From the New York Times, I'm Katrin Benhold. This is The Daily. After failing for decades to cut carbon emissions enough to stop the planet from dangerously overheating, scientists are increasingly looking at backup measures, some that would fight the warming by intervening in the climate itself. Today, my colleague, Christopher Flavel, on the efforts to engineer are a way out of the climate crisis. It's Friday, April fifth. Chris, you've been covering climate change for a while, but recently you've been focused on a very special project. Tell us about this.

Yeah, two things have been happening in climate change recently that are really important. Number one, records have been falling at alarming rates. Last year was, again, the hottest year on record. Much the world surpassed this important threshold of 1.5 degrees celsius above pre-industrial levels. So the world is getting warmer at alarming rates. At the same time, emissions aren't falling. The message of the last generation has been we need to cut emissions really to almost zero by the end of the century. And in fact, the reverse is happening. Emissions are continuing to rise. At the same time, the number and characteristics of weather disasters have become really alarming. The effects of that warming have become really clear, and it's clear that the world is struggling to adapt to those effects. The other thing that's happening is a high level is there's more research and more consideration of, Okay, what if we can't cut emissions fast enough? What if we're going to have this really severe degree of warming? Can we do something else, maybe temporarily, to buffer those effects? That's led to this question of, what kinds of changes can we make deliberately to the atmosphere, to the environment, that will maybe produce some artificial cooling in the meantime?

So earlier this week, I was able to watch as scientists did the first outdoor tests in the US on a technology that will aim to do just that. It's called Marine Cloud Brightening.

So what is this idea of brightening the clouds? Where did it originally come from?

So everyone I talked to pointed back to one really important moment in 1990 when a British physicist named John Latham was taking a hike in Wales with his young son, and they were looking out at the clouds over the Irish Sea. And as Dr. Latham later told it, his son asked him, Hey, why are clouds bright? Dr. Latham said, Well, because they reflect sun back in the sky. And his son said, So they're like soggy mirrors. Dr. Latham went on to write a letter in 1990 that was published in the journal Nature, saying, You know what? If we can deliberately manipulate these clouds, maybe we can make them more reflective and actually counteract the effects of global warming. That was the inception point for this idea, and it led to decades of research culminating in this week's test.

The idea is if you can make clouds more reflective, you can reflect more of the sun's heat back into space so it won't get trapped in the Earth's atmosphere in the first place.

Exactly. That's what they're trying to do.

That's a very simple and at the same time, a very powerful idea. I love actually that they were hiking in Wales. That's where I am right now, and we sure have a lot of clouds here, rain clouds. But tell me more about what you saw at the testing site.

So this Tuesday, a little after 7:00 in the morning, I pulled up in a parking lot on a dock at the edge of Alameda. I'm standing at the gangplank to the USS Hornet, decommissioned aircraft carrier in San Francisco Bay. I'm here for the first test in the US of a machine that was designed to try to brighten clouds, a way of maybe temporarily cooling the Earth. I made my way up one of the massive gangplanks and came in to find a cluster of some of the top atmospheric scientists in the world. Chris. How do you do? I'm welcome. How are you? Looking really excited. They accompanied me out to the flight deck. Here we are. Of this aircraft carrier. Oh, man. Pretty epic. It is pretty great. Which was a bit like a party. They'd set up a little table on the side with some coffee and some sandwiches, and people were chatting and saying hi to each other. I asked them why they were excited. I know a thousandth of what you know, and I still find this exciting. Are you guys walking me through? Is this a big day for you or just one more test?

No, this is a big day for me. They said this was actually a huge day in their research. Just looking at it going, yeah, this is a culmination of years of work, right? Yeah. Or not.

Wow. Tell me about what exactly they were so excited about and what they were doing on this ship.

