climate change may be taking a toll on one of the world's most ancient forests. california's giant sequoia trees attract millions of tourists each and every year, but now scientists are going to extreme heights to study how an historic drought is impacting these natural wonders. jonathan vigliotti got an upclose look. >> reporter: we're here in the sequoia national park perched on one of the largest trees in the world, which just so happens to be a cloud-hugging laboratory for scientists studying the impacts of climate change. from the air, the breathtaking beauty of the sierra nevada covers up an ugly statistic. >> the first estimates that about 130 million trees died in the state of california during this drought. >> reporter: 130 million? >> 130 million.

>> reporter: from a lack of water? >> yeah. >> reporter: tree ecologists anthony ambrose and wendy baxter have been working throughout that drought which lasted from late 2010 to earlier this year. >> it's not much further. >> reporter: but they haven't been studying the pine, firs and cedars that died. they've been analyzing the world famous monsters that survived, the giant sequoias, the largest living creatures on earth. >> they've been living and growing in the same place, some of them for thousands of years. >> reporter: but even these giants have an achilles heel? >> yeah, their demand for water. we've measured that an individual giant sequoia tree uses up to a thousand gallons of water in a single day. if that water supply diminishes, there is going to be an impact on the trees eventually. >> really puts everything into perspective. >> yeah. >> reporter: doing science way out here means more than just a strenuous hike. in fact, that's just the beginning. >> most of the action is happening up in the canopies.

that's where all of the leaves are. >> reporter: so you had to go up? >> we had to go up. >> okay, wendy, i'm heading up. >> reporter: since 2015, they've been scaling trees like this one, 250 feet high in order to record the drought's impact on their health and growth. on this day, they brought me along for the climb. up we go. >> up we go. >> reporter: how many times at your peak were you climbing up tree? >> so i think my record for one day was seven climbs. >> reporter: seven climbs? >> yep. >> reporter: oh. i'm already exhausted. >> i always love being up here. >> reporter: high above, ambrose got to work, downloading data from a science station they previously installed. >> the side branches need to be fairly close? >> yes. >> reporter: while wendy gathered branch samples to be examined back in a is is my jac stock moment for real. it took a little over an hour,

but i eventually joined the pair in the deceptive safety in the tree's canopy. kind of a terrifying place to be doing some science. what has your data that you've collected so far, what has the data told you? >> they are really good at minimizing how much water they lose under drought conditions by shutting down the little tiny cores in their leaves. those tiny cores are also what allows them to absorb carbon dioxide from the atmosphere. >> reporter: it sounds like they're shut down for business. >> yeah that. >> shut down. so they don't take up as much carbon dioxide. >> reporter: and that's troubling for two reasons. the less carbon dioxide trees capture and store, the more of the heat-trapping gas stays in the atmosphere, fueling global warming. also, the trees use carbon dioxide as food to grow. ambrose and baxter have also taken from the sequoias core samples, basically, long thin strips of wood from deep inside the tree they can use to determine its age and growth.

>> so you can see it goes all the way back. >> reporter: 1900, 1300. >> yeah. >> reporter: labs are still analyzing them, but some of those cores are already telling a story. so these three lines very close together indicate not a lot of growth in that period of time? >> exactly. >> reporter: a drought. >> yeah, exactly. >> reporter: but climate is changing. what does that mean future a tree like the sequoia that has has very specific needs in order to survive the way it has for so long. >> yeah, every organism has thresholds that it can't survive. as it gets hotter, snow is going to melt earlier, and there is going to be less water available for these trees. and it may not be a place they can continue to grow into the future. >> reporter: many of these trees have been alive since before the roman empire, which means civilization literally grew up around them. ambrose and baxter are now studying the impacts that civilization is having on these

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city. it's slowly succumbing to the unrelenting wash of the adriatic. one of venice's landmarks, st. mark's basilica is among the hardest hit by the recent tidal surge. worshipers replaced by water. experts can't be sure of the extent of the damage until the flooding recedes, but if treasures from rising water, it's venice. art conservators like this one continued working, even as the floodwaters crept across the floor. it's that kind of quiet dedication to preserving paintings both old and new that we sometimes overlook when we're walking through a museum. paintings like all of us, age and change. dirt and grime are the more common enemy, far more so than flooding or fire. >> so i have to build it up slowly. >> reporter: that's what makes professional art conservators

like rona macbeth at the museum of fine arts in boston as valuable as the art they treat. it's the artist's intent that drives all of this? >> as best we possibly can, we want to be true to that idea of artist intent. what we're trying to do is take away the barriers between the artist's original vision and the viewer. >> reporter: to begin removing that barrier is a delicate process. but it's a bit indelicate to demonstrate. she uses her own spin. why? why use saliva? >> it's an incredibly effective enzyme for removing grime off the surface. >> reporter: it is really? >> yes. and it works incredibly well. >> reporter: do you ever get a dry mouth working? >> yep. >> reporter: the day we were there, she was treating these two rembrandts, twin portraits painted back in 1634. >> they're some of the first rembrandts to enter any public museum in america. so that's pretty important. >> reporter: layers of graying

varnish have clouded rembrandt's intricate brush work, making the young couple appear to be staring out from behind a veil. >> there are these areas where you can see all the dirt. >> reporter: but in the worst cases like this 16th century altar piece, the paint isn't just dulled, it's actually missing. so the white is filler, basically? >> white is filler that i'm adding. and then i carve it down to the surface of the paint. so it makes a completely smooth transition. >> you carve it? >> i carve it with little scalpels. >> oh, my gosh. >> yeah. >> reporter: that's where it gets tricky, because she then has to paint back in what's fallen off, going from this to this. can't tell where it was. >> well, that's good. >> reporter: i think people are surprised to know that some of your work is actually painting in some of what an original artist did. that's kind of shocking to a lot of people, i think. >> i think it, and disturbing too, i think sometimes. >> yes. >> i understand that. but you always have to remember

