[Notes] Could climate change make Earth uninhabitable for humans?

16/​1/​20. Minor edit to re­move lin­ear ex­trap­o­la­tion graph, and com­ment added to ac­knowl­edge the un­cer­tainty, start­ing “We don’t know...”.

Last year I wrote a fo­rum post ask­ing whether cli­mate change de­served more at­ten­tion within effec­tive al­tru­ism. It’s been great to see the re­cent de­vel­op­ments, in­clud­ing Hauke’s com­par­i­son with global dev, Will’s com­ments, the in­ter­est­ing re­sult that cli­mate change is now #2 most pop­u­lar cause area in the EA sur­vey, and the an­swers to this ques­tion on what EAs in­ter­ested in cli­mate change should do. I’ve re­ally en­joyed this dis­cus­sion!

At EA Global in Lon­don 2019, NielBow­er­man gave a talk and Q&A on the re­la­tion­ship be­tween cli­mate change, longter­mism, and effec­tive al­tru­ism.

Niel stud­ied for his PhD in Physics on the topic of ‘Emis­sion tar­gets for avoid­ing dan­ger­ous cli­mate change’ from Oxford Univer­sity. In the US 2008 pres­i­den­tial elec­tion Niel was a mem­ber of Pres­i­dent Obama’s En­ergy and En­vi­ron­ment Policy Team. Niel was pre­vi­ously the Direc­tor of the Cen­tre for Effec­tive Altru­ism, and is now an AI policy spe­cial­ist at 80,000 Hours.

I thought Niel’s talk was a valuable re­source for EAs with a longter­mist fo­cus think­ing about the im­pli­ca­tions of cli­mate change. I’ve sum­marised the key points, in­clud­ing the tran­script with images, and pro­vided links to the sources refer­enced through­out, along with some fur­ther re­sources at the end.

Key points from Niel’s talk

Im­pacts of cli­mate change

  • Cli­mate change is already im­pact­ing a num­ber of ar­eas on Earth, and has already caused hun­dreds of thou­sands of pre­ma­ture deaths (Robine et al, 2008), and this is likely to in­crease to tens or hun­dreds of mil­lions over fu­ture decades (WHO, 2014), and we have a solid case for ad­dress­ing this prob­lem today

  • We can think about the con­tri­bu­tion of cli­mate change to ex­is­ten­tial risk through three differ­ent routes: through po­ten­tially mak­ing earth un­in­hab­it­able for hu­mans; through ex­ac­er­bat­ing con­flict; and through in­creas­ing the risk of so­cial collapse

  • The larger con­tri­bu­tions to ex­is­ten­tial risk are prob­a­bly through the sec­ond and third routes, which are strongly de­serv­ing of fur­ther re­search in­cor­po­rat­ing sys­tems theory

  • We can also iden­tify a highly un­likely but not im­pos­si­ble causal chain where ex­treme cli­mate change could make Earth un­in­hab­it­able for humans

Could cli­mate change make Earth un­in­hab­it­able for hu­mans?

  • We can think about the zone of hab­it­a­bil­ity to be a func­tion of the so­cial and tech­nolog­i­cal ca­pa­bil­ities of fu­ture hu­mans, and Earth’s en­vi­ron­ment.

  • If things con­tinue as they are, it is pos­si­ble that tech­nolog­i­cal de­vel­op­ment will mean there is still a zone of hab­it­a­bil­ity, but it is hard to make long-term pre­dic­tions. Th­ese are con­tested and un­cer­tain ar­eas, de­serv­ing of fur­ther study.

  • We have far more fos­sil fuels than we can safely burn. We have burnt around 500 billion tonnes of CO2 so far, and we should aim to keep our to­tal emis­sions within 1 trillion tonnes to avoid dan­ger­ous lev­els of warm­ing of over 1.5C to 2C of warm­ing. If we burned the to­tal amount of eco­nom­i­cally vi­able fos­sil fuel, a very crude lin­ear model would roughly im­ply 20-30C of to­tal warm­ing.

