Science Friday - Future Of Climate Change, Tongue Microbiome. Dec 18, 2020, Part 1

Episode Date: December 18, 2020

How The Past Hints About Our Climate’s Future Ask a climate scientist how much the earth will warm as a result of the carbon dioxide we’re emitting right now, and the answer will be a range of temperatures: likely anywhere from 1 to 5 degrees Celsius. But all the models we have to predict the future are based on data from the past, most of it collected in the last 140 years. As carbon dioxide rises further past the unprecedented-in-human-history 400 parts per million (ppm), we are increasingly in a world never before seen by human eyes—or measured by thermometers. While we are certain the Earth’s climate will warm as CO2 increases, it’s harder to pin down exactly how sensitive the climate is. Scientists are working hard to narrow down our uncertainties about the coming temperature changes, sea level rises, and new patterns of rainfall and drought. And paleoclimatologists can examine ancient rocks, sediments, ice, and fossilized shells for clues about how past climates changed in response to different levels of carbon dioxide. Climates from past epochs have not only experienced that 400 ppm mark, but also levels higher than 1,000 ppm—and correspondingly, higher temperatures and higher seas. In Science last month, a team of researchers made the case for using more data from these climates, millions of years ago, to help us map out the future we face. Science Friday producer Christie Taylor talks to University of Arizona geoscientist Jessica Tierney, who is lead author on the new research. Mapping Out The ‘Microbial Skyscrapers’ On Your Tongue Your mouth is home to billions of bacteria, and they’re very particular—some prefer to live on the inside of the cheeks, while others prefer the teeth, the gums, or the surface of the tongue. Writing in the journal Cell Reports, researchers describe their efforts to map out the various communities of bacteria that inhabit the tongue. In the average mouth, around two dozen different types of bacteria form tiny “microbial skyscrapers” on the tongue’s surface, clustered around a central core made up of individual human skin cells. In this study, scientists mapped out the locations of tiny bacterial colonies within those clusters, to get a better understanding of the relationships and interdependencies between each colony. Jessica Mark Welch, one of the authors of the report and an associate scientist at the Marine Biological Laboratory in Woods Hole, Massachusetts, talks about what we know about the microbiome of the human mouth—and what researchers would still like to learn. Moderna’s COVID-19 Vaccine May Soon Be Approved In The U.S. As the national rollout of the Pfizer/BioNTec vaccine began this week, Moderna’s own formula looks ready to add to the options for the nation’s healthcare workers and high-priority patients, at least according to a panel tasked with deciding whether the benefits outweigh the risks. On Thursday, the FDA’s independent advisory committee voted 20-0, with one abstention, to recommend the vaccine for emergency use. Now, the FDA itself must decide whether to follow through, a decision that is expected to come in the next few days. Vox staff writer Umair Irfan talks about the similarities and differences between Moderna and Pfizer’s vaccine, what we’re learning about side effects for both injections, and the concerns about COVID-19 transmission to animals. Plus, why researchers say President-elect Biden’s goal for net-zero carbon emissions will require drastic, but feasible changes to how the nation operates. And how to view Monday’s conjunction of Saturn and Jupiter—a phenomenon theorized to be the explanation for the biblical Star of Bethlehem. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. A bit later in the hour, we'll talk about how looking back millions of years into the Earth's climate history can help us better predict climate change. This week, the first people in the U.S. received Pfizer's COVID-19 vaccine just days after the FDA cleared the vaccine for an emergency use authorization. As we discussed on our show last week, the CDC has advised the first available vaccines. That's a stock of 6.5 million doses. should go to health care workers and residents of long-term care homes first, and we've seen that happen this week. But for millions of people in those groups who would not be covered by the initial vaccine stock from Pfizer,

reinforcements may soon be on the way. An independent advisory committee just yesterday voted to recommend Moderna's MRNA vaccine for a similar emergency use authorization, which usually is the green light for FDA approval. Here to explain more on the story, plus other news from the week is Omer Afan, staff writer at Vox. Welcome, Omer. Hi, Ira. Thanks for having me. Let's get into this.

An independent advisory committee for the FDA says Moderna's vaccine is ready for emergency use. We already went through this with Pfizer's vaccine last week. Does this mean we'll see Moderna's dose is shipping out pretty soon? I think that's pretty likely. I mean, if we use the Pfizer vaccine as an example, the, FDA issued its final emergency use authorization about a day after the committee voted in favor, and then a couple of days later, the vaccine began rolling out. And so I expect we'll see something quite similar here. And so there's not much likelihood that the FDA would not go forward on this.

It's unlikely. I mean, the vote here was actually even more in favor of this. It was 20 to zero with the committee, whereas last week's vote was 17 to 1. So it's a pretty solid green light. But there are a few distinctions here between this and the Pfizer vaccine. The Moderna vaccine, for instance, has been authorized for people over the age of 18, whereas the Pfizer vaccine was over the age of 16. And this vaccine also has some less stringent cold storage requirements. You know, the Pfizer Biointech vaccine requires storage on dry ice at temperatures of roughly minus 70 degrees Celsius, while the Moderna vaccine can be stored at ordinary freezer temperatures. And so that should ease some of the supply chain restrictions that the other vaccines were facing.

You know, there was some talk this week about Morda's vaccine being effective after just one dose. Does that mean we have more vaccine available? Well, yes, the data did show that the vaccine started to kick in quite effectively in its protection after the first dose. But the Food and Drug Administration is very careful in its protocol. And that one dose protocol was not assessed. And right now it's very unlikely that they will approve this for on a one dose regimen. and they're probably going to stick to the two doses for now because that was what was tested and that was what was researched.

Also talk about this vaccine protecting against asymptomatic spread. Yeah, that's right. I mean, we know, for instance, that this vaccine and the other vaccines are very effective against preventing disease, you know, where people actually start to get sick and start to have symptoms. But here, you know, we know with COVID-19 that a lot of people who don't show symptoms at all can still spread the disease. and the Moderna trial actually did some screening and testing to find out how those asymptomatic spreaders were being affected,

and they saw that there was, in fact, a decline. And so this is a really good sign for, you know, ending the pandemic and for, you know, reducing transmission with this vaccine. There was also some puzzling news that Pfizer announced in a press release that they have millions of doses just sitting in their warehouses with no instructions from the White House where to ship them. Yeah, that's right. it's showing some of the hiccups in the supply chain here. You know, several state officials have reported that, you know, their allocations for this vaccine were cut, and yet at the same time, the manufacturer is saying that they have a bunch of doses that are still unclaimed. And so it's showing that there's a little bit of a miscommunication here that hopefully will get resolved pretty soon. On the other hand, you may have also seen the news that some pharmacists reported that the vials for

the Pfizer-Biointech vaccine actually had more doses than they realized. And the FDA has approved those extra doses to be used if, you know, pharmacists can actually scrounge them up. Interesting. Also speaking of Pfizer, we also need to mention that a few people have had some extremely adverse reactions in the process. I'm talking about two health care workers in Alaska, two people in the UK. Is that something we should be worried about? That is something to be concerned about because people with severe allergies were actually excluded from the phase three clinical trial pools. And they have their own discretion if they're eligible to get the vaccine on whether or not to get them. And right now,

regulators in both the UK and the U.S. are basically saying that, you know, if you have a history of anaphylaxis or very severe allergic reactions, you probably shouldn't be getting these vaccines right now. But, you know, there are also other side effects to be concerned about as well. You know, their moderna data that was released this week showed that about 16% of trial participants experienced a severe adverse reaction, which was defined as something that requires medical attention or prevents people from going about their lives. You know, these are things like pain, swelling, headache, and fever, but they tend to be a little bit more intense with these vaccines than with other vaccines. You know, one doctor suggested that, you know, if you're going to get one of these

shots, you may want to schedule the day off of work. So that's not like the anaphylactic reaction you were talking about before. Right. These are not, you know, super severe reactions, but health officials want people to be aware of this. You know, part of how we build trust with vaccines is to, you know, make sure people are not surprised by what happens here. And so, since these are two-dose vaccines, you know, we want people to come back for the second dose. So if people do experience some mild to moderate side effects, we want to ensure them that, you know, these are normal. They're within the normal parameters and that you should still come back and finish your course of this vaccine.

Let's move on to the news on the animal front. I'm speaking about a mink in Utah testing positive this week. Yeah, that's right. That follows the news that in Denmark they called about 17 million minks due to COVID infection risk. And now there's one mink, a wild one in Utah that tested positive for this virus. And we've seen already several instances of other animals being infected with this virus, cats, dogs, lions, tigers. You may remember earlier in the pandemic, there were tigers at the Bronx Zoo that got sick. They had a cough with this virus. And, you know, this is more than just, you know, a novelty. I mean, it's kind of concerning because, one, you don't want another reservoir for this disease. If another animal can start transmitting this virus to other animals,

then, you know, that increases the likelihood of a mutation that could potentially bounce back to us. But the other concern is also for animals like endangered species, you know, like mountain gorillas in these wildlife preserves in Africa. Workers there are actually taking COVID precautions to ensure that those animals don't get infected because their respiratory systems are very similar to ours and there's only a few hundred of these gorillas left in many of these reserves. And so they're taking extra care to make sure that they don't get sick with these diseases. Is there anything we can learn about the virus when it shows up in these animals?

It could shed some light on how the virus made the jump from animals to humans in the first place. And so we're trying to see, you know, what are the modes of transmission, what kinds of animals are most vulnerable and what happens when they start transmitting it to each other? And that could potentially help us get ahead of the next pandemic as well. All right. Let's look at some other news this week that did not get so much attention. President-elect Biden had his electoral college when certified, and there's a new report out of Princeton University on his ambitious goal of getting us to net-zero carbon emissions by the year 2050. And that report said it's pretty feasible if we set our minds to it. Yeah, it does.

