第六季第37集：气候变化的宏观经济学

在评估气候变化对不同国家影响的研究中，通常会发现农业比重较高的发展中国家往往遭受的冲击最为严重。

In the research that tries to evaluate the effects of climate change across different countries, you typically find that developing countries with agricultural shares are usually the ones that suffer the most.

欢迎收听Vox Dev Talks，我是蒂姆·菲利普斯。1992年，比尔·诺德豪斯开创了宏观经济建模的新纪元，其中我们的经济活动既影响着自然环境，又受其所处的自然环境影响。三十年后的今天，科学界对气候变化已达成强烈共识，但对于应对气候变化的适当经济政策却仍未形成类似共识。一篇关于宏观经济学与气候的新综述展示了我们在气候建模及其对经济的影响、以及经济对气候反作用方面的研究进展。

Welcome to Vox Dev Talks. My name is Tim Phillips. In 1992, Bill Nordhaus kicked off a a new era of macro modeling in which our economic activity influences and is influenced by the natural environment in which our economy is embedded. Now three decades later, scientific consensus around climate change is strong, but there's not similar agreement over the appropriate economic policies to deal with it. A new review of macroeconomics and climate shows how far we have come in our modeling of the climate and its effect on the economy and the economy's effect on it.

但更重要的是，它指出了我们知识体系中仍存在的空白——这些空白必须填补，才能让受气候变化影响最大的中低收入国家掌握制定良好政策所需的工具。斯坦福大学的阿德里安·比拉尔是该综述的作者之一，他现在与我连线。阿德里安，欢迎来到VoxDevTalks。

But significantly, it points out where the gaps in our knowledge still are. Gaps that we will need to fill if the low and middle income countries most impacted by climate change are gonna have the tools to make good policy. Adrian Bilal of Stanford University is one of the authors of this review. He joins me now. Adrian, welcome to VoxDevTalks.

你好，蒂姆。

Hello, Tim.

你们将综述划分为三个领域：损失与损害、缓解措施、适应策略。这涵盖了海量研究，但你们未考虑的内容意味着什么？

You have divided your review into three areas: loss and damage, mitigation, adaptation. That takes in an enormous amount of research, but what does it mean that you did not consider?

是的，我们在经济学方面力求全面，因此纳入了所有对宏观经济总量有意义的研究，包括气候损害模型与评估、极端事件作用、区域差异和风险等。我们也涵盖了脱碳成本、脱碳策略及适应相关主题。但有些议题因篇幅限制未能深入，比如我们略过了气候科学本身——这方面已有面向经济学家的优秀综述可供参考。

Yes, we try to be as broad as possible on the economic side. So we try to include any research that's meaningful for macroeconomic aggregates, you know, models and estimates of climate damages, the role of extreme events, regional disparities, risk. We also covered decarbonization costs, decarbonization strategies, and topics on adaptation. Now there are a few topics that we would have liked to include but couldn't, mainly for space reasons. So we glossed over the climate science for the sake of space and because there are already some very good reviews out there that cover the climate science specifically and that are economist friendly.

我们也未详细讨论气候金融这一活跃研究领域（尽管它与宏观经济学有一定关联），同时跳过了仅涉及短期波动或更偏向微观经济学性质的研究。

We also glossed over the very active research in climate finance, which is somewhat relevant for macroeconomics as well. We also glossed over research related to short run fluctuations only or research that's more microeconomic in nature.

你在审阅的这些论文是否表明，经济学界对气候变化及其宏观经济影响的关注度与其重要性相匹配？

Do the papers that you were looking at for this review, does it show that the economics profession is giving the topic of climate change and the macroeconomic impact of climate change the attention that it deserves?

是的，我们决定阅读这篇综述很大程度上是因为当前环境经济学和气候问题备受关注且发展迅速。但与此同时，我们未能找到能帮助该领域新晋经济学家系统理解这一议题的高层次概述。虽然已有许多优秀综述，但它们往往聚焦于特定角度，而我们希望提供更像综合指南的内容，帮助经济学家入门。这正是我们试图实现的成果。

Yes, we decided to read this review in large part because there's a lot of interest in environmental economics and climate these days and it's growing very fast. At the same time, we couldn't really find a high level overview that would help economists who were new to the field navigate the topic. Now there are a lot of excellent other reviews out there but they tend to focus on a specific angle of the question and by contrast we wanted something that would be more like a comprehensive guide to help economists get started in this field. That's what we hope we achieved.

在Vox Dev，我们非常关注政策对中低收入国家的影响。显然这与当前议题高度相关。让我们看看你们综述中的部分内容——虽然无法涵盖全部，但先从损失与损害说起。

So at Vox Dev, of course, we're very interested in the impact of policy on low middle income countries. Of course, this is extremely relevant in this case. And so let's have a look at some of what's in your review. We can't cover it all. But starting with loss and damage.