  • Sev­eral re­cent pa­pers have looked at tip­ping points, such as through changes to cloud cover and through in­creas­ing mois­ture in the air, and have put for­ward claims that there are plau­si­ble mechanisms wor­thy of fur­ther in­ves­ti­ga­tion that could lead to rapid and dras­tic run­away cli­mate change

Effec­tive al­tru­ism, cli­mate change, and ex­is­ten­tial risk

  • The biggest con­tri­bu­tions of cli­mate change to ex­is­ten­tial risk prob­a­bly come through the routes of ex­ac­er­bat­ing con­flict and po­ten­tially in­creas­ing the risk of so­cial col­lapse

  • There is suffi­cient ev­i­dence to en­ter­tain the hy­poth­e­sis that cli­mate change could ren­der earth un­in­hab­it­able for hu­mans in the fu­ture. It also seems pos­si­ble that cli­mate change could limit of hu­man­ity’s po­ten­tial in other ways

  • It might now be a good time for some EAs to re­search cli­mate mod­el­ling and un­cer­tain­ties; fu­ture tech­nolog­i­cal de­vel­op­ment, in­clud­ing food and wa­ter; ecosys­tem and bio­di­ver­sity im­por­tance; plane­tary sys­tems and bound­aries; civil­i­sa­tion col­lapse and re­cov­ery; and pos­si­ble as­so­ci­a­tions be­tween cli­mate change and other ex­is­ten­tial risk factors

Selected quotes

This tran­script was pro­duced by the CEA team, and the full text, along with other EA Global talks are available through effec­tivealtru­ism.org. I per­son­ally added the images, links, and refer­ences, and the sum­mary above. With thanks to Aaron Gertler, JP Ad­di­son, and Niel Bow­er­man.

Introduction

Niel: We already know that cli­mate change is caus­ing in the bal­l­park of hun­dreds of thou­sands of pre­ma­ture deaths (Robine et al, 2008). This is likely to in­crease to as many as hun­dreds of mil­lions over the com­ing decades (WHO, 2014). We have a sound eco­nomic case for ad­dress­ing cli­mate change, and it is harm­ing the poor­est peo­ple the most. And yet these are also the peo­ple that have least con­tributed to cli­mate change, cre­at­ing a cli­mate jus­tice is­sue.

Re­la­tion­ship be­tween cli­mate change and ex­is­ten­tial risk

Niel: Now, if I had to guess, I would guess that the sec­ond and third risks here — the con­tri­bu­tion to other ex­is­ten­tial risks (Mach et al, 2019) and to so­cietal col­lapse — are prob­a­bly larger than the first, but they’re also less tractable [for me] to study. And so I’m go­ing to do the thing that aca­demics of­ten do: ig­nore the big im­por­tant things and ad­dress the thing that I know about as a cli­mate physi­cist.

So­cial collapse

Niel: [This would be] some­thing in the vicinity of a com­plete break­down of poli­ti­cal in­sti­tu­tions, a col­lapse of in­ter­na­tional trade, and re­ally a break­down of the fabric of so­ciety. To make this re­ally con­crete, I’m talk­ing about a re­duc­tion in global GDP of more than 80% in less than a decade. This would be dras­tic and very dra­matic, but I have no idea how likely it is to oc­cur. I also have no idea how likely it is that so­cietal col­lapse would con­tribute to ex­is­ten­tial risk.

His­tor­i­cal evidence

Niel pre­sents three ex­am­ples, which provide some ev­i­dence about hu­man adapt­abil­ity within the con­text of tem­per­a­ture change, but which also all have limi­ta­tions that should make us cau­tious about mak­ing com­par­i­sons.

First, the Pa­le­ocene-Eocene Ther­mal Max­i­mum, which hap­pened about 55 and a half mil­lion years ago.

Niel: [This] saw warm­ing of about 12 de­grees above what we cur­rently see to­day, and yet we didn’t see a mass ex­tinc­tion… this may be some ev­i­dence that dra­matic warm­ing could be hab­it­able for hu­mans, but the rate of warm­ing was re­ally a lot slower than it is to­day. So it’s not a perfect anal­ogy.

Next, the ex­am­ple of the Younger Dryas pe­riod, about 11,000 years ago, gives us some ev­i­dence.

Niel: Snow and dust ac­cu­mu­la­tion sam­ples tell us that the earth warmed by about seven de­grees in cer­tain parts in less than a decade. And hu­man­ity also sur­vived that, though it was mov­ing from a much colder cli­mate to the cli­mate we en­joy to­day. So again, not a perfect anal­ogy, but it’s maybe some ev­i­dence that hu­man­ity is able to sur­vive rapid rates of change.