Yeah. The thing everyone was excited about was this machine set up at the far end of the flight deck of this aircraft carrier. It's blue, it's shiny, it looks a bit like a snowmaker or maybe like a spotlight. This machine is a sprayer. What it does is it sprays really, really, really small aerosol particles, in this case, smashed up sea salt, a long distance at just the right size and just the right volume. Because in theory, at some point, you could use this machine to change the size and number of the droplets in the clouds. You can make them brighter. Conceptually, it's possible. The question is, technologically, can we do it? The particles are coming out and super concentrated there. So whatever's coming out of that circle there is basically going to be huge by the time it gets to the cloud. The goal with this test was they spent years building this sprayer that can use really high-pressured air to smash salt particles into super small bits, about one 700, the size of a human hair. Wow. What they I didn't know until this week, and they're trying to find out right now, once you spray it, do those aerosols that are so finely-tuned stay that size?

In theory, they should. What they don't know is things like wind and humidity and temperature could potentially cause them to coagulate, to regroup, which would throw the whole thing off. If the aerosols you're shooting into clouds are too big, you can backfire the whole purpose. You can wreck what you're trying to do because you make clouds less reflective, not more reflective. The whole goal of this experiment is, okay, can they make the spray just so so that even in outdoor conditions, the aerosols that are so finely sized remain the size you want them to be? That's what they're trying to find out.

You watched the actual test of this. What did you see? What happened?

Those instruments are emitting a slight hum. Operating the sprayer is not straightforward. They are filling the tanks with the saltwater that we use to produce the mist. There was somebody crouched on the control deck, the panel of instruments at the side of the sprayer. So I went over and tried to sit next to him and watch him as he turned a series of knobs in careful sequence.

Okay.

Yeah, everybody, we're going to run some air. So the... Matt, we need two minutes here just to have power on this. And after a series of tests to make sure the valves were clear. Okay.

Ear protection, please.

Finally, the moment came, and he got an all-clear over his walkie-talkie, and he turned on the water.

Water on. Copy. Over.

And the air. It's the sound of the compressor. It pushes pressurized air through the sprayer. It's making a a dull, throbbing sensation. You can feel it a little bit through the deck of the ship. We all had ear protectors, and even with the ear protectors, it was really loud. Then you could almost feel this spray bursting out of this machine and watch it travel really hundreds of feet down the deck of the aircraft carrier.

Okay, water off, fan off. Good job. Awesome, guys. You're done? Thank you.

Excellent. First test is done. My first signal that things had gone well was I looked up when the sprayer machine was turned off and saw some scientists high-fiving down the deck. What did you think? It's beautiful. Is it what you thought it would be? It's better. I I'm optimistic that it will tell us a lot about what these things do. This has made me really optimistic. The idea is to do several short bursts like that through the day. Everyone seemed really excited that this thing they'd worked on for years was finally happening in this really important outdoor test.

Okay, so it sounds like this test was a success, right?

Yeah, they stressed that they need a lot of time to really go over the results. They'll be doing this test again and again in different weather conditions, but the initial reaction seemed positive. They seemed to think that the numbers they were getting were what they were hoping to see. Now the goal is, can they maintain the right size aerosols even in different conditions down the deck of this aircraft carrier. That'll give them some confidence that if they decided one day to try and do this on the open ocean to actually brighten clouds, they'd have the ability to do Chris, if all of this works, how and when do these researchers anticipate that this would actually be used? Well, here's a great example. In the month of February, a version of this testing was also happening in Australia, off the Coast of Australia, where researchers were testing whether marine cloud brightening could be used to cool the ocean just a little bit around the Great Barrier Reef. Really high ocean temperatures are causing bleaching of that coral reef. The idea was, could they use marine cloud brightening to save some of those reefs from dying? And that's probably a good idea of the fairly localized situation where you could, in theory, if you do it right, have a fairly quick degree of cooling that could maybe try to avert or mitigate something pretty acute, like a heat wave or a stretch of warm weather that would kill coral.

But the science is probably too new at this point to talk about the right situations to use it. Those conversations are all down the road as researchers look at these and other ideas for what they could do if things get really bad.