在国家层面量化损害时，宏观经济学家已通过大量研究估算了温度上升对产出的影响。目前我们得到的估计值范围大致是怎样的？

To monetize damages at a country level, there has been a lot of research where macro economists have estimated the effect of a rise in temperature on output. What sort of range of estimates are we getting at the moment?

范围较广，但与其他宏观问题的估计区间相差不大。首先关键在于如何准确定义温度——经典方法是观察国家产出随本国温度变化的规律。现代多数估算表明，某国气温每升高1摄氏度，其产出变化介于-5%到+5%之间，具体取决于该国基础温度。因此像马里这样的高温国家可能受损，而挪威等原本寒冷国家可能受益。

It's wide, but I would say that it's not much wider than the range of estimates that we have on most other macro questions. The first thing that's important is what you mean exactly by temperature. So the classic approach is to look at how a country's output changes when temperature in that country changes. And so there most of the modern estimates we have imply that a one degree Celsius increase in the given country's temperature implies somewhere between a minus 5% output change and plus 5% output change depending on the country's baseline temperature. So countries that are already hot like Mali are likely gonna lose and countries that are originally colder like Norway are likely gonna gain.

全球平均而言，每摄氏度升温会导致约3%的产出损失。需注意的是，国家自身温度与气候变化存在差异——后者更关注全球平均温度变化，这正是IPCC等机构始终强调全球均温的原因。毕竟全球均温既包含陆地也包含海表温度，而海洋对各类气候现象至关重要。

So for the world the average hovers around a 3% loss in output per degree celsius. Now it's important to recognize that a country's own temperature is quite different from climate change because when we think about climate change we think more about changes in the global mean temperature. And so that's why institutions like the IPCC always talk about global mean temperature. Now global mean temperature is different from any given country's temperature because, well, it's the global mean. Yes.

我们在综述中讨论的另一篇与合著者Diego Kansick的论文表明：当评估全球均温对产出的影响时，效应更为显著。其影响范围从0%到50%不等（取决于国家），全球平均值约为20%的产出损失。这主要源于海表温度变化，以及全球均温可表征各类极端灾害事件（如狂风或骤雨）的破坏性影响。

And second, because it includes ocean surface temperatures. And we know from the climate science then the oceans are pretty important for all sorts of climatic phenomena. And so what we've shown with my coauthor Diego Kansick in another paper that we discussed in the review is that when you instead evaluate the impact of global mean temperature on output, you find larger effects. And so there the range is larger, it ranges from basically a 0% to a 50% output loss per degree Celsius depending on the country, and the global mean is also quite a bit larger, it's around 20% loss per degree Celsius. And we show that it's largely due to changes in ocean surface temperatures and to the fact that global mean temperature proxies for all sorts of damaging extreme events such as extreme winds or drops.

显然在国家层面分析这些问题在气候议题上是有些人为割裂的。我们目前注意到的一个现象是极端事件频率增加，而这些事件在低收入国家环境中尤其具有破坏性。它们并不尊重国界。我们该如何改进分析以纳入这些事件，尝试评估其影响？这对我们关于气候变化损失与损害的研究结果意味着什么？

Clearly analyzing these things at the country level is somewhat artificial when we're thinking about the climate. One of the things that we note at the moment is the increased frequency of severe events, and they are especially destructive in low income country settings. They do not respect country borders. How can we improve our analysis to take account of these events to try and estimate their impact? What does this do to the results that we're finding about the loss and damage of climate change?

这个观点很到位。这些极端现象——比如干旱或飓风——其发生范围既小于国家尺度（仅影响国内特定区域），又如你所说会跨境同时影响多国地区。一个粗略的方法是构建指数来衡量某国每年遭受极端天气的平均暴露程度，这正是我和迭戈研究中采用的方法。但正如你所言，这远非完美方案。

That's a great point. In these phenomena, these extreme events, say droughts or hurricanes, they occur both at a finer resolution than countries because they hit only specific locations within a country, but they also, as you mentioned, cross borders and affect regions in multiple countries at the same time. So one blunt thing you can do is construct indices that are going to measure a country's average exposure to weather extremes in any given year. That's what we did in our work with Diego. But it's as you said, it's far from perfect.

另一种方案是使用更精细的测量数据，比如实际可获取的每日温度、风速和降水数据，其空间分辨率大致相当于美国的郡县级别。若能在相同分辨率下获取当地经济活动指标，就能用这些细粒度数据评估极端天气对地方经济的影响。现有不少研究采用这种方法，包括我本人的部分工作。

The alternative is then to use more detailed measures say of daily temperature, wind speed and precipitation that are actually available at a pretty granular level say more or less you know the level of something that has the size of counties in The US. And then you can use this much more granular information to assess the impact of these weather extremes on local economic activity if you have good measures of local economic activity at that same resolution. And so there's a fair amount of research that does this in a variety of context, including some of my own research.

近期宏观经济研究在考察气候对家庭、区域及不同人群影响方面取得很大进展。我们应如何借鉴气候科学成果并运用这类研究方法？

Macroeconomic research has advanced a lot in the recent times, looking at the effects on households, on different regions, different types of people. What can we learn about using the climate science and applying it in this way?