I mean, this is a report by researchers at Princeton University, as you noted. They examined the pathways to get to net-zero greenhouse gas emissions of the U.S. economy by 2050. And they said that there are multiple strategies that you could use. anything from going to 100% renewable energy to keeping fossil fuels with carbon and capture and storage and also the infrastructure that would be needed. Now, they said that, you know, a lot of the technology is already there and that money of these changes are already underway, but we would need a lot of drastic changes in the near future as well, things like shutting down all coal power plants by roughly 2030, and by 2030,

half of all new cars would have to be electric. We would need new high voltage transmission systems and even pipelines to move captured carbon dioxide around the country. But one of the things they also found was that this would cost about $2.3 trillion over the next 10 years, which is roughly in the same ballpark as what we would be spending anyway in terms of our energy infrastructure. And so they're saying that we're going to be spending this money anyway, let's do so thoughtfully in a way that actually helps us meet our climate change ambitions. And as far as Biden's chances of making good on his pledge, his team also announced several new key appointments this week who might be influential in getting us there,

I'm speaking about yesterday. New Mexico Representative Deb Holland was picked for interior. She's both the first Native American tap for the job and a big opponent of oil drilling and the Arctic wildlife refuge. Good news for the climate goals. Right. Yeah. You know, as they say in D.C., the personnel is policy. And yes, Representative Deb Holland, a member of the Laguna Pueblo, has a track record of opposing, you know, mining and drilling on public lands.

You know, the Interior Department is kind of overlooked as an environmental agency, but it has jurisdiction over 20% of land of the U.S. And those lands produce about one-fifth of the country's greenhouse gas emissions. There's a lot of mining and drilling. But she has a track record of opposing a lot of that and supporting Native American rights. And so it's very likely that that will be something that will shake out in the future if she takes over this department. Plus, we have the other picks this week of Michael Regan for EPA and Gina McCarthy. Yeah, that's right. Michael Regan is the head of North Carolina's Department of Environmental Quality, and Gina McCarthy herself was the former head of the EPA, and she was brought on board to be a climate advisor, and former Michigan governor, Jennifer Granholm, was also selected to lead the Department of Energy.

That's really interesting picks. One last story, close to my heart, urging us to get outside and take a look at the skies. The great conjunction of Jupiter and Saturn, if you've been watching all week, they've been moving closer and closer together in the sky. and they have their finale. The big night is Monday night. Yeah, that's right. These are the two largest planets in our solar system, and from our vantage point, they will be the closest they've been in 400 years,

and for the first time in 800 years, this will actually happen at night where we can easily see them. You don't need a telescope or even binoculars to see them in the sky. Both planets are moving eastward with respect to the stars, and Saturn will initially be in the lead.

And you can actually start seeing those planets moving closer together this weekend if you want to start warming up and figuring out where to stake out your cameras to take photos of this. The planets will be easy to see with the unaided eye if you looked in the southwestern sky. You know, this is happening also on the same night as the winter solstice. This is sort of a coincidence, but it's an auspicious day for astronomical phenomena. Speaking of coincidences, this is sort of the theorized phenomenon that may have resulted in the Christmas star and the biblical reference.

Yeah, that's right. You know, there are multiple explanations that are out there, but, you know, the timing roughly works here, that this may have been this alignment that might have led to the star of Bethlehem or the Christmas star that appeared about 2,000 years ago. Great news, Amir. Thanks for taking time to be with us today. Glad to be here, Ira. Amir Afan is staff writer for Vox. He joined us from Washington. One quick thing before the break, as this long unusual harrowing and in many ways remarkable year draws to a close, our staff and listeners reflected on some of the most inspirational and impactful

science stories they heard in 2020. Take a look at our year and review science news. It's all there on our website at Science Friday.com slash 2020. After the break, the predictive power of paleo climates, how the past can inform our future, as I say coming up. Hey there, folks. It goes without saying this has been a challenging year, no. And if there's one thing we know for sure, it's that the need for fact-based journalism and the need for science are stronger than ever. At a time when science is continually called into question, Science Friday remains committed to filtering out the noise and discussing the evidence, supporting the science that you need to make informed decisions. You know that the man for Science Friday this year was higher than ever, but you may not know that your donations are what's keeping

us running. And right now, Science Friday has a dollar-for-dollar donation match, which means that any donations will be doubled. So, if you have a few dollars to spare and agree that this world could use more science, please support Science Friday with a donation. Any amount makes a difference. Go to ScienceFriday.com slash give. That's sciencefriiday.com slash give. Thank you. and stay safe. This is Science Friday. I'm Ira Flato. The climate is changing, and more importantly, we are changing the climate by burning fossil fuels and pouring carbon dioxide into the Earth's atmosphere. But as scientists puzzle out how drastically temperatures will rise, they haven't got a lot to work with, just 140 years of direct measurements of the greenhouse gas, temperature, and rainfall.

But there is hidden information locked up in fossils and rocks from millions of years ago. And that's where they are turning for help. Sci-fi producer Christy Taylor has more. It's been several years since our atmospheric carbon dioxide reached 400 parts per million. And human beings have actually never even been alive for such high concentrations of CO2. But you know who was? The dinosaurs. A hundred million years ago, CO2 was well over the 1,000.

PPM mark. And more recently, three million years ago, Earth's atmosphere had the same level of CO2 as we have now, in a changing climate. So could data from those times, ancient rocks, marine sediments, ice cores, be the time machines we need for understanding, temperature, sea level, and everything else we might be in for as the climate changes? That's what a group of scientists concluded in research published in science last month, that the only way to narrow down the range of what could happen is to plug in the numbers on what we know did happen, long before the first thermometer or CO2 detector had been invented by human minds. Here to explain more is Dr. Jessica Tierney, an associate professor of geosciences at the University of Arizona in Tucson.

