# Astronomers can play an important role in explaining the causes and consequences of climate change, says astrophysicist

An episode of [Physics World Weekly Podcast](https://invisiblenetwork.ai/podcast/1400686733), 28 Nov 2024, 37 min.

Audio: https://media.blubrry.com/physicsworldweeklypodcast/content.blubrry.com/physicsworldweeklypodcast/PWWeekly28November2024AstronomersAndClimateChange.mp3

This podcast also looks at the connections between clouds and global warming

## Transcript

[0:07] Hello, and welcome to the Physics World Weekly
[0:11] podcast.
[0:11] I'm Hamish Johnston.
[0:13] In this episode, we're going to be talking
[0:15] about climate change.
[0:17] Coming up a bit later, I'm in conversation
[0:20] with the author of cloudy with a chance
[0:23] of warming,
[0:24] how physicists
[0:25] are studying
[0:26] the dynamical
[0:28] impact
[0:29] of clouds on climate change, and that's a
[0:32] feature article that has just appeared on Physics
[0:35] World.
[0:36] But first, we're going to explore how astronomers
[0:40] can better understand climate change and share that
[0:44] knowledge with their students
[0:46] and the wider public.
[0:56] The book Climate Change for Astronomers,
[0:59] Causes,
[1:00] Consequences,
[1:01] and Communication
[1:03] was published earlier this year by IOP Publishing,
[1:06] which also brings you Physics World.
[1:09] The book weighs in at 527
[1:13] pages
[1:13] and features 19 chapters
[1:16] that were contributed
[1:17] by 20 scientists.
[1:19] The book was edited by Travis Rechter.
[1:22] He's an astrophysicist
[1:24] at the University of Alaska
[1:26] Anchorage
[1:27] and an advocate for solutions to climate change.
[1:31] Living in Alaska, he's witnessed dramatic changes in
[1:35] his home state, and this led him to
[1:37] cofound
[1:38] Astronomers
[1:39] for Planet Earth.
[1:41] Travis joins me down the line from Anchorage
[1:44] to talk about what astronomers can do in
[1:47] response to the climate crisis.
[1:50] Hello, Travis.
[1:51] Welcome to the podcast.
[1:53] Hello, and thank you for, inviting me today.
[1:57] So, Travis, what motivated you to edit climate
[2:00] change for astronomers?
[2:02] Why should astronomers teach climate change and talk
[2:05] about it with the general public?
[2:08] That's a good question. People are often surprised
[2:10] to hear that as an astronomer. I'm
[2:13] actively involved in advocating for climate change.
[2:16] And the reason why is because there's a
[2:19] a big overlap in the science of climate
[2:21] change and the science of astrophysics.
[2:24] And so
[2:25] in our astronomy classes for many years, myself
[2:27] and other astronomers have been teaching climate change
[2:31] as part of our curriculum. When you talk
[2:33] about, like, the atmosphere of Venus and why
[2:35] it's the hottest planet in the solar system,
[2:37] that naturally leads to questions from students about
[2:40] climate change. And so we're talking about climate
[2:43] change in our classes, and
[2:46] our goal is is to help people understand
[2:48] the science of it because often people
[2:52] don't hear about climate change from scientists. They
[2:55] hear about it from the news and social
[2:57] media.
[2:57] And so often in astronomy classes, the last
[3:00] opportunity
[3:02] for people to hear from a scientist about
[3:04] the actual science of it.
[3:06] And, Travis, one aim of the book is
[3:08] to give
[3:09] astronomers themselves a better understanding of climate change.
[3:13] How do you do this in the book?
[3:15] What topics do you focus on?
[3:19] Yeah. So for many years,
[3:20] we have been running workshops to help astronomers
[3:24] be effective teachers of our climate change, and
[3:26] I'd say the the most common concern
[3:29] that my fellow astronomers have is they feel
[3:30] like they don't know the science well enough.
[3:32] I've had people say to me, oh, I
[3:34] didn't really
[3:36] fully understand radiator transfer in grad school. I'm
[3:38] not sure I can effectively convey the science.
[3:41] And the key thing that I want all
[3:43] astronomers to know is is that no matter
[3:45] what you know, you already know enough to
[3:47] be an effective advocate
[3:49] for climate change solutions.
[3:52] But what many astronomers feel is that they
[3:55] want to know more, particularly when it comes
[3:57] to topics like the geologic history of the
[3:59] earth.
[4:00] There's a common misconception
[4:02] that,
[4:03] that
[4:04] climate change is a natural consequence of just
[4:07] natural fluctuations in the earth's climate. And so
[4:10] one of the chapters on the book is
[4:11] devoted to the earth's climate system
[4:14] to help astronomers
[4:16] be better able to teach the difference between
[4:19] natural causes of climate change and the human
[4:22] causes that are creating the crisis we're in
[4:25] right now.