这同样是个关键问题。我认为论证有两个维度：一方面我们能获得更深入认知，因为可以更精准测量目标作用渠道——比如特定类型热带风暴对某地区或特定家庭群体的影响。

That's a very important point as well. And there are two sides to the argument, would say. On the one hand, we can learn a lot more. We learn more because we potentially measure the channel that we're interested in much better. So say the effect of a given type of tropical storm on a given region or in a particular group of household.

通常我们能观察到冲击后的行为反应与调整：家庭是否会迁移？是否寻求不同工作？等等。这也有助于判断他们是否对气候变化进行了部分适应。

Usually we can look at more behavioral reactions, behavioral changes after that shock hits. Do households move? Do they look for a different job? And so on. So we also get a sense of whether they partly adapt to climate change.

另一方面，这种做法会面临经典的加总问题。即便我们在区域或家庭群体层面建模估计了气候现象的影响，最终仍需汇总来理解其对宏观经济的意义。这个加总过程涉及大量难以验证的假设，通常更依赖特定模型的结构设定——这也关联到经典难题：聚焦区域或家庭群体影响时，我们无法估计所谓的'缺失截距'。

Now on the other hand, when we do that, we face the classic aggregation problem. Once we model and estimate the impact of climatic phenomena at the regional or household group level, eventually we're still interested in adding it all back up to understand what it implies for the macroeconomy. And that aggregation exercise involves a lot of assumptions that are not always easy to test and verify. And we typically rely more on the structure of a particular model there. And that's related to the classic issue that we can't estimate what we like to call missing intercept when you focus on impacts at the regional level or groups of households.

因此，当我们进行更细粒度的分析时，通过共同冲击我们能更深入地了解机制和潜在的政策应对措施，但相比直接在国家或全球层面估算气候变化影响时（这并非总能实现），我们需要依赖更多假设。所以我们在某些方面获得了精确性，却在其他方面有所缺失。这就是权衡所在，也是为何这两种方法能形成有力互补。

So when we go more granular, we learn much more about mechanisms and possible policy responses through the common shocks, but we have to rely on more assumptions than when we manage, which is not always possible, but if we do, when we manage to directly estimate the effect on climate change at the country or world level. So we gain on precision on some fronts, but we miss out on others. So that's the trade off. And that's why both approaches strongly complement each other.

宏观经济研究中另一个引人入胜的方向是非市场效应的建模。我们在研究气候变化对犯罪或政治不稳定等方面的影响上取得了哪些进展？

Another fascinating strand of macroeconomic research has been modeling non market effects. How far have we got in looking at the impact of climate change on things like crime or on political instability?

非市场效应非常重要，但相比气候变化对产出的影响，我们在这方面的研究还不够深入。死亡率是个重要例外——它可能是气候变化中被研究最多的非市场效应。这部分研究之所以充分，很大程度上得益于完善的死亡率数据体系，以及我们对其经济损失的量化能力（尽管涉及诸多棘手的哲学问题）。至于您提到的犯罪和政治不稳定等其他非市场损害，现有研究也发现了显著影响，并且我们已掌握如何将这些现象纳入建模框架的方法。

Non market effects are very important, but we haven't gotten quite as far there as for the effect of climate change on, say, output. So there's one important exception, which is mortality. So mortality is presumably the most researched non market effect of climate change. And there's a lot of work there, you know, in large part because we have typically good data on mortality and and we also understand how to monetize mortality damages even though there are a lot of thorny philosophical questions associated with it. For other non market damages such as say crime and political instability as you mentioned, so there's a fair amount of work that finds effects there as well And we understand well enough how to potentially incorporate these phenomena in our modeling frameworks.

但根本挑战在于如何量化这些效应的经济价值。作为经济学家，我们始终追求将所有影响置于统一尺度来衡量——比如比较温度升高1℃通过生产力下降与犯罪率上升两种途径造成的影响。而犯罪或政治不稳定这类影响的货币化计算更为困难，这或许正是相关研究相对较少的原因。但这些领域确实值得深入研究。

The fundamental challenge however is how to monetize these effects. So we're always interested as economists in putting everything on a common scale. So we would like to compare the effect of a one degree Celsius increase in temperature through productivity declines vis a vis through rising crime rates. And it's that second part, the monetizing part, that is harder with crime or political instability, And that's perhaps why there's a bit less work in these areas. But they're important areas to research.

谈到减排政策——显然如果要讨论碳税，我们得另开四五个小时的播客。关于碳税有个问题想请教：特朗普政府反对碳税，理由是（此处引用原话）'它将给经济造成毁灭性打击'。现有研究对这种'毁灭性打击'的规模——即碳税对产出或就业的影响——有何发现？

Turning to mitigation. I mean, clearly, if we're going to talk about carbon taxation, we'd have to set aside another four or five hours on the podcast. There's one aspect of carbon taxation I wanted to ask about. The Trump administration opposes carbon taxation because, and I'm quoting here, what it calls the crippling damages that it would cause to the economy. What does research tell us about this, the impact on output or employment from carbon taxation, the size of those crippling damages?

