But RCPs

Just as I thought I was out the ClimateBall Gods pull me back in. The “but RCP” flythe club got the best of me. For the time lost I found talking points for my Bingo. More on this project in due time. Here are the main ones:

  1. 8.5 is bollocks
  2. 8.5 is not BAU
  3. The IPCC calls 8.5 “BAU”
  4. The IPCC uses it as such
  5. Centuries or millennia separate 8.5 and when we might see 8.5W/m2
  6. We never were on an 8.5 path
  7. Only using 8.5 is bad science
  8. Without 8.5, there is no huge alarm
  9. Don’t present a < 1% scenario like the IPCC does
  10. It is not about blame

RCP stands for Representative Concentration Pathway. The acronym is usually followed with the numbers 2.6, 4.5, 6, or 8.5. Stating numbers will suffice in what follows. BAU stands for business-as-usual and IPCC for Intergovernmental Panel on Climate Change.

Now, for the experimental part of the post. One short paragraph for each talking point. I defer to ClimateBall authorities as much as I can. With your feedback I will revise the responses. I will also add secondary talking points in the comments.

One important caveat. “But RCPs” should not deflect from the main takeaway: global warming will continue until CO2 emissions reach zero. We will need to adapt to warming levels of 1.5C, likely more [Glen]. The answers start with a variation on the main take away, parry the contrarian deflection, correct the misleading information or the falsity, and repeat the main takeaway. A truth sandwich if you please, with a relevant salad, a clarifying soup, and a call to action dessert.


§1. It is common knowledge that getting to 8.5 is unlikely . It has been introduced to depict a relatively conservative business as usual case with low income, high population and high energy demand due to only modest improvements in energy intensity [Keywan & alii]. Things changed since 2011, and some might suggest that 3C is the new BAU. In effect, every dollar spent on mitigation now makes RCP8.5 emissions even more unlikely [Justin]. Scenario selection is not so important for impacts in the next decade or two [Glen]. If you don’t like 8.5, add 10 years [Gernot]. If you think that 8.5 is bollocks, well, that’s your unarticulated opinion.

§2. While 8.5 emissions are not BAU, the 8.5 concentration pathway can still arise from a lower emissions scenario if feedbacks are strong [Richard]. We also need to distinguish between emissions pathways and warming outcomes, which depend on emissions, carbon cycle feedbacks, and climate sensitivity [Zeke]. Without getting to net zero a radiative forcing of 8.5W/m2 will happen eventually [SteveE].

§3. It’s also important to call them “concentration pathways” as they’re named since over a decade ago, and to realise that over a decade ago it was already the extreme case with also bio-physical assumptions that differ from the other three RCPs. They never were “business as usual” [Joris]. Most climate modelling studies that use RCP8.5 are using the scenario in the form defined in terms of concentrations (the amount of CO2 & other GHGs bulding up in the atmosphere), not the form defined in terms of emissions (the amount humans are releasing) [Richard]. While the public and politicians at large discuss if and how we can get on a 2.6, to talk semantics about if we should rename “BAU” may be well intended, but is absurd [August].

§4. It would be incorrect to claim that the IPCC used 8.5 as BAU. First, 8.5 has a much faster rise in emissions than 1970-2010 [Richard]. Second, AR5 explicitly said “the term BAU has fallen out of favour because the idea of business as usual in century-long socio-economic projections is hard to fathom” [AT]. Scenarios without additional efforts to constrain emissions (’baseline scenarios’) lead to pathways ranging between 6.0 and 8.5 [IPCC]. Even the family of SSP5 baseline scenarios don’t all end up at 8.5 w/m^2 [Zeke].

