Why you should listen to Cleaning Up with Professor Roger Pielke Jr

One of the best things about hosting Cleaning Up has been the diversity of guests I get to talk to - from former Australian PM Tony Abbott to the lawyer who stuck herself to the Shell headquarters, from the CEO of Italy's largest utility to a leading Kenyan youth climate activist, from Mark Carney to the guy who climbed El Capitan with no ropes. This week's guest was one of the most controversial, Professor Roger Pielke Jr, and I thought I would explain why I think his is an important voice.

Roger has been a long-time critic of the climate science community. It's not that he doesn't believe anthropogenic climate change is happening, and that it is serious, and that the world needs to take urgent action - he even wrote a book about it in 2011. But he does have serious concerns with the way scientists and the IPCC are using climate scenarios - which he has voiced over the years and summarised in 2020 in a long and detailed paper which he wrote with co-author Justin Ritchie.

The fact that Roger believes anthropogenic climate change is occurring seems to make his criticism particularly difficult for some to engage with: it's always the heretics that garner more vitriol than the outright non-believers. Since his appearance on Cleaning Up aired a few days ago, a fascinating pattern has become evident: newcomers to the minutiae of climate scenarios and event attribution have found it thoughtful, reasoned and fascinating; climate insiders, however, have mainly ignored it, nitpicked, failed to engage with his core points and recommended that their followers not listen to it.

The misuse of climate scenarios is a very real problem, one I have written about before, and fairly easy to illustrate. Here, for instance, is a figure from of the US 4th National Climate Assessment, 2018:

See those column headers "Annual damages under RCP8.5" and "Damages avoided under RCP4.5"? Clearly RCP8.5 being postulated as BAU (whether or not it is actually called that), and RCP4.5 is positioned as what success looks like. First of all, this is a completely illegitimate comparison: RCP8.5 describes a world in which no climate action has ever been taken, but it's a world with a population of 12 billion; RCP4.5 is a policy intervention scenario, but in a world with a population of 8.7 billion. It should be clear to anyone that you can't subtract impacts in one world from impacts in the other and claim the only difference can be credited to climate action.

The second problem with the analysis is that far from being a scenario that represents successful action on climate change, RCP4.5 is more or less where we are headed under current policies! And this is not a fringe position, this is the position of the UNFCCC itself. In the run-up to COP26 in November 2021, it published an Update to the NDC Synthesis Report, which included the following figure:

What you can immediately see is that the NDCs - Nationally Determined Contributions, or the summary of countries' current climate plans - are tracking just below the scenario SSP2-4.5 (an updated incarnation of RCP4.5) and there is no sign of RCP8.5 (or its most updated version, SSP5-8.5). Privately many of the leading figures in the IPCC have also conceded that RCP8.5 is completely lacking in plausibility, but publicly they continue to promote its use.

Does any of this scenario stuff matter? Well, yes.

What you can also see from the UNFCCC Update to the Synthesis Report is that following RCP4.5 (or SSP2-4.5) will not get us anywhere near staying within 2C or 1.5C of warming. We need to take dramatic, substantial and immediate action to achieve that. But what is needed from our academics is to understand what it takes to bend the curve from where we are headed. We don't need more scare stories about a completely implausible, apocalyptic future - even though that is what gets the best headlines.

And misusing scenarios certainly guarantees lurid headlines. In its summary, the 2018 National Climate Assessment stated that “annual losses in some economic sectors are projected to reach hundreds of billions of dollars by the end of the century—more than the current gross domestic product (GDP) of many U.S. states.” This was heavily promoted by the report authors and editors, and earned front-page stories around the world:

Think of this next time someone tells you about the epidemic of climate anxiety. To what extent is it driven by stories based on the wildly implausible RCP8.5 scenario?

There are, of course, those who say none of this matters because we appear to be tracking the extreme edge of scenarios, with worse and worse news on the climate front each year? I would urge them to differentiate between emissions scenarios and climate sensitivity. Emissions scenarios relate to the trajectory of human activity - energy, transport, industry, agriculture, deforestation and so on; sensitivity is how the planet's systems respond to those emissions.

It is entirely logically possible that we are tracking a middle scenario for emissions, and that we keep getting bad news on sensitivity. As scientists, though we don't account for the latter by exaggerating the former: instead we improve our understanding of sensitivity. And as policy makers, heightened concerns over sensitivity at lower levels of emissions means we need to accelerate our investment in adaptation and resilience.

And then there are potential feedbacks. I explored these in my conversation with Johan Rockstr?m. The bottom line is that there is no way that feedbacks can deliver enough of an emissions amplifier to get from where we are headed - RCP4.5 or better - back to the RCP8.5 scenario. That doesn't mean feedbacks are not real and no scary, it just means they operate too slowly (century-scale) to hit 8.5W/m2 of forcing by the year 2100. Does this give us more leeway in how we deal with them? Maybe, maybe not. But it's very hard to have the discussion when much of the public is convinced we are likely to suffer catastrophic global crop failures and many metres of sea level rise in the next few decades.

Despite all this, I have been astonished over the past few years at the number of scientists who push back against reforming the use of climate scenarios. They are seem unaware of the real data on energy emissions; or maybe they genuinely conflate scenarios and sensitivity; but often my sense is they are so keen to get people to pay attention to climate change that they are prepared to depart from scientific methods.

We know from history that when scientific communities become self-referential and defer to gatekeepers, they don't do good science and society suffers. That’s why I am openly disrespectful of Professor Mann – he is so clearly out of the scientific mainstream in his claims and behaviour, yet his peers won’t do anything about it. If you think this is an extreme statement, here he is claiming that climate change-related wildfires, droughts, floods, heatwaves and coastal inundation are already killing more people than Covid - an easily-debunked claim that is out by at least two orders of magnitude.

There are some that think that Professor Mann's antics accelerate action on climate change. I disagree. I think sustained action over decades by the majority of peoples and countries can only be based on the most robust, rigorous science. Easily-debunked exaggeration empowers the opponents of action and slows it down.

That is also why I think it’s important to listen to voices like Roger’s. It's not that his positions should be accepted without criticism. They should be challenged as hard as he challenges those of others.

I wish I had challenged him harder on the subject of Event Attribution - in other words the science of deciding to what extent any individual extreme event bears the fingerprint of climate change. If we demand that any change in weather patterns manifest itself over a decadal time period, the possibility of identify very rapid changes becomes a logical impossibility. Roger's criticism of Event Attribution, pointing out the motivations those doing them have expressed - gives ammunition to those who claim his real aim is to slow down climate action, of which I have seen no sign in my interactions with Roger. In fact since we recorded our conversation, Roger has sent me a link to his Forbes piece on three rules by which Event Attribution studies can be judged, which seem eminently sensible to me and, I suspect, to anyone with a robust non-climate-science background.

The bottom line is this that he cannot be ignored. Is Roger always right? No one is. Does he enjoy his role as contrarian? Yes, he appears to. But if anyone tells you that you should not be listening to the Episode 93 of Cleaning Up with Professor Roger Pielke Jr, please ignore them. Listen anyway and make up your own mind.

As always, I am extremely grateful for the support in producing Cleaning Up of Capricorn Investment Group, Gilardini Foundation and Liebreich Foundation. I believe these are important and useful conversations.