Ariel: Hello, and a belated happy Earth Day to everyone. I'm Ariel Conn, your host of The Future of Life podcast. And in honor of Earth Day this month, I'm happy to have two climate-related scientists joining the show. We've all heard about the devastating extreme weather that climate change will trigger; We've heard about melting ice caps, rising ocean levels, warming oceans, flooding, wildfires, hurricanes, and so many other awful natural events.

And it's not hard to imagine how people living in these regions will be negatively impacted. But climate change won't just affect us directly. It will also impact the economy, agriculture, our mental health, our sleep patterns, how we exercise, food safety, the effectiveness of policing, and more.

So today, I have two scientists joining me to talk about some of those issues. Doctor Nick Obradovich is a research scientist at the MIT Media Lab. He studies the way that climate change is likely impacting humanity now and into the future. And Doctor Fran Moore is an assistant professor in the Department of Environmental Science and Policy at the University of California, Davis. Her work sits at the intersection of climate science and environmental economics and is focused on understanding how climate change will affect the social and natural systems that people value.

So Nick and Fran, thank you so much for joining us.

Nick: Thanks for having us.

Fran: Thank you.

Ariel: Now, before we get into some of the topics that I just listed, I want to first look at a paper you both published recently called "Rapidly Declining Remarkability of Temperature Anomalies May Obscure Public Perception of Climate Change." And essentially, as you describe in the paper, we're like frogs in boiling water. As long as the temperatures continue to increase, we forget that it used to be cooler and we recalibrate what we consider to be normal for weather. So what may have been considered extreme 15 years ago, we now think of as normal.

Among other things, this can make trying to address climate change more difficult. I want both of you now to talk more about what the study was and what it means for how we address climate change. But first, if you could just talk about what prompted this study.

Fran: So I've been interested for a long time in the question of: as the climate changes and people are gradually exposed to this new weather in their everyday life that used to be very unusual but because of climate change more and more typical, how do we think about defining things like extreme events under those kind of conditions?

I think researchers have this intuition that there's something about human perception and judgment that goes into that or that there's some kind of limit of how humans kind of understand the weather that define what we think of as normal and extreme, but no one had really been able to measure it. What I think is really cool in this study, and working with Nick and our other coworkers, we're able to use data from Twitter to actually measure what people think of as remarkable, and then we can show that that changed quickly over time.

Ariel: I found this use of social media to be really interesting. Can you talk a little bit about how you used Twitter? And I was also curious if that — aside from being a new source of information — does it also present limitations in any way or is it just exciting new information?

Nick: The crux of this insight was that we talk about the weather all the time. It's sort of the way to pass time in casual conversation, to say hi to people, to awkwardly change the topic — if someone has said something a little awkward, start talking about the weather. And we realized that Twitter is a great source for what people are talking about, and I had been collecting billions of tweets over the last number of years. And Fran and I met, and then we got talking about this idea and we were like, "Huh, you know, I bet you could use Twitter to measure how people are talking about the weather." And then Fran had the excellent insight that you could also use it to get a metric of how remarkable people find the weather by how unusually much they're talking about unusual weather. And so that was kind of the crux of the insight there.

And then really what we did is we said, "Okay, what terms exist in the English language that might likely refer to weather when people are talking about the weather?" And we combed through the billions of tweets that I had in my store and found all of the tweets plausibly about the weather and used that for our analysis and then mapped that to the historical temperatures that people had experienced and also the rates of warming over time that the locations that people lived in had experienced.

Ariel: And what was the timeframe that you were looking at?

Fran: So it's about three years: from March of 2014 to the end of 2016. But then we're able to combine that with weather data that goes back to 1980. So what we can then look at — we can match the tweeting behavior going on in this relatively recent time period, but we can look at how is that explained by all the patterns of temperature change across these counties.

So what we found that, firstly, maybe exactly what you would expect, right, which is that the rate at which people tweet about particular temperatures depends on what is typical for that location, for that time of year. And so if you have very cold weather but that very cold weather is basically what you should be expecting, you’re going to tweet about that less than if that very cold weather is atypical.

But then what we were able to show is that what people think of as “usual” that defines this tweeting behavior changes really quickly, so that if you have these unusual temperatures multiple years in a row the tweeting response quickly starts to decline. So what that indicates is that people are adjusting their ideas of normal weather very quickly. And we're actually able to use the tweets to directly estimate the rate at which this updating happens and, to our best estimate, we think that people are using approximately the last two to eight years as a baseline for establishing normal temperatures for that location for that time of year. When people think of, look at the weather outside, and they're evaluating is it hot, is it cold, the reference point they're using is set by the fairly recent past.

Ariel: What does this mean as we're trying to figure out ways to address climate change?

Nick: When we saw this result, we were a bit troubled because it was faster than we would perhaps hope. I'm a political scientist by training, and I saw this and I said, "This is not ideal," because if you have people getting used to a climate that is changing on geologically rapid scales but perhaps on human time scales somewhat slow — if people get used to that as it changes, then some of the things that we know helps to drive political action, policy, and political attention is just awareness of a problem. And so if you're having people's expectations adapt pretty quickly to climate change, then all of a sudden a hundred-degree day in North Dakota would have been very unusual in 2000 but maybe it's fairly normal in 2030. And so as a result, people aren't as aware of the signal that climate change is producing. And that could have some pretty troubling political implications.