[4:26] And the book also gives advice and suggestions
[4:29] for how astronomers can incorporate
[4:32] climate change into university astronomy courses.
[4:36] Can can you talk about some of the
[4:37] strategies that that can be pursued?
[4:41] Yeah. So
[4:42] there's so many ways in which our astronomy
[4:46] and physics courses
[4:47] touch on key concepts that are really important
[4:50] for people
[4:51] to help understand
[4:52] the problem. So,
[4:54] for example,
[4:55] simply understanding
[4:56] how long a 1000000000 years is
[4:59] can give people an understanding
[5:01] of the difference between
[5:02] natural climate change and this the long time
[5:05] scales on which it occurs
[5:07] and
[5:08] the and and the short term climate change
[5:10] that we're causing right now by using fossil
[5:13] fuels. There's many other examples. So, for example,
[5:16] talking about different kinds of light, if you're
[5:19] discussing infrared light versus optical light or if
[5:21] you're talking about spectroscopy
[5:23] and absorption features.
[5:25] These are all topics that naturally lead themselves
[5:28] to people being in a better position to
[5:31] understanding
[5:31] what causes climate change. It can also lead
[5:34] to a better understanding of solutions. So, for
[5:37] example, in a physics class,
[5:39] energy is a essential concept in every physics
[5:42] class. And so
[5:43] if people have
[5:45] a a fundamental understanding of how energy works
[5:47] and how it can be transitioned from one
[5:49] source of energy to another,
[5:51] then they're going to be in a better
[5:53] position to understand
[5:54] the many different solutions that are out there,
[5:56] whether it be wind or solar or nuclear
[5:59] and how these different energy sources can work
[6:01] together.
[6:03] I see. And and climate change for astronomers
[6:07] also looks at how the community can better
[6:09] communicate
[6:10] climate change to the public.
[6:13] What's the best practice when doing climate change
[6:17] related outreach? How do you get the message
[6:19] out to the general public?
[6:22] I think one of the biggest challenges that
[6:24] astronomers face when communicating with climate change, whether
[6:27] it be with students or the public,
[6:29] is understanding and appreciating
[6:31] that
[6:31] there are many different places again where people
[6:34] are hearing about climate change. It's not just
[6:37] from scientists. And as astronomers, we're
[6:40] accustomed to people being interested
[6:42] in hearing what we have to say. They
[6:44] love hearing about black holes and exoplanets
[6:47] and,
[6:48] life, beyond the earth. But then when you
[6:51] start talking about climate change, there's an additional
[6:54] element to it. It's emotionally charged. It's politically
[6:57] contentious,
[6:59] and there's a lot of feelings in the
[7:00] room. And so as scientists,
[7:03] we're accustomed to just simply telling people what
[7:06] we know and anticipating that they're going to
[7:08] accept that.
[7:09] And so it's very important for us
[7:12] to be good listeners. It's not something that
[7:14] we're often accustomed to doing. We're accustomed to
[7:17] being in front of an audience and and
[7:20] talking to people rather than listening.
[7:22] But if you take the time to listen
[7:24] to the questions people have, it'll give you
[7:26] a better sense of
[7:28] how they're feeling, what their concerns are, what
[7:31] maybe they've heard elsewhere,
[7:33] and give you a better opportunity
[7:37] to give them information that can help them.
[7:39] The most important thing, I think, in any
[7:41] interaction is for people to feel like that
[7:44] they were heard and they were listened to
[7:46] and respected
[7:48] and that they'll be interested in in learning
[7:50] more about it in the future either from
[7:52] you or from others. So
[7:54] having a positive interaction where people felt feel
[7:57] good afterwards is very important.
[8:01] I see. And and the book also looks
[8:04] at,
[8:05] the I suppose the vexing question
[8:08] of how astronomers can advocate for action
[8:11] on climate change without compromising their roles
[8:16] as scientists.
[8:17] And and that must be very difficult in
[8:20] in what you say has become a very
[8:22] polarized debate.
[8:24] How how how can scientists
[8:26] do that?
[8:28] Yeah. That's another common concern I hear from
[8:31] scientists is that
[8:33] they feel like they shouldn't enter the fray,
[8:35] that we should essentially be in our ivory
[8:37] tower from which we give information to people,
[8:40] but it is for others
[8:42] to to solve the problem. And I don't
[8:45] think that's true. I think there's a long
[8:47] history of scientists being advocates.
[8:50] And the reason why it's important for us
[8:53] to do it is because
[8:54] we need to share what we know
[8:57] to help people understand not only the problem,
[9:00] but what solutions are out there.