Fi­nally, there are the range of con­di­tions that hu­mans are able to live in to­day.

Niel: Hu­mans thrive in cli­mates as di­verse as Bahrain and St. Peters­burg — cli­mates that vary in av­er­age over 16 de­grees centi­grade. So this is maybe some ev­i­dence that even [on a warmer planet], pro­vided that ev­ery­thing else didn’t fall apart around us, we would be able to sur­vive in a range of differ­ent cli­mates pro­vided that the en­vi­ron­ment and ecosys­tems adapted. But again, re­ally not a perfect anal­ogy be­cause these are static con­di­tions as op­posed to mov­ing ones.

Is there a causal chain lead­ing to po­ten­tial hu­man ex­tinc­tion?

Niel: Dur­ing my PhD, I would talk about this ques­tion a fair bit with my old su­per­vi­sor. He would always say that in or­der to ad­dress cli­mate change as a con­tri­bu­tion to X-risk, you need a story you can tell about what events oc­cur that get us from now to a point where earth is un­in­hab­it­able or where hu­mans have gone ex­tinct. And so what I want to do for the rest of this talk is to try and sketch out a story that I find [vaguely] plau­si­ble for how we could get there. I’m not say­ing this is likely. I’m not say­ing this is go­ing to hap­pen. I think this is in­cred­ibly un­likely. But the challenge I gave my­self was: could I tell a story where we get to a world like that? So that’s what I’m go­ing to do here.

Long-range po­ten­tial of global car­bon emissions

In the talk, Niel referred to this graph (Figure SPM10 from the IPCC AR5). The chart shows cu­mu­la­tive to­tal an­thro­pogenic CO2 emis­sions (i.e. the to­tal car­bon re­leased into the at­mo­sphere by hu­man ac­tivi­ties) against sur­face mean av­er­age global tem­per­a­ture change. Note that this ex­cludes po­ten­tial tip­ping points, is av­er­age tem­per­a­ture change, and the im­pacts of cli­mate change on weather vari­abil­ity in­crease non-lin­early.

Niel: For con­text, in­ter­na­tional cli­mate ne­go­ti­a­tions are aimed at keep­ing us be­low two de­grees. Five de­grees would be a dra­mat­i­cally and dras­ti­cally differ­ent world from the one that we en­joy to­day, with mass loss of species, [many risky] tip­ping points…

The world was warmed by around 1.1C so far, and there are dis­cus­sions in the IPCC on the com­par­i­son be­tween 1.5C and 2C of warm­ing. The Cli­mate Ac­tion Tracker gives a baseline of 4.1 to 4.8C by 2100, and 2.8 to 3.2C, as­sum­ing that cur­rent poli­cies are im­ple­mented.

Niel: To­day, we have burnt about half a trillion tons of car­bon diox­ide; by the year 2100, if we carry on burn­ing CO2 un­der busi­ness as usual sce­nar­ios, we’ll get up to about 2 trillion tons of car­bon burnt. And that’s burn­ing the amount of car­bon that we would un­der busi­ness as usual. What if we some­how got re­ally car­bon-hun­gry and [even­tu­ally] ended up burn­ing all the po­ten­tially eco­nom­i­cally vi­able car­bon [in fos­sil fuel re­serves]?

Niel then ex­tends the range of the chart above, from 0-2500 TtC, to 0-9,500 TtC, to show the to­tal po­ten­tial eco­nom­i­cally vi­able fos­sil fuel re­sources that hu­man­ity could burn.

We don’t know ex­actly how large global fos­sil fuel re­serves are, and we don’t know how much burn­ing all that fos­sil fuel would warm the world. But one pa­per high­lighted by Linch in the com­ments of this post sug­gests 10 or even 12 de­grees of warm­ing, which would be a very differ­ent world in­deed from the world that we live in. If cli­mate and car­bon cy­cle feed­backs are worse than ex­pected, then it could warm even fur­ther.

Niel: There’s a bunch of fac­tors that are go­ing to go into this. But this is more to prime your in­tu­itions that our burn­ing that much fuel would prob­a­bly lead to a very bad world.

Cloud-based tip­ping points

Ru­n­away green­house effects work as fol­lows: in­creased ther­mal forc­ing heats up the ocean, which leads to leads to more evap­o­ra­tion and wa­ter va­por in the at­mo­sphere, which traps ther­mal ra­di­a­tion, and in turn heats up the ocean. Is this fea­si­ble on Earth?

