Spark Climate Solutions Chief Scientist, Phil Duffy, submitted the comment below in response to the Federal Register Notice: United States Global Change Research Program; Availability for Public Comment on the Proposed Amendment to the Fifth National Climate Assessment (NCA5)

Excerpt from Federal Register Notice: The proposed amendment would clarify that results dependent on these pathways [RCP8.5 and SSP8.5] should not be presented as expected, baseline, business-as-usual, likely, central, or ordinary Federal planning futures unless the same result is independently reproduced under a presently plausible scenario and evaluated against observations.

Comments on the proposed amendment:

NCA5 very clearly and consistently (throughout the entire document) describes RCP8.5 and SSP8.5 as "very high" emissions scenarios, not as BAU or central-tendency scenarios, and consistently assesses outcomes not only from RCP8.5/SSP8.5 but from a range of lower-emissions scenarios as well. A cursory review of NCA5 confirms the truth of this, and this, of course, is an example of appropriate use of scenarios. Thus, the premise of the proposed amendment—that NCA5 and actions which may have been influenced by it, or may in the future be influenced by it, are based on a presumption of implausibly high GHG emissions—is fundamentally incorrect. The proposed amendment therefore addresses a non-problem and is not necessary. Beyond being unnecessary, the proposed amendment is harmful because it creates the false impression that Federal agencies have been taking actions to address climate change, when in fact under this administration Federal agencies have been rolling back, rather than implementing, climate policies. The proposed amendment is additionally harmful because it propagates the incorrect narrative that the NCA5 gave undue weight to findings based on very high emissions scenarios.

Along those lines, it is ironic that OSTP is putting so much effort into discrediting the plausibility of a high emissions scenario at the same time that the Administration is taking steps to increase GHG emissions by blocking the implementation of low-carbon technologies, promoting fossil fuels, and opposing international climate action. 

If OSTP feels that it is important to retroactively reassess the plausibility of emissions scenarios used in NCA5, it should also reassess SSP1-1.9, a low-emissions scenario which is also used in NCA5. This low-emissions scenario is clearly now implausible because (among other reasons) it assumes that global net CO2 emissions peaked in 2020 and have declined since then–when, in fact, actual CO2 emissions have continued to increase since 2020. Hence, this scenario is at least as implausible as RCP8.5 and SSP8.5, and the fact that OSTP is focusing only on those high-emissions scenarios suggests that OSTP’s actions are an attempt to promote the false narrative that NCA5 overstated the risks of climate change. 

If NCA5 were to be amended, then the full NCA5 should be restored to the USGCRP and other Federal websites, since it would be inappropriate and biased to have only the amendment but not the original document (NCA5) easily available to the public. Furthermore, the unavailability of NCA5 on the USGCRP website obscures the false premise (noted above) of this proposed amendment to NCA5, and therefore calls into question the legitimacy of this public comment process by making it difficult for the public to see for themselves the untruth of the premise of the proposed amendment.

It is not appropriate or proper for OSTP  to "amend" NCA5 without the consent of the authors who wrote it. Only the authors can legitimately amend their own work. The fact that OSTP released NCA5 does not give them the right to amend it, any more than a book publisher has the right to amend a book it previously published, without the involvement or consent of the author.