IS JUST THE INCREDIBLE BEAUTY OF THE LANDSCAPE.

BUT I THINK IT'S THROUGH THE SCIENCE THAT HEIDI IS DOING THAT YOU CAN SEE HOW QUICKLY THAT LANDSCAPE IS CHANGING.

FOR ME, IT'S THE FIRST TIME GOING TO A PLACE LIKE THAT.

SO IT JUST LOOKS AMAZING.

BUT THE MORE YOU KNOW ABOUT IT AND THE MORE YOU UNDERSTAND IT, THE MORE CONCERNING IT CAN BE.

>> WHEN IT COMES TO CLIMATE CHANGE, GREENLAND IS ONE OF THE MOST IMPORTANT PLACES ON THE PLANET.

IT'S GOTTEN ABOUT 5.5 DEGREES WARMER OVER THE LAST 40 YEARS.

MORE AND MORE OF ITS ICE IS MELTING, RAISING THE SEA LEVEL AROUND THE WORLD.

IT IS EXTREMELY REMOTE, AND SCIENTISTS RARELY HAVE AN OPPORTUNITY TO STUDY THE AREA AROUND IT.

>> HEIDI, MOST OF THE PLACES THAT THIS EXPEDITION WENT TO ARE PLACES THAT HUMANS DON'T GET A CHANCE TO WALK MUCH LESS TAKE SCIENTIFIC OBSERVATIONS OF.

SO GIVE US AN IDEA OF THE RANGE OF MEASUREMENTS THAT YOU WERE TAKING ON REALLY THE APPROACH TO WHERE ALEX AND HIS TEAM WERE GOING TO CLIMB.

>> I JOINED THIS EXPEDITION WAS REALLY A DREAM COME TRUE FOR A SCIENTIST, BECAUSE THIS IS ONE OF THE LEAST EXPLORED, LEAST STUDIED PARTS OF GREENLAND.

WE WERE IN EAST GREENLAND, THIS FJORD OF LEGENDS.

AND FOR SIX WEEKS, ACTUALLY WE TRAVERSED A BIG PART OF THIS FJORD, CROSSING GLACIERS, ICECAPS, COLLECTING MEASUREMENTS IN THE VERY DEEP FJORD, INSTALLING INSTRUMENTS ON THESE MASSIVE CLIFFS.

AND IN TOTAL, WE WORKED WITH 12 DIFFERENT RESEARCH INSTITUTES ON THIS EXPEDITION, INCLUDING NASA.

AND WE PERFORMED 18 DIFFERENT RESEARCH PROTOCOLS FROM GOING INTO GLACIERS, COLLECTING ROCK CORES, MEASURING ICE THICKNESS AND WATER TEMPERATURE.

THIS WAS KEY FOR THE RESEARCH COMMUNITY.

AND I'M REALLY GLAD TO SEE HOW MUCH DATA WE WERE ABLE TO BRING BACK AND SHARE WITH THESE DIFFERENT RESEARCH INSTITUTIONS.

>> HEIDI, I KNOW IT TAKES A WHILE FOR SCIENTISTS TO PORE DATA AND COME TO SOME CONCLUSIONS.

ARE THERE EXAMPLES OF THINGS YOU HAVE FOUND DURING THIS EXPEDITION THAT ARE ALREADY ADVANCING WHAT WE UNDERSTANDING GLACIERS OR ABOUT PERMAFROST THAT IS HAPPENING THERE?

>> ABSOLUTELY.

SCIENCE TAKES TIME.

IT WILL PROBABLY TAKE ANOTHER COUPLE OF YEARS TO GET ALL THE RESULTS FROM THIS EXPEDITION.

WE ALREADY HAVE SOME PRELIMINARY RESULTS, ESPECIALLY REGARDING THE INSTRUMENTS THAT WE LAUNCHED FOR NASA IN THE WATER IN THE FJORD.

SO THIS INSTRUMENT IS CALLED A FLOAT, AND WE LAUNCHED IT FOR A PROJECT CALLED OCEANS MELTING GREENLAND.

