A recent working paper from the National Bureau of Economic Research (NBER) reveals that summaries of IPCC climate assessments tend to emphasize the most severe outcomes, and media coverage further amplifies this bias. The study compared newspaper articles from ten major U.S. and U.K. outlets with scientific evidence from all six IPCC assessment reports between 1990 and 2023. The authors found that the Summary for Policymakers (SPM), a politically negotiated document, skews toward the more severe end of the technical evidence. This bias then carries over into news reporting, as editors select claims based on novelty, urgency, and salience, favoring higher-impact scenarios.
Two Stages of Bias
The first stage occurs during the IPCC's condensation process: scientific assessments are summarized into a Technical Summary (TS) and then further into the SPM. The SPM is approved line-by-line by representatives of 195 member governments, making it a political artifact rather than a neutral summary. Using large language models, researchers found that for every assessment report, the SPM leans toward severity. In the second stage, journalists and editors use the SPM to write articles, giving more weight to severe climate impacts. This bias appears across both left- and right-wing news outlets in the U.S. and U.K., and likely extends to Canadian media.
Implications for Policy
Activists and politicians have also exploited this bias to push sweeping government interventions. For example, Mark Carney, in his 2021 book Value(s), advocated for large-scale climate initiatives based on the RCP 8.5 scenario, which projected a 4.5°C temperature rise by 2100. However, RCP 8.5 was always an extreme scenario, and the latest scenario framework published in 2024 excludes it as implausible. A 2020 Nature article described RCP 8.5 as dystopian and increasingly unlikely, requiring a fivefold increase in coal use. Ross McKitrick also noted in 2020 that its assumptions were contradictory. Despite this, Carney and others continued to use it to stoke climate alarm.
The study underscores how biased science reporting can fuel public concern and policy decisions that may not align with the full range of scientific evidence.
