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We could still limit global warming to just 2˚C — but there's an 'if'

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Listen to the latest from the world of science, with Benjamin Thompson, Nick Petrić Howe and Shamini Bundell.

In this episode:

00:46 What COP26 promises will do for climate

At COP26 countries made a host of promises and commitments to tackle global warming. Now, a new analysis suggests these pledges could limit warming to below 2˚C – if countries stick to them.

BBC News: Climate change: COP26 promises will hold warming under 2C

03:48 Efficiency boost for energy storage solution

Storing excess energy is a key obstacle preventing wider adoption of renewable power. One potential solution has been to store this energy as heat before converting it back into electricity, but to date this process has been inefficient. Last week, a team reported the development of a new type of ‘photothermovoltaic’ that increases the efficiency of converting stored heat back into electricity, potentially making the process economically viable.

Science: ‘Thermal batteries’ could efficiently store wind and solar power in a renewable grid

07:56 Leeches’ lunches help ecologists count wildlife

Blood ingested by leeches may be a way to track wildlife, suggests new research. Using DNA from the blood, researchers were able to detect 86 different species in China’s Ailaoshan Nature Reserve. Their results also suggest that biodiversity was highest in the high-altitude interior of the reserve, suggesting that human activity had pushed wildlife away from other areas.

ScienceNews: Leeches expose wildlife’s whereabouts and may aid conservation efforts

11:05 How communication evolved in underground cave fish

Research has revealed that Mexican tetra fish are very chatty, and capable of making six distinct sounds. They also showed that fish populations living in underground caves in north-eastern Mexico have distinct accents.

New Scientist: Blind Mexican cave fish are developing cave-specific accents

14:36 Declassified data hints at interstellar meteorite strike

In 2014 a meteorite hit the Earth’s atmosphere that may have come from far outside the solar system, making it the first interstellar object to be detected. However, as some of the data needed to confirm this was classified by the US Government, the study was never published. Now the United States Space Command have confirmed the researchers’ findings, although the work has yet to be peer reviewed.

LiveScience: An interstellar object exploded over Earth in 2014, declassified government data reveal

Vice: Secret Government Info Confirms First Known Interstellar Object on Earth, Scientists Say

Subscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday.

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doi: https://doi.org/10.1038/d41586-022-01100-8

Transcript

Listen to the latest from the world of science, with Benjamin Thompson, Nick Petrić Howe and Shamini Bundell.

Host: Benjamin Thompson

Hi, Benjamin from the Nature Podcast here. Something a bit different this week – we're going to take a bit of a dive into some of the stories that have appeared in the Nature Briefing over the past few days and weeks, and joining me to do so in this episode of the podcast are Nick Petrić Howe. Nick, how are you doing today?

Nick Petrić Howe

I’m doing well, Ben. How are you?

Host: Benjamin Thompson

I’m doing a-okay, thank you very much. And also joining us is Shamini Bundell. Shamini, hi.

Shamini Bundell

Hello, I’m very excited. All three of us at once discussing science. This is going to be fun.

Host: Benjamin Thompson

Yeah, it’s a rarity, isn’t it. Well, let’s crack on then. Nick, do you want to go first this week? What have you got?

Nick Petrić Howe

I certainly can go first. So, I've been looking into a couple of things that are sort of climate change-related and, well, the first one is very much related. There was a paper that came out in Nature that's been assessing how well we're going to do with climate change based on the promises made at COP26, and I was reading about this in the BBC News.

Shamini Bundell

And COP26 was the most recent one in Glasgow.

Nick Petrić Howe

Yes, COP26 was the most recent one, last year in November, and this was a big one because it was 5 years on – well, actually 6 years because of COVID – from the Paris talks, and so this was a time where countries are supposed to be ratcheting up their promises and sort of pushing the boat out a bit further.

Host: Benjamin Thompson

Yeah, and a bunch of promises were made, and you talked about them on the podcast at the time. So, this paper then, is it sort of breaking them down and looking at what will happen as a result of them? Is that right?