AND THE FLOAT WAS BASICALLY GOING UP AND DOWN THE WATER COLUMN, MEASURING WATER TEMPERATURE AND WATER SALINITY.

AND WHAT THIS ROBOT WAS ABLE TO TELL US IS THAT THE FJORD IS DEFINITELY GETTING WARMER.

THIS IS NOT GOOD NEWS, BECAUSE IF THE WATER AROUND THE PERIPHERY OF THE ICE SHEETS IS WARMING UP, IT MEANS IT CAN EAT AWAY AT THE ICE AROUND THE ICE SHEET AND REALLY CATALYZE CALVING AND CATALYZE SEA LEVEL RISE AROUND THE WORLD.

>> ALEX, LET'S START TALKING A LITTLE BIT ABOUT THIS CLIMB.

I MEAN, WHEN YOU SHOWED THE SCALE OF, SAY, THE EMPIRE STATE BUILDING, EL CAPITAN, WHICH IS ALREADY ENORMOUS, WHICH YOU ASCENDED WITHOUT ANY ROPES, THIS ROCK, THIS SEA CLIFF IS A MONSTER.

IT'S EVEN BIGGER.

WHEN YOU CAME UP TO IT ON THE BOAT, KIND OF SAW IT FOR THE FIRST TIME, WHAT WENT THROUGH YOUR MIND?

>> OH, SURE.

HEIDI AND I BOTH SMILE BECAUSE WE BOTH REMEMBER SEEING IT FROM THE BOAT FOR THE FIRST TIME, AND WE ALL THOUGHT OH, NO, IT LOOKED TOO BIG AND IT LOOKED TOO DAUNTING.

IT LOOKED VERY CHALLENGING.

BUT, YOU KNOW, THEN WE SET TO WORK AND STARTED CHIPPING AWAY AT IT SO TO SPEAK, STARTED CLIMBING AND MAKING SOME PROGRESS.

AND ULTIMATELY WE WERE ABLE TO CLIMB IT.

BUT IT IS A VERY INTIMIDATING WALL.

IT'S VERY BIG.

AND IT LOOKS -- IT LOOK ALMOST EVIL JUST THE WAY THE SWIRLS ON THE ROCK ARE.

IT LOOKS VERY DAUNTING.

>> ICE, ICE.

>> ICE!

>> IF WE MANAGE TO CLIMB IT -- >> ROCK, ROCK, ROCK!

>> IT WILL BE THE BIGGEST CLIMB WE'VE EVER DONE.

>> WE JUST DON'T KNOW WHAT WE'LL FACE UP THERE.

>> SO SCARY!

>> I WAS DEFINITELY HOPING THAT CONDITIONS WERE GOING TO IMPROVE.

AND THEY HAVE DEFINITELY NOT IMPROVED.

>> HEIDI, ONE OF THE THINGS THAT WE NOTICED WAS AMOUNT OF ICE FALLING ON THE CLIMBERS, WHICH WAS AN INCREDIBLY SIGNIFICANT THREAT AND A DANGER, AND THERE WAS ONE POINT WHERE ALEX EVEN GETS CUT ON HIS NOSE BY A PIECE OF FALLING ICE.

BUT I WONDER, YOU KNOW, ASIDE FROM GREENLAND, ARE WE SEEING THESE KIND OF CLIMATE CHANGE IMPACTS IN OTHER ROCK FACES, OTHER MOUNTAINS AROUND THE PLANET AS THE TEMPERATURES WARM UP?

>> YEAH, DEFINITELY.

AND I'M SURE ALEX HAS LOTS OF STORIES TO TELL ABOUT HOW CLIMATE CHANGE IS IMPACTING THE SAFETY OF THESE MOUNTAINS.

BUT, YOU KNOW, I COME FROM THE FRENCH ALPS.

AND IN THE FRENCH ALPS, WE'RE STARTING TO SEE MORE AND MORE ROCK FALLS.

THEY'RE MORE FREQUENT.

THEY'RE BIGGER AND BIGGER EVERY YEAR.

