Lots to agree with in his post, but, with respect, his assertion that climate policy explains the difference between RCP8.5 and the new high scenario is wrong. That's why, for example, @jritch was able to publish a paper in 2017 showing that the coal assumptions of RCP8.5 strained physical credulity. We also knew about the implausibility issues (caused by coal, economic growth, pessimistic renewable tech assumptions, etc.) enough back in the early 2020s that IPCC AR6 explicitly mentioned them, citing @hausfath's paper, ours, and Justin's. (Justin, @RogerPielkeJr and I drew the below figure in 2022.) And yet, 8.5 still dominated the literature and the AR6 WGII assessment (see the figure). IEA's CPS and STEPS scenarios have been way off RCP8.5 for years and getting gradually more optimistic. Even the creators of RCP8.5 intended it to be a worst-case scenario, not "business as usual". Anyway, I think these new CMIP7 developments show that the field is updating (contrary to what some critics assert), but I don't think it's accurate to say that nothing at all went wrong here, and we shouldn't pretend otherwise just because POTUS is intemperately tweeting about it and drawing conclusions from it he shouldn't (as I pointed out in my post).

- RCP8.5 is indeed dead and that's a good thing for climate science. - Technological improvements, and to some extent climate policies, have made RCP8.5 even less plausible, but it was always implausible, for reasons we knew (thanks to @jritch) for a decade and have been widely known since 2020. - Climate impact research continued to heavily rely on RCP8.5 for years after we knew better, and there are still too many papers making it into top journals with headline findings based on RCP8.5/SSP5-8.5 (or, worse, SSP3-8.5). Reviewers and editors are not pushing back hard enough. - Many journalists and policymakers have stuck their heads in the sand about RCP8.5 and continue to do so. But there have also been some notable exceptions. E.g., @dwallacewells was one of the first to cover the changing scenario understanding, something I've always admired him for. - The scientific community *is* gradually correcting course, as evidenced by RCP8.5 being discontinued for AR7, and by all the papers and other materials that led them to that decision. - Climate change is real and IPCC's Working Group I reports (The Physical Science Basis) are solid. Their conclusions have high overlap with the DOE CWG report, as @RogerPielkeJr has noted. - Large majorities of Americans want the President and Congress to do more to address global warming, according to consistent polling for the past two election cycles at least. - There are some bastions of alarmism/bias within climate change academia, but they are largely *not* in the federal civil service. In my experience, most federal climate scientists are hard-working, rigorous (mostly physical) scientists who take their Hatch Act responsibilities for non-partisanship seriously. Gutting NOAA and other federal science is bad for the country (as @RyanWeather and others have argued) and won't save us from alarmism. - A great way to get to the bottom of how deep the RCP8.5 effect on climate impact science goes and create a more balanced picture would be to convene a new National Climate Assessment, with a broad and viewpoint-diverse author team. Thank you for your attention to this matter.

Good to see the IPCC moving on from RCP8.5 and other implausible high-emission scenarios. Climate impact researchers, take note! Kudos to @jritch for starting the conversation a decade ago.