Nick Petrić Howe

Yeah, that's right. So, the paper basically looks at what were the promises made, how they sort of improve on the Paris promises, and where that might leave us. And the headline is, we can keep things under 2°C, if all of the promises and pledges are completely fulfilled, and that will get close to around 1.9-2°C, according to the analysis.

Shamini Bundell

And 1.5°C, has that now been left and 2°C is the next sort of benchmark that we’re aiming for?

Nick Petrić Howe

Yeah, well, sadly, there’s slightly more pessimistic news on that because they did an analysis of how likely we are to get to 1.5°C as well, and based on what countries have pledged, our chances of getting there are around 6-10%. So, most likely, we're going to overshoot 1.5°C. And the question is now like how much we're going to overshoot it by and whether we can actually bring it back down if we do so.

Host: Benjamin Thompson

I mean, Nick, you said the paper is looking at what would happen if everyone stuck to their commitments? I think that word ‘if’ is doing an awful lot of heavy lifting.

Nick Petrić Howe

It certainly is because the getting it down below 2°C relies on every country sticking to every promise that they've made and so, yeah, there's quite a big ‘if’ there. And it really relies on, as well, the sort of short-term goals, so that's up to 2030. So, you've probably heard that emissions need to peak basically now. So, what's actually happening, according to analyses, is emissions are going to go up by 13% up to 2030, and that's not really the direction we need to be moving in. So, they really need to go down by 45% if we want to try and get those more ambitious targets, like 1.5°C. But as the analysis says, it's still possible to get under 2°C.

Shamini Bundell

So, where does that leave the next steps in terms of climate change?

Nick Petrić Howe

Well, it feels like the same sort of thing I say every time we do a climate change story, and that's that we need action and we need it quicker. Countries need to fulfil their pledges, and they need even more aggressive pledges. And there needs to be money to make this sort of energy transition, especially for middle- and lower-income countries that haven't really contributed to climate change but will bear the brunt of the consequences of it. But thinking about sort of solutions, the other story that I was looking at this week was about a potential way to get energy that has been stored, and efficiently store energy and do so in sort of like a clean way.

Shamini Bundell

Oh, that’s very mysterious. What kind of energy storage are you talking about?

Nick Petrić Howe

So, I've been looking into what are called thermophotovoltaics, and this was a paper that was again in Nature and was covered in Science.

Host: Benjamin Thompson

Right, well, pray, tell, then. What is a thermophotovoltaic? What does it do?

Nick Petrić Howe

Well, that is a very good question and to sort of give you the answer I need to give you a bit of background. So, when we're thinking about the energy transition, one of the key things is thinking about storage of energy because you need to store energy from renewables when the sun isn't shining or the wind isn't blowing. And you can use batteries for that, but they tend to store energy for only a short amount of time and are quite expensive. If you need to store it for a long amounts of time, there are other things, and that's where these thermophotovoltaics come in. So, what you can do is you can heat up a large mass to ultrahigh temperatures, and then you can tap into that when you need the energy, and the way you can tap into that, or one way at least, is using these thermophotovoltaics. And the ‘photo’ part of these thermo photovoltaics is that what you do is you heat up a metal to very high temperatures so that it glows like a light bulb, and then you use these thermophotovoltaics to sort of capture that energy in a similar sort of way as solar cells work.

Host: Benjamin Thompson

Oh, so they’re turning heat into light, and then using that light to generate electricity. Is that right?

Nick Petrić Howe

Yeah, that's right, and this is a way that you can actually store surplus energy from renewables. The problem has been that, since around the 1980s, the efficiency has been stuck at around 30%. And this is quite an expensive thing to do, so it's not high enough, really, to actually make these things workable in reality. But now, in this new paper, they've got it up to 41% – the efficiency – and they've done it in quite a clever way.

Shamini Bundell

Yeah, so to get over a 10% jump all at once I feel like they must have been being quite creative. What was their solution?