§5. The idea that we might see 8.5W/m2 in centuries or millennia is bollocks. The remaining carbon budget in SSP5-8.5 is 7700 GtCO2, so 192 years of current emissions. If emissions increase, we reach it faster. Hence why it’s super important countries meet their Paris agreement commitments. For instance, in the high-end of the current policies estimates you’d get to 8.5 w/m^2 concentrations by 2150, assuming constant emissions of ~65 GtCO2 after 2100 [Zeke]. Its all based on MAGICC model runs. The 8.5 w/m^2 scenario being used in CMIP6 is the SSP5 REMIND Baseline [Zeke].

§6. While we may dispute the likeliness of getting to 8.5W/m2 in 2100, we are indeed in an 8.5 path [Kathryn]. Despite its long term aggressiveness, to date our cumulative emissions are closest to RCP 8.5 [Bob]:

§7. RCP8.5 is popular because trying it first is the best use of finite computational resources. If an effect can’t be found in 8.5, then there’s no point in trying the lower RCPs. However, if 2.6 is tried first, and there’s no effect, it says nothing about the higher RCPs [PaulW]. Anyone saying that 8.5 is a standalone forecast is at best in error; those who know the facts should be held to a higher standard [Bill].

§8. The fact remains that 5C is the baseline warming [Zeke]. Five degrees less is what separates us from the ice age [Gavin]. The claim that without 8.5 there is no “huge alarm” implies that *any” lower value would not be a huge alarm [me]. There will be ONE takeaway from this whole “but RCPs” thing, for most people in policy, business & media, and it will be this: “We can worry less about the effects of climate change!” Great work, guys. Really good stuff [Kate].

§9. If the IPCC could attribute a valid statistic to scenarios, they would make predictions, not scenarios. The that there is a 1% probability to 8.5 certainly doesn’t come from the IPCC [PaulS].

§10. Some may pretend that “but RCP” isn’t about blame. Yet they can’t prevent themselves from appealing to INTEGRITY, credibility or whatnot. (Examples on demand.) The following meme format should reveal how our usual suspects are squirreling with “but RCPs”:

  • Tired – arguing about 8.5
  • Wired – working toward 2.6 [Costa]
  • Inspired – 2.6 is just a milestone, not a final goal [Jonathan]
  • Bored – let’s just get a policy in place that seriously limits emissions and drives toward a broad international emissions trading system [Kevin].

Srsly, the obsession with RCPs is misplaced [mt]. Who cares about “but RCPs” if the conclusion is that we need to stop using fossil fuels no matter what scenario [Somite]. Getting to carbon zero is key in every way. In any event, those who still care about the “but RPCs” ClimateBall fight could take a look at Pietro’s synopsis:


Posted in ClimateBall, ClimateBall Bingo | 186 Comments

feedbacks, runaway, and tipping points

There’s been some discussion on Twitter about feedbacks, runaways, and tipping points. The issue is that some seem to confuse these and sometimes imply that we could cross thresholds where we’ll undergo a runaway. I thought I would briefly try to explain these terms.

In the context of climate change, external factors that can lead to warming are typically called forcings. This would be things like changes to the solar flux, volcanic eruptions, and our release of greenhouse gases into the atmosphere. Feedbacks are then responses to this externally driven warming that either act to amplify, or suppress, the warming. Some of these are fast, such as water vapour and clouds, while others are slower, such as changes to vegetation or ice sheets. Some are also negative and quite strong (such as the Planck response). This means that even though the overall effect of these feedbacks is to amplify the externally-driven warming, it is limited (the negative feedbacks eventually balance the the effect of the change in forcing and the resulting positive feedbacks). For example, if we were to double atmospheric CO2, we’d expect to eventually warm by about 3oC.

A runaway, on the other hand, typically refers to what happened on Venus. Essentially, virtually all of the CO2 was released into the atmosphere, the warming was so substantial that any liquid water evaporated and was eventually lost to space, most atmopsheric molecules lighter than CO2 were also lost to space, and the surface warmed by many 100s of oC. On the Earth, such a runaway is simply not possible, because most of the carbon, that can then form CO2, is locked up in the lithosphere. We can’t emit enough CO2, either through anthropogenic influences or naturally, to undergo a runaway.