you're not the artist, right? you're not there to make any improvements. >> you have to kind of separate yourself in the moment or you'd be constantly in a state of fear. >> reporter: alison langly is head of painting conservation at the art institute of chicago where they're working on any number of paintings, including this massive 17th century french masterpiece. >> a lot of what we do as conservators is a little like csi. we use ultraviolet light, x-ray, infrared to examine the surface and to look below the surface. >> okay, that's good. >> reporter: francesca casadillo is use something called microscopic x-ray to analyze individual pigments. >> so we've got some yellows and green. epor in this , the pigment is in a vincent van gogh. what does it tell you? the makeup of the paint? >> it tells us the makeup of the paint. >> reporter: the chemicals? >> the chemicals in the paint.

>> reporter: really? those chemicals are important because some of the paints van gogh use ready discoloring over time. the yellow leaves are now more of a mustard color. so all of these leaves would have looked more like that? welcome, have looked more like this, yes. >> reporter: van gogh's reds have faded too. through digital imaging, computers can show us what his bedroom series may have actually looked like when van gogh painted it. instead of the blue walls we see today, the pigment may actually have been a little closer to violet. >> one of the joys of computers is we can change them back without touching the painting. we can do reconstructions digitally. >> reporter: even more recent pieces like this priceless jackson pollock need some tlc, although this is perhapsle less. do you ever wonder what jackson pollock would think of what you're doing to his painting? >> oh, always. actually, when you're working on any artist's work you wonder

what they would think. work, making it last for inghe posterity, i think he'd be thrilled. >> reporter: chris was hired by the museum of contemporary art in los angeles not too long ago to make pollock's drips and dribbles look as vibrant as the day he dribbled them. >> it's a very interactive process. >> reporter: and intimate it sounds like. >> incredibly intimate. it's always -- it's funny to think i spent more time looking at this painting than jackson pollock ever would have. >> reporter: still, there are those who say fine art should just be left alone, that any fading or dirt or even damage is part of the natural life of a painting. >> you're making choices all the time. and one very legitimate choice is to do nothing, but you have to understand what that choice means. it means accepting the appearance of something which is potentially very different than how it originally looked. >> reporter: the restoration of

the court of appealing of the sistine chapel, for example, was often the subject of sometimes angry debate. some claim michelangelo's frescos were restored too much, but in the end the hope of almost any artist is that their work stands the test of time and the science of conservation is and has always been the art of keeping time at bay. >> the "cbs overnight news" will be right back.

well, we end tonight with the story of a dying man in georgia who thought all hope was lost. that is until he met a nurse who helped him find a new heart and then filled it with love. here is steve hartman "on the road". >> reporter: during her 35 years as a nurse, laurie wood has been a hero, many times over. >> beat sweetie, i'm going take temperature. you've saved lives before. >> yes. >> reporter: but never like this? >> no. >> i wouldn't even be here today if it wasn't for her. >> reporter: when jonathan pinkard met laurie, he was homeless. >> staying in my car. >> reporter: jonathan was autist autistic. he was raised by his grandma, but she died a few years ago and there was no one else. then to add illness to injury, doctors here at piedmont noonan

hospital near in georgia diagnosed jonathan with heart failure at the age of 26. it was so bad, he actually needed a heart transplant or else. >> six months. >> reporter: six months they gave you? >> there was no hope. >> reporter: part of the problem is you can't get a new heart, can't even get on the transplant list if you don't have a home or some kind of support system to help you post-surgery. and since jonathan has no family to speak of, his fate was sealed. basically, death by loneliness. >> i mean, that just doesn't seem right. it doesn't seem fair. so. >> reporter: so, although there was nothing laurie could do for her patient as a nurse, she decided there was something she could do as a mom. >> it was just in my heart that there was no other choice other than to bring him home. >> howdy, howdy, howdy! >> reporter: after knowing jonathan just three days, laurie invited him home and became his legal guardian. >> you had a good day? >> i did.

>> reporter: jonathan now lives here full-time. >> a long with laurie's son austin. and because of her boundless compassion -- >> ooh, thisooks good. >> reporter: jonathan was able to get on the transplant list, and just a few months ago got his new heart. in a few weeks, he'll be well enough to live on his own again, although laurie says she has no plans to release him from her care. this isn't over when he gets better? >> no, no. he is going to go down to my family's house for christmas with us and go to a wedding. he is a part of the family. >> i call her mama now. >> reporter: you call her mama? >> i do. she is like a second mam to me, heaven-sent. >> reporter: she is heaven-sent? >> heaven-sent. >> reporter: any medical professional can make you healthy, but sometimes only an angel can make you all better. steve hartman, "on the road" in noonan, georgia. >> and that is the "overnight news" for this tuesday. for some of you, the news continues. for others, check back later for the morning news and of course

"cbs this morning". from the broadcast center in new yorkity, i'm ola lenghi. it's tuesday, november 19th, 2019. this is the "cbs morning news." critical witnesses. the latest round of impeachment inquiry hearings begin today with testimony from people who listened in on president trump's phone call with the ukrainian president. guilty of murder. a jury convicts a man accused of killing the mother of his child. and epstein aftermath. new legal trouble following the disgraced financeer's death. this as trouble mounts for prince andrew after a controversial interview about their friendship. >> state what he knows to law >> state what he knows to law enforcement. captioning funded by cbs