Fran: My takeaway from this is that I think it certainly points to the risk that these conditions that are geologically or even historically very, very unusual — that they are not perceived as such. We're really limited by our human perception, and that's even within individuals, right — what we're estimating is something that happens within an individual's lifetime.

So what it means is that you can't just assume that as climate change gets worse it's going to automatically rise to the top of the political agenda in terms of urgency. And that, like a lot of other chronic, serious social problems we have, that it takes a lot of work on the part of activists and norm entrepreneurs to do something about climate change. And that just because it's happening and it's becoming, at least statistically or scientifically, increasingly clear that it's happening, that won't necessarily translate into people wanting to do something about it.

Ariel: And so you guys were looking more at what we might consider sort of abnormalities in relatively normal weather: if it's colder in May than we'd expect or it's hotter in January than we'd expect. But that's not the same as some of the extreme weather events that we've also seen. I don't know if this is sort of a speculative question, but do you think the extreme weather events could help counter our normalization of just changing temperatures or do you think we would eventually normalize the extreme weather events as well?

Nick: That's a great question. So one of the things we didn't look at is, for example, giant hurricanes, big wildfires, and things like that that are all likely to increase in frequency and severity in the future. So it could certainly be the case that the increase in frequency and intensity of those events offsets the adaptation, as you suggest. We actually are trying to think about ways to measure how people might adapt to other climate-driven phenomena aside from just regular, day-to-day temperature.

I hope that's the case, right? Because if we're also adapting to sea level rise pretty rapidly as it goes along and we're also adapting to increased frequency of wildfires and things like that, a few things might happen; one being that if we're getting used to semi-regular flooding, for example, we don't move as quickly as we need to — up to the point where basically cities start getting inundated, and that could be very problematic. So I hope that what you suggest actually turns out to be the case.

Fran: I think that this is a question we get a lot, like, "Oh, well temperature is one thing, but really the thing that's really going to spur people is these hurricanes or floods or these wildfires." And I think that's a hypothesis, but I would say it's as yet untested. And sure, a hurricane is an extreme event, but when they start happening frequently, is that going to be subject to the same kind of normalization phenomenon that we show here? I would say I don't know, and it's possible it would look really different.

But I think it's also possible that it wouldn't, and that when you start seeing these happen on a very regular basis, that they become normalized in a very similar way to what you see here. And it might be that they spur some kind of adaptation or response policy, but the idea that they would automatically spur a lot of mitigation policy I think is something that people seem to think might be true, but I would say that we need some more empirical evidence.

Nick: I like to think of humans as an incredibly adaptable species. I think we're a great species for that reason. We're arguably the most successful ever. But our adaptability in this instance may perhaps prove to be part of our undoing, just in normalizing worsening conditions as they deteriorate around us. I hope that the hypothesis that Fran lays out ends up being the case: that, as the climate gets weirder and weirder, there is enough signal that people become concerned enough to do something about it. But it is just an empirical hypothesis at this point.

Fran: What I thought was a really neat thing that we were able to do in this paper was ask: are people just not talking about these conditions because they've normalized them and they're no longer interesting or have people actually been able to take action to reduce the negative consequences of these conditions? And so to do that we used sentiment analysis. So this is something that Nick and our other author Patrick Baylis have used before: Just based on the words that are being used in the tweets, you can measure the overall mood being conveyed or the kind of emotional state of people sending those tweets and what very hot and very cold temperatures have negative effects on sentiment. And we find that those effects persist even if people stop talking about these unusual temperatures.

What that's saying is that this is not a good news story of effective adaptation, that people are able to reduce the negative consequences of these temperatures. Actually, they're still being very negatively affected by them — and they're just not talking about them anymore. And that's kind of the worst of both worlds.

Ariel: So I want to actually follow up with that because I had a question about that paper that you just referenced. And if I was reading it correctly, it sort of seemed like you're saying that we basically get crankier as the weather falls onto either extreme of our preferred comfort zone. Is that right? Are we just going to be crankier as climate gets worse?

Nick: So that was the paper that Patrick Baylis and I had with a number of other co-authors, and the key point about that paper is that we were looking at historical contemporaneous weather and we weren't looking for adaptation over time with that analysis. So what we found is that at certain level of temperature, for example when it's really hot outside, people's sentiment goes down — their mood is worsened. When it's really cold outside, we also found that people's sentiment was worsened; and we found that, for example, lots of precipitation made people unhappy as well.

But with that paper what we didn't do was examine the degree to which — changes in the weather over time, people got used to those. And so that's what we were able to do in this paper with Fran, and what we saw was, as Fran points out, troubling, which is that people weren't substantially adapting to these temperature shocks over time, to longer term changes in climate —  they just weren't talking about them as much.