She's lead author of the new research. Welcome to Science Friday, Dr. Tierney. Thanks for having me. So the paper that you co-authored for science last month states that past climate informs our future. And you're talking about how climates from millions of years ago can help us understand what's happening to us right now under human-induced climate change. So why do we need to look that far back? Right. So as we look into the future, we're looking at a future with high CO2 levels in the atmosphere. Already we've surpassed 400 ppm CO2. The last time that CO2 was that high, was that high, was.

three million years ago, actually, which is a long time ago, right? So we're kind of trotting into the unknown here. And the problem is we can't actually understand the potential climate changes that we're going to experience if we only look at, for example, the historical record of temperature change or the historical record of precipitation change, because that's occurred over a very narrow range of CO2, right? So if we go back deeper into Earth history, though. Three million years ago, we saw 400 ppm, but if we go back even farther, we find ancient warm climates, the so-called greenhouse climates, where CO2 levels are up near 1,000 ppm, and that's a really warm climate. So in order to really understand where we're headed, we have to look back.

When you're talking about that historic climate data, you're talking about temperatures that we have recorded with instruments by human agents. Why isn't that data enough? Well, if you think about the historical change in temperature. We've seen a little bit over a degree of global warming in Celsius units. And some regions have warmed more than others. But what we're looking at into the future, you know, the end of the 21st century, we're talking about warming that could be three degrees Celsius or it could be as high as five degrees Celsius. And that level of climate change is way outside of what we've experienced in the historical time. It doesn't sound like big numbers, but for context, the last glacial maximum, which was the last ice age were huge glaciers covered

North America. That was a 6 degree Celsius temperature change. You know, pretty big, but that's still a single digit number. So you can see how dynamic the Earth system is. We go back to the Pleistine three million years ago and the temperature changes only three degrees. Celsius, warmer than present. And yet the Greenland ice sheet was completely melted. It was gone. You mentioned this range of temperature changes we might see as a result of this increase in carbon dioxide in the atmosphere. What are the biggest unknowns there creating that range? Yeah. So the first source of uncertainty, of course, is how much carbon are we going to put into the atmosphere? And so what will the CO2 levels be? Obviously, that depends on us and the sort of

decisions that we make. But in addition, even for a set emission scenario, let's say, there's actually a wide range of predictions from climate models, which we use to kind of forecast out into the future. And that actually relates to the sensitivity of the climate model to changes in CO2. So it turns out that different models have different sensitivities. And so some models are very sensitive. They, for doubling of CO2, maybe they experience five degrees Celsius of warming. So that would be a high sensitivity. Others are quite low. Let's say they experience only 2 degrees C warming. So for the same projected emissions, the low sensitivity model will give you a much lower warming answer than the high sensitivity model. So the problem is, you know, what is

climate sensitivity? You know, in order to narrow those projections, we would need to narrow that number. And in order to figure that out, this is where the ancient record of climate change, the Pellate Climate record can really play a strong role because we have all these different climates to sample. You know, we can go to a warm climate, we can go to a cold climate, we can determine what was the change in CO2, what was the change in temperature, and then come up with a range of plausible climate sensitivity. So we can either rule in or rule out, for example, a high sensitivity model based on the study of these ancient climates. So I feel like this is the question that is going to be burning in everyone's mind, how do you look back that far in time and have a sense of the accuracy

of what you're finding? Right. Great question. So we no longer have thermometers when we're going back into ancient climate. No time machine. No time machines. Unfortunately, we all wish that we could go back as geoscientists. We actually have to use the remnants of living things often that are preserved in rocks and sediments. And we have to use chemical tricks to actually decipher what is the temperature and what is the carbon dioxide. The ice cores that are from Antarctica, they trap bubbles of ancient air directly. And so that's really cool because from an ice core, we can actually directly measure ancient CO2. So that's kind of easy. But that only takes us back a little less than a million years. So one of the archives that we really rely on for some of these ancient warm climates that have occurred in the last tens of millions of years are marine sediment cores.

They're collected from the middle of the deep ocean with a very, very large ship with a very, very large coring apparatus. And so you're going out there collecting these cores and they go back millions of years, this tube of mud. In that tube of mud are tiny fossils of single-celled organisms called foramenopura. And these guys are protists. They live in the upper areas of the ocean. And they're useful to us because they've been around for a long time in the geological record. Their shells are made of calcium carbonate, chalk, essentially, and they're well preserved in sediments. So we can find them and we can measure different aspects of their chemistry, which can tell us about both temperature and CO2, actually. Measuring different isotopes in particular is a big thing for us in climate

science, what we call stabilized tubes. Each atom has a slightly different number of neutrons. And basically, these stabilized tips serve as tracers for temperature and also CO2, which is really interesting and kind of a newer technique. But now using those shells, we can actually measure that chemistry in the lab and come back with numbers of temperature and CO2. That's amazing. So how far back can we look? So the Marine Sentiment Corps records, goes back about 100 million years. That's a long time. That takes us back to the Mesozoic and the time of the dinosaurs and covers several really warm climates, including the Eocene, warm period 50 million years ago, and also the Middle Cretaceous, which is a very steamy time.

