RCP8.5 Is Dead, What Comes Next? Ep260: Roger Pielke, Jr.

Why It Matters

Declaring RCP 8.5 implausible reshapes climate risk modeling and signals that mitigation and realistic scenario planning are essential for effective policy and investment decisions.

Key Takeaways

• RCP 8.5 deemed implausible, shifting climate scenario baselines
• Aggressive mitigation reduces risk of abrupt climate tipping points
• Scientists must choose roles: advocate, ivory‑tower, or honest broker
• Policy debates expose tension between science advice and political agendas
• Emerging energy mix favors renewables and nuclear over coal dominance

Summary

The episode marks a turning point in climate modeling after the worst‑case emissions pathway known as RCP 8.5 – and its successor SSP 5‑8.5 – was declared implausible by leading scientists. Host Michael Lubrike and senior fellow Roger Pielke Jr. explain why the scenario, long used as a baseline for “do‑nothing” projections, no longer reflects realistic socioeconomic trajectories.

Pielke argues that aggressive mitigation still matters because it lowers the probability of abrupt climate tipping points, even if the exact timing cannot be priced. He also revisits his “honest broker” framework, stressing that experts can act as advocates, ivory‑tower researchers, or neutral providers of policy options, and that the choice shapes public debate.

The conversation highlights recent policy frictions: the Trump administration’s short‑lived executive orders, the failed “red‑team” review led by Energy Secretary Chris Wright, and the broader push to silence climate scientists. Pielke cites his own work on extreme events, noting it was heavily referenced in the withdrawn report, and points to the rapid decline of coal in electricity generation and a resurgence of nuclear power.

The demise of RCP 8.5 forces climate analysts to adopt scenarios grounded in plausible demographic and energy pathways, which in turn influences risk assessments, investment decisions, and international negotiations. For policymakers, recognizing the shift underscores the urgency of mitigation, the need for transparent scientific advice, and the accelerating transition toward renewables and nuclear energy.

Original Description

For more than 15 years, the RCP8.5 climate scenario has shaped headlines, policy decisions, financial stress tests and public understanding of climate risk. Now, the scientific community has declared it implausible. So what comes next?

This week on Cleaning Up, Michael Liebreich welcomes Professor Roger Pielke Jr. back to explore why RCP 8.5 became the dominant "business as usual" climate scenario, and what its demise means for climate research, policymaking and public debate.

They discuss the origins of the scenario, how assumptions about coal consumption drove projections beyond plausible futures and ask whether fear-based climate communication has ultimately helped or hindered public support for climate action. They tackle tipping points, extreme weather, climate policy, scientific self-correction, and the crucial question of how societies should respond to climate risk in a world that is still warming.

Until recently, Roger was a tenured professor at the University of Colorado at Boulder. He is now senior fellow at the American Enterprise Institute and publishes an influential Substack called The Honest Broker. He last made an appearance on Cleaning Up in June 2022. If you want to know the background to the RCP8.5 controversy you should listen to that episode, linked below.

Leadership Circle:

Cleaning Up is proud to be supported by its Leadership Circle. The members are Actis, Alcazar Energy, Arup, Copenhagen Infrastructure Partners, Cygnum Capital, Davidson Kempner, Ecopragma Capital, EDP, Eurelectric, the Gilardini Foundation, KKR, Mitsubishi Heavy Industries, National Grid, Octopus Energy, Quadrature Climate Foundation, Schneider Electric, SDCL and Wärtsilä. For more information about the Leadership Circle, visit cleaningup.live

Links:

• Van Vuuren’s 2026 paper on RCP8.5 becoming implausible: https://gmd.copernicus.org/articles/19/2627/2026/

• Van Vuuren’s 2011 paper on the development of the Representative Concentration Pathways (RCPs): https://link.springer.com/article/10.1007/s10584-011-0148-z

• The Honest Broker Substack: https://rogerpielkejr.substack.com/

• Michael's writeup on RCP8.5: https://mliebreich.substack.com/p/rcp-85-is-officially-bollox

• Roger Pielke Jr’s past appearance on Cleaning Up: https://www.youtube.com/watch?v=K2LpMpkrP1w

• Johan Rockström on Cleaning Up: https://youtu.be/eIJkt_mY12s

• Jim Skea on Cleaning Up: https://youtu.be/oAWUdL5ZKsk

Chapters:

00:00 - Coming Up

00:55 - Intro

05:00 - The Honest Broker

08:00 - US Climate Policy

10:30 - Chris Wright’s Review

14:00 - Renewables Overtake Coal

15:37 - RCP8.5 is Dead

19:00 - Why Does It Matter?

22:00 - Plausability

25:00 - Trends in Coal

31:00 - What Do Policymakers Do?

35:30 - Alternative Scenarios

40:00 - The New High Scenario

45:30 - Tipping Points

50:00 - Aggressive Mitigation

54:00 - Self Correction

57:00 - Hurricane Damage

01:01:47 - Outro