At Climate Etc today’s discussion was about a post by Nic Lewis about a recent PAGES 2k Consortium paper in Nature. I had a look at a plot below from a prior PAGES 2k study. I noticed a 5 dot V starting in about 1800 and ending in about 1900, followed by a trendline breakpoint. I speculated that the V showed synchronization as things started warming compared to the long term trend. Synchronization may occur followed by the climate jumping to another attractor. The new attractor may be warmer or cooler and it may either attempt to warm or cool the atmosphere. A theory accepted by some is that there is glacial and an interglacial attractor. If that is true, then shorter time scales could also have attractors. To understand attactors, look up Lorenz. Nic Lewis had discussed the low amount of forcing by CO2 in the 1830s. So I thought that with variable sensistivity (see Ghil) it could be possible that CO2 was detectible back then in a somewhat related way. Using the PAGES 2k plot below, the climate may have hit a lower threshold while the sensitivity value increased enough to cause some attractor jumps. I started looking for other indications of a 1800 to 1900 V shape in the climate measures.
And Then There’s Physics:
Contribution of solar and greenhouse gases forcing during the present warm period: