Thread by @ThierryAaron

Is climate change going to be worse than expected?

Have scientists been systematically underestimating the impacts?

And if so how should we as science communicators convey this to the public & policy makers?

I delve into this unsettling topic in this 🧵 1/n
(Pic: L. Hogarth)

It’s a topic I’ve been pondering for some time. I wrote this blog post back in 2013 before IPCC’s AR5 report was published.

So what has happened since then? Are scientists still saying things are worse than predicted? 2/n

blog.rsb.org.uk/why-climate-ch…

The evidence certainly seems to point in that direction.

Let’s now turn to look at just a few of the many recent examples of scientists who have pointed this out.

I’ll then explore what is causing this bias and how we can perhaps address it. 3/n

"It is clear that climate change is already having a greater impact than most scientists had anticipated, so it's vital that international mitigation & adaptation responses become swifter & more ambitious" - @JPvanYpersele IPCC Vice-Chair for AR5 4/n

enn.com/articles/38449…

"It’s appropriate to be scared. We predicted temperatures would rise, but we didn’t foresee these sorts of extreme events we’re getting so soon" -
@Sir_David_King, Founder & Chair @RepairClimate & @ClimateCrisisAG 5/n

bbc.co.uk/news/science-e…

"...crop yields will be negatively affected by climate change much earlier than expected... we've seen a shift in consensus, telling us that the impacts of climate change in temperate regions will happen sooner rather than later” - @AndyChallinor 6/n

leeds.ac.uk/news/article/3…

“What we see with European heatwaves is that all the climate models are underestimating the change that we see” @FrediOtto, Associate director @ecioxford 7/n

theguardian.com/environment/20…

“The Arctic is figuratively and literally on fire - it’s warming much faster than we thought it would in response to rising levels of carbon dioxide... this warming is leading to a rapid meltdown and increase in wildfires”- @GreatLakesPeck 8/n

apnews.com/article/health…

"I am myself quite surprised despite working on this everyday... how we have underestimated the pace of change... everything from permafrost thawing, to ice melt, to coral reef damage, to forest die-back" @jrockstrom, Director @PIK_climate 9/n

@jrockstrom @PIK_Climate “It is more and more likely that the IPCC projections are too optimistic in the Arctic." -@xavierfettweis 10/n

rollingstone.com/politics/polit…

"The more observations we get, the more sophisticated our models become, the more we’re learning that things can happen faster, and with a greater magnitude, than we predicted just years ago”- @MichaelEMann 11/n

yaleclimateconnections.org/2019/08/video-…

@MichaelEMann Elsewhere @MichaelEMann has said "We're seeing increases in extreme weather events that go well beyond what has been predicted... Increasingly, science suggests that many of the impacts are occurring earlier & with greater amplitude than was predicted"12/n insideclimatenews.org/news/26122017/…

@MichaelEMann "Things are happening. They are happening faster than we expected.” - @IVelicogna 13/n

apnews.com/article/547d9c…

@MichaelEMann @IVelicogna "The melting is overtaking the climate models we use to guide us, and we are in danger of being unprepared for the risks posed by sea level rise"@_tslater 14/n

leeds.ac.uk/news/article/4…

“We always expected the Arctic to change faster than the rest of the globe... But I don’t think anyone expected the changes to happen as fast as we are seeing them happen” Prof. Walt Meier of @NSIDC 15/n

washingtonpost.com/climate-enviro…

@NSIDC "It's looking like things are actually going to be worse than our worse case analysis" -@AndrewDessler 16/n

cnbc.com/video/2021/07/…

@NSIDC @AndrewDessler Perhaps most revealing is to look at the shifts in the estimates in the @IPCC_CH’s burning embers diagram. Across all categories every subsequent report has assessed the risks as greater than previously understood. As summarised here by Zommers et al 17/n
nature.com/articles/s4301…

Particularly concerning is how our perception of the risks of triggering earth system tipping points has advanced as our scientific understanding has improved over time. As Lenton et al point out: 18/n

nature.com/articles/d4158…

Even where changes in geo-physical variables have been accurately predicted we have been discovering that the social & ecological systems (eg. Coral reefs) are more vulnerable than anticipated & the impacts are far greater than expected. 19/n

This phenomenon of “scientific reticence” has caught the attention of historians & philosophers of science, who have provided a variety of explanations for what leads to this bias towards underestimation 20/n