Finally, a tipping point refers to us crossing some threshold where the climate system changes (tips), irreversibly, into a new state. There is the possibility of a global tipping point, but this is seen as very unlikely. However, it is possible that we could cross thresholds where some parts of the system undergo essentially irreversible changes. Examples would be melting of the West Antarctic Ice Sheet, the Greenland Ice Sheet, Amazon rain forest die-off, release of carbon from the permafrost, and the disappearance of summer Arctic sea ice.

If we were to cross any of these tipping threshold, then the changes would further amplify the warming (through either releasing additional CO2, or methane, or changing the albedo) and – in the case of the ice sheets – would lead to substantial sea level rise. There are a few things to bear in mind, though. The timescales are typically long; if we cross a tipping threshold it will still take a long time (centuries) for the full effect to manifest. Also, we don’t have a particularly good idea of where these thresholds might lie; we could already have crossed some, or might not do so unless we were to warm substantially. Additionally, there is still debate as to whether or not some of these are truly irreversible; if we could artificially draw down atmospheric CO2 would some, like Arctic summer sea ice, then reverse?

So, one does have to be slightly careful as to what one implies about tipping points and their significance. On that note, I was going to highlight a recent paper by James Annan that might initiate an interesting discussion about using tipping points in the public narrative. However, this has got long enough, so I will leave that to another post.

Update: Something I meant to stress, is that even though crossing some tipping point might lead to irreversible changes that would amplify our warming, it is still limited. There is only so much that these effects can change the albedo, and there is a limit to how much CO2, or methane, that they could release.

Update 2: If you want to read a more detailed description of the runaway greenhouse effect there is a very good Skeptical Science post by Chris Colose. There is a formal aspect to a runaway that I hadn’t appreciated, but was made aware of by MarkR’s comment. It involves a condensable greenhouse gas (such as water vapour) in equilibrium with a surface reservoir, accumulating in the atmosphere so that it eventually limits the outgoing longwavelength flux. If the incoming flux exceeds this, then energy will accumulate without there being any way to balance this. The surface will then undergo runaway warming until the entire surface reservoir of the condensable greenhouse gas has been depleted.

For water vapour, this longwavelength limit would occur at about 310W/m^2, which – given our albedo of 0.3 – is currently greater than the flux we’re receiving from the Sun. This essentially means that water vapour in the atmosphere is in a regime where it condenses, rather than accumulates. We, therefore, can’t undergo such a runaway in our current state, and no level of CO2 emissions will trigger it.

Posted in Climate change, Climate sensitivity, Global warming, Severe Events, The scientific method, Uncategorized | Tagged , , , , , , | 209 Comments

RCP8.5 – another update

In case anyone is interested, Zeke Hausfather and Glen Peters have a Nature comment about the whole RCP8.5 issue. Unfortunately, they used misleading in the title, which seems to have produced an unfortunate headline on a BBC article. Otherwise, Zeke and Glen’s article is pretty reasonable.

Most of the continued social media discussion is not, though. There do seem to be a large number of people who have strong views about how science/research should be done, while illustrating a lack of understanding of how it actually works. If you’re going around telling people in other disciplines what they should, or should not, do, you’re probably mostly demonstrating your own ignorance.

There are also a couple of other comments about this. Gavin Schmidt has a Realclimate post that largely echoes my views. “Okay, fine, let’s stop using business as usual. Is that it?” Michael Mann also has a short response.

I still find this entire discussion very unfortunate. There were far more constructive ways in which it could have been conducted. I get the impression that some think that they tried this and it didn’t work, so feel that a blunter, more divisive, style was warranted. The problem, though, is that this then ignores the possibility that the original argument wasn’t as convincing as it might have seemed. We all have a tendency to think that our arguments are well thought out and correct. We can’t all be right.

