WEBVTT

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You have any questions?

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All right, okay.

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Thanks very much for putting me on the program.

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It's an honor to be here.

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I should self disclose I'm an economist.

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Is there any other economist in the room?

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That's what I fear.

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So I'm going to talk to you about what economists do about climate change and how we figure out if it's a serious problem.

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The very serious problem, not such a serious problem, which tends to make economists amongst the most hated people in the space.

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But don't fear.

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I think we have good things to contribute.

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And today I want to talk to you about how we incorporate tipping points in the climate system into economic impact estimates of climate change.

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And my co-first and I, we've built a model.

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We call a meta stands for model for economic tipping point analysis.

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And I'm going to show you what this model does, how it works, and maybe get you interested in using it or working with it.

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And it's in Julia.

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Okay, so it's a, it's a collaboration that's not just me.

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The core team has seven deets in James Rising Simon.

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I would say it's the core architect of the model.

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James is the reason we could manage to put this into Julia.

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And we've partnered with Frustian Delphor project.

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He's a methane scientist.

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And we've gone on blackness.

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A climate economist.

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It's kind of between climate science and climate economics largely speaking.

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So tipping points are climate systems.

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What are they?

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Well, there's different definitions around that the definition we like to use is that you do a little small push in terms of emissions or temperature change and something large this continuous happens.

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Or it doesn't even have to be discontinuous. Something very large happens.

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So there's this proportionality of impact to output.

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Other people have a more strict definition.

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But if you take this wider definition, you get a lot of things that you might have heard about.

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Let's just look at one.

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For example, the green and I sheet here.

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It's a big ice sheet.

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That as the earth warms melt.

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And as it melts, it adds to sea level rice.

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And so for additional warming, you get additional sea level rice.

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More than you would have gotten just from thermal expansions.

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And there are the tipping points that add emissions.

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For example, the permafrost.

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If the permafrost unfreezes top zone Siberia, that leads to organic matter coming to contact with surface air.

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You get fluxes of methane and fluxes of emissions, the warming accelerates.

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So these are the kind of things we think about.

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Perhaps the most pressing one or the most lowering one that keeps the scientists up at night today is the Atlantic marion overturning circulation.

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That transports heat around the Atlantic.

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And there's signs that slowing down.

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But we don't really have longstanding time series.

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So we don't quite know if that's just a fluctuation or is that the start of a collapse.

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And there's no good way of putting probabilities to that.

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So if you risk averse, you should say we should probably not play around with this.

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Because if it does collapse, we have a big problem.

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On the other hand, maybe it doesn't.

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And then what should we do with that?

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So what does economics have to say about this?

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What can we learn from that in economics?

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Well, we back in 2017, we started work that came out in 2021.

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And we did a literature survey.

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We thought, okay, what do economists think about these stepping points?

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And we discovered to our surprise that there were more than 50 papers that modeled or estimated some kind of tipping point.

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And economic impacts of climate change, which is very good.

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But then we realized many of these were at-hawks studies.

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And it sends that, you know, you have a study that's carefully modeled.

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And then you assume tipping points exist.

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So something bad happens.

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But that's something bad.

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Was not calibrated to anything in the natural sciences.

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So it's basically what economists thought might happen.

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It wasn't any quantitative calibration and then underlying those.

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So we thought these studies aren't really useful for getting policy relevant quantifications.

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But the good thing is, there were about 20 studies that did have some kind of geophysical realism.

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So if you think about the green and ice sheet, they would do a small ice sheet model,

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emulator model or an emulator model that would emulate the larger ice sheet models.

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And you couple that with an economic model and you have some kind of geophysical realism.

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You push on, on emissions, you push on temperature and something happens.

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And that's something is calibrated to the science fully.

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And there were about 21 studies, which are about, often they're about the same tipping points.

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About eight, nine tipping points, half in modeled and climate economics.

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Now the problem we have is that these studies come from different research teams.

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They come from different models.

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Even if they come from the same model, they run under different parameters for different scenarios.

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So there's no way to do a normal meta analysis,

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where you take the individual estimates and then you do something to some of them into one big estimate,

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which is what we wanted to do.

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Instead, we quickly realized that you really needed to produce what we call an integrated assessment model.

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It's a model that has a climate model and an economic model,

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where we can emulate each single one of these studies precisely.