Niel: On Earth, if this were to oc­cur in a very im­pos­si­ble worst-case sce­nario, you could imag­ine boiling all the oceans or some­thing like this if the effect didn’t stop. Peo­ple have looked into this and they’ve said, “Ac­tu­ally, this isn’t re­ally very plau­si­ble. You’d need a lot more in­com­ing so­lar ra­di­a­tion than is ever re­ally go­ing to oc­cur, be­cause we know how the Earth or­bits the sun and we know the range of so­lar ra­di­a­tion that tends to reach Earth and we know this is re­ally not go­ing to hap­pen any­time soon.” I think we can rule out this run­away green­house effect. But is there some­thing like this that could hap­pen?

Re­cent de­vel­op­ments in cli­mate modelling

Niel refers to a pa­per by Popp et al (2016), Tran­si­tion to a Moist Green­house with CO2 and so­lar forc­ing, look­ing at cloud feed­back loops.

Niel: A very sim­ple cli­mate model with a strange effect: cloud feed­back kicked the tem­per­a­tures up to sta­bi­liz­ing at about 20 de­grees [cel­sius above cur­rent tem­per­a­tures]. So you ba­si­cally saw this run­away af­fect that I’ve been talk­ing about. Popp et al.’s model wasn’t very plau­si­ble; it was in­cred­ibly sim­plis­tic and it made enough as­sump­tions that no one re­ally be­lieved it. But it started to get peo­ple scratch­ing their heads and won­der­ing: is this a thing that could hap­pen? Is there a fea­si­ble mechanism here?

Niel also refers to a pa­per by Sch­nei­der et al (2019), Pos­si­ble cli­mate tran­si­tions from breakup of stra­tocu­mu­lus decks un­der green­house warm­ing, also look­ing at cloud-based feed­back loops.

Niel: It uses an­other sim­plis­tic model of the at­mo­sphere. And what hap­pens in this model is they triple car­bon diox­ide con­cen­tra­tion (the amount of CO2 in the at­mo­sphere). And what they find is that the stra­tocu­mu­lus cloud layer in the trop­ics would burn away. Clouds have this lovely white fluffy prop­erty that makes them re­ally re­flec­tive to in­com­ing sun­light. And so that stops the Earth from warm­ing too much. But when the clouds dis­ap­pear, the dark ocean un­der­neath of them ab­sorbs a lot of sun­light. And that in turn heats up the ocean.… you see eight ex­tra de­grees of warm­ing on top of the tripling of CO2 con­cen­tra­tions that hap­pened sim­ply from what they did in the model.

How­ever, this is has had a range of re­ac­tions from cli­mate sci­en­tists.

Niel: This model, [like Popp et al (2016)], had a mixed re­cep­tion from sci­en­tists. Some peo­ple said, “Hmm, that’s re­ally in­ter­est­ing.” Others said, “No, it’s a sim­ple column model. It’s not go­ing to ap­ply globally. We shouldn’t kid our­selves enough about this.” But I think it is fair to say that we now at least have a phys­i­cally plau­si­ble mechanism here. Some­thing worth in­ves­ti­gat­ing fur­ther.

Fi­nally, there is an open ques­tion on the link be­tween dras­tic tem­per­a­ture change and un­in­hab­it­a­bil­ity.

Niel: We don’t know if this is go­ing to be a big deal or a small deal, but at least there’s some ev­i­dence that maybe this is the thing we should be wor­ry­ing about. And so what I’ve been do­ing here is scratch­ing my head and ask­ing my­self: can I tell a plau­si­ble story about how earth be­comes un­in­hab­it­able due to cli­mate change? Th­ese are the two main pillars that I’m look­ing at. How does that lead to un­in­hab­it­a­bil­ity? Well, mainly I’m go­ing to ask you to use your imag­i­na­tion re­gard­ing a world with 20 to 30 de­grees [centi­grade] of warm­ing.

Summary

Niel con­cludes by sum­maris­ing the points raised, that cli­mate change con­tributes to ex­is­ten­tial risk through the three routes de­scribed above, and that the sec­ond and third are prob­a­bly the larger terms.