The reason that the sediments don't go back further is simply because, you know, we're getting them from the deep ocean. And, well, because of plate tectonics, The ocean crust is over these timescales being recycled. So it actually gets subducted under another plate and then recycled. So we can't find marine sediments in the ocean that are older than that. Of course, we can go and switch to rocks on land. And rocks on land can take us back even farther. Do we know exactly what the Earth was like for its entire history at this point?

Or are there gaps? Right. So I think we have a sense of the best. broad-scale changes, for example, when the Earth was experiencing overall a cold climate, which we define in part by whether there's large ice sheets at the poles. And then when it's experiencing warm climates where we don't see a lot of continental ice sheets left behind. And we know those changes fairly well for, you know, I would say, even the last billion years, We've got 700 million years ago, Snowball Earth.

Okay, what was that? Yeah, Snowball Earth is pretty spectacular. That's the coldest known climate that we've observed on Earth. And basically in that time, ice extended all the way to the equator. And so it was basically the Earth froze over. We have evidence of ice sheets and tropical locations persisting there for quite a long time. And then eventually, actually, when the earth came out of snowball earth, it warmed up really rapidly and went to the other extreme, went to some extremely warm climates in the aftermath. But it's pretty incredible.

And those incidents of snowballers were really recorded by the fact that we do physically see evidence of ice sheets in what would be tropical latitudes. So it's pretty wild. And then, you know, moving forward in time, we have extreme warm climates, for example, probably the first one that we understand really well is the Permian Triassic transition, which is also the most extreme extinction in Earth history when you have more than 90% of all the species on Earth die. And it's also a very warm climate associated with really high CO2 levels, extremely high temperatures, in this case in response to persistent volcanic eruptions, which will emit CO2.

And so that's something on the other extreme. So how does this understanding of deep time, geologically speaking, you know, under some of these worst predictions for carbon emissions, what does this tell us our future Earth could look like? So the first thing we can tell from this long-term Earth history is the importance of CO2. So every time in Earth history when the climate gets hot, it's CO2. And so there's this really tight link between CO2 and global temperature that persists across millions and even billions of years, basically the entirety of Earth history. And then looking at the future, one of the things we can learn from the past is actually how does the Earth system recover from a very rapid emission of carbon dioxide? So a lot of people ask me, you know, what's going to happen? And is the Earth just going to spiral off, become Venus in the future in response of CO2 emissions that humans are doing?

And the answer is no, it won't. It will actually recover. But, you know, the timescale of recovery is geological and not a human time scale. So it can be hard to understand. The full recovery is on the order of 100,000 years. And how do we know that? So we've actually seen events in Earth history where all of a sudden a large amount of CO2, was emitted to the atmosphere.

So one of the best studied events is something called the Paleocene-Eocene Thermal Maximum. It's what we call a hyperthermal event that occurred 55 million years ago. And basically a bunch of CO2, you know, emitted into the atmosphere through volcanism in the North Atlantic. And we see that the Earth's temperature, you know, sky rockets up, an increase of around in between 4 and 6 degrees Celsius or something. And then we can watch what happens in the aftermath, right? So the first thing that happens in this event is that the oceans acidify. So a lot of the CO2 we're emitting right now is taken up by the ocean. And in fact, the ocean is sort of helping us out that way because, you know,

CO2 that's taken up by the ocean is no longer in the atmosphere and no longer warming the atmosphere. and the pH of the ocean will drop to the point where actually the calcium carbonate sediments on the bottom of the ocean, the chalk sediments that are actually made up of those forminaferior shells I was talking about earlier, start to dissolve. And the good news about that process is that when this chalk dissolves, it neutralizes the acid. So it actually neutralizes the CO2. So it is part of the recovery. But, you know, you can imagine that that has consequences.

for things that are living in the ocean and experiencing these low pH. But you see that there's a recovery. It's very slow as the rest of the CO2 is essentially neutralized by those calcium carbonate sediments. And then on very long time scales, actually CO2 starts to react with rocks on land. And that neutralizes it and brings a system back to where it was before. But as I said, that's taking place over a time scale of about 100,000 years. We're talking about. talking about time scales that are much longer than sort of living things are used to. Just a reminder that this is Science Friday from WNYC Studios. I'm Christy Taylor.

Talking to Dr. Jessica Tierney about how past climates can inform our future. Is this a tricky thing to communicate when we live also in a world where climate change has been politicized? And, you know, there's this contingent of people who say, well, you know, the Earth was hotter than this before. therefore climate change isn't something we need to act on. How do you work with that? Yeah. So, you know, for sure, the Earth has been so much hotter than now, but I like to remind people that we weren't around then and we're not adapted to it. Fundamentally, humans, we evolved only 300,000 years ago. In the Pleistocene, we're an ice age species. You know, we're used to having a lot of ice on planet Earth. We're used to the temperature ranges that we've evolved in. If you just dropped us

into the Middle Cretaceous, I'm not sure how well we would do, you know. It's very warm and different set of organisms were adopted to do well in that time. And so suddenly shoving the earth into a high CO2 planet, yeah, sure, it's happened before. But these ecosystems and us, we're not ready for it. And so, you know, you think about the magnitude of sea level rise that companies warm climates, right? Even in the Pliocene, you know, which we consider a moderately warm greenhouse climate. You know, Greenland's gone. West Antarctica's gone.