Posted in Climate change, ClimateBall, Gavin Schmidt, Michael Mann, Research, Scientists, The scientific method | Tagged , , , , , , | 65 Comments

Slow travel

If you’ve been following my Twitter threads, you should be aware that I’m just back from a trip to Austria that I decided to do via train. The meeting was for a collaboration that developed after I spent some time in Vienna and my decision to travel by train was partly motivated by my giving a talk at a flight free event, and partly by me just wanting to see what it would be like.

TGV Lyria in Zurich Hauptbahnhof

I started my journey just over a week ago, by catching a local bus to Edinburgh’s Waverley train station, from which I got the West-Coast train to London. It would have been faster to go down the East-Coat mainline, but I was trying to minimise the costs. I spent the night in London and then caught the early Eurostar to Paris, getting to Paris at 10am. I had to get the Metro from Paris Gare du Nord to Paris Gare de Lyon, but it was pretty straightforward and I had plenty of time. I then caught the TGV Lyria from Paris to Zurich which – at times – was travelling at close to 300km/hr.

I had a couple of hours in Zurich and then had a Railjet train from Zurich to Innsbruck, getting there just after 10pm. The next morning I had a short train trip from Innsbruck to Brixlegg, and then a 20 minute bus ride to Alpbach, where our meeting was being held (the bus stop was actually right outside where I was staying). The meeting was pretty intensive, so I didn’t get much free time, but it was a beautiful venue.

The meeting ended at lunchtime on Wednesday, so I headed back to Innsbruck, had some time to look around, and then found a nice beerhall for dinner. I had a mid-morning train on Thursday from Innsbruck to Zurich, a mid-afternoon train from Zurich to Paris, and then an early evening train from Paris back to London. I then caught the early morning train on Friday back to Edinburgh and arrived back in time for our exam board meeting.

It all went pretty smoothly, there were no delays, and it was quite a relaxing way to travel. I’d certainly consider doing it again.

The emissions from train travel are substantially less than those from flying. My rough estimate was ~40kg of CO2 (train), versus around ~300kg of CO2 (plane). It is also a pleasant way to travel, you get to see the scenery, and can get some work done (I finished a draft of a proposal, finalised the talk I was going to be giving, responded to emails, and also managed to prepare somethings that I’d thought I might only be able to do this coming week). I also watched a few movies that I had downloaded.

Although the price of the train tickets wasn’t much higher than what I think it would have cost to fly (especially as I would probably have had to fly to a major city and then catch at least one train anyway), I did have to leave a day earlier, and come back a day later. So, there were essentially two extra days, and two extra hotels.

The Man in Seat Sixty-One… – a great site with all sorts of tips about train travel through the UK, Europe, and Worldwide.

Posted in Uncategorized | 36 Comments

Sherelle's Bingo Squares

Yesterday Michael Brown alterted me (see “@nevaudit”) to this contrarian editorial:

As many of you already know, I am currently developing a ClimateBall Bingo. That bingo consists of squares that I identify with a “but.” The central square is “but CAGW” – CAGW standing for Catastrophic Anthropogenic Global Warming. Most if not all contrarians visiting AT’s allude to it from time to time.

My bingo squares are not linked to claims but to memes. In principle, the Contrarian Matrix of all the best lines of arguments would suffice to play ClimateBall. In reality, contrarians evoke a variety of ideas using a specific bag of talking points. Arguments are secondary when the name of the contrarian game is to repeat over and over again the same fighting words.

These characteristics shine through Sherelle’s editorial. Following along her disciplined meme game also helps test which bingo squares I am missing.

* * *

The title lists the main squares: “but consensus,” “but elite,” and “but doom.”