We'll be right back. Chris, when I think about solutions to climate change. It usually involves these very hard things we need to do, like change the way we live, the way we drive, what we eat. We need these international treaties, we need carbon taxes, regulation. There's lots of hard stuff, and we haven't gotten far. But here you've just told me about this technology that if it ends up working, could actually help cool the planet without anyone needing to do any of these hard things. It sounds great.

It does sound great. Now, we got to say, first of all, that whenever anybody working on this stuff talks about it, the first thing they say is this is not an alternative to reducing emissions. This is looking for ways to buy time as we try to cut emissions. There's no way to really deal with climate change that doesn't entail burning less fossil fuel and quickly. But yes, in addition to brightening clouds, there's other ways of trying to bounce more sunlight back into space. Other ideas. My colleague David Gellis wrote the first piece in our series, Looking at the idea of removing carbon dioxide directly from the air, reversing our past emissions. Other ideas Ideas include finding ways to suck up more of the CO₂ in the oceans. There's even ideas that my colleague, Kara Buckley, covered of, could we build a a giant parasol way out in space that would reflect or scatter more of the sunlight and prevent that sunlight from even reaching the Earth in the first place. There's a huge number of ideas that until very recently seemed just so bizarre and/or so expensive and/or so dangerous that they were hardly worth pursuing seriously.

What's changed really quickly in the last year or two is all of a sudden, those ideas have switched from being too wild to spend much time on to being so important because the situation is so dire that we can't not look at them. That's the pivot that my team has been trying to cover.

What characterizes all these initiatives is that rather than reducing our own emissions, we're now trying to intervene in the climate in a proactive way, engineering the climate in a way.

Yes. You hear the phrase geo to describe these ideas collectively. What people who research this will stress is we're already geoengineering. For more than a century, we've been geoengineering in the sense of putting climate-changing pollution into the atmosphere that's caused the planet to change by trapping more heat in the atmosphere. The question is, do we want to deliberately geo engineer in a way that will ease that pressure rather than just making it worse. Of course, there's some controversy attached to this, and there are some pretty valid concerns about what the consequences might be if we keep on pursuing these ideas.

Why are they controversial?

Well, the first concern that you hear is this idea of moral hazard, that if people come to think that there are ways of addressing climate change that don't require them to change their lifestyle or sacrifice conveniences or change the kinds of cars they drive or how their power is generated, that they will lose interest in those tough changes and the momentum, such as it is, towards cutting emissions will fade even more. But we don't know yet whether politicians or governments or companies or just people will misuse these ideas to try to shirk the harder work of reducing the amount of greenhouse gasses we emit. Another really important argument you hear is, Okay, side effects. Do we really know what would happen if we tried these things? Marine cloud brightening is one of those situations where there are known unknowns and unknown unknowns, as they say. The known unknowns are, well, what would happen to things like ocean circulation? What would happen to precipitation? What would happen to the effect on the amount of energy reaching the ocean? What would happen to the fisheries industry? We don't really know, and research are trying to find out what those effects might be.

Then there are the unknown unknowns. If you start deliberately changing the cloud system, well, what else might happen that we haven't anticipated? Do you move the location of where rainfall happens? Do you perhaps upset the monsoon cycle in India? Do you change the ability to grow food in parts of the world? So if you do this at a bigger scale, the consequences of those potential side effects get more and more severe. And I talked to environmentalists who said, That's a real concern. You just model those risks. You, to a degree, by pursuing this, have to accept that that risk is real and almost roll the dice.

I guess much like climate change, where you have a group of countries that is most responsible for CO₂ emissions that have caused the global warming, and then a whole other group of countries that are probably suffering the worst consequences, even though they haven't contributed to those emissions nearly as much, you might see a situation where this interference with the climate at the initiative of some countries, presumably the wealthy countries that have that technology, would then have unintended consequences in countries that have no control over this. So that's tricky.