So if you think though that there is no adaptation, then yeah, if the world becomes much hotter, on the hot end of things — so in the summer, in the northern hemisphere for example — people will probably be a bit grumpier. Importantly though, on the other side of things, in the wintertime, if you have warming, you might expect that people are in somewhat better moods because they're able to enjoy nicer weather outside. So it is a little bit of a double-edged sword in that way, but again important that we don't see that people are adapting, which is pretty critical.

Ariel: Okay. So we can potentially expect at least the possibility of decrease in life satisfaction just because of weather, without us even really appreciating that it's the weather that's doing it to us?

Nick: Yes, during hotter periods. The converse is that during the wintertime, in the northern hemisphere, we would have to say that warming temperatures, people would probably enjoy for the most part. If it was supposed to be 35 degrees Fahrenheit outside and it's now 45 Fahrenheit, that's a bit more pleasant. Now you can go with a lighter jacket.

So there will be those small positive benefits — although, as Fran is probably going to talk about here in a little bit, there are other big countervailing negatives that we need to consider too.

Fran: What I like about this paper that Nick and Patrick wrote previously on sentiment, they have these comparisons to it being a Monday or to home team loss. Sometimes it's hard to put these measures in perspective, and so Mondays on average make people miserable and it being very, very hot out also makes people miserable in kind of similar ways to it being a Monday.

Nick: Yeah. We found that particularly cold temperatures, for example, were a similar magnitude of effect on positive sentiment. A reduced positive sentiment of a magnitude that was equivalent to a small earthquake in your location and things like that. So the magnitude effects of the weather are much larger than we necessarily thought that they would be, which we thought was I guess interesting. But also there was a whole big literature from psychology and economics and political science that had looked at weather and various outcomes and found that sometimes the effect sizes were very large and sometimes the effect sizes were effectively zero. So we tried to basically just provide the answer to that question in that paper: The weather matters.

Ariel: I want to go back to the idea of whether or not extreme events will be normalized, because I tend to be slightly cynical — and maybe this is hopeful for once — that the economic cost of the extreme events is not something we would normalize too, that we would not get used to having to spend billions of dollars a year, whatever it is, to rebuild cities.

And Fran, I think that touches on some of your work if I'm correct, in that you look at what some of these costs of climate change would be. So first, is that correct? Is that one of the things that you look at?

Fran: Yeah. A large component of my work has been on improving the representation of climate change damages, so kind of what we know from the physical sciences about how climate change affects the things that we care about and including the representation of that in the thing called the social cost of carbon, which is a measure that's very relevant for the regulatory and policy analysis for climate change.

Ariel: Can you explain what the social cost of carbon is? What is being measured?

Fran: So if you think about when we emit a ton of CO2, right, and that ton of CO2 goes off into the elements of the earth and it's going to affect the climate, that change in the climate is going to have consequences around the world in many different sectors and is going to stay in the atmosphere for a long time. And so those effects are going to persist far out into the future.

What the social cost of carbon is, it’s really just an accounting exercise that tries to quantify what are all those impacts and then add them all up together and put them in common units and assign that as a cost of that ton of CO2 that you emitted. You can see in that description why this is an ambitious exercise in that we're talking about, theoretically there should be all these climate change impacts around the world for all time. And then there's another step too, which is in order to aggregate these to add them up, you need to put everything into common units. So the units that we use are dollars, so that's a critical economic valuation step in order to think about these things that happen in agriculture or they happen along coastlines or they affect mortality risk and how do you take all them and then put them into some kind of common unit and value them all.

And so depending on what type of impact you're talking about, that's more or less challenging. But it's an important number because at least in the United States, we have a requirement that all regulations have to have passed a cost-benefit analysis. So in order to do a cost-benefit analysis of climate regulation, you need to understand what are the benefits of not emitting CO2? So pretty much any policy that's affecting emissions needs to account for these damages in some way. That's why this is very directly relevant to policy.

Ariel: I want to keep looking at what this means. In one of your papers you have a sentence that reads, "impacts on the agriculture increase from net benefits $2.7 ton per carbon to net cost of $8.5 per ton of CO2." I think that seemed like a really good example for you to explain what these costs actually mean?

Fran: Yeah. This was an exercise I did a couple of years ago with coauthors Tom Hertel and Uris Baldos and Delavane Diaz. The idea was that we know now a lot about how climate change affects crop yields. There's been an awful lot of work on that in economics and agricultural sciences. But that was essentially not represented in the social cost of carbon, where our estimates of climate change damages really came from studies that were either in the late 80s or the early 90s, and really our understanding of how climate change will affect agriculture has really changed since then.

What those numbers represent, the benefits of $2.7 per ton is what is currently represented in the models that calculate the social cost of carbon. So the fact that it's negative, that indicates that these models were thinking that agriculture on net is going to benefit from climate change. This is largely because a combination of CO2 fertilization and a fair bit of assumption that in most of the world crops are going to benefit from higher temperatures. Now we know that's more or less not the case.

