Can We Change the Weather (and do we really want to?) Derek Posselt, Jet Propulsion Lab

Dr. Derek Posselt is a research scientist with NASA's Jet Propulsion Laboratory and one of the participants in this year's science workshops sponsored by Telluride Science. He and his colleagues have been studying ways to modify the weather, using computer modeling and other advanced techniques to pursue an old idea, since humans have been trying to change the weather for over a century. He spoke about the ways people have tried to modify the weather, what has worked (and what hasn’t), and whether it is, in fact, a good idea to try in the first place.

Dr. Posselt addressed a live audience at the Telluride Mountain Village Conference Center in Colorado and the session was moderated by veteran broadcast journalists Judy Muller and George Lewis.  If you have questions or comments, please contact us at sciencestraightup@telluridescience.org

Transcript

Science Straight Up, Season 7, Episode 1

Transcript

Moderators: Judy Muller and George Lewis

Guest Speaker: Dr. Derek Posselt, Jet Propulsion Laboratory

(theme hold for a few seconds then under)

JUDY: From Telluride Science, this is the seventh season of Science Straight Up. I’m Judy Muller.

GEORGE: And I’m George Lewis. On this edition, a few words about the weather.

DEREK: Can we change the weather, and if we could, would we really want to?

GEORGE: Dr. Derek Posselt is a research scientist with the Atmospheric Physics and Weather group at NASA’s Jet Propulsion Laboratory in California and he knows a thing or two about human efforts to control the weather.

JUDY: Every summer, Telluride Science gathers noted researchers like Dr. Posselt to participate in more than 50 workshops…a sort-of high altitude think tank in the Colorado mountains. Once a week, they share their cutting-edge ideas with the local community in a series of “Town Talks.” 

GEORGE: Dr. Posselt gave his talk at the Telluride Mountain Village Conference Center, with Judy and me as the moderators.

(applause from audience)

DEREK: Thank you so much. It's truly an honor to be the one that kicks off this season, I'm a huge fan of Telluride Science. When I volunteered to give the town talk, I was thinking about what might the audience actually be interested in, and what might be highly relevant to the conference that we have going on here this week, and so I thought, all right, weather modification, let's get into it, and so I titled the talk, Can we change the weather, and if we could, would we really want to? So, if you live on the planet Earth, at some point you've had to worry about the weather, and it's something that we love to talk about. We love to complain about it. It's an easy topic of conversation among friends, colleagues, people you've just met.

And severe weather is dangerous, frightening, and disruptive, life-threatening, and so we have a group of things that we would characterize as weather, short-term processes, things that operate on the scales of minutes to hours to maybe a week, but we'd also like to worry about the climate.

We're seeing the effects of climate change everywhere now, and we're curious about what can we do as a species to mitigate those effects, so that the question is, can we change the weather?

(thunder sound effects)

JUDY: Not exactly a new question.  Science has been talking about changing the weather since the 19th century when experimenters tried using loud cannons to create sound waves that would disrupt storms. They also talked about building giant walls to block tornadoes. Over the years, there were lots of ideas that came and went.

GEORGE: More recently there were proposals to drop nuclear bombs on hurricanes to disrupt them. Never mind all that radioactive fallout that would have been spread by the high winds.

JUDY: These days, Dr Posselt concentrates a lot of his research on aerosols, microscopic particles like dust, pollen, pollution from smokestacks. These particles play an essential role in the formation of clouds.

DEREK: Did you know every single cloud droplet you see has formed on an aerosol particle? It is impossible, actually, to nucleate liquid water or ice out of of nothing on our planet, and so if you want to modify clouds, maybe we think about adding aerosols.

GEORGE: Humans have been seeding clouds for some time now to produce more rain. But getting it to work consistently has proven elusive for science.

DEREK: In theory, cloud seeding for precipitation enhancement could work, but, but to know for sure what you would have to do in the real atmosphere is you'd have to find two identical clouds, exact same environment, exact same shape, exact same like distribution of particle sizes, all that. You'd have to seed one of them and then not seed the other, and then to be a good scientist, you'd have to repeat this like 1000 times, just to be sure. (LAUGHTER)

JUDY: And while we’re working on changing the weather, why not figure out ways of mitigating climate change?

