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Showing posts from May, 2026

On the Post-Relevance of RCP8.5

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A lot of misinformation has been circulating in recent weeks concerning the IPCC's decision to remove RCP8.5 from use in the upcoming AR7 report. I agree that the decision is a good one, and I think I can show why below with a simple toy model I created. I think it's fair to say that RCP8.5 is no longer a plausible future for us, given current emission reductions and the shrinking cost of renewable energy. For some very insightful comments from others about the death of RCP8.5, see Zeke Hausfather's post at Climate Brink  (also Michael Mann's comments on it here), a factcheck by Carbonbrief , Reto Knutti's comments , and the wonderful information at Climate Action Tracker . But the the usual suspects among contrarian political activists have been portraying the IPCC's decision as a win for "skeptics" and/or as an admission that the IPCC's projections have been fraudulent, such that over a decade of research that used RCP8.5 can now be safely disc...

Some Notable Hockey Stick Reconstructions

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 For fun I've been collecting hockey sticks. The following are not complete, but I think they're pretty representative. In fact, I even collected the much maligned Loehle 2008 reconstruction, which has been the darling of contrarian "science." There are numerous issues with that reconstruction, which I document here , but I'm including it because doing so doesn't change the fact that all known temperature reconstructions covering anywhere from NH-extratropical temperatures to global mean temperatures have a hockey stick shape if you include the 21st century. I decided to break this up into three graphs, one showing GMST reconstructions, one showing NH and NH-extratropical reconstructions, and one showing NH-summer and/or NH-growing season reconstructions. I'm showing each with their respective instrumental counterparts (global, NH, and NH-summer). For reconstructions with annual resolution, those are shown faded, but I show running 10-year means for all of...

Calculating ECS from The Indicators of Global Climate Change 2025

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A prepublication version of the Indicators of Global Climate Change 2025 (IGCC25) has recently been released. This report provides an annual update to IPCC's AR6 WG1 report concerning human emissions and global warming. The data provided as excel spreadsheets related to this report was extensive, and this allows me to produce some graphs I haven't been able to do before. These data do a really good job of showing the relative impact of human and anthropogenic forcings since 1750.  Using HadCRUT5 (1850-1900 Baseline) First I decided to show these forcings with GMST anomalies from HadCRUT5 to see how well the quantifications of forcings agree with observations for warming. This means for this section I'm limiting myself to values from 1850 to present. The graph below shows an update to Gillett's analysis used in AR6 that made it possible to conclude that human activity is responsible for virtually all the warming above the 1850-1900 mean. For this graph, I set HadCRUT5 to...