Roger Pielke Jr.

Roger A. Pielke Jr. (born 2 November 1968) is an American political scientist and professor at the University of Colorado Boulder, specialising in science policy, climate change policy, disaster economics, and sports governance. He is the son of atmospheric scientist Roger A. Pielke Sr. Pielke Jr. is known for research on the relationship between climate change and extreme weather events — particularly hurricanes and tornadoes — and for sustained criticism of the use of high-end emission scenarios in climate projections and policy. He communicates publicly through his Substack publication The Honest Broker and has been both awarded and contested for his positions on climate science communication.

Personal profile

Education

Career

Research areas

Pielke’s academic work spans political science, environmental studies, science policy, and the governance of sports. Within climate-related research, his focus areas include:

• The relationship between climate change and normalised economic losses from natural disasters (hurricanes, tornadoes, floods)
• The appropriate role of scientists in policy debates — a theme developed in his book The Honest Broker (2007)
• Emissions scenarios used in climate modelling, particularly high-end pathways
• Climate economics methodology
• Science governance and the boundary between scientific expertise and political advocacy

Books

Positions on climate science and policy

Acceptance of IPCC findings and greenhouse gas science

Pielke accepts the scientific consensus that human greenhouse gas emissions cause global warming, as documented by the IPCC. He has stated that emissions reductions are desirable but argues that the timeline for perceptible climate impact of any policy is necessarily multi-decadal: “Any conceivable emissions reductions policies, even if successful, cannot have a perceptible impact on the climate for many decades.” On this basis he argues that adaptation — reducing the vulnerability of populations and infrastructure to weather and climate variability — deserves equal or greater policy attention than near-term mitigation.

Extreme weather and disaster losses

Pielke’s research methodology normalises economic losses from natural disasters by adjusting for changes in wealth and population, asking how much damage a historical storm would cause if it struck today. His principal finding is that, on this normalised basis, there is no detectable long-term upward trend in losses from hurricanes, tornadoes, or floods in the United States attributable to climate change. He attributes observed increases in absolute disaster costs primarily to societal and economic factors — more people and more wealth in exposed locations — rather than to changes in storm frequency or intensity.

These conclusions are contested. Climatologist Kevin E. Trenberth and others have argued in peer-reviewed literature that the normalisation methodology used by Pielke fails to account for changes in storm intensity and precipitation, and that attribution science increasingly demonstrates climate change signals in extreme weather events.

IPCC emissions scenarios: RCP8.5 and SSP5-8.5

Pielke has been a sustained and prominent critic of the use of the high-end emission scenario RCP8.5 — and its successor SSP5-8.5 — as a primary or default scenario in climate research, impact assessments, and media reporting.

RCP8.5 is the highest-emission pathway in the IPCC’s Representative Concentration Pathway framework, associated with approximately 8.5 W/m² of additional radiative forcing by 2100. It assumes, among other conditions, a large expansion of global coal consumption over the twenty-first century. Pielke and colleagues argued — in publications including a 2019 paper in Proceedings of the National Academy of Sciences — that this assumption is implausible given observed and projected coal trajectories, and that RCP8.5 had come to be used in scientific literature and media as a de facto “business as usual” scenario rather than a high-end tail risk, overstating likely future warming.

A parallel critique was published by Zeke Hausfather and Glen Peters in Nature (2020), arguing that RCP8.5 was “not a business as usual scenario” and that its widespread use as a baseline was creating misleading public impressions of the most likely future.

In 2023, the IPCC Working Group III and several national and international research programmes moved toward de-emphasising RCP8.5/SSP5-8.5 as a primary scenario, with SSP2-4.5 and SSP3-7.0 receiving greater weight as central cases reflecting current policy trajectories. Pielke characterised this shift as “the most significant development in climate research in decades.”

Media coverage of the phase-out of extreme scenarios

The de-emphasis of RCP8.5 received notably asymmetric coverage across media outlets, a disparity that Pielke has documented and analysed. Dutch newspaper De Volkskrant published a front-page article; German outlets including Berliner Zeitung, Die Welt, and watson.ch covered the development. Major English-language outlets including The New York Times, The Guardian, BBC News, Science, Nature, and Carbon Brief — several of which had published extensive reporting based on RCP8.5 projections over the preceding fifteen years — were largely silent on the discontinuation.

Pielke argued that outlets with the greatest prior investment in RCP8.5-based coverage had the least institutional incentive to acknowledge the shift.

Detlef van Vuuren (Utrecht University, PBL Netherlands Environmental Assessment Agency), one of the principal architects of the shared socioeconomic pathway (SSP) framework, explained the revision in terms of changed real-world conditions: “The world has developed favourably. Renewable energy became much cheaper faster. Although still insufficient, climate policy now exists.” Van Vuuren acknowledged that existing projections based on RCP8.5 would require recalculation.

Controversies

Congressional investigation (2015)

In February 2015, US Representative Raúl Grijalva (Democrat, Arizona) sent letters to seven universities requesting information on the external funding sources and financial disclosures of climate scientists whose testimony before Congress Grijalva considered potentially influenced by outside interests. Pielke was among the seven. Pielke disclosed his funding sources and stated they showed no conflicts of interest; he subsequently announced he would cease writing about climate policy, citing what he described as a “political attack on academic freedom.” The investigation drew criticism from some scientists and academic freedom advocates as an inappropriate use of congressional oversight to scrutinise scientific opinion.

FiveThirtyEight (2014–2015)

Pielke contributed articles on climate and disasters to the data journalism site FiveThirtyEight after its re-launch under Nate Silver in 2014. His columns attracted public criticism from climate scientists and advocacy groups, including a letter from several researchers arguing his disaster-loss analyses were misleading. In 2015, he ceased contributing to FiveThirtyEight; emails later disclosed by WikiLeaks (from the 2016 Clinton campaign hack) indicated that external pressure from climate advocates contributed to this outcome.

DeSmog and Skeptical Science listings

Pielke appears in the DeSmog Climate Disinformation Database, which characterises him as a source of climate misinformation, citing his disaster-loss analysis and scenario critiques. Pielke has publicly contested this characterisation and the methodology used to compile such lists, arguing they conflate scientific disagreement with misinformation.

Recognition

The Honest Broker (Substack)

Since the early 2020s, Pielke has published the Substack newsletter The Honest Broker, which he describes as “making sense of science, policy and politics.” Topics covered include:

• IPCC scenario methodology and its evolution
• Normalised disaster loss data (tornado, hurricane, flood)
• Climate economics — including critiques of published discount rate and damage function assumptions in integrated assessment models
• Science governance — the appropriate role of scientific expertise in policy-contested questions
• Media coverage gaps in science reporting
• Population dynamics and demographic projections

The Substack, with more than 10,000 subscribers, is Pielke’s primary public communication channel since reducing his activity on academic and legacy media platforms.

Context: the “honest broker” framework

In The Honest Broker (2007), Pielke proposed a typology of roles that scientists can play in policy debates:

• Pure scientist: focused on knowledge for its own sake, minimal policy engagement
• Science arbiter: answers specific factual questions posed by decision-makers
• Issue advocate: uses scientific standing to promote a particular policy outcome
• Honest broker of policy alternatives: presents the full range of options made visible by scientific knowledge, without pre-selecting among them

Pielke argued that scientists who adopt the issue advocate role while presenting themselves as neutral experts undermine public trust in science. This framing has been cited approvingly by those who argue that climate science communication has become too advocacy-oriented, and contested by others who argue that the honest broker model creates a false equivalence between scientifically supported and unsupported policy positions.