DEREK: So, what about climate? Earth is warming, and I would tend to say that it's there's a vanishingly small group of people that don't think the earth is warming. Now, they can debate why and what to do about it, and I think it's healthy to debate what to do about it, but I think it's pretty clear that we do need to do something about it, and clearly it would be great if we could cool off the earth. So, here's another aspect of cloud aerosol interaction: cloud droplets compete for water vapor, so if you only have a few of them, there's not as much competition, and they, those few, grow bigger as they grow bigger, they fall. If you have a lot more of them, then there's a lot more competition. Each individual cloud droplet doesn't grow as much, and you have a lot more small cloud droplets. So, here's the interesting thing: is that if you have more smaller droplets, it reflects more sun, so more reflected sunlight means you cool off the atmosphere.

GEORGE: But, scientists worry about the unforeseen consequences. So, the bulk of this research uses computer models instead of physical experimentation.

DEREK: So computer models are our laboratory, and we're getting better and better at this, and we're seeing this in our conference this week, lot of people doing very detailed computer modeling to understand better how cloud and aerosol processes work. 

Because if it goes really, really wrong in the computer, we haven't hurt anybody. So I'm going to finish up here. So I guess the question is, can we change the weather? And I would say that using our knowledge of the atmosphere properties of clouds and aerosols, we might - I think it's promising - and our models can help us to know the answer and whether it's a good idea to try, so I'll leave it there. Thank you,

(applause)

JUDY: George kicked off the question-and-answer session with Dr. Posselt.

GEORGE: The Government Accounting Office recently concluded the benefits of cloud seeding remain largely unproven. Are these computer models you speak of going to help prove that now?

DEREK: They'll help point us in the right direction. I think I mean our models are getting more and more realistic, especially with respect to cloud processes, aerosols, and precipitation. So I think, honestly, some of the answer to that is yes, it's inconclusive, and I mentioned that, and it's hard to find an identical environment where you can seed one and not seed the other, and see exactly what would have happened if you had or hadn't seeded. I think something, though, that we don't talk often about is, so say I make it rain more over Telluride, what happens downstream? Do they get less rain? What does that, what does that mean? There's a finite amount of water vapor,

JUDY: Bad for fishing.

GEORGE: In California, Santa Barbara has had a cloud seeding project for a long time, and they claim that it helps increase the levels of water in their reservoirs. They tried it in another part of Southern California, in Santa Ana, south of LA, and it didn't work. So, what are we to conclude from that?

DEREK: Yeah, it's a great question, and I love that, because the two are so close to one another that the kinds of clouds you're likely to get in Santa Ana and Santa Barbara are going to be pretty similar. It's low clouds off the coast, driven by the fact that you've got warm inland and cold ocean, so I would posit that, and I would, you'd have to do experiments to prove this, but thinking about Santa Barbara area, there's no major industry in that area, whereas farther south, Santa Ana, you have the Port of LA and Long Beach, two of the biggest ports in the world, huge amount of emissions there, and so to have cloud seeding work effectively, you have to perturb an unstable system, right? So you have to have a system where the cloud wants to rain and it can't, because we, because it doesn't have quite the right kind of impetus to do it, and I would think that Santa Barbara, the clouds have less of the aerosol around, and perhaps that's that's part of the story.

JUDY: As droughts get more extreme in the West, for instance, is there more political pressure to start cloud seeding, and before the science is actually ready?

DEREK: Yeah, it's interesting. There may be. I think the whole story of water in the West is long. Yeah, and it's, and it's going to be important. I think. There's a, there's a quote out there that says whiskeys for drinking, water is…

JUDY AND DEREK..for fighting,

DEREK And, and it's, it's not going to get less contentious. I haven't seen a lot of push for cloud seeding in California, and in part, I think that's because almost all of our water comes from huge storm systems. They roll in off of the Pacific. I don't know if the term atmospheric river resonates. Yeah, so, so I mean, this is transport via a really strong wind flow of water, pushing that water up the mountains. Rain forms, that's where California gets most of its water. It's debatable as to whether cloud seeding would help much in coastal California.

JUDY: This is playing a little bit off what George said before, but if one region seeds clouds and essentially steals moisture from a neighboring region, how do we detect that, and what are the worst-case scenarios from a large-scale weather program? I mean, there's going to be a fight.