[9:02] Examples, obviously,
[9:04] Einstein was
[9:05] a major advocate for
[9:07] solutions about nuclear warfare.
[9:11] Carl Sagan is actually one of the first
[9:13] scientists to testify in front of congress about
[9:16] climate change back in the eighties.
[9:18] So
[9:19] what we can do as scientists that is
[9:21] share what we know and share how we
[9:24] understand
[9:25] different solutions
[9:28] to make
[9:30] decision makers in a better position to make
[9:32] good decisions. And so I don't think, as
[9:35] scientists, we should advocate for specific solutions or
[9:39] sole solutions. I don't think, as scientists,
[9:41] we should say that, for example, just wind
[9:44] power or just nuclear or just this or
[9:46] that is going to have a solution. But
[9:48] but by providing
[9:50] the information we have
[9:52] about all the different solutions are out there,
[9:54] then I think we can we can do,
[9:57] good to help people understand the problem. So
[9:59] one of the chapters we wrote in the
[10:00] book
[10:01] is just the just describes the pathways
[10:04] towards solutions. That is how can we go
[10:07] from the energy we use
[10:10] now to the energy we want,
[10:12] and what are the different ways that we
[10:14] can do that?
[10:15] And, Travis,
[10:16] Jeffrey Bennett, who's at the University of Colorado,
[10:20] has written a chapter called
[10:22] Teaching with Inspiration,
[10:25] Not Only Fear.
[10:27] How can astronomers
[10:28] provide students and the public with a positive
[10:32] pathway
[10:32] to addressing climate change
[10:35] and building
[10:36] a better future. I think you you hinted
[10:38] at one way,
[10:40] just a minute ago. Yeah. So I think
[10:42] this is incredibly important for us to understand,
[10:46] especially with our our students who are younger,
[10:49] and that is there is a lot of
[10:50] fear.
[10:51] It's called climate doomism. It's the the sense
[10:55] that it's too late, that nothing can be
[10:57] done.
[10:58] And what's important I mean, I have students
[11:00] telling me that they aren't going to have
[11:02] kids because they don't wanna bring children into
[11:05] a a ruined world.
[11:07] And there is a recent study that found
[11:09] that 75%
[11:11] of people under the age of 25 are
[11:13] terrified of their futures. They're scared of their
[11:15] future.
[11:16] So one of the most important things that
[11:18] we can do for our students is to
[11:20] help them see that we can actually create
[11:22] a world
[11:23] that is gonna be good to live in.
[11:25] And one of the things that I really
[11:27] like about, Jeff Bennett's chapter is he talks
[11:30] about
[11:31] helping students understand what our world can look
[11:34] like after we solve the problem of climate
[11:36] change. So often, we don't even talk about
[11:38] what
[11:39] that could
[11:40] be. And, yes, climate change is serious. It
[11:43] is a terrible problem. Every day in the
[11:46] news, we're seeing stories about firestorms and flooding
[11:49] and people's lives being affected or destroyed.
[11:53] And we're not trying to sugarcoat the reality
[11:55] of the problem,
[11:56] but we do know that there is a
[11:58] path forward. We have nearly all the solutions
[12:01] we need to address climate change,
[12:03] but the biggest issue here is getting people
[12:05] motivated
[12:06] to actually want to work towards a future
[12:09] that they could be excited to live in.
[12:12] And you you mentioned that some of your
[12:14] students are, perhaps rightly so,
[12:18] have neg sort sort of negative thoughts about
[12:21] the the implications of climate change. But I
[12:24] mean, do you also find that that the
[12:26] people you teach, there's some positiveness
[12:29] in there that that people think, yes, this
[12:32] is something that that we can we can
[12:34] fix, we can address this, and if I
[12:36] if I study astronomy, if I study science,
[12:39] I can make a a major contribution to
[12:43] solving the problem. Well, I'll say every semester
[12:47] I'm really impressed with the students that I
[12:49] have. And so many of them are already
[12:52] motivated and involved in working towards solutions.
[12:56] And it doesn't have to be big solutions.
[12:58] It can be community level solutions working,
[13:02] within your neighborhood, working within your school or
[13:05] your classes.
