There’s an interesting paper by Seltzer et al. called [w]idespread six degrees Celsius cooling on land during the Last Glacial Maximum, which I became aware of through a Twitter thread by Werner Aeschbach. The reason it’s interesting is that it uses noble gases in groundwater to estimate the cooling over land in low-to-mid latitudes during the last glacial maximum (LGM). They find that it cooled by 5.8 ± 0.6oC.
As the figure on the right illustrates, this is somewhat cooler than other estimates and potentially resolves a slight discrepancy between climate sensitivity estimates based on LGM cooling, and other estimates. Although they have typically been consistent, estimates based on LGM cooling have tended to suggest that the equilibrium climate sensitivity (ECS) may be on the low side of the range.
This new estimate of LGM cooling, however, suggests as ECS of around 3.4oC (not sure of the uncertainty), potentially rules out the lowest part of the range and is somewhat more consistent with other ECS estimates. It also probably rules out some of the very high ECS estimates coming from some of the CMIP6 models.
Of course, this is just one study, so it would be interesting to know what others think of this. It does, though, seem to be a very useful update to our understanding of the last glacial maximum and what this might imply with regards to climate sensitivity.