The lead announces two other important memes, “but Greta” and “but complexity”:

I won’t add the “slavish” hyperbole for the moment – we need to cut somewhere. The first paragraph repeats “but elite” and “but consensus,” this time with “but hypocrisy”:

The second paragraph repeats “but Greta” and winks at “but activists”:

Let’s not wonder why Sherelle forgets that Greta’s main takeaway is to listen to scientists, and let’s read paragraph 3:

You guessed it: “but CAGW.” Not sure why Sherelle attributes it to teh Donald. Her main counterargument lies underneath her “but complexity.” This meme is rather inexact regarding the IPCC’s main conclusions: there’s nothing complex in the conclusion that dumping CO2 in the atmosphere like there’s no tomorrow is not a Good Thing. Onto the next paragraph, which redirects the reader toward the Australian fires:

The Australian fires are not quite relevant here, except by coincidence – it’s recent. Sherelle’s argument would work if our confidence about AGW depended on its proper contribution to fires, i.e. the meteorological fallacy, to be introduced another time.

Here’s a part of the next para (I’m lazy and won’t glue the two columns together):

The crux of Sherelle’s “but complexity” is pure assertion and amounts to “but CAGW.” Notice the shift from AGW to CAGW. Crumbly prose indeed.

In the next para, the precaution “you don’t need to doubt AGW to dispute CAGW” hides the AGW pea under the CAGW thimble. Hence perhaps why our editorialist shifts to “but billions,” “but proof,” and Niv’s crap, a “but teh sun” guru:

Next para shows “but uncertainty,” “but evidence,” “but teh modulz,” “but cult,” and once again “but CAGW,” with a “but funding” bow:

No contrarian editorial is complete without “but Galileo”:

Sorry, René. Next para is “but Enlightenment” and “but Inquisition” (will add that one), with a whiff of “but conspiracy:”

(Note the handwaving to undetermined contrarian papers.)

We’re almost finished. The penultimate para features “but Dark Ages” (to be added), “but elite,” “but communism,” and “but complexity”:

Perhaps I should add “but central planning”; “but one world governement” may do. Sherelle ends by hammering her main memes, i.e. “but Greta,” “but elite,” and “but complexity”:

As we can see, Sherelle is obviously skilled at rinsing and repeating. Let’s see how it reads if we render her editorial into tags:

#ButConsensus, #ButElite, and #ButDoom. #ButGreta and #ButComplexity. #ButElite, #ButConsensus, and #ButHypocrisy. #ButGreta and #ButActivists. #ButCAGW. #ButCAGW. #ButBillions, #ButProof, and #ButTehSun. #ButUncertainty, #ButEvidence, #ButTehModulz, #ButCult, #ButCAGW, #ButFunding. #ButGalileo, #ButEnlightenment, #ButInquisition, #ButConspiracy. #ButDarkAges, #ButElite, #ButCommunism, #ButComplexity, #ButOneWorldGovernement. #ButGreta, #ButElite, #ButComplexity.

Lots of memes for just a few uninformative paragraphs, don’t you think? In any case, my ClimateBall Bingo seems to be holding up. This analysis helped me add a few squares, but I think it’s getting there. It should be ready soon.

UPDATE. Seems that AT came up with the Climate Wars Bingo in 2015 already:


Posted in ClimateBall | Tagged , , , , | 78 Comments

Consensus messaging, an update

If you’re a regular follower of this blog, you’ll know that some of the most active threads have concerned the scientific consensus about climate change and, more specifically, the issue of consensus messaging. Recently, a new book has been released that covers Contemporary Climate Change Debates and includes this as one of the topics. It has a chapter that asks [i]s emphasising consensus in climate science helpful for policymaking? and involves a debate between John Cook – who thinks it is – and Warren Pearce – who thinks it isn’t.

I’ve published a couple of consensus papers with John Cook, so will acknowledge a bias. However, I did like his chapter and though his point that [c]limate communication is not a zero sum game was well made. Clearly, how we communicate and what we focus on should depend on the circumstances and the audience. Consensus messaging shouldn’t always be the focus of communication strategies, but neither should it simply be dismissed.

Warren Pearce’s response suggests that there shouldn’t be a focus on the consensus because it’s narrow and human values are important. I agree that human values are important, but I think he’s wrong to suggest that it’s narrow. The scientific consensus is simply that humans are causing climate change and it essentially underpins this entire topic.