[13:07] So many kids now understand
[13:09] the problems of the world in ways that
[13:11] I feel like that
[13:12] my generation did not. Our our students
[13:16] have access to social media and provides
[13:19] information to them in a way that,
[13:23] I don't think earlier generations had. I'm continually
[13:26] impressed with my daughter and her awareness of
[13:28] of the issues in the world. So this
[13:30] is a generation that unfortunately is inheriting a
[13:33] problem that was created by prior generations,
[13:36] but I'm also very impressed with how motivated
[13:38] many of them are to address it. And
[13:41] so
[13:42] one of the things that scientists often focus
[13:44] on is trying to convince people that climate
[13:47] change is happening. And I think what's more
[13:49] important now is convincing people that we can
[13:52] address the problem and that they can have
[13:54] a
[13:55] role in fixing it. And so so many
[13:57] of my students, the first question really is,
[13:59] well, what can I do? How can I
[14:01] be involved? And so
[14:03] giving students resources and information,
[14:06] like, for example, project drawdown is a wonderful
[14:09] resource
[14:10] that helps people see all the solutions out
[14:12] there. It gives them an opportunity to find
[14:14] the place where they are gonna be most
[14:16] interested in working.
[14:19] I see. Well, that that sounds very positive.
[14:21] And, Travis,
[14:23] if I can, I'd I'd like to ask
[14:25] you maybe
[14:27] something on a more personal level. I mentioned
[14:30] in the introduction that you've noticed
[14:32] changes in in your native Alaska
[14:36] that that have concerned you.
[14:38] Is it possible for you to to give
[14:40] us a a few examples of things that
[14:42] are changing,
[14:43] because of because of global warming climate change?
[14:47] Yeah. So I've been in Alaska for over
[14:50] 20 years now, and
[14:52] in that time, we've seen quite a bit
[14:54] of change. The Arctic
[14:56] in general is warming at about 3 times
[14:58] the rate as the rest of the world
[15:00] due to the ice albedo feedback loop with
[15:02] the with the Arctic sea.
[15:05] I've seen glaciers recede to the point now
[15:08] where
[15:09] I have pictures of myself when I first
[15:11] got here that if I was standing in
[15:12] that same location and took a picture, you
[15:14] would not be able to see the glacier.
[15:16] In fact, there's a glacier near Anchorage called
[15:18] Portage Glacier
[15:20] that they built a visitor center for you
[15:22] to look at it, and you can't see
[15:23] the glacier from there anymore. It's receded so
[15:26] much.
[15:27] There's also,
[15:28] dire effects for, seafood. When off when often
[15:32] we think about climate change, we think about
[15:34] global warming. We think about how the earth
[15:36] is getting warmer.
[15:37] But another side effect of climate change is
[15:40] ocean acidification.
[15:42] The carbon dioxide releasing the atmosphere,
[15:44] about a quarter of that is being absorbed
[15:46] by the earth's oceans,
[15:48] and that is creating carbonic acid and making
[15:50] the oceans more acidic.
[15:52] The fishing industry is the largest employer in
[15:55] the state of Alaska, and, species like salmon
[15:58] and king crabs and Tanner crabs are not
[16:01] only a major part of our economy, but
[16:03] also part of our our culture and our
[16:05] identity.
[16:06] And so
[16:07] in recent years, we've had the collapse of
[16:10] several fisheries due to warmer waters and ocean
[16:13] acidification.
[16:14] And that's the part that's hardest for me
[16:17] to see, is to see how
[16:19] our lives and traditions here in Alaska are
[16:21] being affected by climate change. And it really
[16:23] is a major driver for the advocacy work
[16:26] that I do.
[16:28] Yeah. It is it is interesting. I mean,
[16:30] you know, from my point of view, I'm
[16:32] I'm from Canada originally, but I I've lived
[16:34] in the UK for for many, many years.
[16:37] And the the thing that,
[16:39] you know, I've I've I sort of had
[16:41] this emotional
[16:42] tie to to the concept of winter.
[16:45] And and it seems to me that, you
[16:47] know, if if whenever I get back to
[16:49] Canada in the winter,
[16:51] there seems to be less of it.
[16:54] And,
[16:54] you know, there there's
[16:56] culture and tradition,
[16:58] where I come from, you know, things like
[17:01] ice fishing or skating on a on a
[17:04] frozen lake,
[17:06] things that I really enjoyed doing
[17:08] when I was a child. And
[17:10] I realize now that,
[17:13] well, the last time I was there, you
[17:14] just couldn't do it. There was no ice
[17:16] on the lakes, which was a big shock
[17:19] to me.
[17:20] And I suppose I struggle to, to to
[17:23] not be sad about it.
[17:25] But it's great to, you know, to hear
[17:27] that astronomers like yourselves are
[17:29] are clubbing together to to try to make
[17:31] a difference, and also that that the young
[17:34] people that you teach are
[17:36] are positive that they want to do something
[17:39] about it. That's that's really nice to hear.
[17:42] Yeah. It's a it's a it's a mix
[17:44] of of sadness and optimism.
[17:47] As I've heard said before, hope is a
[17:49] choice.
[17:50] And I think it's important for us to
[17:53] acknowledge
[17:54] the the sadness that we feel. I I
[17:57] like you, I love winter. It's my favorite
[17:59] time of year. I love snow. I love
[18:01] ice skating.
[18:03] And it's been hard to watch how Alaska
[18:06] has changed in that way. Our winters are
[18:07] shorter.
[18:08] We're getting
[18:10] we get good snow, but we also are
[18:11] getting more rain.
[18:13] And
[18:14] I think every community in the world now
[18:16] is feeling the effects of climate change. Most
[18:19] everyone I talk with nowadays
[18:21] can identify
[18:22] an event
[18:23] that has happened that was climate change enhanced,
[18:26] whether, again, be a firestorm
[18:28] or flooding.
[18:29] So people understand things are different now, and
[18:32] there's sadness associated with thinking that our our
[18:35] lives and our world has changed.
[18:38] But
[18:38] the goal here, I think, is to help
[18:40] people see that we can still avoid
[18:43] the worst consequences.
[18:44] And,
[18:46] I've heard it quite recently
[18:48] that if you're not optimistic, you're not paying
[18:51] attention. There's a lot of good news out
[18:53] there right now about
[18:54] the solutions that are out there, and and
[18:56] they're taking effect. I mean, wind and solar
[18:59] has grown much faster than anyone,
[19:02] dared anticipate 10 years ago. So there's lots
[19:05] to be sad about, but there's also a
[19:07] lot to be
[19:08] excited about.
[19:09] Well, that's great, Travis. That's a great place
[19:11] to, to to leave it. Thanks so much
[19:14] for speaking to me today. And listeners, you
[19:17] can find climate change for astronomers
[19:20] on the IOPscience
[19:22] website.
[19:30] The central thesis of climate change is simple.
[19:33] A relentless
[19:34] increase in carbon dioxide in the atmosphere
[19:38] is reducing the amount of heat that earth
[19:41] radiates into space,
[19:43] and that's warming the planet.
[19:45] There are, however, myriad other factors that affect
[19:49] how the climate is changing,
[19:52] including the role that clouds play in both
[19:55] heating
[19:56] and cooling the planet.
[19:58] To talk about clouds and climate, I'm joined
[20:01] down the line by the science writer,
[20:04] Michael Allen,
[20:05] who has penned the Physics World article,
[20:09] cloudy with a chance of warming,
[20:11] how physicists
[20:12] are studying
[20:13] the dynamical
[20:15] impact of clouds
[20:16] on climate change.
[20:18] Hi, Michael.
[20:20] Welcome to the podcast.
[20:22] Hi, Hamish. Nice to be here. So, Michael,
[20:24] can you give us a a a basic
[20:26] idea
[20:27] of how clouds affect climate? I mean, we
[20:30] all know that when we're outside
[20:33] and,
[20:34] a cloud comes over, covers the sun, it
[20:36] cools down.
[20:38] Many of us are also aware that
[20:40] at night
[20:42] cloud cover can can sort of increase the
[20:45] temperature
[20:46] that we experience once the sun goes down.
[20:49] But I'm guessing that there's lots of ways
[20:51] that, clouds can impact
[20:53] the climate.
[20:55] Yes. But the basic issue is quite simple,
[20:59] really.
[21:00] Clouds
[21:01] essentially play a role in the Earth's radiation
[21:04] budget, so that's the balance between the amount
[21:07] of energy that comes in from the sun
[21:09] and the amount of energy that kind of
[21:11] is reflected out to space as thermal
[21:14] energy
[21:15] from the Earth.
[21:16] And, essentially,
[21:17] clouds play 2 simple roles in this. 1
[21:21] is they reflect some clouds are reflective,
[21:24] so they reflect the sun's energy back into
[21:27] space,
[21:28] cooling the earth.
[21:29] And then then some clouds
[21:31] act a bit more like a blanket.
[21:33] They absorb that thermal energy that's radiators from
[21:36] the earth, and then they radiate it back
[21:38] towards the earth.
[21:39] And the balance between this, you know, the
[21:43] cooling of the clouds and the warming of
[21:44] the clouds
[21:45] impacts
[21:47] how much heat reaches the Earth's surface.
[21:50] But as you pointed out, we can see
[21:51] clouds when we look up, and
[21:54] there are lots of clouds around. And researchers
[21:57] tell me that the basic problem is that
[22:00] a small shift
[22:02] in cloud amounts
[22:04] between these different clouds that are reflective
[22:06] or acting like a blanket can have quite
[22:09] a significant impact
[22:11] on the Earth's radiation budget.
[22:13] And, basically, climate change plays into this because
[22:16] it affects
[22:17] how clouds kind of form and develop.