And so you've got like, you know, 10 meters, 20 meters of sea level rise, that's extraordinary. Not as I mentioned when you go back to these ancient warm climates and there's no land ice at all. So the question is, yeah, sure, it's been warm before, but, I mean, first of all, we're not prepared for it. And secondly, there's the issue of the rate of change.

So when I talk about these ancient climates, you know, a lot of them are the consequences of millions of years of changes in greenhouse gases, and then the Earth system can kind of adjust and catch up, right? We have never observed anything in a geological record that is as fast as the anthropogenic perturbation. Quite honestly, we don't have a perfect analog, right? We don't really know, I mean, we know what happens,

but it's happening so much faster. And so in terms of the preservation of our society and the ecosystems that we have on this planet, you ought to be concerned about that. And that's all the time we have. Dr. Jessica Tierney, an associate professor of geosciences at the University of Arizona in Tucson, and lead author on new research in science last month

about the power of paleo climates. Thank you so much for being with me, Jess. Thanks. For Science Friday, I'm Christy Taylor. After the break, the tongue microbiome. That's right. Stay with us. This is Science Friday. I am Ira Flato.

When you go to the doctor for a regular checkup, what's one of the first things that happens? The doc says, stick out your tongue and say, ah, right? But when you stick out your tongue, did you know you're not just showing off one of your body's more useful muscles? You're showing off a collection of billions of bacteria that make their home within your mouth, the tongue's microbiome. Science Fridays, Charles Berkwist, has more in this interview from the SciFRI archives. It turns out that there are a lot of different things loving in your mind.

mouth. And scientists are trying to map out exactly what lives where. They're hoping that the information could provide clues to health and disease. In work published in the journal Cell Reports, a team of researchers have taken a first taste at mapping some of the relationships between the bacterial colonies that live on a human tongue. Joining me now is Jessica Mark Welch. She's an associate scientist at the Marine Biological Laboratory and one of the authors of that study. Welcome to Science Friday. The pleasure to be here. Thank you. Let's talk about what's going on in the environments in your mouth. Are all mouth bacteria the same?

There are a lot of different bacteria that live in your mouth. And in fact, there are different kinds of bacteria that live on your teeth and on your tongue and on your gums and on your cheek cells. So all the different environments in your mouth have different bacterial communities that live on them. In this particular study, you were looking specifically at the tongue. How are the, how are the backeramins? bacteria arranged there? The bacteria on your tongue build these little skyscrapers. They build these little microbial apartment buildings. When we looked at them through the microscope, we said, wow, there's so much more structure there than we'd expected.

It was really amazing. Is it just bacteria stacked up on top of bacteria, or are they glommed on to some, I don't know, support structure? Oh, yeah. So the bacteria on your tongue, they're arranged on your tongue epithelial cells. So there's a core cell at the center of these clusters of bacteria. that's human. And onto that human cell, these bacteria grow, and they grow out in little clusters,

and different bacteria live in different places in the clusters. So there are some bacteria that seem to like to live right down in with the human skin cell, the human epithelial cell that's on your tongue. And then there are other bacteria that form a crust on the outside and others that form clumps in the middle. So it's a really very complex, complicated structure. You're developing a map of how the bacteria are organized vertically in those skyscrapers you mentioned. It's sort of who's living on what floor and who's next to the laundry room and all that.

Yeah, exactly. Yeah, what we want to know is how are the bacteria arranged relative to each other at these really fine scales, these micrometer scales, so a thousandth of a millimeter. You know, which bacteria are next to who, which other bacteria are, which bacteria are next to which other bacteria, which are right next to the human cells. And how do they arrange themselves? So this isn't a map of the tongue in terms of who's living on the tip of the tongue versus the sides of the tongue versus... Exactly. What we were interested in was really the fine scale structure at the bacterial scale, the scale at which the bacteria are really living and interacting with each other. What's the structure and what's the map there?

Looking at the pictures in the paper, it doesn't look like there's a ton of large-scale patterns or organization. Does it really matter who's living where? So the reason it matters is that bacteria interact with whatever's right next to them. So the bacteria are taking up nutrients and then they're secreting other nutrients. They take up molecules and secrete molecules. And they do that most dramatically, most importantly, with all the bacteria that are right next to them. And the bacteria that are right next to the human cells are also in the best position

to influence human cell biology. Are these bacteria living on what we would call the taste buds, or are they influencing how we, are the flavors we're experiencing? Yeah. So if these clusters of bacteria that we see aren't right on the taste buds, they're certainly right next to the taste buds. And it's certainly possible that exactly what kind of bacteria you have on your tongue influences how you taste food.