我认为能源转型的确切成本尚无定论。近期不少研究发现，碳定价对就业和产出等经济活动的实际影响相当有限（如果存在影响的话）。这类研究通常对比不同碳定价政策变化的国家，或分析企业对碳价变化的不同敏感度。这里我们面临着与损害评估相同的聚合难题。

I would say that the jury is still out on how much the energy transition exactly costs. Yeah. There's a fair amount of recent research that finds that carbon pricing actually has pretty modest effect on economic activity, say employment and output, if any effect at all. So what this research does is it typically compares countries that experience different changes in carbon pricing regimes, or it compares different firms that are differentially exposed to changes in carbon prices. Here we face the same aggregation problem as for damages.

我的合著者Jago关于欧盟碳定价的研究另辟蹊径——通过分析欧盟碳排放交易体系市场中的碳价意外波动时间序列，成功规避了聚合问题。有趣的是，他发现碳定价对经济活动的影响更大，基本符合能源价格冲击的相关研究结论。这使得估算结果存在较大浮动区间。而对于劳动力从碳密集型产业转移的过程，我们认知更少——美国对中国贸易冲击的研究表明，这种转移对高度依赖单一产业且缺乏替代选择的社区而言，可能是个缓慢而艰难的过程。

My co author Jago has some very interesting work on carbon pricing in The EU in a separate paper that actually sidesteps the aggregation problem by looking at carbon pricing surprises in the EU ETS market in the time series. And there interestingly he finds larger effects of carbon pricing on economic activity more or less in line with what we know from research on any energy price shocks. So that gives you a fairly wide range of estimates as well. And what we would know even less about is how the relocation of workers away from carbon intensive industries is going to play out. And there the lessons that we've learned from exposure to Chinese trade say in The US have shown that this relocation can be slow and difficult for communities that are heavily exposed and that have few other options.

因此，我认为在这些领域我们需要更多的工作来弄清楚未来会发生什么。

And so I would say we need a lot more work in these areas to figure out what's going to happen.

在发展背景下尤为重要的一个减缓领域是高收入国家与中低收入国家之间的贸易导致的碳泄漏。这种碳泄漏可能会削弱能源转型的效果。那么，研究对此有何发现？有哪些政策可能有助于抵消这种影响？

One area of mitigation particularly important in the development context is carbon leakage for the trade between high income countries, low middle income countries. The carbon leakage that might come from that is undermining the impact of the energy transition. Again, what's the research telling us about this and any policies that might help offset this?

如果说估算能源转型对就业和产出的影响已经很难，那么估算泄漏的作用就更难了。是的，是的。贸易理论告诉我们，泄漏确实可能是个问题。但同样重要的是要记住，很多经济活动及其内含的排放实际上并不涉及贸易。

If estimating the effect of the energy transition on employment and output is difficult, estimating the role of leakage is even harder. Yep. Yep. Now trade theory tells us that leakage can be a real problem. But it's also important to remember that a lot of economic activity and the emissions embedded in that economic activity is actually not traded.

因此，泄漏问题比我们有时想象的稍微轻一些。让我们聚焦于泄漏，即碳密集型产品的生产转移到另一个国家，然后这些产品带着内含的排放重新进口回来。四分之一的排放来自交通运输，四分之一来自发电，四分之一来自工业流程，剩下的四分之一中15%来自住宅和商业能源使用，10%来自农业。除非美国所有人都在加拿大给车加油，否则交通运输领域的泄漏不会太多。发电和其他一些领域也可以做类似的论证。

And so leakage is a little bit less of a problem than the impressions we sometimes get. So let's focus on leakage understood as production of carbon intensive goods that is shifted to another country and then the goods you know are re imported back with embedded emissions. So one quarter of emissions is transportation, one quarter of emissions is power generation, one quarter of emissions is the industry industrial processes, and the last quarter is 15% residential and commercial use of energy and agriculture 10%. So unless everybody in The US can manage to refuel their car in Canada, there's likely not a ton of leakage in transportation. You can make a similar argument for power generation and some of these other items.

农业和工业领域确实可能出现更多泄漏，因为这些产品确实涉及贸易。大致来说，约60%的排放不易发生泄漏，而约40%的排放来自农业和工业，更容易受到泄漏影响。遗憾的是，目前我们对泄漏的估算数据不多，但现有的研究显示，一旦从整个经济层面来看，泄漏的影响相对有限。这也是我们需要更多研究的领域。假设我们正视泄漏风险，那么问题就在于，如你所提到的，我们能做些什么来降低这种风险？

Now for agriculture and industry there you can have more leakage because these goods are indeed traded. And so more or less you have about 60% of emissions that are shielded from leakage and about 40% of emissions that are agriculture and industry that are more exposed to leakage. Now we don't have a ton of estimates of leakage so far, unfortunately, but those that we have seem to find relatively modest effects at most once you aggregate to the level of the whole economy. That's an area where we need a lot more research as well. Say you take the risk of leakage at face value, the question is then as you mentioned what can we do to reduce that risk?