When we look at how we think temperature and CO2 is going to affect the major crops around the world, we use these estimates from the IPCC, and then we introduce those into an economic model. This is a valuation set. That economic model will kind of account for the fact that countries can shift what they grow, they can change their consumption patterns, they can change their trading partners. A lot of these economic adjustments that we know can be done, and this modeling accounts for all of that. We find a fairly large negative effect of climate change on agriculture, which amounts to about $9 per ton of CO2, and those are kind of discounted paths. So you emit a ton of CO2 today, that’s the dollar value today of all the future damages that ton of CO2 will have via the agricultural sector.

Ariel: As a reminder, how many tons of CO2 were emitted, say, last year, or the year before? Something that we know?

Fran: We do know that. I'm not sure I can tell you that off the top of my head. I would caution you that you also don't want to take this number and just multiply it by the total tons emitted, because this is a marginal value. This is merely about do we emit this ton or not? It's really not a value that can be used for saying, "Okay, well the total damages from climate change are X." There's distinction between total damages and marginal damages, and the social cost of carbon number is very much about marginal damages.

So it's like at the margin, how much should we tax CO2? It's really not going to tell you, should we be on a two-degree pathway, or should we be on a four-degree pathway, or should we be on a 1.5-degree pathway? That you need a really different analysis for.

Ariel: I want to ask one more follow-up question to this, and then I want to get onto some of the other papers of Nick's. What are the cost estimates that we're looking at right now? What are you comfortable saying that we're, I don't know, losing this much money, we're going to pay this much money, we're going to negatively be impacted by X number of dollars?

Fran: The exercise that the Obama administration went through, a fairly comprehensive exercise to take the existing models and standardize them in certain ways to try and say, “What is the social cost of carbon value that we should use?” They have a number that's around $40 per ton of CO2. If you take that number as a benchmark, there's obviously a lot of uncertainty around it, and I think it's fair to say a lot of that uncertainty is on the high end rather than on the low end. So if you think about probability distribution around that existing number, I would say there's a lot of reasons why it might be higher than $40 per ton, and there's a few, but not a ton, of reasons why it might be lower.

Ariel: Nick, was there anything you wanted to add to what Fran has just been talking about?

Nick: Yeah. The only thing I would say is I totally agree that the uncertainty is on the upper bound of the estimate of the social cost of carbon, and possibly on the extreme upper bound. So there are unknowns that we can't estimate from the historical data in terms of being able to figure out what happens in the natural system and how that translates through to the social system and the social costs. We and Fran are basically just doing the best we can with the historical evidence that we can bring to bear on the question, but there are giant “unknown unknowns," to quote Donald Rumsfeld.

Ariel: I want to sort of quantify this ever so slightly. I Googled it, and it looks like we are emitting in the tens of billions of tons of carbon each year? Does that sound right?

Fran: Check that it's carbon and not CO2. I think it's eight to nine gigatons of carbon.

Ariel: Okay.

Nick: CO2 equivalence.

Ariel: Anyway, it's a lot.

Nick: It's a lot, yeah.

Ariel: That's the point.

Nick: It's a lot; It's increasing. I think 2018 was an increased blip in terms of the rate of emissions. We need to be decreasing, and we're still increasing. Not great.

Ariel: All right. We'll take a quick break from the economic side of things and what this will financially cost us, and look at some of the human impacts that we many not necessarily be thinking about, but which Nick has been looking into. I'm just going to go through a list of very quick questions that I asked about a few papers that I looked at.

The first one I looked at is apparently — and this makes sense when I think about it — climate change is going to impact our physical activity, because it's too hot in places, or things like that. I was wondering if you could talk a little bit about the research you did into that and what you think the health implications are.

Nick: Yeah, totally. So I like to think about the climate impacts that are not necessarily easily and readily and immediately translated into dollar value because I think really we live in a pretty complex system, and when you turn up the temperature on that complex system, it's probably going to affect basically everything. The question is what's going to be affected and how much are the important things going to be affected? And so a lot of my work has focused on identifying things that we hadn't yet thought about as social scientists in doing the social impact estimates in the cost of carbon and just raising questions about those areas.

Physical activity was one. The idea to look at that actually came from back in 2015 — there was a big heat wave in San Diego when I was living there, and I was in a regular running regimen. I would go running at 4:00 or 5:00 PM, but there were a number of weeks, definitely strings of days, where it was 100 degrees or more in October in San Diego, which is very unusual. At 4:00 PM it would be 100 degrees and kind of humid, so I just didn't run as much for a couple of weeks, and that threw off my whole exercise schedule. I was like, "Huh, that's an interesting impact of heat that I hadn't really heard about."

So I was like, "Well, I know this big data set that collects people's reported physical activity over time, and has a decade worth of data on randomly sampled US, I think about a million randomly sampled US citizens." Over a million. So I had those data, and I was like, "Well, I wonder if you see the weather and the climate that these people are living in, does that influence their exercise patterns?" What we found was a little bit surprising to me because I had thought about it on the hot end: "Oh, I stopped running because it was too hot." But the reality is that temperature, and also rainfall, impact our physical activity patterns across the full distribution.