BECAUSE WE HAVE WHAT WE CALL PERMAFROST IN THESE HIGH MOUNTAINS.

AND PERMAFROST IS LIKE A GLUE THAT KEEPS THESE MOUNTAINS TOGETHER.

UNFORTUNATELY, IT IS THAWING DEEPER AND DEEPER EVERY YEAR.

SO THESE MOUNTAINS ARE BECOMING INCREASINGLY DANGEROUS.

>> ALEX, WHAT ARE SOME EXAMPLES THAT YOU HAVE SEEN OF HOW CLIMATE CHANGE MIGHT BE AFFECTING ROCK FACES THAT YOU MIGHT HAVE CLIMBED EARLIER IN YOUR LIFE AND HOW SITUATIONS HAVE CHANGED AND THE PLACES THAT YOU GO TO?

>> YEAH, I MEAN, HEIDI HAS JUST AS MANY EXAMPLES.

WE BOTH HAVE SEEN SO MUCH OF THIS IN THE NATURAL WORLD.

AS A CLIMBER, YOU PROBABLY NOTICE IT THE MOST WITH THE APPROACHES AND OUT OF THE MOUNTAINS.

THE WAY YOU HIKE INTO THE MOUNTAINS AND THE WAY YOU NAVIGATE GLACIERS.

JUST IN THE FEW SEASONS I'VE CLIMBED IN PATAGONIA IN SOUTHERN ARGENTINA, SOME OF THE GLACIERS HAVE RECEDED ENOUGH THAT YOU USED TO HIKE ON THE SOUTH AND NOW YOU HIKE ON THE NORTH, THE GLACIER HAS MOVED SO MUCH AND NOW YOU CAN'T GET AROUND.

THINGS LIKE THAT.

LANDSCAPES THAT LOOK LIKE THEY SHOULD BE PERMANENT ARE IN FACT CHANGING INCREDIBLY QUICKLY.

AND THAT'S PRETTY SOBERING.

BECAUSE NORMALLY WHEN YOU GO INTO THE MOUNTAINS LIKE THAT, YOU'RE STRUCK BY SORT OF THE HUMAN INSIGNIFICANCE.

YOU THINK OF HOW SMALL YOU ARE AND HOW BIG AND PERMANENT THOSE MOUNTAINS ARE.

IN CASE YOU GO TWO YEARS IN A ROW AND THE MOUNTAINS HAVE CHANGED EVEN MORE THAN WE HAVE.

THAT'S A VERY SCARY THING TO SEE.

>> HEIDI, PUT THAT IN PERSPECTIVE FOR US.

WHEN WE LOOK AT CORE SAMPLES, AND YOU DO YOUR DRILLING, AND YOU FIND ALMOST A HISTORY BOOK OF WHAT'S BEEN HAPPENING TO A SPECIFIC PIECE OF LAND, HOW CONCLUSIVE IS THE HUMAN IMPACT, WHETHER IT'S ICE CORE OR ROCK CORE?

AND PUT IN PERSPECTIVE THAT CHANGE.

BECAUSE THESE THINGS HAVE BEEN LITERALLY HERE FOREVER, COMPARED TO US AND OUR IMPACTS.

>> ABSOLUTELY.

THESE LANDSCAPES HAVE SO MANY STORIES TO TELL, WHETHER IT'S THE ROCK, THE ICE.

WE CAN REALLY GO SUPER FAR BACK IN TIME BY ANALYZING THESE DIFFERENT MATERIALS.

YOU KNOW THAT CLIMATE HAS ALWAYS CHANGED, ABSOLUTELY.

BUT THE RATE OF CHANGE WE'RE SEEING AT THE MOMENT IS ABSOLUTELY UNPRECEDENTED, AND IT IS WITHOUT A SHADOW OF A DOUBT THAT THE CURRENT CHANGE IN CLIMATE WE'RE ALL EXPERIENCING IS DIRECTLY CONNECTED TO THE BURNING OF FOSSIL FUELS, TO DEFORESTATION, BASICALLY TO HUMAN ACTIVITIES.