欧盟正在实施的碳边境调节机制（CBAM）实际上是一个不错的选择。如果像欧盟那样有雄心勃勃的国内脱碳政策，你可以对进口产品内含的碳进行与国内相同的定价。这样基本上消除了泄漏的动机，因为大家都知道，如果把生产转移到国外再进口产品，他们将不得不支付相同的碳价。实际上，像CBAM这样的机制甚至可以激励贸易伙伴实施自己的国内碳定价方案。为什么？

Something like the carbon border adjustment mechanism or CBAM that the EU is implementing is actually a good option. If you have ambitious domestic decarbonization policies in place like the EU has, you can price carbon embedded in imports to the same extent as you're pricing carbon domestically. And so that largely nullifies the leakage incentives because everybody then understands that if they move production abroad and then re import goods they're going to have to pay the same carbon price. In fact something like the CBEM can even incentivize trade partners to actually put in place their own domestic carbon pricing scheme. Why?

因为这样一来，贸易伙伴可以从碳定价中获得收入，而不是让欧盟获得这笔收入。我们刚开始看到评估CBAM有效性的研究，但目前为止它似乎正在发挥作用，确实限制了泄漏。

Because that way the trading partner collects the revenue from carbon pricing rather than leaving the revenue to the EU. And so we're just starting to see research that evaluates the effectiveness of the CBAM, but so far it seems that it is working. It is a limiting leakage.

缓解措施还意味着劳动力和资本的重新分配。您之前稍微提到过这一点。我们该如何理解这种影响？这总是带来创伤性的。特别是在新兴发展中经济体，我们该如何理解这些影响？

Mitigation also implies reallocation of labour and capital. You mentioned this a little bit earlier. How can we understand the effect of this? This is always traumatic. How can we understand the effects of this, especially in developing emerging economies?

这是个非常重要的问题，我们之前简要讨论过能源转型对劳动力市场的影响。有些研究关注了美国《清洁空气法案》监管下工厂裁员后工人的去向。这些论文发现其影响与其他失业情境类似。但关键问题在于，《清洁空气法案》案例是否足以代表更宏大的脱碳转型将带来的影响。核心在于企业是否会在能源转型的大背景下缩减工作岗位。

That's a very important point, and we already talked briefly about it, the labor market effects of the energy transition. There's a little bit of work that looks at what happens when workers are let go after plants become regulated by the Clean Air Act in The US. And what these papers find is that pretty similar effects to what happens when workers lose their jobs in other contexts. But the key question is more whether the Clean Air Act case is representative enough to understand what's going to happen when we engage in more ambitious decarbonization transition. Key question here is really whether businesses are going to end up cutting back on jobs in that broader context of the energy transition.

这方面我们已有一些讨论过的证据，但更多实证研究当然不会有害。关于资本重新分配，我想提及一个新兴研究领域——我们称之为'资本代际'理论，它试图评估资本投资是否与特定能源结构绑定，及其对能源转型的启示。我们需要替换多少现有资本存量才能成功转型？成本几何？这正是该领域研究试图解答的问题。

And there we have some evidence that we've already discussed before, but we certainly wouldn't be hurt with by more evidence. On capital reallocation, let me mention that there's a young and growing literature on what we like to call capital vintages that tries to assess whether capital investments are specific to a particular energy mix and what that implies for the energy transition. So how much of the existing capital stock do we need to replace for a successful transition? How much will it cost? That's what this literature is trying to figure out.

目前我们已建立完善的资本代际企业理论模型，但挑战仍在于实际测量——我们通常难以准确判断资本是否专属于某种能源类型。发达国家尚且如此，发展中国家的相关数据更为匮乏。我期待这个研究领域能够持续发展壮大。

Now we have good you know theoretical models of firms with capital vintages but the challenge is again measurements here because we typically don't have very good information on whether capital is specific to a particular type of energy. Developed countries and developing countries typically that information is even scarcer. And so I'm hoping that this literature is going to continue to grow.

从对话中可以明确，我们要探讨的问题远未穷尽。但谈到适应措施时，您在论文中指出相关研究相对较少。原因何在？

Now it's clear from our conversation that we're not running out of questions to ask anytime soon. But when we get to adaptation, you note in the paper that there has been comparatively less work on adaptation. Why is that?

有四个原因。首先长期以来我们其实不确定气候变化的经济影响——如果连影响是否存在都存疑，自然不会费心研究社会适应机制。如今我们掌握了更多气候影响的证据，经济学家才开始重视适应研究。其次是我们缺乏直接研究适应机制的理想方法。

There are four reasons. The first one is that for a long time we've actually been unsure of the economic effect of climate change. So if you're unsure that there's even an effect at all, you're not going to bother studying whether society is adapting to it. Now we have more evidence of climate impact and so economists are starting to study adaptation more. The second reason is that we actually don't have a lot of great ways to directly study adaptation.