Niel: We then saw what it would look like to burn a lot of fos­sil fuels, and how that could lead us to a re­ally warm cli­mate. And then we hy­poth­e­sized and spit­balled about cloud-based tip­ping points, and how maybe that’s a thing that we should pay at­ten­tion to. Maybe, I don’t know. And to­gether, these things ges­ture in the di­rec­tion of a story of how Earth might be­come un­in­hab­it­able.

There are some sug­ges­tions for fur­ther re­search.

Niel: I’d love for peo­ple to go away and think about each of these differ­ent parts — un­in­hab­it­a­bil­ity, con­tri­bu­tion to other X-risks, and so­cietal col­lapse — and maybe in­ves­ti­gate some of these un­cer­tain­ties, with a par­tic­u­lar fo­cus on think­ing about the chance of cli­mate change re­ally con­tribut­ing to hu­man­ity go­ing ex­tinct al­to­gether.

Q&A

Epistemic sta­tus of cli­mate change science

Niel Bow­er­man: We know for cer­tain that the world is warm­ing, we know for cer­tain that car­bon diox­ide con­cen­tra­tions are go­ing up, and there’s a lot of con­sen­sus on the phys­i­cal mechanisms whereby those car­bon diox­ide con­cen­tra­tions would lead to warmer tem­per­a­tures. I think that 97% of sci­en­tists agree that cli­mate change is most likely caused by hu­mans.
When we zoom out and talk about cli­mate change as a con­tri­bu­tion to ex­is­ten­tial risk, now we’re just con­duct­ing pure spec­u­la­tion.… This is more of a prompt to en­courage peo­ple to go and work on this ques­tion a bit more and try and pin down some of these an­swers. Be­cause I think that other than maybe my first slide, ev­ery­thing I’ve said to­day is largely spec­u­la­tion — but it’s spec­u­la­tion try­ing to get at the ques­tion of where this chance of ex­tinc­tion might lie, which is very im­por­tant from a longter­mist per­spec­tive. If we come at the prob­lem from this per­spec­tive, then I think there are a bunch of re­ally in­ter­est­ing ques­tions to ask that I’d love to see the broader com­mu­nity ad­dress­ing.

Sever­ity of cli­mate change

Nathan: Stick­ing with more main­line ques­tions just for a sec­ond: Some of your ear­lier com­ments to­ward the be­gin­ning of the talk sug­gest that your out­look would be: “Hu­man­ity will be pretty adapt­able. Yes, there will be costs to cli­mate change, but in the ab­sence of a story where other things hap­pen as knock-on effects, the main­line ex­pec­ta­tion is not so bad.” Is that a fair read­ing of your view?
Niel: Yeah. It de­pends on what you mean by “not so bad”. I ex­pect tens of mil­lions, maybe even hun­dreds of mil­lions of peo­ple to die pre­ma­turely be­cause of cli­mate change. And that’s re­ally bad. It’s similar on a vague scale of bad­ness to things like the num­ber of peo­ple that die in traf­fic ac­ci­dents. So when you look at cli­mate change [hav­ing this level of im­pact] over many decades, it’s very much a big prob­lem.
And then, from a longter­mist per­spec­tive, my ques­tion is: “Where does it rank rel­a­tive to the other ex­is­ten­tial risks?” If I had to guess, I would guess that it’s maybe lower down on the list of things likely to con­tribute the most to ex­is­ten­tial risks than, say, AI or biorisk. I’d put it more among the cluster of things like nu­clear weapons and geo­eng­ineer­ing.
For me, that’s still very much a thing de­serv­ing of at­ten­tion and worth work­ing on, and whether it’s re­ally bad de­pends a lot on your defi­ni­tion of “re­ally bad”.

Ur­gency of tack­ling cli­mate change

Niel: I think we should be cut­ting car­bon emis­sions much, much more dra­mat­i­cally than we are right now. I think we should be go­ing to net zero emis­sions. I think there’s a rel­a­tively solid eco­nomic case. So this is a good idea and [will give us] a pos­i­tive re­turn on our in­vest­ment. My guess is that we should be keep­ing the to­tal amount of car­bon that hu­man­ity ad­mits to less than a trillion tons, which would hope­fully keep us at less than two de­grees of warm­ing… [we need to make] pretty dra­matic and quick re­duc­tions.