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And then put them into the same framework into the same structure,

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so that we control the assumptions that go into that.

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So we can run that under consistent assumptions and the different assumptions,

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and see what the overall effect of all these tipping points is on economic impacts, estimates of climate change.

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The model we created is called the model for economic tipping point,

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the analysis meta, which is why I put this in the talk.

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It's freely available on GitHub.

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You can do whatever you want with it.

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And it belongs to something economists, a climate economist,

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called Social Cost Integrated Assessment Models.

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The bigger ones out there are the gift model by resources for the future

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that's been used to advise the US government,

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and the climate impact labs de-SIM model.

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I think it's dynamic, spatial, climate impacts models,

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I'm feeling like that.

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And both of these use are used to inform policy makers.

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So if someone in government wants to know what's the economic impact of climate change,

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in 2050, they probably use one of these two models.

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There are the ones out there, but that's the latest generation.

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It's modular, they tend to be quite good.

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It's been calibrated to recent climate signs,

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and they've had a features, but for an economist, it's not as interesting.

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So a work on software.

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So when we created meta in the paper in 2021, I'm very embarrassed,

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but it wasn't Excel.

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It was not just an Excel.

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It used to commercial plug-in, because we needed to run

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onto color simulations.

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And I'm very sorry.

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It's very embarrassing.

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We knew that at the time.

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It makes it very hard to check code.

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I mean, we had to put it on GitHub.

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But it makes it much harder to check code.

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It makes it much harder to access.

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You notice this plug-in?

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I think it costs a thousand euros to run it.

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I mean, it's...

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When we released it, the company contacted us and said,

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how are you using a plug-in?

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Would you like to do a webinar?

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So more people subscribe to our services.

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And we thought, no, we'd rather work on putting this into open software.

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But the reason we had it in Excel is because climate economists had worked

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with this software before.

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So it's just a legacy issue.

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You start.

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And then you have some skills in that.

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And you put that into the next version.

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But we made a choice to part it into open software.

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I should also say there is a person Dominic from the Fundman's

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program, I think, who just took the whole thing from Excel and

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ported it fully into Gams, which is incredible.

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I mean, Gams is not my preferred software.

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But he checked everything we did.

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And he found very few code errors.

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Of course, there always is something in there that was

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influential for the results in any way.

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So we are very thankful for him for checking all of that.

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But still we thought it was a lot of value in putting that into

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Julia.

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The reason we went for Julia and not Python, say it's because

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there is a big community of climate economists that live in

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Julia.

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And that's thanks to the Mimmy framework, or Mimmy JL.

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That's the effect or standard in climate economics.

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Now, it comes out of a Berkeley group.

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Mostly David, Anta's group.

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These are Randall's, Frank Garrick's, and many more people

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involved.

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And they're very, very helpful, very nice people.

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And the reason this started to be created is that there was

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some standardization in the United States as a result of a report

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by the National Academy of Sciences of the United States on

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how to best advice government on an economic impact of climate change.

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And Mimmy JL takes some of these recommendations, or is the basis

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to making some of these recommendations more readily usable.

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For example, this is a framework that allows you to build

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integrated assessment models in a way that they can talk to each other,

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in a way that you can swap out different modules and components.

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And I show you in a second what I mean with that.

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So this structure of meta is twofold.

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There's a climate model, and then they're economic impacts of climate change.

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For economists who might watch this, maybe this is an economist.

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It's not an optimization model.

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It's a model that runs scenarios.

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You feed the models scenarios to have emissions of CO2,

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of methane, and of other forces.

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And CO2 and methane are explicitly modeled.

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So what you do is you take emissions, you convert it into concentrations.

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Greenhouse gas is near atmosphere.

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You convert it into radiated forcing,

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that's to change in Earth's energy balance as a result of that concentration.

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And then you convert that radiated forcing change into global means of

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a temperature change.

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So you go from emissions to concentrations to radiated forcing to warming.

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Very standard stuff.

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So far, this is basically only climate science.

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And the neat thing is, thanks to the Mimmy framework,

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we can take the model that was created to standardize

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how economists and other emulator models use climate science

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to convert emissions to concentrations ready at the forcing.

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That's called fair.

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And people involved with the Mimmy framework built Mimmy fair,

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which is an exact version of fair, but in Mimmy.