[22:21] I see. And
[22:22] I suppose that there's lots of different
[22:24] types of clouds.
[22:26] I'm going to show my ignorance here by
[22:29] referring to high level clouds and low clouds.
[22:33] I'm sure that there's much more technical terms,
[22:36] available. But those clouds at at different
[22:39] altitudes
[22:40] play very different roles, don't they, in in
[22:44] Earth's temperature?
[22:46] Yes. I mean, I'm also fairly ignorant
[22:49] on the different types of clouds too. But
[22:51] I think, again, as you point out, on
[22:53] a relatively simple level,
[22:56] low altitude clouds, so the clouds that sit
[22:59] in the troposphere,
[23:00] the kind of lowest
[23:02] level of the Earth's atmosphere
[23:04] are generally reflective, so they are reflecting sunlight
[23:08] back out to space, while
[23:11] the higher altitude clouds, which again sit in
[23:14] the same part of the atmosphere, the troposphere,
[23:16] but right at the top of it tend
[23:19] to have more of this blanket warming effect.
[23:22] I see. And and so how are rising
[23:25] global temperatures
[23:27] affecting
[23:28] cloud cover and formation?
[23:31] Sure. So when it comes to these
[23:34] higher clouds,
[23:36] on a simple level, the heat into the
[23:38] atmosphere is causing the troposphere to expand
[23:41] and basically to rise higher. So that's this
[23:44] lower part of the atmosphere
[23:46] is rising to a higher altitude. So this
[23:48] means that those higher level clouds themselves can
[23:52] also
[23:53] rise higher.
[23:55] And then
[23:57] issues
[23:58] with rising temperatures
[24:01] and the effect of them on, like, the
[24:03] stability of the atmosphere
[24:05] is affected the kind of formation of clouds
[24:08] and how
[24:09] clouds in the lower atmosphere, particularly these lower
[24:12] level clouds that reflect sunlight back. Basically, kind
[24:15] of how they form
[24:17] and the kind of cloud fraction. That is
[24:19] the amount of kind of cloud in space.
[24:21] I see. And so so does that mean
[24:23] that in general,
[24:25] we're
[24:26] we're experiencing,
[24:28] less lower cloud cover
[24:31] and more higher cloud cover,
[24:34] which in itself
[24:36] is
[24:36] increasing
[24:37] the temperature
[24:39] of the planet? Or, I'm I'm I'm guessing
[24:41] it's not quite that simple. But is that
[24:43] sort of a a general trend
[24:46] that,
[24:47] climate scientists are seeing?
[24:50] So I think the evidence on low clouds
[24:53] is reasonably
[24:55] clear
[24:56] that
[24:57] rising temperatures are reducing
[25:00] the amount of low cloud cover, particularly over
[25:03] kind of tropic and subtropical
[25:05] regions. When it becomes to the higher level
[25:07] clouds,
[25:08] I think that the science is a little
[25:11] less clear at the moment. So these clouds
[25:14] are rising,
[25:16] and the assumption is that that also
[25:19] increases
[25:20] this kind of blanket
[25:21] blanketing effect,
[25:23] but
[25:23] it's not really clear, I don't think yet,
[25:26] exactly what else is happening to these clouds
[25:28] as they rise.
[25:29] So there could be other changes in them
[25:32] that also
[25:34] impact
[25:35] their impact on the Earth's radiation budget.
[25:38] Right. And I I think in your article,
[25:40] you do mention
[25:41] things like, you know, what percentage of a
[25:44] cloud,
[25:46] is made up of liquid droplets,
[25:48] and how much is ice, and how that
[25:51] is changing, and how that affects,
[25:54] climate. So it is it is a very
[25:56] complicated system, isn't it?
[25:58] So, yeah, now we are getting into what
[26:00] are known as mixed flay phase clouds, which
[26:03] exist in the northern and southern hemisphere, kind
[26:05] of outside of the tropical regions. And these
[26:08] are clouds that are a mixture
[26:10] of liquids,
[26:12] water,
[26:13] and ice.
[26:15] And the basic
[26:17] problem here is that as these clouds warm,
[26:20] they shift from being
[26:23] more ice to being more liquid, and thus
[26:25] they become more reflective.
[26:28] So they are bouncing more of the sun's
[26:30] energy back into space,
[26:32] and this has a dampening effect on climate
[26:35] change.
[26:36] But problems have arisen around how these clouds
[26:39] are modeled,
[26:40] so it appears
[26:42] well, research has shown that
[26:45] simulations
[26:46] have been modeling these clouds to to start
[26:49] off being
[26:50] having higher proportions of ice than they actually
[26:53] do.