Recently @NaomiOreskes @ClimateOpp & Dale Jamieson provide 3 key reasons…“the push for univocality, the belief that conservatism is socially & politically protective,& the reluctance to make estimates at all when the available data are contradictory” 21/n blogs.scientificamerican.com/observations/s…

As @ProfBillMcGuire says the @ippc_ch is “conservative, because insufficient attention has been given to the importance of tipping points, feedback loops & outlier predictions; consensus, because more extreme scenarios have tended to be marginalised” 22/n
bbc.co.uk/news/science-e…

Scientific practice is inherently conservative. We encourage skepticism of novel claims & demand the accumulation of compelling evidence. We tend to start with conservative assumptions to persuade our peers. We build from what we’re sure of & don't go out on a limb. 23/n

We also design statistical tests to avoid false ➕ves, but are more tolerant of false ➖ves. “When applied to evaluating environmental hazards, the fear of gullibility can lead us to understate threats” 24/n

nytimes.com/2015/01/04/opi…

As @rahmstorf warns “It would be foolish to just play on until the loading of the dice finally becomes evident even in highly noisy statistics. By then we will have paid a high price for our complacency. 25/n

realclimate.org/index.php/arch…

@rahmstorf Another key factor was that scientists have been under sustained attack from vested interests & have moderated their language accordingly to make it harder to be accused of fear-mongering. That is we ‘err on the side of least drama’ 26/n

sciencedirect.com/science/articl…

@rahmstorf As Prof. Chris Rapley candidly admits here to @alisong “we were already being accused of being alarmists, so if we had told those stories [i.e. warned vividly of the risks] it would have undermined the level of trust in us”. 27/n

@rahmstorf @alisong Former IPCC co-chair Prof. Watson also stressed how they acted defensively “I think we should always be slightly on the side of being conservative, otherwise we are going to ripped apart by the climate deniers if we even make the most simple mistake” 28/n

@rahmstorf @alisong If we consider the @IPCC_CH process to be a means of cautiously establishing robust scientific knowledge claims, then it has clearly done a phenomenal job. 29/n

https://twitter.com/simondonner/status/1434933924895985664

However as @MichaelEMann says we need to be aware of its limitations. 30/n

https://twitter.com/MichaelEMann/status/1032097236161900544

In particular the IPCC isn't a reliable means of conducting a risk assessment of the full range of threats the #climatecrisis poses (it was never intended to!). It’s therefore vital that policy makers must also pay close attention to long tailed risks & worse case scenarios 31/n

A point made clear by @Sir_David_King et al. in the @CSciPol climate risk assessment… 32/n

csap.cam.ac.uk/projects/clima…

This is why climate scientists such as @rowan_sutton of @AtmosScience are increasingly stressing that we must “take the needs of risk assessment much more seriously” in our work & in how we communicate to the public & policy makers 33/n

journals.ametsoc.org/view/journals/…

@rowan_sutton @AtmosScience Perhaps one way we can do such risk assessment effectively is through developing narrative scenarios using event-based storylines as is common in fields such as disaster management. 34/n

agupubs.onlinelibrary.wiley.com/doi/full/10.10…

@rowan_sutton @AtmosScience This form of risk assessment is particularly common amongst military & intelligence communities. These imaginary ‘war game’ scenarios can be especially effective for thinking though & communicating the kinds of risks we face from climate breakdown. 35/n
jstor.org/stable/10.7864…

@rowan_sutton @AtmosScience There is actually a fascinating example of such scenarios being used in the the @IPCC_CH 1.5C report in “Cross-Chapter Box 8, Table 2 | Storylines of possible worlds resulting from different mitigation options” tucked away on pages 279-281. 36/n

ipcc.ch/site/assets/up…

@rowan_sutton @AtmosScience @IPCC_CH To conclude, I’d urge scientists to not hold back on expressing your concerns about worst case scenarios for fear of being labeled an alarmist - speak your mind!

Its important people are made fully aware of the full range of risks we face. 37/n
billmcguire.substack.com/p/an-alarmists…

Where possible try to work with scenario planners & storytellers to create plausible narratives of the world in possible future climates so as to help stake holders & decision makers think through and 'get a feel for' potential consequences 38/n

As for the public & policy makers going to #COP26, be precautious and assume the worst. Remember: “it is more than plausible that the impacts of climate will be at the high end of these uncertainties rather than the low end” 39/39

Thanks for reading!

blog.rsb.org.uk/why-climate-ch…