通常我们观察气候冲击下关键指标（如产出、工资、就业）的变化，这反映的是包含适应行为在内的总效应。要量化适应程度就需要更多结构性分析。例如我们可以追踪气候变化效应是否随国家或家庭富裕程度而演变——如果发现特定热带风暴或热浪的影响随国家富裕程度减弱，就可以推断：随着经济发展，社会可能更有效地适应极端高温或风暴。

Typically what we do is we look at what happens to an outcome of interest, say output wages employment when there's a climate shock. That tells us what the total effect of the shock is inclusive of adaptation. Now to learn about the extent to which there is adaptation we need more structure. For instance we can exploit whether the effect of climate change evolves over time as countries or households become richer. So if we see that the effect of a given tropical storm of a heat wave becomes weaker as countries become richer, we're going to infer that potentially you know as countries become richer they're able to adapt more efficiently to extreme heat or storms.

但你需要更多信息，因为你需要追踪气候变化随时间推移产生的影响。因此，尽管这种方法有些间接，但它是文献中最常用的方法，例如已成功用于评估是否存在针对热应激导致死亡的适应措施。第三个可能解释为何适应研究较少的原因是，在三度升温的世界中，适应方式可能与过去0到1度升温的世界截然不同。如果适应主要涉及大型固定成本投资，比如堤坝和防洪墙，那么利用过去数据进行大规模适应的成本效益分析将非常困难。第四个原因与之前提到的第二个原因相关，即在某些情况下我们可以直接观察经济主体是否正在采取适应措施。

But you need a lot more information because you need to trace out the effects of climate change as time goes by. So even though this approach is a bit indirect, it's the most common one that's used in the literature and it's for instance been used successfully to evaluate whether there's adaptation to heat stress for mortality. The third reason is that that may explain why adaptation has been a little bit less studied is that adaptation might be very different in the three degree world than in the past zero to one degree world. If adaptation is mostly about large fixed cost investments such as say levies and dikes, it's very hard to run a cost benefit analysis on adaptation using past data at large scale. And the fourth reason which is related to the second one I mentioned before is that there are a few instances in which we can directly observe whether economic agents are taking measures to adapt.

你需要观察他们是否实际安装了空调等设备。移民是一个重要的例外，因为在那里相对更容易观察家庭是否通过迁移来应对气候变化。但即便如此，我们仍需要以某种方式评估移民如何减少他们面临的气候风险。因此，我希望未来能看到更多关于适应方面的研究。

You need to observe whether they're actually installing an air conditioning or things like that. Migration is an important exception because there it's relatively easier to observe whether households are responding to climate change by moving between locations. But then again we then still need to evaluate somehow how migration reduces their exposure to climate checks. So I hope that we'll see a lot more work on adaptation in the future.

移民是许多发展中国家工作者极为关注的问题。我们对此了解多少？在当前背景下研究移民是否为时过早？

Migration is something that concerns a lot of people working in developing economies greatly. Do we know much? Is it too early to know very much about migration in this context?

我们有所了解，但知之不多。尽管有时会看到相关头条新闻，但实际上我们没有证据表明因气候冲击导致大规模国际移民，特别是从低收入国家向高收入国家的移民。如果有的话，移民似乎主要发生在国内，因此可以看到对气候冲击更强烈的反应，但跨国反应较少。这是现有证据告诉我们的。由于移民数据往往有限，特别是跨国数据，我们实际上仍需要了解更多关于移民是否可能在未来对气候冲击做出反应（如果有的话）。

So we know some, but we don't know a ton. So despite the headlines that we sometimes see, we actually don't have evidence of massive international migration in response to climate shocks, in particular from low income countries to high income countries. If anything it seems that migration is happening within borders, so there you see stronger responses to climate shocks but you see less responses across borders. That's what the available evidence so far is telling us. Now because migration data is often limited, in particular across borders, we actually you know still need to learn a lot more about whether migration you know might respond at some point to clam chowks if at all.

我们还需要更多了解移民对输出国和接收国经济的影响。目前有一个非常活跃的研究领域，研究移民对本地人和移民自身的影响，这部分研究与气候变化相对独立。因此，将这两个领域结合起来似乎是未来非常重要的研究方向。

And we also need to learn a lot more about its effects on the sending and receiving economies. Now there's a very active field of research that studies the effects of migration on natives, on migrants themselves that is somewhat independent of climate change. And so you know, bringing these two fields together seems like a very important strand of research going forward.

农业可能是我们能够直接观察适应需求和适应效果的领域之一。发展中国家的经济活动中有更高比例集中在农业。未能适应的风险有多大？哪些政策会带来更好的适应？

One area where potentially we can observe directly the need for adaptation and the effects of adaptation is in agriculture. Development settings have a higher proportion of their economic activity in agriculture. How much of a risk is the failure to adapt? What sort of policies would lead to better adaptation?