When it's really cold outside, people don't report being very physically active and one of the main reasons for that is one of the primary ways Americans get physical activity is by going outside for a run or a jog or a walk. When it's very nasty outside, people report not being as physically active. We saw on the cold end of the distribution that as temperatures warmed up, people exercised more. That was actually up to a relatively high peak in that function. It was an inverted U shape, and the peak was relatively high in terms of temperature. It was somewhere around 84 degrees fahrenheit.

What we realized actually is that at least in the US, at least in some of the northern latitudes in the US, people might exercise more as temperatures warm up to a point. They might exercise more in the wintertime, for example. That was this small little silver lining in what is otherwise, from my research and from Fran's research and most research on this topic, a cascade of negative news that is likely to result from climate change. But the health impacts of being more physically active are positive. It's one of the most important things we can do for our health. So a small, positive impact of warming temperatures offset by all the other things that we've found.

Ariel: I know from personal experience I definitely don't like to run in the winter. I don't like ice, so that makes sense.

Nick: Ice, frostbite.

Ariel: Yeah.

Nick: All these things are ... yeah. So just observationally, if I look out my window, and there's a running path near me, I see dramatically more people on a sunny, mild day than I do during the middle of the winter. That's how most people get their exercise. A lot of people, we know from the public health literature, if they're not going out for a walk or a stroll, they're not really getting any physical activity at all.

Ariel: Okay. So potential good news.

Nick: A little bit. Just a little bit.

Fran: Yeah. Nick moved from San Diego to Boston, so I think he's got a better appreciation of the benefits of warmer wintertime temperatures.

Nick: I do! Although, and this is an important limitation in that study, is we didn't really, again, look at adaptation over time. And what I found moving to Boston was that I got used to the cold winters much faster than I thought I would coming from San Diego, and now do go running in the wintertime here, though I thought I would barely be able to go outside. So perhaps that's a positive thing in terms of our ability to adapt on the hotter end as well, and perhaps that undercuts a little bit the degree to which warming during the winter might increase physical activity.

This is a broader and more general point. A lot of these studies — it's pretty hard to look at long-term adaptation over time because some of the data sets that we have just don't give us enough span of time to really see people adapt their behaviors within person. So, many of the studies are kind of estimating the direct effect of temperature, for example, on physical activity, and not estimating how much long-term warming has changed people's physical activity patterns. There are some studies that do that with respect to some outcomes — for example, agricultural yields. But it's less common to do that with some of the public health-related outcomes and psychological-related outcomes.

Ariel: I want to ask about some of these other studies you've done as well, but do you think starting these studies now will help us get more research into this in the future?

Nick: Yeah. I think the more and the better data that we have, the better we're going to be able to answer some of these questions. For example, the physical activity paper, also we did a sleep paper — the self-report data that we used in those papers are indeed just self-report data. So we're able to get access to what are called actigraph data, or data that come from monitors like Fitbit and actually track people's sleep and physical activity. We're working on those follow-up studies, and the more data that we have and the longer that we have those data, the more we can identify potential adaptation over time.

Ariel: The sleep study was actually where I was going to go next. It seemed nicely connected to the physical activity one. Basically we've been told for years to get eight hours of sleep and to try to set the temperatures in our rooms to be cooler so that our quality of sleep is better. But it seems that increasing temperatures from climate change might affect that. So I was hoping you could weigh in on that too.

Nick: Yeah. I think you said it pretty well. The results in that paper basically indicate that higher nighttime temperatures outside, higher ambient temperatures outside, increase the frequency that people report a bad night of sleep. Basically what we say is absent adaptation, climate change might worsen human sleep in the future.

Now, one of the primary ways you adapt, as you just mentioned, is by turning the AC on, keeping it cooler in the room in the summertime, and trying to fight the fact that it's — as it was in San Diego — it's 90 degrees and humid at 12:00 AM. The problem with that is that a lot of our electricity grid is currently still on carbon. Until we decarbonize the grid, if we're using more air conditioning to make it cooler and make it comfortable in our rooms in the summers, we are emitting more carbon.

That poses something else that Fran and I have talked about and others are starting to work on: the idea that it's not a one-way street. In other words, if the climate system is changing, and it's changing our behaviors in order to adapt to it, or just frankly changing our behaviors, we are potentially altering the amount of carbon that we put back into the system and the positive feedback loop that's driven by humans this time, as opposed to permafrost and things like that. So, it's a big, complex equation. And that makes estimating the social cost of carbon all the harder because it's no longer just this one-way street. But if it means emitting carbon through behavioral effects of emitting that carbon causes the emission of more carbon, then you have a harder-to-estimate function.

Fran: Yeah, you're right, and it is hard. I often get questions of like, "Oh, is this in the social cost of carbon? Is this?" And usually the answer is no.

Ariel: Yeah. I guess I've got another one sort of like that. I mean, I think studies indicate pretty well right now that if you don't get enough sleep, you're not as productive at work, and that's going to cost the economy as well. Is stuff like that also being considered or taken into account?

Fran: I think in general, I think researchers' ideas a few decades ago was very much that there were a very limited set of pathways by which a developed economy could be affected by climate. We could enumerate those, and they were things like agriculture or forestry and coastline affected by sea level rise. The newer work that's being done now, like Nick's papers that we just talked about, and a lot of other work, is showing that actually we seem to be very sensitive to temperature on a number of fronts, and that has these quite pervasive economic effects.