Nick Petrić Howe

So, they’ve done something that's quite different from previous work in this area. So, typically, the way these things will work is they'll heat up something called an emitter, which is emitting the light up to 1400°C because this is the temperature at which the light coming out of this emitter is the best wavelength to be sort of captured by the thermophotovoltaics. What they've done instead is they've got 1000°C higher, and they've heated up tungsten to 2400°C. Now, the reason this hasn't been done in the past is because there's a much broader spectrum of light that's emitted at this temperature. But what they've done is they've changed the thermophotovoltaic so it can capture a much broader range of different wavelengths of light. And then they also put a layer of gold on the bottom, which reflected photons that couldn't be absorbed back into the metal, so that energy wasn't lost.

Host: Benjamin Thompson

So, it can work at a higher temperature and absorb more of the wavelengths of light, therefore it works at a higher efficiency?

Nick Petrić Howe

Yeah, that's exactly how it's working. And they’ve actually got ideas as well to get it up to 50% because in 2020, in Nature, there was a paper about a mirror that was able to reflect like 99% of infrared photons, and they reckon they could actually incorporate this mirror into their design and get that efficiency above 50%.

Shamini Bundell

And then, hopefully, we’ll basically be able to use this to make the use of renewable energy much more efficient because we can now store it.

Nick Petrić Howe

That's the idea. So, previous work has suggested that you need to get these to around 35% efficiency to make the technology economically viable. This one's looking at 41% so theoretically should be economically viable. And the researchers involved have launched companies that are trying to get into this space and trying to set up this endeavour, so maybe we'll hear more about thermophotovoltaics in the future.

Host: Benjamin Thompson

Nice, well, that's a great story. Thank you, Nick. Let's keep going round. Shamini, would you like to go next?

Shamini Bundell

I would love to. How do we feel about leeches on the Nature Podcast?

Host: Benjamin Thompson

I've only ever seen them in films, I guess.

Nick Petrić Howe

Yeah, normally treating some sort of mediaeval ailment. Is that where we're going with this one?

Shamini Bundell

No, this is the leeches out there helping conservationists monitor animals. I should say, this is an article in Science News that I've been reading. I love leeches. I'd like to put in a small plug for how fantastic leeches are, and I might have enjoyed the job in a national park in China where they basically sent out a load of park rangers and people to hunt for and collect as many leeches as possible as a way to monitor how the wildlife in the park was doing.

Host: Benjamin Thompson

Ah, so when you say that the leeches were helping conservationists, they weren't going out with a clipboard then and counting the different species in this area.

Shamini Bundell

No, the researchers wanted to find out if they could use blood from inside leeches to figure out what the leeches had been eating and actually collect DNA from different species around the park just via the leeches.

Host: Benjamin Thompson

So, a kind of a proxy count of the different species that were there.

Shamini Bundell

Yeah, and this sort of idea – so it's called environmental DNA – it's kind of like let's monitor the DNA from the environment. In this case it's leeches, but the story references another paper from earlier this year, where the researchers were trying to test out essentially using little vacuums to try and like suck DNA out of the air. They were testing it in a zoo to see if they could figure out like how much DNA they could get and where the DNA was floating about. You can do it in the sea as well. You can get DNA from seawater to find out what animals have been around. And it's obviously much easier than going out and trying to find all these animals directly. You don't need camera traps, which only kind of work on the big animals. You don't need to have sort of trained up loads of people to try and spy and identify the species because you can get the DNA from the leeches.

Nick Petrić Howe

Well, it seems like a really fascinating way to get DNA from animals, and what was it able to tell the researchers about this park?

Shamini Bundell

Well, in this particular instance, one of the things that they noticed was in the high-altitude interior of this park, the leeches were eating a much higher proportion of the sort of biodiversity and wild species, as opposed to close to the edges of the park, they were feeding more on sort of like domestic sheep and cattle and goats. Now, the wildlife of the park ideally should be able to live anywhere in it. So, this could suggest to the people running the park that actually human activity is disturbing the creatures and pushing them away from certain areas, so perhaps that could be useful information for them to try and address that.