AND IT IS REALLY WHAT SCARES US, THE SCIENTISTS, HOW QUICKLY THINGS ARE CHANGING, BECAUSE IT'S REALLY PUSHING OUR CAPACITIES OF ADAPTATION TO THEIR VERY LIMITS.

THIS IS WHY WE NEED MORE DATA FROM THESE PLACES TO BE ABLE TO PREPARE FOR A FUTURE THAT WE'RE TRYING TO SEE IN THESE ROCKS AND THE ICE.

>> HEIDI, THERE IS A SCENE IN THE FILM WHERE YOU BASICALLY DIG A HOLE, AND ALEX DIGS ANOTHER ONE NEAR YOU.

AND BOTH OF YOU GET INTO THIS HOLE, AND YOU KIND OF LOOK IN BETWEEN.

AND YOU SEE THE DIFFERENT LAYERS.

THIS IS ALMOST WITHIN A YEAR'S WORTH.

AND THERE ARE THESE LINES.

EXPLAIN WHAT THE LINES ACROSS WERE AND WHY THAT'S SIGNIFICANT.

>> THAT WAS SO MAGICAL.

AND I'M GLAD THAT I HAD THESE SUPER FIT ATHLETES AROUND ME HELPING ME TO DIG THESE HOLES IN THE SNOW.

AND ALEX WAS WAY FASTER THAN ME.

BUT IT IS REALLY IMPORTANT ACTUALLY TO DIG THESE SNOW PITS, BECAUSE THE DEEPER YOU GO, THE FURTHER BACK IN TIME YOU CAN BE.

AND WHAT WE SAW WAS A SERIES OF ICE LANCES.

AS BEAUTIFUL AS THEY ARE, THEY'RE NOT A GOOD SIGN.

THESE ICE LANCES TELL US THAT THERE WERE MOMENTS DURING THE PAST FEW MONTHS ON THIS ICECAP THAT AT THE PERIPHERY OF THE GREEN ICE SHEETS, MOMENTS WITH MELTS WITH RAIN.

AND THIS WAS HIGHLY UNEXPECTED ACTUALLY FOR THIS SPOT OF GREENLAND THAT IS SUPPOSED TO BE QUITE COLD AT THIS HIGH ALTITUDE.

>> ALEX, LET'S TALK A LITTLE BIT ABOUT HOW YOU KIND OF FELT ON THIS CLIMB.

BECAUSE WHILE DOING A FREE SOLO IS A TOTALLY DIFFERENT CHALLENGE, AND IT WAS SORT OF ONE PART OF YOUR LIFE, HERE YOU ARE YEARS LATER TAKING ON A SIX-WEEK EXPEDITION WITH, AS LOTS OF THINGS HAVE, A VERY SIGNIFICANT AMOUNT OF RISK INVOLVED.

AND I WONDER IF YOU APPROACH THE PREPARATION DIFFERENTLY, IF YOU THINK ABOUT THINGS DIFFERENTLY, I KNOW THAT YOU'RE MARRIED AND A DAD?

>> NO, HONESTLY, THIS WAS ONE OF MY FAVORITE EXPEDITIONS THAT I'VE EVER BEEN ON, AND I GO ON CLIMBING TRIPS EVERY YEAR.

I'M FREQUENTLY DOING EXPEDITIONS SIMILAR TO THIS, BUT WITH DIFFERENT OBJECTIVES.

THIS WAS ONE OF MY FAVORITE TRIPS BECAUSE I HAD THE RIGHT COMBINATION OF A GREET TEAM, GREAT PURPOSE, GREAT OBJECTIVES.

THE CLIMBING WAS INSPIRING ENOUGH FOR ME TO BE EXCITED TO GO THERE.

BUT THEN THE SCIENCE WE WERE DOING, THE TEAM WERE DOING IT WITH, EVERYTHING ELSE ABOUT THE TRIP MADE THE WHOLE THING SEEM TOTALLY WORTHWHILE TO ME IN A WAY THAT KIND OF PUT IT BEYOND A NORMAL TIME AND OBJECTIVE.