Fran: And so, yeah, the sleep question is a huge one, right? If you don't get a good night's sleep, that affects how much you can learn in school the next day, it affects your productivity at work the next day. So we do see evidence that temperature affects labor productivity in developed countries. Even in sectors that you think should be relatively well insulated against them, let’s say because there’s work that's being done inside, there's evidence too that high temperatures affect how well students can learn in school and their test scores. That has potentially a very long term effect on their educational trajectory in life and their ability to accumulate human capital and their earning potential in the future.

Fran: And so, these newer findings I think are suggesting that even developed economies are sensitive in ways that we're only beginning to learn to climate change, and pretty much none of that is currently represented in our current estimates of the social cost of carbon.

Nick: Yeah, that's a great point. And to add an example to that, I did a study last year in which I looked at government productivity, so government workers' productivity. Because we had seen a number of these studies, as Fran mentioned, that private sector productivity was declining, and I was wondering if government workers that are tasked with overseeing our safety, especially in times of heat stress and other forms of stress, if those workers themselves were affected by heat stress and other forms of environmental stress.

We indeed found that they were, so we found that police officers were less likely to stop people in traffic stops even though there was an increased risk of traffic fatalities and also crime increases with higher temperatures as well. We found that food safety inspectors were less likely to do inspections. The probability of an inspection declined as the temperature increased, though the risk of violation conditional on an inspection happening increased. So it's more likely that there's a food safety problem when it's hot out, but food safety inspectors were less likely to go out and do inspections.

That's another thing that fits into, "Okay, we're affected in really complex ways.” Maybe it's the case that the food safety inspectors were less likely to go do their job because they were really tired because they didn't sleep well the night before, or perhaps because they were grumpy because it was really hot outside. We don't know exactly, but these systems are indeed really complicated and probably a lot of things are in play all at once.

Ariel: Another one that you have looked that I think is also important to consider in this whole complex system that's being impacted by climate change is democratic processes.

Nick: Yeah, yeah. I'm a political scientist by training, and what we political scientists do is think a lot about politics, the democratic process, voting, turnout, and one of things that we know best in political science is this thing called retrospective voting or perhaps economic voting — basically the idea that people vote largely based on either how well they individually are doing, or how well they perceive their society is doing under the current incumbent. So in the US for example, if the economy is doing well the incumbent faces better prospects than if the economy is doing poorly. If individuals perceive that they are doing well, the incumbent faces better prospects.

I basically just sat down and thought for a while, and was like, you know, climate change across all these dimensions is likely to worsen both economic well-being, and also just personal, psychological, and physiological well-being. I wonder if it's the case that it might somewhat disrupt the way that democracies function, and the way that elections function in democracies. For example, if you're exposed to hotter temperatures there are lots of reasons to suspect that you might perceive being yourself less well-off — and whoever's in office, you might just be a little bit less likely to vote for them in the next election.

So I put together a bunch of election results from a variety of countries around the world, a variety of democratic institutions around the world, and looked at the effect of hotter temperatures on the incumbent politicians’ prospects in the upcoming elections: So, what were the effects of the temperatures prior to the election on the electoral success of that incumbent? And what I found was that as you had unusual increases in temperature the year prior to an election, and as those got hotter on the distribution — so hotter places — you saw that the incumbent prospects declined in that election. Incumbent politicians were more likely to get thrown out of office when temperatures were unusually warm, especially in hotter places.

And that, as a political scientist, is a little bit troubling because it could be two things. It could be the case that politicians are being thrown out of office because they don't respond well to the stressors associated with added temperature. So they could, for example, if there was a heatwave, and it caused some crop losses, maybe those politicians didn't do a good enough job helping the people who lost those crops. But it also might just be the case that people are grumpier, and they're not feeling as good, and there's really no way the politician can respond, or the politician has limited resources and can only respond so much.

And if that's the driving function then what you see is this exogenous shock leading to an ouster of a democratically elected politician, perhaps not directly related to the performance of that politician. And that can lead to added electoral churn; If you see increased rates of electoral churn where politicians are losing office with increasing frequency, it can shorten the electoral time horizons that politicians have. If they think that every election they stand a real good chance of losing office they may be less likely to pursue policies that have benefits over two or three election cycles. That was the crux of that paper.

Ariel: Fran, did you have anything you wanted to add to that?

Fran: I think it's a really really fascinating question. This is one of my favorite of Nick's papers. We think about how these really fundamental institutions that we think when we go to the ballot box, and we do our election, there's a lot of factors that go into that, right? Even the very fact that you can pick up any kind of temperature signal on that is surprising to me, and I think it's a really important finding. And then trying to pin down these mechanisms I think is interesting for trying to play out the scenarios of how does climate change proceed in terms of the effects of changing the political environment in which we're operating, and having, like Nick said, these potentially long term effects on the types of issues politicians are willing to work on. It's really important, and I think it's something that needs more work.