[26:54] So
[26:55] that means that they can become
[26:58] there's a kind of bigger shift in their
[27:00] reflectiveness, and it's happening in reality. So that
[27:03] kind of affects
[27:05] how these climate models
[27:07] simulate
[27:08] the change in the radiation budget
[27:11] as these clouds move from ice to liquid.
[27:14] And one important part of this is that
[27:16] at some point, these clouds become kind of
[27:18] predominantly
[27:19] or entirely
[27:20] liquid.
[27:21] So that means
[27:23] they their their increasing reflectiveness
[27:26] stops.
[27:27] So whilst the earth is warming with climate
[27:30] change,
[27:31] to start with, the reflection this is this
[27:33] of these clouds is increasing, having a dampening
[27:35] effect, but then it slows,
[27:37] and then it stops increasing. So the reflectiveness
[27:40] is still there,
[27:42] but it remains at that level whilst the
[27:44] heat of the earth continues to
[27:47] increase. So you get a slowdown
[27:50] in this dampening effect that the clouds have.
[27:53] So, yeah, Michael. I mean, it sounds like
[27:55] it is a very complicated,
[27:58] relationship between clouds
[28:00] and climate.
[28:01] In your article, you also mention other sort
[28:05] of effects that humans
[28:08] are having on clouds, and and in particular,
[28:11] aerosols.
[28:12] It you you point out that,
[28:15] if we reduce,
[28:17] aerosol
[28:18] emissions, which is very important because aerosols can
[28:21] be lethal,
[28:23] in terms of,
[28:25] causing things like lung disease.
[28:27] That could actually lead to more
[28:30] warming.
[28:31] So why,
[28:33] our efforts to cut
[28:35] aerosol
[28:36] emissions,
[28:38] Why are they counterproductive
[28:40] when it comes to battling
[28:42] climate change?
[28:43] Yeah. Sure. I mean, you point to quite
[28:45] a dilemma here for kind of climate scientists.
[28:49] You know, we need to reduce aerosol pollutions
[28:52] because like you said, they have a huge
[28:53] health health impact.
[28:55] They're globally, something like 8,000,000 people die every
[28:58] year from air pollution.
[29:01] But,
[29:02] basically,
[29:03] when it comes to clouds,
[29:06] aerosols
[29:07] in the air pollution
[29:10] reduce the size of the cloud droplets,
[29:12] and this makes them more reflective.
[29:15] So they bounce again more of the sun's
[29:17] energy back out into space. So when we
[29:20] cut the amount of aerosols we're producing to
[29:22] tackle this dangerous air pollution,
[29:25] we make the clouds less reflective.
[29:28] So more of the sun's energy gets through
[29:31] and heats the earth.
[29:33] And so there you know, there's a bit
[29:34] of debate around this,
[29:36] but, you know, some people started to argue
[29:39] that actually if we were to cut all
[29:41] the aerosols
[29:42] and slash pollution,
[29:44] you know, in the way that some countries
[29:46] are trying to do, it could have a
[29:48] pretty significant
[29:49] impact on our chance of keeping global warming
[29:51] below 2 degrees.
[29:53] And other people I've spoken to suggested that,
[29:56] essentially, if we removed all aerosol pollution, we
[29:59] could create anywhere between an extra point 2
[30:01] to 0.6 degrees of additional warming.
[30:04] But, of course, we have to do it
[30:06] because we can't allow people just to be
[30:09] kind of dying from
[30:10] heart and lung disease because of pollution.
[30:14] Right. And I suppose the other thing is
[30:16] that some of that aerosol
[30:18] emission will will be related to
[30:21] carbon dioxide
[30:22] emission as well, won't it? So, you know,
[30:25] burning dirty fossil fuels, etcetera.
[30:28] So, I suppose in in some cases, you
[30:31] could you could reduce both aerosol emission
[30:35] and carbon dioxide emission at the same time.
[30:37] But I suppose that's you you have to
[30:39] be worried about the effect of reducing the
[30:42] aerosols.
[30:44] Yeah. Of course, these things are linked. They're
[30:47] they're not necessarily
[30:49] always the same sources, but they come but
[30:51] they do come from very similar
[30:54] industrial processes, fossil fuel
[30:56] burning processes.
[30:58] And I don't cover this in the article,
[30:59] but I think research has suggested that one
[31:02] of the best ways to deal with this
[31:03] really is just
[31:05] to slash both. So you are cutting the
[31:08] global warming element of the carbon dioxide emissions,
[31:12] and
[31:13] this kind of
[31:15] feedback
[31:16] from the aerosols.
[31:18] I see. And and I I suppose something
[31:21] that's related to aerosols
[31:23] is,
[31:24] the idea of cloud
[31:26] seeding.