NORMALLY YOU'RE JUST CLIMBING FOR YOURSELF.

IN THIS CASE IT FELT WE WERE REALLY DOING SOMETHING USEFUL, AND IT MADE THE WHOLE TRIP FEEL A LOT MORE MEANINGFUL.

>> ALEX, I WONDER, THERE IS A TEAMMATE OF YOURS, MIKE AND YOU, YOU HAVE A DISAGREEMENT, A AND YOU HAVE A HEART TO HEART.

A AND THE CAMERAS ARE WELL ENOUGH POSITIONED TO CAPTURE SOME OF THAT.

WHAT GOES THROUGH YOUR MIND AS YOU LOOK BACK.

HIS CONCERN WAS I DON'T FEEL NECESSARILY COMFORTABLE AND I DON'T FEEL HEARD.

AND AGAIN, FROM A VIEWER'S PERSPECTIVE, I WONDER IF THEY'RE MISALIGNED HERE.

>> HONESTLY, I THINK THE FILMMAKERS DID A GREAT JOB SHOWING THE ENTIRE EXPEDITION.

BUT THE REALITY IS THAT WE HAD CONVERSATIONS LIKE THAT MUCH MORE THAN YOU SEE ON CAMERA.

WE WERE CONSTANTLY TALKING ABOUT RISK.

WE'RE CONSTANTLY TALKING ABOUT HOW TO MITIGATE RISK AND MANAGE AND WHETHER OR NOT WE FEEL COMFORTABLE, WHETHER OR NOT WE FEEL SAFE.

YOU CERTAINLY SEE GLIMPSES IN THE FILM.

THE REALITY, WE WERE TALKING ABOUT IT ALL THE TIME BECAUSE WE ALL WANT TO COME HOME SAFELY.

BUT ONE OF THE THINGS THAT ISN'T SHOWN IN THE FILM IS AFTER THAT CONVERSATION, MIKEY DECIDED THAT HE DIDN'T WANT TO PARTICIPATE IN THE CLIMB ON THE FACE.

BUT INSTEAD, WHAT HE DID WAS GUIDE THE CAMERA CREW UP THE BACK SIDE OF THE MOUNTAIN SO THEY COULD FILM IT.

BECAUSE HE IS BASICALLY A PROFESSIONAL MOUNTAIN GUIDE AND A FILMMAKER HIMSELF.

AND SO PART OF WHAT ISN'T SAID IN THAT WHOLE EXCHANGE IS THAT HE WAS DECIDING TO USE HIS UNIQUE SET OF SKILLS IN A DIFFERENT WAY TO HELP THE TEAM IN A WAY HE FELT WAS SAFER BUT STILL INCREDIBLY USEFUL.

>> HEIDI, WHAT'S IT LIKE BEGINNING YOUR CLIMBING EXPERIENCE WITH WORLD CLASS EXPERTS ON -- IN A REGION THAT NOBODY'S EVER REALLY CLIMBED BEFORE?

>> I'LL BE HONEST.

I REALLY DIDN'T WANT TO DO ANY CLIMBING.

AS LITTLE AS POSSIBLE.

BUT, YOU KNOW, THIS WAS ONE IN A LIFETIME OPPORTUNITY.

AND ALSO, YOU KNOW, I FELT THE PRESSURE OF THE IMPORTANCE OF COLLECTING THESE ROCK SAMPLES ON THIS WALL THE RIGHT WAY.

NOT THAT THE CLIMBERS WERE NOT GOING DO IT THE RIGHT WAY.

BUT I REALLY WANTED TO BE THERE TO SEE IT HAPPENING.

AND LUCKILY, YOU KNOW, THEY TRUSTED ME.

THEY THOUGHT THAT BY GIVING ME THE RIGHT TRAINING, I WOULD BE ABLE TO DO IT.

AND IT WAS -- IT WAS EQUALLY MAGICAL AND TERRIFYING A THE SAME TIME.

BUT I'M SO GLAD THAT WE'RE ABLE TO COLLECT THESE ROCK CORES ALONG THE WAY.