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So instead of us having to re-program that,

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we can just take that off the shelf and put it into our model,

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which is great because it minimizes errors.

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It minimizes different climate modules,

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because the economists should agree on the climate science.

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We should disagree on the economics and check what that changed.

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So that's very good.

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So what we do is, as I said, we take emissions.

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We convert it into global means of a temperature change.

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But this is about tripping points.

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So how do the tripping points come in?

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Well, you can add the tripping points.

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You can switch them on or off.

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Each of these modules is independent.

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You can switch them on.

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You can switch them off.

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I discussed the permafrost current feedback before.

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So what happens when you switch that on is that

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global means surface temperature change gives you

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more permafrost melting.

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And then you have more trumps all in Siberia and other places in the north.

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It comes into contact with the surface air.

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And from organic decomposition mostly,

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to get fluxes of methane and to get fluxes of CO2.

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And they go back up there and generate additional warming estigo back through the climate model.

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The same happens.

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First one, dissociation of ocean emission hydrates.

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You can think of those as kind of submerged permafrost

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on the continental slopes and the oceans.

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But this is a very uncertain tipping point.

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So for the most part, we don't include it in the standard runs.

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We used to do that, but we decided not to do it anymore

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because the science has become less clear rather than more clear.

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And there are other ones, like the Amazon forest,

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rainforest, dive back, but no time to go through the mob.

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So as I said, we produce global means surface temperature change.

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This is the climate change variable.

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The drives and damages and impacts in this model.

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And so on the damage aside, we start with global means surface temperature change.

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And there's two damages channels, one from temperature.

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And one from sea level rise.

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Now you could say that's incomplete.

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There are might be other ones.

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You know there might be things like ocean acidification.

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Also it's a thing.

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But economists haven't been able to create

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mappings from global means surface temperature change to these outcomes.

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So that's working progress.

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I think these people working on biodiversity loss as well.

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And this is just a snapshot of very our economics.

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It's not us saying other channels are important.

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So keep this in mind.

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Missing channels usually means your underestimate damages of climate change.

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Because most of the time, these things tend to be negative.

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Not always, but any time is there.

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All right.

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So we take global means surface temperature change.

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We do something called statistical downscaling or pattern scaling.

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That gets us national means surface temperature change.

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And then we have damages at the national level that calibrated

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to a study in climate economics, which we think is still the best out there.

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Despite a lot of flaws.

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So the difficult part is in climate economics is to map geophysical change

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like temperature change to economic outcomes.

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We do this, and we think it's better than not doing it at all.

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But it has a lot of caveats.

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It's very uncertain.

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So keep that in mind.

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We don't think a precise quantification is possible at this point.

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But a quantification, we believe, is better than no quantification.

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Similarly, on the sea level rise damages channel.

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So you have without any tipping points, you have thermal expansion.

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So the oceans just become larger as the water heats, needs more space.

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And then you have melting of small ice caps and glaciers.

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That contributes to water and sea level rise.

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Now you can add tipping points to this.

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So if you have the disintegration of the large ice sheets in Greenland and in the Antarctic,

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these melt and give you additional sea level rise.

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Very simple.

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That's implemented here.

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That gets us total sea level rise.

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That gets us national sea level rise damages.

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Which in the end affect consumption per capita.

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That's the variable economists like to use to think about

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how much do people suffer or how much do people gain from climate change.

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Aimock, as I said before, is the Atlantic meridional overturning circulation that

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transports heat across the Atlantic.

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If that were to fully disappear, the climate of the Sun Europe would be very, very different.

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And not very nice.

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And then we have a tipping point that just affects India.

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So it's a bit outside of the channel.

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There is a change to India and some amongst the reliability.

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So these are all the tipping points we can model at the moment in climate economics.

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But this is by no means an exhaust of list of tipping points.

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It's also by no means us saying this is the right implementation.

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This is a metal study for the moment for the most part.

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We have taken what people in climate economics thought was the right thing to do.

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In some cases we change the calibration a little bit.

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But mostly this is trying to assess what climate economists believe.

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And you might disagree.

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You might say, well, maybe this is a component on aimot.

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It needs a different calibration.

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It needs a different implementation.

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And there is indeed work being done.

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So there is a really good work by two PhD students in Hamburg.

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They took the aimock module here and added a different channel and refined the calibration.