是的，农业密集型国家有几种适应方式。他们可以采取更多保护措施，比如增加灌溉。他们可以保持农业在经济中的比重不变，但改变种植的作物类型，或者完全放弃农业，增加食品进口。让我依次讨论这三种选择。像灌溉这样的保护性投资显然最容易实施，特别是在有政策支持的情况下，但其效果也有限。

Yeah, there are a few ways that countries that are intensive in agriculture can adapt. You know, they can put more protective measures in place, say more irrigation. They can keep the same amount of agriculture in the economy but change the type of crops they grow or they can switch away from agriculture altogether and import more food. So let me go through these three options in turn. So protective investments such as irrigation are clearly the easiest to put in place, especially if you have some policy assistance, but their efficacy is also limited.

通过灌溉可以在一定程度上保护作物免受干旱影响，但要防范极端高温则困难得多。大量关于农业与气候变化的文献表明，反复遭遇极端高温会导致产量急剧下降，在发展中国家尤其如此。改种其他作物看似相对容易，或许还需要政策支持，比如培训农业工作者种植更耐高温的品种。但关于这类项目成效的实证评估并不多见。况且，土壤条件和基础气候仍需适宜这些新作物。

You can protect your crops to some extent against droughts with irrigation, but it's going to be much harder to protect them against extreme heat. And we know from a large literature on agriculture and climate change that yields start to drop precipitously with repeated exposure to extreme heat, in particular in developing country context. Now switching crops seems a bit easier, again perhaps with some policy assistance, say you train agricultural workers in using different crops that are more resistant to heat. But we don't have a ton of empirical evaluations on the efficacy of those programs. And then again you still need your soil and your baseline climate to be able to receive these other crops.

彻底退出农业转型更为艰难，因为通常缺乏具有比较优势的其他产业来承接经济活动，以支撑粮食进口。若真存在这样的产业，该国农业占比本就不会太高。总体而言，农业占比较高的国家除了依靠常规发展进程外，适应气候变化并非易事，而不适应的代价可能极其高昂。在评估气候变化对各国影响的研究中，农业占比高的发展中国家往往受损最严重。补充一点，虽然无法改变国家层面的结果，但若建立完善的保险体系（如某些国家针对歉收的保险），仍可减轻个体农户遭受的损失。

Switching away from agriculture altogether, that's hard because you typically don't have an obvious other sector where you have comparative advantage that you can use, move economic activity into to finance your food imports. Because if you had that sector, chances are you probably would have a lower agricultural share to begin with. So overall, it's actually not that easy to adapt if your agricultural share is high except through the normal process of development and the cost of not adapting could be pretty high. In the research that tries to evaluate the effects of climate change across different countries, you typically find that developing countries with higher cultural shares are usually the ones that suffer the most. One thing to add, even though it's not going to change anything for the country level outcomes, you can still mitigate the harm experienced by individual farmers if you have a well functioning insurance system in place against say bad harvests like you have in some countries.

在发展中国家推行农业保险并非易事，但如果能让保费合理调整（这本身是个难题，因为农业保险常面临压低保费的巨大压力），这些调整后的保费既能限制受灾农户的个体损失，又能激励国内农业部门放弃过于脆弱的作物品种。

It's not always easy to put in place insurance in particular in developing country context, but if you let insurance premium adjust correctly, that's again a big if because there's always a lot of pressure especially for agriculture to keep these premiums low, but if you let these premiums adjust then they will limit to some extent the individual harm experienced by those farmers who get hit by climate shocks while at the same time incentivizing the aerial sector in that country to switch away from crops that are too exposed.

这方面存在大量研究机遇。从您的视角来看，填补这些知识空白最有前景的方向是什么？

There are so many opportunities for research here. Personally, from your point of view, what are the most promising directions to fill these gaps in our knowledge?

我们讨论过若干领域，若要总结的话，我认为能源转型与广泛适应措施对劳动力市场和资本市场的影响最为关键。

We talked about a few areas, but if I had to summarize, I would say, you know, the labor and capital market effects of the energy transition and adaptation broadly.

如今我们也获得了更优质、更细化的数据，甚至可能有私营部门数据开放获取。这对研究有帮助吗？

We are also seeing much better data, much more granular data now. We are seeing potentially private data as well-being made available. Does this help with the research?

确实有帮助。更多、更细致的数据总是有益的，使我们能够测量以往无法观测的新渠道。举例来说，若能结合街区/地址层面的房产价值数据、地面高程信息和洪水地图——虽然操作困难，但利用现有的公私数据组合在理论上是可行的。

Yes, it does. More data, more detailed data is always good. It lets us measure new channels that we couldn't before. Let me give you one example. Say if you can pair block level or address level property value information together with ground level elevation information and with flood maps, you know that's something that's difficult to do but is in principle feasible with constellation of private and public data that's out there.

这将让你更全面地了解沿海洪水带来的总体风险价值。因此，我希望未来能看到更多这样的组合研究，这将显著提升我们的认知水平。

That's going to give you a much better sense of the aggregate value at risk from coastal flooding. And so I'm hoping that in the future we'll see pairings like that, you know, more and more often. That's going to improve our state of knowledge.