THIS WAS A BIG MISSION COMPLETE FOR ME.

>> SO, ALEX, HOW WAS SHE?

>> OH, SHE WAS GREAT.

HEIDI DID FINE.

NONE OF US HAD ANY DOUBT SHE WOULD MAKE IT UP THE WALL JUST FINE AND BE TOTALLY SAFE.

AS SHE WAS JUST ALLUDING TO, THE SCIENCE, I FOUND CONSISTENTLY THROUGHOUT THE EXPEDITION, IT WAS HARDER TO DO THE SCIENTIFIC EXPERIMENTS, IT WAS HARDER TO COLLECT DATA THAN I MAYBE EXPECTED, BECAUSE A LOT OF THE THINGS, A LOT OF THE PROTOCOLS, OH, DRILL A SAMPLE INTO THE ROCK.

BUT THEN IT TURNS OUT IT'S REALLY HARD AND IT'S HARD TO LINE UP THE DRILL PROPERLY AND HARD TO MANAGE THE BATTERIES.

EVERYTHING WAS MORE CHALLENGING THAN WE EXPECTED.

SO I THINK IT WAS ACTUALLY INCREDIBLY HELP TO FEEL HAVE HEIDI OVERSEEING EVERYTHING.

LIKE THERE IS NO CHANCE WE COULD HAVE DONE ANY OF THE SCIENCE WITHOUT HEIDI ON THE TEAM.

IT JUST TURNED OUT THAT IT WAS ALL TOO DIFFICULT FOR US.

>> IS THERE, ALEX, A MOMENT THAT GAVE YOU PAUSE ON THIS, IN THE MIDDLE OF THIS FACE WHERE YOU KIND OF ARE MAKING SOME OF THE FINAL ASCENTS?

>> A LITTLE BIT.

I THINK OUR FINAL DAY CLIMBING, WHICH WAS THE HIGHLIGHT OF THE SHOW, HAZEL AND I ARE CLIMBING THE FINAL HEDWALL OF THIS GIANT MOUNTAIN.

THERE WAS DEFINITELY A LOT OF UNCERTAINTY AROUND HOW WE COULD DO IT.

PHYSICALLY, WHERE WE SHOULD NAVIGATE ON THE WALL AND WHAT ROUTE WE SHOULD CHOOSE.

REALLY, THAT'S THE CHALLENGE OF DOING A FIRST ASCENT BECAUSE NOBODY HAS BEEN THERE.

SO YOU DON'T REALLY KNOW WHICH WAY TO GO.

WE DEFINITELY BOTH FELT VERY UNCOMFORTABLE THE WHOLE TIME.

LIKE THERE WAS A LOT OF TENSION AROUND HOW TO WEAVE OUR WAY UP THE WALL.

BUT THERE WAS NO SERIOUSLY DRAMATIC MOMENT, BUT IT WAS MORE LIKE ATTENTION THAT YOU CARRY THE ENTIRE DAY AS YOU WORK YOUR WAY UP.

WE BOTH FELT INCREDIBLE RELIEF AT THE END OF THE JOB.

WE WERE GENUINELY VERY EXCITED TO MAKE IT TO TOP.

>> AND HEIDI, WHEN DID YOU FIGURE OUT OR HEAR THAT THEY HAD ACTUALLY PULLED IT OFF?

>> YEAH, WE HAD RADIOS FROM BASE CAMP, AND WE HEARD THE GOOD NEWS.

THE RELIEF WAS ALSO ENORMOUS AT BASE CAMP.

WE WERE SO ANXIOUS.

WE WERE REALLY TENSE THE WHOLE TIME.

AND WE FELT -- YOU KNOW, WE FELT SO PROUD LULL TULLY OF WHAT YOU GUYS HAD ACHIEVED.

AGAIN, A MASSIVE CONGRATULATIONS.

>> GLACIOLOGIST DR. HEIDI SEVESTRE AND CLIMBER AND EXPEDITION LEADER ALEX HONNOLD, THANK YOU BOTH.

>> THANK YOU.

>> MY PLEASURE.