Host: Benjamin Thompson

And, Shamini, do you think we're going to see leeches are taking a bigger role in kind of environmental censuses as we move forward?

Shamini Bundell

I hope so. I would like to be interviewing leech scientists on the podcast, ideally, leech conservationists. I think this is the first time this has been done, so I think it's all a little bit experimental, as with the other sort of vacuuming DNA out of the air idea. But it's definitely another piece in the toolkit of conservationists that could be useful in monitoring wildlife around the world.

Nick Petrić Howe

That is a fascinating proof of concept of how to use leeches in this sort of science, Shamini. But Ben, you've been quite quiet so far this week. Do you have a couple of stories for us?

Host: Benjamin Thompson

Oh, do I. And the first one, let's stick in the kind of animal world, and I've got one about how acoustic communication has shifted, and specifically shifted in some fish that live in underground caves in Mexico, and this was a paper that was in Nature Communications, and I read about it in New Scientist.

Nick Petrić Howe

When you say ‘acoustic communications’, are these just the sounds the fish are making and these have changed?

Shamini Bundell

Wait, do fish make sounds? Is that a thing?

Host: Benjamin Thompson

Fish make a lot of sounds, particularly bony fish. But I think what hasn't necessarily been well understood is how these sounds do evolve and do change. And this story particularly looks at a group of fish called Mexican tetra. Now, these are small fish that grow to about 10 centimetres long, give or take, and there’s kind of two forms, two groups, I would say. One lives outside in rivers, it's got good vision, it's got lots of colours, it swims about, all the rest of it. And the other lives in these cave systems in Mexico, and they are translucent, and they've lost their eyes as well because they're in the dark all the time, and they've evolved a number of ways to survive in these kinds of food-poor areas. We've covered it in the podcast in the past. And these adaptions evolved later on, but not much was known about the way they chat, I guess, and so these researchers have been looking at these two different groups of fish and see how their, yeah, how their fish chat differs.

Shamini Bundell

How do you listen to a fish?

Host: Benjamin Thompson

You use a lot of time in a lab with a microphone. So, these researchers behind this work recorded dozens of hours of the different fish, and it turns out that tetra fish make six quite distinct noises, right. But one of them in particular they looked at in this paper was this kind of sharp click sound, okay. Now, the fish that live overground in the rivers, they use this, well, when things are getting a bit aggressive. But for the fish that live in the cave system, they make the same noise, but they actually use it while they're foraging for food, so totally different. And the fish will act in different ways if they hear it. The overground fish, they’ll emit it when there's another fish in their tank or if they hear it, their behaviour will change. But the cave fish, if they hear this noise, other fish will come towards them. They're like, ‘Oh, there must be some foraging going on for some food.’ And what keeps going with this work is they then looked at specifically these underground fish and in the a different cave system, and saw that the noises that they made were similar but different. They had kind of different accents, as well.

Nick Petrić Howe

I'm imagining some of these fish with like a Cockney accent, some of them with like a Brummie accent, maybe some with like a southern drawl from the US. Is that the sort of thing we're getting?

Host: Benjamin Thompson

It might be slightly hard to make those kind of differentiations. But what they did find, the researchers, was that one of these groups, the clicks were kind of deep and booming, and another, they were kind of pitched a bit higher. So, there's a lot going on there, and this all seems to have happened kind of independently because these different populations live, say, in different cave systems that aren't necessarily linked.

Shamini Bundell

So, languages sort of diverge naturally, and the same kind of thing is happening in evolution. Is that what they think is happening here or is it something more driven, this process?

Host: Benjamin Thompson

Well, a lot of questions, Shamini, to answer about this one. I think in the article I read, they were saying that they think it's kind of genetic drift, so just random chance, that might be driving this. But it's the first time that it's been seen and, of course, the two different groups of fish live in very, very different areas, so it could actually give us insights into if there is a drive, how communication does evolve over time. And they say that potentially this could be involved in speciation. One of the authors says that maybe in time over millions of years, the communication would have drifted so far apart that the different groups won't be able to understand each other anymore.