Nick: Fran makes an excellent point embedded in there, which is the understanding of what we call causal mediation. In other words, if you see that hot temperatures lead to a reduction in GDP growth, why is that? What exactly is causing that? GDP growth is this huge aggregate of all of these different things. Why might temperature be causing that? Or even, for example, if you see that temperature is affecting people's sleep quality, why is that the case? Is it because it's influencing the degree to which people are stressed out during the day because they're grumpier, they're having more negative interactions, and then they're thinking about that before they fall asleep? Is it due to purely physiological reasons, circadian rhythm and sleep cascades?

The short of it is, we don't actually have very good answers to most of these questions for most of the climates impacts that we've looked at, and it's pretty critical to have better answers, largely because if you want to adapt to coming climate changes, you'd like to spend your policy money on the things that are most important in those equations for reducing GDP growth or causing mental health outcomes or worsening people's mood. You’d like to really be able to tell people precisely what they can do to adapt, and also spend money precisely where it's needed, and it’s just strictly difficult science to be able to do that well.

Ariel: I want to actually go back real quick to something that you had said earlier, too: the idea that if politicians know that they're unlikely to get elected during the next cycle, they're also unlikely to plan long term. And I think especially when we're looking at a situation like climate change where we need politicians who can plan long term, it seems like can this actually exacerbate our short-term thinking?

Nick: Yeah. That's what I was concerned about, and still something that I am concerned about. As you get more and more extremes that are occurring more and more regularly and politicians are either responding well or not responding well to those extremes it may be somewhat like our weather and expectations paper — similar underlying psychological dynamics — which is just that people become more and more focused on their recent past, and their recent experience in history, and what's going on now.

And if that's the case then if you're a politician, and you've had a bunch of hurricanes, or you're dealing with the aftermath of hurricanes in your district, really should you be spending your policy efforts on carbon mitigation, or should you be trying to make sure that all of your constituents right now are housed and fed? That's a little bit of a false dichotomy there, but it isn't fully a false dichotomy because politicians only have so many resources, and they only have so much time. So as their risk of losing election goes up due to something that is more immediate, politicians will tend to focus on those risks as opposed to longer-term risks.

Ariel: I feel like in that example, too, in defense of the politicians, if you actually have to deal with people who are without homes and without food, that is sort of the higher priority.

Nick: Totally. I mean, I did a bunch of field work in Sub-Saharan Africa for my graduate studies and spent a lot of time in Malawi and South Africa, and talking to politicians there about how they felt about climate change, and specifically climate change mitigation policy. And half the time that I asked them they just looked at me as if I was crazy, and would explicitly say, like, “You must be crazy if you think that we have a  time horizon that gives us 20 years to worry about how our people are doing 20 years from now when they can't feed themselves, and don't have running water, and don't have electricity right now. We're working on the day to day things, the long term perspective just gets thrown out the window.” I think to a lesser degree that operates in every democratic polity.

Fran: This gets back to that question that we were talking about earlier: Are extreme events kind of fundamentally different in motivating action to reduce emissions? And this is exactly the reason why I'm not convinced that it's the case, in that when you have the repeated extreme events, yes, there's a lot of focus on rebuilding or restoring or kind of recovering from those events — potentially at the detriment of longer-term, less immediate action that would affect the long-term probability of getting those events in the future, which is reducing emissions.

And so I think it's a very complex, causal argument to make in the face of a hurricane or a catastrophe that you need to be reducing emissions to address that, right, and that's why I'm not convinced that just getting more and more disasters is going to automatically lead to more action on climate change. I think it’s actually almost this kind of orthogonal process that generates the political will to do something about climate change.

Having these disasters and operating in this very resource-constrained world — that's a world in which action on climate change might be less likely, right? Doing some things that are quite costly involve a lot of political will and political leadership, and doing that in an environment where people are feeling vulnerable and feeling kind of exposed to natural disasters I think is actually going to be more difficult.

Nick: Yeah. So that's an excellent point, Fran. I think you could see both things operating, which is I think you could see that people aren't necessarily adapting their expectations to giant wildfires every single summer, that they realize that something is off and weird about that, but that they just simply can't direct that attention to doing something about climate change because literally their house just burnt down. So they're not going to be out in the streets lobbying their politicians as directly because they have more things to worry about. That is troubling to me, too.

Ariel: So that, I think, is a super, super important point, and now I have something new to worry about. It makes sense that the local communities that are being directly impacted by these horrific events have to deal with what's just happened to them, but do we see an increase in external communities looking at what's happening and saying, “Oh, we've got to stop this, and because we weren't directly impacted we actually can do something?”

Nick: Anecdotally, somewhat yes. I mean, for example, if you look at the last couple of summers and the wildfire season, when there are big wildfire outbreaks the news media does a better than average job at linking that extreme weather to climate change, and starting to talk about climate change.

So if it is the case that people consume that news media and are now thinking about climate change more, that is good. And I think actually from some of the more recent surveys we've actually seen an uptick in awareness about climate change, worry about climate change, and willingness to list it as a top priority. So there are some positive trends on that front.