Methane clathrates

Nathan: Is there a story about methane de­posit re­lease that would crack your set of pos­si­ble nar­ra­tives here? I don’t know a ton about it, but it’s sup­posed to be the most pow­er­ful green­house gas. There’s a lot of it sit­ting at the ocean floor and in the Tun­dra.
Niel: Yeah, methane clathrates. This is one of the things that I’ve always been a lit­tle wor­ried about. The thing about methane clathrates is that they are very slow to bub­ble up. So in most of the plau­si­ble sce­nar­ios that we see, un­less you go into the sorts of crazy sce­nar­ios that I was talk­ing about, you end up see­ing methane clathrates not emerg­ing for some­thing like hun­dreds or maybe even a thou­sand years af­ter you see your ini­tial warm­ing.
If we got the cli­mate sci­ence wrong, or if the bot­tom of the ocean heated up way faster than we ex­pected, then you could see [clathrate emer­gence] hap­pen­ing faster. But the ocean doesn’t re­ally turn much in the ver­ti­cal di­rec­tion. Al­most all the move­ment in the ocean is hori­zon­tal. So this just makes it very hard for heat to prop­a­gate down­wards. And that means it’s go­ing to take a lit­tle while for those methane clathrates to heat up.

Po­ten­tial fu­ture re­search areas

Nathan: Okay, cool. That’s very in­ter­est­ing. So you’ve cov­ered this one a lit­tle bit, but: how im­por­tant is it for peo­ple to work on this? I think your sug­ges­tion would be that ex­plor­ing the cor­ner cases or the far-out cases is re­ally where the high­est value work is to be done.
Niel: That’d be my guess. Yeah. I’m ex­cited to see peo­ple ex­plor­ing so­cietal col­lapse like the peo­ple at Cam­bridge are do­ing. [More peo­ple should be] look­ing at some of these worst-case sce­nar­ios and [how fea­si­ble they are]. And also, geo­eng­ineer­ing is a gi­ant ques­tion mark in my head. I don’t re­ally un­der­stand how that in­ter­acts with ex­is­ten­tial risk [from so­cietal col­lapse]. But my guess is that peo­ple should be figur­ing that out, too.
Nathan: You may want to pass on this be­cause we don’t have a ton of time, but how does this 20-de­gree warm­ing trans­late to true un­in­hab­it­a­bil­ity?
Niel: This part I didn’t re­ally know, I would again just be spit­bal­ling here, but when you look at agri­cul­tural yields, they start drop­ping off a cliff at some point. And then if we move agri­cul­tural zones up into the poles, you end up with very differ­ent grow­ing sea­sons than the ones that they were built for. We don’t have a great sense of how that would work. But the most likely story you could tell is some­thing in­volv­ing so­cietal col­lapse, and the break­down of so­ciety hav­ing a bunch of other bad knock-on effects.

Rel­a­tive im­por­tance of cli­mate change for effec­tive altruism

Nathan: How have your views changed about all of this over time?
Niel: My guess is that my views on cli­mate change have stayed rel­a­tively sta­ble over time, and my views on the im­por­tance of work­ing on AI have gone up. For me, cli­mate change still seems just as im­por­tant as when I worked on it as my full-time job. And now that there’s a ton of folks flood­ing into AI policy and AI safety and things like that, my guess is that it’s time for EAs to re­visit work­ing on cli­mate change tail risks and nu­clear weapons and geo­eng­ineer­ing and some of the other prob­lems in this space.

Car­bon tax and other interventions

Nathan: How do you think about a more con­ven­tional car­bon tax, ver­sus a car­bon cap­ture (which might fall un­der geo­eng­ineer­ing, de­pend­ing on the strat­egy). What do you think we should be pur­su­ing first to re­duce car­bon?
Niel: On the im­me­di­ate ques­tion of car­bon tax­a­tion ver­sus car­bon cap­ture: car­bon cap­ture is an un­proven, very ex­pen­sive tech­nol­ogy, and car­bon tax­a­tion is a very proven but some­what poli­ti­cally in­fea­si­ble mechanism. I’d be way more ex­cited about a car­bon tax. A car­bon tax of the right size, if im­ple­mented across the world, could go a re­ally long way to helping solve cli­mate change. I don’t know about the poli­ti­cal fea­si­bil­ity of this, but if it were im­ple­mented, it would do a lot of good. Car­bon cap­ture, I think, is go­ing to be very ex­pen­sive and is a long way off, but it’s hope­fully part of the solu­tion in the fu­ture.