Now, on the other hand, the food comes through your mouth really quickly, just in a few seconds. So the bacteria would have to be acting pretty fast to make a difference for your taste. The food's moving through my mouth, the saliva is sloshing around. What's keeping the bacteria in place? Is there some kind of glue or, I don't know, tendrils or something that they have? Yeah, exactly. So all the bacteria that are in your mouth, they have to be hanging on to something or else they're going to end up in your stomach. And they don't want to be in your stomach. They want to stay in the mouth. So every bacterium in your mouth is adhered to something. It's either adhered to your cells or to your teeth or it's adhered to other bacteria that are hanging

on to your teeth. We ask our volunteers to basically just clean their tongues and then we collect the stuff that they've scraped off their tongue and we look at it under the microscope and we see these lumps and clusters that stick together really pretty well through all of our experimental manipulations because they're sticking together in the mouth with the way they grow. So the volunteers are using one of those tongue scraper things that some people use for oral care. Yeah, exactly. They're just using a little ridged plastic tongue scraper like your dentist might hand you and say, here, you should scrape your tongue.

And should people scrape their tongues? Do you have any sense of whether it makes a difference? So when you scrape your tongue, it certainly reduces the number of bacteria in your mouth, and that does seem to be a good thing. You can't get rid of all of them. There's always more of them coming up behind, but when you scrape your tongue, the same as when you brush your teeth and floss your teeth, you can reduce their numbers. And that's probably good. What about mouthwash?

So the interesting thing about mouthwash and the bacteria on the tongue and the rest of the mouth is that using mouthwash seems to have an effect on your blood pressure because of the bacteria. Right. So what these bacteria can do that your body doesn't do very well is they take a certain nutrient. that's in your food, it's called nitrate. The bacteria can convert nitrate to nitrite, which your body doesn't do very well. Then your body takes the nitrite and turns it into nitric oxide, and that has a lot of effects, including regulating your blood pressure. So the interesting finding is, this is other people's work, it's not our own,

is that if you eat a diet that's rich in green leafy vegetables and other healthy foods, that will lower your blood pressure by a little bit, small but measurable amount, but not if you're using an antiseptic mouthwash. So the bacteria are an important part of that effect of the healthy diet. So, wait, using mouthwash can alter my blood pressure, with all those other things taken into account. Yes, so all those things take into account. Yes, using mouthwash, so there have been scientific studies where people have shown

that, yes, if you consume a high nitrate diet and then use mouthwash, that will alter your blood pressure, just a little bit. Zooming out from just the tongue, how many different species of bacteria are in an average mouth? Yeah, there are about, oh, a couple hundred species of bacteria in the average mouth. There are about 500 species of bacteria, 500 or 500 or 700 that are known from the human mouth as a whole in all the people all over the world than any one person has, maybe a couple hundred. And how much do different people have in common? How similar are my mouth bacteria to your mouth bacteria?

What we've found, and this is something we're learning only just recently, what we've found is that different people have pretty much the same species of bacteria. So we all have pretty much the same species. And in fact, the bacteria on your tongue are the same as the bacteria on my tongue. The bacteria on your teeth are the same as bacteria on my teeth, pretty much. But we all have slightly different proportion. of those bacteria. So somebody will have a lot of one kind, somebody else will have a lot of another kind. And we also have slightly different strains of bacteria. So if I take a sample

from your mouth and then a year later you come back, I can identify you. At least I could pretty much guess, you know, which person you are based on what bacteria I find in your mouth. So you could actually, I mean, would this be a reliable forensic technique? Could you identify somebody based on, I don't know, scraping off their tongue? It's certainly not as reliable as your genome would be, but one could certainly make a good guess based on the bacteria that you have, your specific strains of bacteria. You're developing this map of the bacteria that are there,

and I guess there are people that are working on sort of the microbial census of the mouth. Do we have any sense yet of what is healthy, what is normal, what is a standard mouth? We're starting to get a sense, I think, of what is, what's the range of normal that you find in the mouth? The human microbiome project did a lot of sequencing, DNA sequencing from the bacteria in the mouth, and they've shown what bacteria tend to be there. So what we're still working on on the imaging side is finding out what kinds of structures are normal. What's the range of normal in the structures of bacteria that you see in the mouth?

What does that get you? I mean, what's the goal in knowing that information? Yeah, so the goal really is to be able to understand how the bacteria work, how these communities work. First of all, why are there so many different kinds of bacteria? Why aren't there just two or three or four? Why do we have hundreds? What are they all doing in the mouth?

And we know that some people's microbiomes, some people's sets of bacteria, you know, work well for them, seem to promote health. But then other sets of bacteria, other microbiomes can cause disease or can contribute to disease. And we'd like to understand what are the characteristics of a healthy microbiome, what are the characteristics of disease? And then, really, the ultimate goal is to be able to shift the microbiome from a disease state into health. So if we can really understand how these bacteria work together, then we can understand what conditions the good bacteria need to grow. So the reason to look with imaging is to see

exactly what environment a good bacteria needs to live in. You know, who does it have to be next to? And then how can we tweak the environment, tweak the community to push it toward health? Are these things that grow in a petri dish? Can you do some of these experience? What What nutrients do they need? What other supports do they need in the lab? Yeah. So one really interesting thing about bacterial communities that we've been learning is that if you go out and sample bacteria from the soil, say, or from the ocean, really only a tiny