DEREK: Yeah, it's a great question. I'm not so worried about fighting, in part because I think there's going to be limited amount of utility in one for one, and then for another, you seed clouds, it, you could get the rain falling over your property, you could just as easily have it fall over your neighbor's property, and so I suspect that if you really took a look at that, it would almost certainly equalize

GEORGE: Here in Telluride, and in the other ski resort areas of Colorado, they've just been through a lousy season where they just didn't have enough snow. Have people been bugging you about that since you've been here?

DEREK: They've had experiment, not, not, not me personally. (LAUGHTER) Yeah, thankfully they're not holding me responsible.

GEORGE: But do you have a possible solution to their problem? I guess…

DEREK They've been experiments over the northern Rockies to for cloud seeding for snow modification. I have colleagues that have been involved in that, and I wish I could tell you that I knew what the results were, or that they were conclusive, but I do know that it's an ongoing topic of research, and I am sorry. This has been a horrible season, snowfall wise.

JUDY: I know that maybe it was DoD that predicted this, but that the next major war will be fought over water. I don't know if that's true or not, but it does raise the question of cooperation, and how really reasonable would that be to expect in this world we're living.

DEREK: I won't speak to the politics. We certainly, sorry, not my area, but we have the capacity to do this. We already have a global supply chain. There's no lack of resources, but, but we do have a tendency as human beings to compete with one another, to fight one another, and that's a hard thing.

Do you have international cooperation at something like this? I mean are there….

DEREK: Oh, yeah, all…

JUDY: countries..

DEREK: We have people come from from all over the world. We've had lots of international participation in this meeting, the missions, the gloat, the observing system that we use to predict the weather and climate is truly a global observing system. And if it wasn't, we'd be sunk. If the United States only kept its own observations to itself, and Europe and other nations, the world did the same. If we didn't share data, we would be in a whole lot worse position.

GEORGE: Some researchers have raised questions about whether the weather cloud seeding might disrupt the ozone layer. To what degree is that a concern?

DEREK: That is a fantastic question. I'm a dynamic meteorologist, which means….

GEORGE (interrupting) You ARE a dynamic meteorologist..I can tell. (laughter)

DEREK: I appreciate that, but boy, we could go really the wrong way with what I'm about to say next, but I know nothing about chemistry, so I would defer to my colleagues in the audience to answer whether that's an issue. One thing I will say is that one of the potentially most effective ways to cool the planet is to put highly reflective particles into the stratosphere, and we know this because there have been several major volcanic eruptions throughout history, and every time that happens, and I think the most recent one was the Hunga Tonga volcano that happened a few years ago, but maybe the most well-known was Pinatubo in the Philippines in the 1990s It erupted in 1992 cooled the planet by about five degrees Fahrenheit for two years. So we know that it could work, and if you put particles in the stratosphere, they tend to stay there for somewhere between one and three years, the question is, what are the unintended consequences of doing something like that?

JUDY: Right. Well, people who live near Pinatubo could tell you. But is there a danger of too many players acting precipitously? I mean, I can tell that too many people doing their own thing if it's not coordinated. What are the dangers of that?

DEREK: Yeah, no, I agree with you. I think that the fact is, as soon as you introduce, say, cloud seeding, you don't just change the sort of individual little droplets. When you do that, as droplets grow, as vapor condenses to cloud, you release a lot of energy that has a dynamic effect on clouds, that's one of the things that we don't understand well. I know there are projects, actually in the United States right now, where various funding agencies are paying people to try to understand how do we detect whether another country is doing geoengineering, because even if we don't do it ourselves, we want to know if someone else is doing it.

GEORGE: Do you think it could be weaponized?

DEREK: It's tough to say. 

GEORGE: Yeah. Stay tuned.

DEREK: Yeah.

GEORGE: What about what about the legal consequences of all of this? Do you worry about. Lawsuits, if somebody's house gets swept away in a flash flood, and you've been seeing the clouds,

JUDY: That's a good question. 

DEREK: Yeah, so I, I don't know the specifics, but I am aware that there have been lawsuits associated with the with the hail cannons, because the idea is that if you disrupt hail somewhere, and then it hails on your neighbor's field. That's a big deal. And so there have been lawsuits over that.