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Which improved the estimates.

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And they used the model for this purpose.

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So they forked the model.

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They changed this aimock component and they were in everything.

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With this change component, which I think is exactly why we wanted to put this on

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the first place.

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Okay.

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I think that's on the model structure and on what we have done now.

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I'll show you a few results before we get to the Q&A.

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So the first thing, the main result of this paper we published in 2021 was that if you look at damages that you come

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from a meeting one ton of CO2 today.

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We want to know what's the additional damage you get if they're tipping points in the climate system.

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So what if no percent of this ton on economists?

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So the social cost of carbon is the damage from a meeting one ton of CO2 today.

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You sum up all the damage over the lifetime of this ton of CO2.

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It might be near atmosphere for hundreds of years.

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And you take the present value of that in terms of how much it affects humans around the world.

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Very complex but basically think of this as damages from a meeting CO2, but just for one ton.

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Okay.

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But I didn't even tell you what the absolute level is.

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It's just an estimate of we estimate these damages without tipping points and with tipping points.

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And this graph what it tells you is what's the difference between the estimate with tipping points.

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And the estimate without tipping points and the different model configurations.

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That's why you have this distribution.

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There's a lot of parameters to some scenarios we run there.

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And so a positive number means that tipping points run has a higher damage than the non-tipping points run.

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Okay.

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And so you can see that there's basically no run in which tipping points help us.

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They almost always make damages worse.

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Our best estimate is about 25% increase in damages.

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But we think this is quite conservative.

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So we try to be under conservative side of things.

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If you take the full uncertainty you get something like a 40% increase in damages from having tipping points.

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From considering that they exist.

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And we calculate about a 0.1 probability of them doubling.

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So you just sum up everything here.

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Or a 0.02 probability of troubling.

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So it's more than 200%.

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That's the first result.

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So they make damages worse and the way that we can measure.

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The second is they're almost worse for almost everyone around the world.

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So no good news here.

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And this is work not by us, but again by the people who've used our model.

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And they used it to quantify future impacts and stock indices.

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And they find that climate change.

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They create a stock market returns and tipping points worse and that.

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And lastly that's the paper we're working on now.

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It's its submission at the moment where we asked okay.

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What can we learn from tipping points in terms of climate policy?

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So if we do ambitious climate policy does this decrease the likelihood of tipping points occurring.

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And we've done a paper off on global methane action.

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So cutting methane around the world.

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And quickly does that change tipping points?

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And indeed we find that if you do ambitious a methane action.

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You decrease tipping point intensity across all the tipping points.

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Something between depending on where you are and 2050 between two and 10%.

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Depending on which tipping points you're looking at.

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That's unpublished.

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So numbers might still change, but roughly that's where we are.

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Okay, let me conclude.

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So we've made quite a lot of progress in economics and in on how we model tipping points.

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There's people who do different work in this.

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It's starting to be integrated in conversations with US authorities.

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So they're taking part of meta at the moment to put that into the other model.

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Stay using.

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And we think quantification is useful because people do do benefit cost analysis.

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And if you don't quantify tipping points, the estimate that's used is zero.

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Other people widely disagree to say, well, if you're trying to do a partial quantification.

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Because you might not have the ocean acidification or you might underestimate worst case scenarios.

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That's dangerous because you make it seem like not such a big problem and it's really a gigantic problem.

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That's a fair criticism.

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So you're in this tension.

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Should we quantify?

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Should we not quantify?

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I'm large.

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And certain she's remain in particular about how economists think about impacts of certain physical change.

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And what has happened recently is that we have improved calibration of some of these tipping points.

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Likely hoots.

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The Antarctic model is a recent paper by Macau Frisam and the son of his PhD students.

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Sorry if one of his master students I think.

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We've recorded this thing in Julia.

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So it's accessible to community now.

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And the different things you could do if you interested.

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First you just fork it and run it yourself under different scenarios.

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You write your own research paper.

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That's perfectly fine.

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You could try to maintain or contribute or improve calibration of some of the components or add a new component.

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Or you could even change other parts of the model.

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You could add different damages functions.

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So you want to study not national consumption per capita,

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but maybe financial stability or something like that.

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So you could produce a component that does that.

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So if you're interested, do reject.

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Very happy to chat.

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And you find everything on GitHub.

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Thanks.

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Thank you.