Warren argues that the consensus tells us nothing about the future of climate change, such as human and non-human impacts, policy options or the range of human values and cultures which interact with local climates. It may not tell us anything directly, but how can we possibly discuss these issues if those involved don’t accept that humans are causing climate change?

As examples of important topics that are unrelated to the scientific consensus, Warren highlights the disagreement about carbon budgets and debates about discount rates. Well, carbon budgets are entirely based on limiting human caused climate change and the debate about discount rates is associated with estimates of the future cost of human caused climate change discounted to today. How can one possibly engage in discussions about these topics if there isn’t an acceptance that humans are causing climate change?

So, I think Warren’s argument doesn’t make any sense. I agree that human values are important, and that there are many other aspects of this issue that are very important. However, I really don’t see how it’s possible to address these other issues if there isn’t a general acceptance of the scientific consensus that humans are causing climate change.

Of course, it’s always possible that I’m missing some subtlety in Warren’s argument. If so, maybe someone who understands it can try and explain it in the comments. My impression is that those who oppose consensus messaging either don’t understand the consensus, or don’t accept it. I would, however, be more than willing to be convinced otherwise if someone were willing to put some effort into explaining the argument in more detail.

Is Emphasising Consensus In Climate Science Helpful For Policymaking? – Chapter with John Cook’s and Warren Pearce’s articles about consensus messaging. I should have added that it’s worth reading John’s article to see some of the other arguments against what is presented in Warren’s article.

Posted in Climate change, ClimateBall, Global warming, Philosophy for Bloggers, The philosophy of science, The scientific method | Tagged , , , , , , | 311 Comments

Zharkova et al.: an update

Last year I wrote a couple of posts about a paper by Valentina Zharkova and colleagues, which suggested that global warming was partly due to the Earth moving closer to the Sun as the Sun moves around the Solar System barycentre. If you read my posts, the comments, and this pubpeer thread you’ll notice a number of people pointing out that this was wrong; the Earth-Sun distance doesn’t change as the Sun goes around the Solar System barycentre.

Recently, an editorial response and comments from two reviewers have been released, as has a response from the authors. They’ve also released an erratum. You can find some discussion of this on Geoff Sharp’s post.

Unsurprisingly, the editorial response and the recviewers agree with the criticisms of the paper. The editor says:

There is a legitimate, and based on my reading, completely correct concern about the Earth-Sun distance calculation.

Similarly, reviewer 1 says:

Earth is orbiting about the sun and the barycentric motion of the sun is irrelevant for computing/predicting Earth’s temperature. In a simpler term, the Sun is very close to being the prime focus of the Earth orbit.

In their erratum, the authors acknowledge that they were wrong to suggest that the Earth-Sun distance changed as the Sun goes around the Solar System barycentre. However, they then go on to claim that there is still quite a substantial change in the Earth-Sun distance on century timescales. However, as pointed out in Geoff Sharp’s post, what they’ve done is to consider only the perihelion distance. This is the distance between the Sun and the Earth when the Earth is closest to the Sun. It’s well known that there is a slow change in the eccentricity of the Earth’s orbit; it goes from being almost circular, to being slightly elliptical.

This does indeed then lead to a slow change in the perhelion distance. However, there is an equivalent, but opposite, change in the aphelion distance, so that the average distance remains unchanged. This is illustrated in the figure in this comment. So, despite acknowledging a pretty fundamental error when discussing the motion of the Sun around the Solar System barycentre, they’ve gone on to make another pretty fundamental error.

I don’t know what the outcome of this is yet. It’s the authors who have released the editorial response, reviewers comments, and their erratum. Their erratum is still not published and it may be that it goes through further review. Would certainly hope so.

Posted in Global warming, Philosophy for Bloggers, Research, Sound Science (tm), The philosophy of science | Tagged , , , , , | 44 Comments