[31:28] I suppose this is a
[31:29] is this called a a geoengineering
[31:32] technique where we we try to increase,
[31:36] the right kind of cloud cover in order
[31:39] to
[31:40] counteract
[31:42] climate
[31:44] change. Yes. So
[31:47] I guess
[31:48] the issue with the aerosols
[31:50] kind of opens up a question, which is
[31:52] basically,
[31:53] well, can we use
[31:54] aerosols that are perhaps nonpolluting
[31:57] to mitigate climate change? Can we make the
[32:00] clouds more reflective
[32:02] ourselves?
[32:04] And the idea behind this or the sort
[32:06] of idea that people proposed this is basically
[32:09] to use
[32:11] salt water
[32:12] spray
[32:13] as an aerosol. So I guess you would
[32:15] take a ship or something like that. You'd
[32:17] suck up
[32:18] seawater.
[32:19] You spray it out, and the idea
[32:22] is that this that this that the that
[32:24] it kind of evaporates
[32:26] and the fine haze of particles,
[32:28] the salt, and the other things in the
[32:30] seawater
[32:31] are transported into the clouds by air currents,
[32:35] and that reduces
[32:37] the droplet size in clouds
[32:39] and increases
[32:40] their brightness.
[32:41] I see. But I suppose the problem there
[32:43] is that if if country a is really
[32:46] suffering
[32:48] from climate change and decides to do this,
[32:51] aren't some of those clouds going to drift
[32:54] over, let's say, country b?
[32:57] And,
[32:58] you know, I suppose block out the sun
[33:00] and maybe affect
[33:02] its agriculture,
[33:03] or maybe country b is not suffering as
[33:06] much from from climate change. Maybe it's a
[33:08] bit further north or or something. There's aren't
[33:12] there huge geopolitical
[33:13] issues here
[33:15] when, when these sort of schemes are rolled
[33:17] out? Yes. I mean, obviously, we're moving beyond
[33:19] physics here and,
[33:22] there is something for
[33:23] politicians
[33:24] and society to discuss about how these
[33:28] technologies would be deployed. But exactly,
[33:31] you can't
[33:33] really
[33:36] just do this
[33:37] in one place.
[33:39] No. If you start if you just chose
[33:42] chose one location in the world to do
[33:45] this because you want to increase the reflection
[33:47] of the clouds there, that's gonna going to
[33:49] start to have kind of few, you know,
[33:51] it has the potential to have knock on
[33:53] effects to local
[33:55] circulation patterns and things if you're kind of
[33:57] cool in the air in that area. You
[33:58] know, it yeah. It it becomes really
[34:01] complicated.
[34:02] So a lot of research really is needed
[34:05] to model
[34:06] exactly how this
[34:08] such a technique
[34:10] would alter the clouds, but then
[34:13] going up to a much larger scale,
[34:16] how does that alter the clouds then affect
[34:18] the local climate
[34:20] and then a kind of larger, I guess,
[34:23] local climate and then the
[34:25] Earth's global climate.
[34:28] And then really, yes, I guess, as a
[34:30] society or societies,
[34:31] we need to decide
[34:33] whether or not we want to allow this
[34:35] technology to go ahead and how we manage
[34:37] it to ensure that
[34:39] everyone is getting the benefits from it rather
[34:42] than the situation like you suggest
[34:44] where some countries are doing this and benefiting
[34:47] themselves
[34:48] whilst having negative knock on effects for people
[34:51] elsewhere.
[34:52] Well, thanks for talking about clouds and climate
[34:54] change, Michael. It's, I mean, it's an it's
[34:57] an incredibly
[34:58] complicated,
[34:59] field of endeavor, and I'm sure there's lots
[35:01] of physicists and other researchers out there working
[35:05] very hard on improving
[35:08] our understanding of it. And if you'd like
[35:10] to, to read Michael's article, you can find
[35:13] it on the Physics World website.
[35:16] It's under the headline,
[35:17] cloudy with a chance of warming, how physicists
[35:21] are studying
[35:22] the dynamical
[35:23] impact of clouds
[35:25] on climate change. Thanks for coming on the
[35:27] podcast, Michael, and thanks for writing that article
[35:30] as well.
[35:31] No problem, Hamish. Thank you for talking to
[35:33] me.
[35:41] I'm afraid that's all the time we have
[35:42] for this week's podcast.
[35:44] Thanks to Travis Rechter and Michael Allen for
[35:48] joining me today.
[35:49] And a special thanks to our producer, Fred
[35:52] Ailes.
[35:53] We'll be back again next week when we'll
[35:55] be exploring the amazing properties
[35:58] of metamaterials.

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