Shamini Bundell

You know what I really want now is to interview a tetra fish on the podcast. Did not know that they could talk.

Host: Benjamin Thompson

Well, listen, I think we've got time for one more, and let's go to a story that's about as far away from that as I think it's possible to get. Okay, now, this is something that I read about in LiveScience, and it centres on a small meteorite that hit the Earth's atmosphere in January 2014. It was only maybe half a metre across or so, but it might have come from a very, very, very, very long way away.

Nick Petrić Howe

There were a lot of ‘very’s there and I was about to say, stuff hits the Earth all the time, what's so important about this one, but I'm guessing it's one of the ‘very’s.

Host: Benjamin Thompson

Yeah, so, let’s fast forward then to 2019, and a couple of researchers wrote up a paper and put it on the preprint arXiv server, where they kind of analysed the flight path of this meteorite. And apparently, they've estimated it was going at more than 130,000 miles an hour, which is much faster than the average velocity of meteors orbiting within the Solar System. And the shape of its orbit as well, it was kind of something they looked at. And they reckon that this suggests that it came from beyond the Solar System, maybe somewhere in the distant Milky Way.

Shamini Bundell

I read about this one as well because it's one of the very few objects that we've ever sort of seen that could have come from outside of our Solar System, so interstellar travel, right?

Host: Benjamin Thompson

100% and if this is confirmed, it would be the first identified interstellar object, putting it before the cigar-shaped 'Oumuamua, which was discovered in 2017, which is something we definitely covered on the podcast, and would put it before 2I/Borisov, this rogue comet that was discovered a couple of years back.

Nick Petrić Howe

But one thing you said there was that this hit the Earth in 2014. How come we're only hearing about it now?

Host: Benjamin Thompson

Well, the paper was put up on the arXiv in 2019, but there's a bit of a gap in it, Nick, and this is where the story takes a bit of a turn. So, this work hasn't been peer reviewed or published yet, and the reason for that seems to be that some of the key verifying data was apparently considered classified by the US government, so they weren't able to put that in the paper.

Nick Petrić Howe

I mean, I really want to just say aliens now. That makes me immediately think aliens. Is that what this is, Ben? Is this aliens?

Host: Benjamin Thompson

I don't think so, Nick. I mean, I think we probably would have led with that story, if it were.

Shamini Bundell

So, I actually read an article in Vice about this story, and it was basically saying that some of the sensors that are detecting the sort of fireballs that come to Earth are operated by the US Department of Defense, and they're using the technology to look for nuclear detonations. But that's why some of the data is basically classified. And there's a quote in this Vice article with the researchers trying to get the US government to kind of confirm the data, and they've quoted the researcher describing it as ‘a whole saga’, and it actually took several years of sort of bureaucracy for them to find to get this.

Host: Benjamin Thompson

Yeah, and fast forward to just a few weeks ago, when the US Space Command, which is, I believe, part of the US Department of Defense, did release a memo confirming the researchers’ findings. But there was no data in this memo, as far as I could see, and the paper hasn't been peer reviewed, as I say, so I think there's still a healthy amount of scepticism about whether this meteorite was the first identified interstellar object. But I guess only time will tell when the scientific process continues. Well, let's call it there then for this special Briefing chat edition of the Nature Podcast. We'll put links to all of those stories in the show notes, so, listeners, you can have read them if you'd like to. And if you'd like even more stories like this delivered directly to your inbox, then don't forget to sign up for the Nature Briefing, and we'll put a link on how you can do that as well.

Nick Petrić Howe

There’s also just time to mention that one of our episodes has been nominated for a Webby, and we need your help to win it. There’s a public vote. We’ll put a link of where you can do that in the show notes as well.

Host: Benjamin Thompson

Yeah, voting closes very, very soon, and it would be amazing if you’d cast your vote for us. So, that’s all for this week, and I think all that remains to say is, Nick Petrić Howe and Shamini Bundell, thank you so much for joining me.

Nick Petrić Howe

Thanks so much, Ben. See you soon.

Shamini Bundell

Thanks. See you next time.

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