fraction of them will grow on your petri dish in the lab, right? They need something that we don't know how to give them, and probably they need to be next to some other bacterium. And we don't know what it is. that's another reason we want to do the imaging and find out who's next to who. In the human mouth, it turns out that about half of the bacteria can be grown in a petri dish. And for those other half, there is probably, again, there's something that they need or somebody that they need to be next to that we don't know yet. So that's one of the things we're trying to learn. I can't help but notice

you're at the marine biological laboratory. What relation do tongues have to do with marine life? Yeah, that's a great question. We do a lot of really basic biological research at the marine biological lab. So we started using the giant axon of the squid to ask questions about neurobiology, using the great big oocytes and surf clams to ask questions about cell divisions. So what we've really been about for more than 100 years is using these marine model organisms to ask basic science questions. But because of that, we have a lot of innovative microscopy that you can really see put to work in this project. And then we also have a lot of experts who study bacterial communities anywhere in the world in the Arctic and the

deep sea in coastal marshes. And here we're just applying that to an environment that's a little bit closer to home. And then I'm doing that with my colleagues at the Forsyth Institute, who are real experts in oral microbiology as well. Are there marine organisms that have tongues that you've looked at? That's a good question. You know, there are marine organisms with tongues, and I haven't looked at them yet, but I'd love to. Yeah. I'd love to find out where else, besides, the human mouth, you find such fantastic structure. So it's amazing bacterial structures that these bacteria build. You're listening to Science Friday from WNYC Studios. I'm Charles Berkwist, talking with Dr. Jessica Mark Welch from the Marine Biological Laboratory at Woods Hole. We're talking about tongue

bacteria. When I go to the dentist and I leave with those nice, clean-feeling teeth, how long does it take for them to get recolonized by the bacteria communities in my mouth? minutes. So when the dentist cleans your teeth, your teeth are really pretty clean, the dentist do a great job of getting all the bacteria off, at least 90% of the bacteria. But then within seconds, your nice, clean enamel of your teeth gets coated with saliva. There's a coating called the salivary pellicle that goes onto the enamel, and a different coating called the mucosal pellicle goes on your tongue and your cheeks. And bacteria within minutes start attaching. to that pellicle.

The bacteria start reattaching to your teeth. And there are initial colonizers that are really good at binding to those pretty clean teeth with a little coating of saliva. And then there are other bacteria that come in and bind to the initial colonizers. So it's a whole ecological succession really going on in your mouth. And actually, it goes on every time you brush your teeth every day. And when bacteria start to colonize apart, is it just sort of luck of the draw who happens to get into that niche first and start multiplying and growing outwards, or are there ones that really

like the squishy places and other ones that like the not so squishy places or some other environmental variable that they're looking for? Yeah, so some bacteria are really good at attaching to that first salivary coating on the teeth. So to some extent, it's which bacteria are particularly good at being the first colonizers, but then there is also probably a lot of chance involved. So for these structures on the tongue, when a new piece of, you know, human tongue cell becomes available in the mouth when it shows up in the mouth to be colonized, whichever bacteria land on it first probably have a pretty big influence on what kind of community grows out over time. Where else are you planning to go with this? Do you want to develop a map of what lives on my

tip of my tongue versus the sides? Or is that not of anything? interest or what other directions do you have for this? Yeah, so we'd love to know what kinds of bacteria live exactly where on your tongue. So what kinds of structures we see if you look at the very back of the tongue or in the crevices between the papilli versus on the front of your tongue or the sides. We'd also really love to push this forward to looking at the dynamics of the community. So so far, everything we've looked at, we've had to take the sample out and fix it. It's all dead.

We'd love to be able to watch these bacteria growing. and see how they grow, how they accrete. I think that'll tell us a lot about how they're working together. And how would you go about doing that? Is it, you know, looking at, I don't know, cadaver tongues or peeling pieces of tape off my tongue surface, or what are you doing? Right. So, yeah, to discover how the bacteria are arranged on the tongue, it would.

So one thing, the simplest thing we can do is just take little scrapings from all over the tongue and look at them. We have certainly thought about trying to get cadaver tongues or to put tape. on the tongue and peel it off and see exactly what's where. We've also thought about going to piercing parlors where people are having their tongues pierced and collecting little samples. This is all in the future. We haven't tried this yet. But yeah, but then for the live imaging, to image these microbial communities live,

we'd really have to change the whole way that we're labeling them. So it's another whole transformation of how we're doing the science, but we're really excited to try to push the microscopy in that direction. It's tough to paint fluorescent probes all over somebody's time. Yes, we have a little trouble getting permission to do that from our human subjects review board. Yeah, it's true. Well, thank you very much for taking time to talk about it with me today. Thank you so much. It was a pleasure.

That was Cy Frye Director Charles Berkwist speaking with Jessica Mark Welch, associate scientist at the Marine Biological Laboratory in Woods Hole. Charles Burquist is our director. Our producers are Alexa Lim. Christy Taylor, Katie Feather, and Kathleen Davis. B.J. Leiterman composed our theme music. And of course, if you missed any part of the program, or you'd like to hear it again,

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