GEORGE: Have I read somewhere that cloud seeding could actually decrease the size of hail stones, and therefore the damage?

DEREK: That's the, that's part of the theory. The problem is, as soon as you introduce more aerosol into cloud, I mean, this is the whole marine cloud brightening thing, right? You know, you increase the number of small droplets, that's like the first effect that you see, more small droplets tend to get swept up higher in clouds, and it's the freezing of small droplets on ice that makes hail, so potentially you could actually do the opposite, and you could make hail worse by seeding the clouds. 

JUDY What about the unintended consequences of cleaning up power plants? I saw this… 

DEREK: Great question.

JUDY …which has reduced cloud reflectivity and worsened climate change, possibly. I mean, what about that?

DEREK: This is one of the best examples of an unintended consequence. So, I mean, I'm I'm old enough, but maybe just barely, to remember the press about acid rain, and I'm sure, like, there are many folks here that remember much better than I do, and they traced that to the sulfur emissions from coal-fired power plants, sulfur dioxide, and then, through various chemical mechanisms, which I have, again, will admit that I have no understanding of that, gets converted to hydrosulfuric acid, and then acid rain, so the major initiative to clean up the power plants, scrubbers reduce the emissions. There's been, in addition, a large-scale conversion from coal to natural gas, which doesn't release sulfuric compounds, so that has decreased acid rain tremendously, but those same sulfur compounds also make aerosols, and those aerosols are light in color, and so they reflect sunlight. They also seed the clouds, and that also reflects sunlight. So, yes, unintended consequence, we may have warmed the planet by cleaning up our coal emissions.

JUDY: Oops.

GEORGE: Shall we go to questions from the audience..

JUDY:  This is a great audience, so let's go to questions. 

QUESTION FROM AUDIENCE: There was a news report this week about the administration dismantling ocean observation and my initial question was, How much damage has the administration and Doge done to NOAA and to this new news report?

JUDY: Politics!

GEORGE: This is a guy who wants to keep his job,

JUDY: But that's a good question.

DEREK: No, it's a great question, and I'll take off my NASA hat, and put on another hat that I wear, which I'm a co-chair of a NOAA advisory committee, and so we pay very, v ery close attention to this. We actually write a report to Congress every year, where we report on typically it's reporting on how NOAA has addressed the challenges in front of them. Last year our report was very different, and it was, it was very clear about the dangers that our entire society faces when you dismantle a public service like NOAA, and thankfully Congress acted and restored almost all of NOAA's budget, but it is exceedingly difficult to operate and plan as an agency, when the funding is so tremendously uncertain, and so what I will say, and I just love it that you asked that question, because we actually just had our 2026 report to Congress approved. One of the things that we highlighted in there is just the tremendous work that the NOAA staff does. Um, they were, they were decimated, tremendous number of layoffs, people took the early retirement option, and no blame there, and the remaining people stepped up, and so the mission of NOAA was met to a very large extent. There were some notable failures, the Texas floods being one of them, but to a large extent, their staff stepped up and really got the job done. But it is a short-term win, and we have to keep supporting those public service agencies.

QUESTION: What about ocean monitoring?

DEREK: The ocean is a tough one, because the monitors that they're taking out are some of the most important long term observatories, the ones that have the most impact on our day to day life are the coastal observations, and they're dismantling the ones in the deep ocean, which I think is the reason why more people aren't as alarmed about it, but if they remove those, then that really does reduce our ability to understand not just climate, but how weather communicates from place to place around the globe. The ocean is a massive driver of our weather. We need those observations.

JUDY: Should we write to people in Congress?

DEREK: Please do. 

QUESTION FROM AUDIENCE: I have a question and the microphone. I'm Sarah Holbrook. I'm not a scientist, but I raised them through the work I do at the Pinhead Institute. Thank you for being here before I heard your talk today. Most of the information that I've gotten on this area of expertise is from fiction that I've read, right? So, Termination Shock by Neal Stephenson and Ministry for the Future, and because I raised, you know, kids that hopefully will care about this kind of stuff and go into it as a field, I'm wondering if you could point to any other inspirations, whether they'd be, you know, podcasts or movies or fiction, or any other things that that I can bring back to the kids that I'm raising up in this world to inspire them. And thank you for your talk.