That's right. And that takes us to our third category of concerns, which is, okay, let's assume that things are bad enough, that collectively, societies want to take those risks of those side effects. Well, then who chooses? Who decides when we get to that point? Is there even a mechanism that would allow you to get informed consent from everybody who'd be affected? If these would affect everybody, it's hard to imagine how you would build a governance mechanism that would allow you to say, before we push the button, are we sure everybody's okay with this? The only counter to all of these concerns is, compared to what? This is the point that researchers make, Okay, this is dangerous. Okay, it presents challenges. But compared to what? Their point is, don't compare it a situation where everything's fine. Compared to a situation we're actually in, where the trajectory of global warming is so serious and isn't looking like it'll get better anytime soon. Well, compared to those risks, How do these risks compare? The question is, would you rather have a world of basically uncontrolled warming? We have an idea of what that brings, wildfires and droughts and sea level rise and storms and diseases.

Is that better than some of these more perhaps controlled risks associated with deliberately tinkering with the environment. It's almost like pick your poison. What threats do you want to embrace? That's the overwhelming dilemma that we face with this technology.

In a way, what it makes me think is that these crazy initiatives that we've been hearing about from you are, yes, they're a testament to our failure in a way to combat climate change so far because they're such a last resort, really, such an act of desperation. But at the same time, it seems like this urgency has actually unleashed a lot of energy and money to tackle the problem.

Yeah, and there's good news in this. The good news is the research we're talking about demonstrates the really amazing capacity of scientists to come with new ideas, develop new technologies, test them quickly, and at least build some options. If there's any raise of hope around climate change, it's that humanity's capacity to innovate and find new ideas is almost endless. The question is not, are we pursuing the wrong research ideas? The question is, can we find good ideas fast enough to avert the really serious consequences of climate change that we're already facing?

Chris, I just remember that scientist we heard in the tape from your visit, and she was so excited, and she said that she was really optimistic. I wonder, how are you feeling?

I think the frustration that you'll hear among climate reporters, and I'm in this group, is that most people seem not to appreciate the severity of the situation that we're in. There seems to be a view that we're dealing with this. People are buying electric cars and we're getting more solar power and wind power, and things are going the right way, and this will be okay. Things are not going the right way. Not only are we on the wrong trajectory in terms of emissions. We are so far away from being on the right trajectory for emissions that it's hard to imagine us cutting emissions globally at a rate anywhere near fast enough to avoid almost unbearable consequences of global warming. So that's the downside. Here's the good news, though. I do think, and this, again, I think is a view among other climate reporters, the capacity of scientists and of companies to change track and to find new products and apply new ideas is really impressive. It just doesn't feel like there's a connection yet between the urgency of the situation in the way people and companies and governments are responding. And so I guess if the question is how I feel about this, I am constantly amazed at the ingenuity of the researchers I come across in my job every day.

What I don't yet know about is whether or not society will move fast enough to adopt and apply those ideas before the conditions that face from climate change become almost unbearable.

Well, Chris, on this cautiously optimistic note, thank you very much.

Thank you.

We'll be right back. Here's what else you need to know today. In a tense phone call with Israel's leader, Benjamin Netanyahu, on Thursday, President Biden called the airstrikes that killed aid workers this week unacceptable and threatened to condition its future support on how Israel addresses concerns about civilian casualties and the humanitarian crisis in Gaza. It was the The first time that Biden explicitly sought to leverage American aid to influence Israel's conduct of the war against Hamas, although he stopped short of saying he would hold arms supplies or impose conditions on their use. Hours later, Israel responded by saying it would increase aid deliveries and reopen at least one border crossing into Gaza that's been closed since the October seventh attack. American officials said they'd watch how and when the new measures actually go into effect, making clear ongoing support would depend on Israel's next step. Today's episode was produced by Michael Simon, John Johnson, Eric Krupke, Luc Van der Plug, and Rochelle Bonja. It was edited by Patricia Willens. Contains original music by Ron Nemistow, Alicia by Etup, and Marion Lozano, and was engineered by Chris Wood. Our theme music is by Jim Brunberg and Ben Lantzberg of WNDYLE.

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