当你翻阅经济学教材时，环境经济学往往作为补充内容出现在宏观教材的末尾。这种情况正在改变吗？是否应该加速变革？我们是否需要设立更多独立的环境经济学课程？

When you look at economic textbooks, environmental economics is sort of a supplement. It's something that comes near the back of the macro textbook. Is this changing? Should it change more? Should we be creating more environmental economics course, standalone courses?

确实在改变，而且速度相当快。许多大学已建立了成熟的环境经济学专业课程体系，知名项目层出不穷。虽然传统上环境经济学在广泛的经济学系中占比偏低，但由于学生需求激增，这一现状正快速转变。例如我们经济系现已开设多门相关课程，学校还成立了可持续发展学院，正在构建围绕社会科学与可持续性的全新教学体系。

It is changing, and it seems to be changing quite fast. There are a bunch of universities that have well established programs that specialize in teaching environmental economics. There are a lot of prominent programs. But then you're right that across the broad range of economics department, environmental economics has historically been a little bit less represented than other disciplines, but that's changing rapidly in large part because there's a lot of demand from students. And so here in the economics department, we now have several courses on offer and the university we have a whole sustainability school that's building a whole new program around social sciences and sustainability.

COP30即将召开。我们常听到来自全球南方参会者的抱怨：政治讨论与经济讨论被割裂。当前全球政策辩论高度两极分化，地缘政治色彩浓厚，这与我们过去半小时讨论的内容相去甚远。

We're coming up on COP thirty. One of the complaints that we often hear from attendees at COP thirty from the Global South is that the political discussion and the economic discussion gets separated. A lot of the global policy debate is very polarized. It's very geopolitical at the moment. And it doesn't really have a lot to do with what we've been talking about for the last half hour.

如果政策辩论的主要参与者并不重视科学，这些研究的现实意义何在？

How relevant is all of this research if the main actors in the policy debates aren't really taking much notice of the science?

我认为我们必须坚持本职工作，科学终会找到知音。无论政策制定者是否立即采纳，科学的价值都不会改变。在某些领域，科学成果可能需要百年才能转化为实践。对社会科学而言，缓慢消化直至潜在应用本就是常态过程——虽然在两极分化环境下，这个过程可能更为漫长。

Well, I would say that we just have to keep doing our job and maybe the science eventually finds a receptive ear. I would say the science is relevant regardless of whether policy actors pick it up immediately or whether it takes a few years. In other disciplines, sometimes it takes one hundred years before the science eventually makes it into something practical. For social science, it's part of the normal process to be slowly digested until it is potentially put in practice. Now in a polarized context, this process might be slower than usual.

作为学术经济学家，我们唯一能做的就是持续产出和阐释客观知识。至于这些研究如何融入公共辩论和政策制定，某种程度上已超出我们的掌控范围。

Really, the only thing that we can do as academic economists is to continue doing our job, which is to produce and explain objective knowledge. How this research is then incorporated into the public debate and into public policy is, I would say, partly beyond us.

非常感谢你所做的工作，Adrian。感谢你进行这次综述，正如你所说，这对任何学习经济学或想要深入了解当前研究现状的经济学家来说，都是一个极好的入门指南。谢谢你今天与我们分享这些。

Thank you very much for the work that you're doing, Adrian. Thank you for doing this review, which, as you say, is a great introduction for anyone studying economics or economists who really want to know far more about the state of research at the moment. Thanks for talking about it today.

谢谢你，Tim。

Thank you, Tim.

这篇论文名为《宏观经济学与气候变化指南》，作者Adrian Bilal和James Stock（如果你正在学习计量经济学，可能会对这个名字感到熟悉）。论文编号为NBER工作论文第33567号，方便你查找。本期是Vox Dev Talks节目。确保不错过任何一期的最佳方式，是在你获取播客的平台关注或订阅我们。

The paper is called A Guide to Macroeconomics and Climate Change. The authors, Adrian Bilal and James Stock, a name that might be familiar to you if you are studying and doing econometrics. It is NBER Working Paper thirty three thousand five hundred sixty seven if you want to find it that way. This has been a Vox Dev Talk. Best way to make sure you don't miss an episode, follow us or subscribe wherever you get your podcasts.

我们就在那里。你可以在voxdev.org找到我们所有往期节目，以及相关主题的文章。如果你喜欢我们的内容，请向他人推荐并为我们留下评价。VOX Dev Talks由Talk Normal制作，助理制作人是Megan Bieber，编辑是Andre Zargarian。

We are there. You can find all our past episodes at voxdev.org with articles about the topics that we feature. If you like what you're hearing, please tell someone else about us and also leave us a review. VOX Dev Talks is a Talk Normal production. The assistant producer is Megan Bieber, and our editor is Andre Zargarian.

感谢Voxdev的Oliver Hany和Iman Siddik。

Thanks to Oliver Hany and Iman Siddik at Voxdev.