DEREK: Oh, no. The two books that you've mentioned, I think, are fantastic. I think, especially Ministry for the Future, because they dig deep into what are some possible solutions that we can implement, and they, and they do a great job, I think, with translating that science. So I actually, I don't, off the top of my head, have another one that I could recommend to you, but let me, let me do some thinking about it, and get back to you. 

QUESTION FROM AUDIENCE: So, a layman, I observe the monsoon seasons that inundate communities in other parts of the world in water, the tsunamis that do damage elsewhere, and that the predominance of our globe is actually water, not earth. How do you react to the comment that suggests our limited resources might be better placed at figuring out science that could transport water, desalinate water, or affect it in other ways than looking to drop water from the sky into limited geography. Ours is a geographic limitation, not a shortage to scarcity.

DEREK: Yep, it's a great point, and I agree with you. I think the surest water, sorry, the surest way to get water from to a community that doesn't have enough is to transport it from someplace that has an abundance, and it's not an unusual thing for California to float the idea to build a pipeline to the Great Lakes, for example. Now, as a native Midwesterner, I know quite a few people there that would take exception to that, but right, but it is one of the most effective ways to increase your water supply is to rely on proven engineering methods to do it. Desalinization, yes, it works. It's been implemented all over the globe. There are other considerations, right, ecology, environment, all of that. I think we need to take that into account. Anytime you take water from one place to transport it to another, you have to think about what has happened to the place that you've taken the water from, and that's that's more of a geopolitical challenge, but the science we can work that out.

GEORGE: How much are you following the coming El Niño, the warming of the Pacific, and what's what's in store for us?

DEREK:  As a Southern California resident very closely.

JUDY: Could you just explain El Niño? Just…

DEREK: oh, sorry, yeah, okay, 

JUDY:..get a base.

DEREK: Yep, yeah, so, so El Niño, the phrase was coined because there's an oscillation in the sea surface temperature in the Pacific, and the effects of that oscillation would often be felt around Christmas time, and so El Niño was sort of coined as for the name for the Christ child. So, what it is, is that is periodically you'll get warmer waters that migrate from the Western Pacific to the Eastern Pacific. When that happens, it changes the patterns of thunderstorms, and when that happens, it changes the whole circulation of the planet, because most of our sunlight gets received at the equator, that heats up the equator, more buoyancy, more thunderstorms around the equator, and that drives a whole global circulation, but it's not just equator versus higher latitudes, it's which part of the ocean actually receives that thunderstorm activity that drives another circulation. So, when that happens, and when that circulation shifts, it shifts the whole pattern of rainfall over the northern hemisphere. The tendency is that when we have a strong El Niño, which is the warmer water in the eastern Pacific, the rainfall tends to shift and we tend to get more rainfall in the southern Rockies and Southern California, and it tends to get drier over the Midwest. The prediction is that we are going to have an extremely strong El Niño this year. I have colleagues at NASA that do seasonal prediction for a living. They tell me that they think it is a little overblown, but it is going to still be it's not going to be historically like 500 year El Niño event, but it is going to be a strong event,

JUDY: So rain here…

DEREK: Hopefully. Don't, don't hold me to it.

GEORGE: I'm afraid that's about all the time we have. But first, before we go…

JUDY: We'd like to thank our sponsors, the Telluride Mountain Village Owners Association, for giving us this space, and Alpine Bank.

GEORGE: And let's give a big hand to Dr. Derek Posselt for a wonderful evening, thank you..

(APPLAUSE) (theme under)

JUDY: We’d also like to thank Telluride Science and CEO, Mark Kozak as well as managing director and CFO, Cindy Fusting.

GEORGE: Sarah Friedberg is lodging and operations manager and Annie Carlson is in charge of donor relations.

JUDY: If YOU’D like to donate to the cause, or hear all of our podcasts, go to telluride science dot o-r-g.  

GEORGE:  And if you want to email us with questions or comments, here’s how:  sciencestraight up—all one big long word—sciencestraightup at telluride science dot o-r-g. This podcast was recorded by Max Ordoñez. I’m George Lewis…

JUDY: And I’m Judy Muller, inviting you to join us next time on Science Straight Up. 

(THEME UP AND FADE OUT)