The bigger question is still an empirical one, though, which is what happens when you have 10 years of wildfires every summer. Maybe people are now not talking about it as much as they did in the very beginning.

Ariel: So I have two final questions for both of you. The first is: is there something that you think is really important for people to know or understand that we didn't touch on?

Nick: I would say this, and this is maybe more extreme than Fran would say, but we are in really big trouble. We are in really, really big trouble. We are emitting more and faster than we were previously. We are probably dramatically underestimating the social cost of carbon because of all the reasons that we noted here and for many more, and the one thing that I kind of always tell people is don't be lulled by the relatively banal feeling of your sleep getting disrupted, because if your sleep is disrupted it's because everything is being disrupted, and it's going to get worse.

We've not seen even a small fraction of  the likely total cost of climate change, and so yeah, be worried, and ideally use that worry in a productive way to lobby your politicians to do something about it.

Fran: I would say we talked about the social cost of carbon and the way it's used, and I think sometimes it does get criticized because we know there's a lot of things that it doesn't capture, like what Nick's been talking about, but I also know that we're very confident that it's greater than zero at this point, and substantially greater than zero, right? So the question of, should it be 40 dollars a ton, or should it be 100 dollars a ton, or should it be higher than that, is frankly quite irrelevant when right now we're really not putting any price on carbon, we're not doing any kind of ambitious climate policy.

Sometimes I think people get bogged down in these arguments of, is it bad, or is it catastrophic, and frankly either way we should be doing something to reduce our emissions, and they shouldn't be going up, they should be going down, and we should be doing more than we're doing right now. And arguing about where we end that process, or when we end that process of reducing our emissions is really not a relevant discussion to be having right now because right now everyone can agree that we need to start the process.

And so I think not getting too hung up on should it be two degrees, should it be 1.5, but just really focused on let's do more, and let's do it now, and let's start that, and see where that gets us, and once we start that process and can begin to learn from it, that's going to take us a long way to being where we want to be. I think these questions of, “Why aren't we doing more than we're doing now?” are the most important and some of the most interesting around climate change right now.

Nick: Yeah. Let's do everything we can to avoid four or five degrees Celsius, and we can quibble over 1.5 or two later. Totally agree.

Ariel: Okay. So I'm going to actually add a question. So we've got two more questions for real this time I think. What do we do? What do you suggest we do? What can a listener right now do to help?

Fran: Vote. Make climate change your priority when you're thinking about candidates, when you're engaged in the democratic process, and when you're talking to your elected representative — reach out to them, and make sure they know that this is the priority for you. And I would also say talk to your friends and family, right? Like these scientists or economists talking about this, that's not something that's going to reach everyone, right, but reaching out to your network of people who value your opinion, or just talking about this, and making sure people realize this is a critical issue for our generation, and the decisions we take now are going to shape the future of the planet in very real ways, and collectively we do have agency to do something about it.

Nick: Yes. I second all of that. I think the key is that no one can convince your friends and family that climate change is a threat perhaps better than you, the listener, can. Certainly Fran and I are not going to be able to convince your friends, and that's just the way that humans work. We trust those that we are close to and trust. So if we want to get a collective movement to start doing something about carbon, it's going to have to happen via the political process, and it's also just going to have to happen in our social networks, by actually going out there and talking to people about it. So let's do that.

Ariel: All right. So final question, now that we've gone through all these awful things that are going to happen: what gives you hope?

Fran: If we think about a world that solves this problem, that is a world that has come together to work on a truly global problem. The reason why we'll solve this problem is because we recognize that we value the future, that we value people living in other countries, people around the world, and that we value nature and nonhuman life on the planet, and that we've taken steps to incorporate those values into how we organize our life.

When we think about that, that is a very big ask, right? We shouldn't underestimate just how difficult this is to do, but we should also recognize that it's going to be a really amazing world to live in. It's going to provide a kind of foundation for all kinds of cooperation and collective action I think on other issues to build a better world.

Recognizing that that's what we're working towards, these are the values that we want to reflect in our society, and that is a really positive place to be, and a place that is worth working towards — that's what's giving me hope.

Nick: That's a beautiful answer, Fran. I agree with that. It would be a great world to live in. The thing that I would say is giving me hope is actually if I had looked forward in 2010 and said, "Okay, where do I think that renewables are going to be? Where do I think that the electrification of vehicles is going to be?" I would have guessed that we would not be anywhere close to where we are right now on those fronts.

We are making much more progress on getting certain aspects of the economy and our lives decarbonized than I thought we would have been, even without any real carbon policy on those fronts. So that's pretty hopeful for me. I think that as long as we can continue that trend we won't have everything go poorly, but I also hesitate to hinge too much of our fate on the hope that technological advances from the past will continue at the same rate into the future. At the end of the day we probably really do need some policy, and we need to get together and engage in collective action to try and solve this problem. I hope that we can.

Ariel: I hope that we can, too. So Nick and Fran, thank you both so much for joining us today.

Nick: Thanks for having me.

Fran: Thanks so much for the interesting conversation.

Ariel: Yeah. I enjoyed this, thank you.

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