Fur­ther reading

Avin, Sha­har, Bon­nie C. Win­tle, Julius Weitzdörfer, Seán S. Ó hÉigeartaigh, William J. Suther­land, and Martin J. Rees. ‘Clas­sify­ing global catas­trophic risks’; Fu­tures 102 (2018): 20-26.

Robine, J., et al. ‘Death toll ex­ceeded 70,000 in Europe dur­ing the sum­mer of 2003’, Com­pes Ren­dus Biolo­gies (2008)

WHO, ‘Quan­ti­ta­tive risk as­sess­ment of the effects of cli­mate change on se­lected causes of death’, 2030s and 2050s’ (2014)

Di­a­mond, J. ‘Why so­cieties col­lapse’, TED talk (2008), see Col­lapse and Upheaval.

Bostrom, N., ‘Ex­is­ten­tial Risks’, Jour­nal of Evolu­tion and Tech­nol­ogy (2001)

Mach, et al. “Cli­mate change as a risk fac­tor for armed con­flict” Na­ture (2019)

Beard, S., et al. “Assess cli­mate change’s con­tri­bu­tion to ex­is­ten­tial risk” in draft(2019), see https://​​www.cser.ac.uk/​​team/​​simon-beard/​​ and ‘The Cli­mate Cri­sis as an ex­is­ten­tial threat’, Fu­ture of Life In­sti­tute Pod­cast, 2019.

Kemp, L., et al. “Cli­mate end game” in draft, see https://​​www.cser.ac.uk/​​team/​​luke-kemp/​​ and see also

Steffen et al. (2018) ‘Tra­jec­to­ries of the Earth Sys­tem in the An­thro­pocene’

King et al. (2015) ’Cli­mate Change: A Risk Assess­ment’Sluijs, A., et al. ‘Sub­trop­i­cal Arc­tic Ocean tem­per­a­tures dur­ing the PETM’ Na­ture (2006)

Raup, D. & Sep­koski, J. ‘Mass ex­tinc­tions in the marine fos­sil record’, Science (1982)

Alley, R. et al. ‘Abrupt in­crease in the Green­land snow ac­cu­mu­la­tion at the end of the Younger Dryas event’, Na­ture (1993)

Stocker, et al. Sum­mary for Poli­cy­mak­ers of IPCC Work­ing Group 1 Fifth Assess­ment Re­port. Figure SPM.10, doc here

Matthews, D. et al. ‘Fo­cus on cu­mu­la­tive emis­sions, global car­bon bud­gets and the im­pli­ca­tions for cli­mate miti­ga­tion tar­gets’ En­vi­ron­men­tal Re­search Let­ters (2018)

Bruck­ner, et al. Ch 7 of IPCC Work­ing Group 3 Fifth Assess­ment Re­port. See table 7-2, shown be­low. (Fos­sil fuel re­serves + re­source (po­ten­tially eco­nom­i­cally vi­able to be ex­tracted in the fu­ture) are es­ti­mated at 9.5-14.5 TtC.)

Sch­nei­der, T., Kaul, C., & Pres­sel, K. ‘Pos­si­ble cli­mate tran­si­tions from breakup of stra­tocu­mu­lus decks un­der green­house warm­ing’ Na­ture Geo­science (2019)

Popp, M., Sch­midt, H., & Marotzke, J. ‘Tran­si­tion to moist green­house with CO2 and so­lar forc­ing’ Na­ture Com­mu­ni­ca­tions (2016)

Gold­blatt, C. & Wat­son, A. ‘The run­away green­house: im­pli­ca­tions for fu­ture cli­mate change, geo­eng­ineer­ing and plane­tary at­mo­spheres’ Phil. Trans. Roy. Soc. A (2012)

Po­ten­tial rele­vant organisations

The fol­low­ing or­gani­sa­tions, among many oth­ers, are re­search­ing ex­treme cli­mate change, civil­i­sa­tion col­lapse, and ex­is­ten­tial risk:

Cen­tre for the Study of Ex­is­ten­tial Risk

ALLFED

Global Pri­ori­ties Institute

The Forethought Foun­da­tion

The Fu­ture of Hu­man­ity Institute

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