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Of course, consistency with the IPCC (or not) says little about policy preferences. Democrats remain the party championing action on climate policy and Republicans remain much less supportive. Of course, the key question here is, What action? I have long argued that there are unexplored opportunities for greater bipartisan support for pragmatic energy and adaptation polies that would accelerate decarbonization and reduce vulnerabilities — but that’s a topic for another day.
Policy aside, with respect to the IPCC and climate science, Democrats are currently the party of RCP8.5 and “billion dollar disasters,” while many Republicans express views much more in line with the findings of the IPCC.⁵
One consequence of this shift in perspective is that some climate activists have sought to delegitimize the IPCC. For instance, Naomi Oreskes has called for the IPCC Working Group 1 to be shut down:
One step that could help that happen would be for the IPCC to declare the job of WG1 to be done and close it down.
After all, if human-made warming is as unequivocal as these scientists insist, then why do we need more reports to tell us the same thing?
Others argue that the IPCC has been corrupted by “contrarians”:
. . . contrarian views against anthropogenic climate disruption can lobby the scientific community, and the IPCC in particular, to be conservative and so reinforce contrarian views in a vicious, self-reinforcing circle
The battle for the soul of the IPCC has really only just begun — just wait for the coming battle over letting go of extreme, implausible scenarios.
The science of detection and attribution of extreme events under the IPCC’s longstanding framework can only change very slowly, as the additions to the observational record accumulate slowly as time passes, even under the seemingly glacial pace of IPCC assessments.⁶ In other words, five years more data on hurricanes, floods, drought, and so on will not alter the fundamental conclusions of the IPCC Working Group 1 on its assessment of long-term trends. At the same time, understandings that the extreme scenario once characterized as “business as usual” is now implausible means that projections of future trends will necessarily be less extreme.
Give these realities, I expect to see more attacks on the IPCC and mainstream climate science by climate activists, including those within the scientific community.
Consider the case of the U.S. National Climate Assessment, which I have argued has been fully taken over by climate activists. In 2014, the Third U.S. National Climate Assessment highlighted the importance of the IPCC’s framework for detection and attribution. The figure below comes from that report.
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US NCA 2014
Similarly, in 2017, the Fourth U.S. National Climate Assessment (NCA) included a chapter on the detection and attribution of trends in extreme events, following the framework of the IPCC, explaining:
Detection and attribution studies are important for a number of reasons. For example, such studies can help determine whether a human influence on climate variables (for example, temperature) can be distinguished from natural variability. Detection and attribution studies can help evaluate whether model simulations are consistent with observed trends or other changes in the climate system. Results from detection and attribution studies can inform decision making on climate policy and adaptation.
However, in 2023, the authors of the Fifth U.S. NCA decided — amazingly — to eliminate its chapter on the detection and attribution of trends in extreme events and the IPCC framework, and instead to emphasize billion dollar disasters as an indicator of changes in extreme events.⁷
The number and cost of weather-related disasters have increased dramatically over the past four decades, in part due to the increasing frequency and severity of extreme events and in part due to increases in exposure and vulnerability. In 2022 alone, the United States experienced 18 weather and climate disasters with damages exceeding $1 billion (Figures 2.6, A4.5). There is increasing confidence that changes in some extreme events are driven by human-caused climate change (KM 3.5).
Though it hasn’t been much discussed (probably due to its poor quality), the Fifth U.S. NCA rejected the scientific framework of the IPCC. This should not be a surprise — I’ve long argued that the placement of the U.S. NCA in the Executive Office of the President makes it a tempting target for political meddling, by Republican and Democratic administrations. Thus, the 2023 U.S. NCA represents the current Democratic view of climate science that disfavors the IPCC.
Over recent decades, both Democrats and Republicans have shifted in their views of the IPCC. Given this shifting landscape, leaders of the IPCC and the broader scientific community should prioritize steps to ensure the institutional integrity of it Working Group 1, so that it can continue to effectively assess the science of climate change, regardless which elected officials cite their work.
